engine runs rough

[freak]

My engine has been running a little rough. It lopes as if it has a spark miss. The fuel system is very good all the way through the carb. I pulled wires 3 and 4 today (both at the same time) and it sits there and runs as it was with the wires on. I pulled the plugs and they look ok. I ran it with the plug connected and grounded and spark was present. It has a high compression head, autolite 3923 plugs and what I would call a modern style distributor cap. I have no idea where to get a cap for it since is isn't the original. I ran a compression test on #3 and it showed steady 100psi. I'm worried that a valve could be stuck. Any other ideas?

[Tom Endy]

My experience has been that a Model A engine will lope if you have the GAV valve open too far. The Zenith on my Victoria was rebuilt by me with all the jets flow tested and re-sized. If I open the GAV too far the engine will lope. A Zenith with properly sized jets provides for actual GAV control. Many improperly rebuilt Zeniths have the comp jet too large and it ports so much fuel into the secondary well that the GAV valve no longer has any control. This is the same as having the GAV valve open too far and it will cause the engine to lope at idle or low speed.

Tom Endy

[Patrick L.]

What is the compression on the other cylinders ? We should probably know that before going much farther.
But, a lope is generally from a too rich a fuel mixture. Where are the fuel settings, both of them ?

[freak]

I ran out of time tonight. Will run more compression test tomorrow. What do you make of the fact that I can pull #3 and #4 wires with no effect? Pulling #1 or #2 kills the engine.

[freak]

My GAV was set about 1/2 to 5/8 which is pretty much where I always run it unless cold. I haven't touched the mix screw since the carb was tuned by the carb builder. The rough running developed today as I was driving. It was loping a bit a few days ago and got worse today. Lost some power as this happened.

[Trailwanderer]

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I keep reading about "lope" could someone care do describe what that exactly is... or sounds like to a knewb?... Thanks in advance!

[freak]

It is a quick up and down surging in engine speed.

[Trailwanderer]

Originally Posted by freak

It is a quick up and down surging in engine speed.

Thank ya kindly!

[Purdy Swoft]

I've got to agree with Tom Endy in post number 2. If the engine is running rich it will lope at idle and sometimes emit small puffs of black smoke at the exhaust . Loping sorta sounds like a race cam . When cold I crank my engines with the GAV opened 1/2 to one full turn open in the counter clockwise direction. In a short time when the engine warms it will start to lope and I reach over and close the GAV down in the clockwise direction to about 1/4 turn off the seat for model A Zenith carbs and close the GAV completely on B carbs after warm up. The GAV does have an effect on idle

[Tom Wesenberg]

Originally Posted by Trailwanderer

I keep reading about "lope" could someone care do describe what that exactly is... or sounds like to a knewb?... Thanks in advance!

I hear it all the time when my neighbor runs his lawn mower, which is running too rich. He needs to clean the air filter or adjust the mixture needles.

It's always better to short plugs to ground rather than pull wires. The high voltage tries to reach ground, even if it has to short through the coil windings or tower.

[freak]

Originally Posted by Tom Wesenberg

I hear it all the time when my neighbor runs his lawn mower, which is running too rich. He needs to clean the air filter or adjust the mixture needles.

It's always better to short plugs to ground rather than pull wires. The high voltage tries to reach ground, even if it has to short through the coil windings or tower.

It's a nice jolt when it reaches ground through your hand!!

[freak]

Originally Posted by Tom Wesenberg

I hear it all the time when my neighbor runs his lawn mower, which is running too rich. He needs to clean the air filter or adjust the mixture needles.

It's always better to short plugs to ground rather than pull wires. The high voltage tries to reach ground, even if it has to short through the coil windings or tower.

Ok everyone thinks GAV and I will work with it but does a rich condition explain why I can pull 3 and 4 with no change?

[freak]

Originally Posted by Purdy Swoft

Loping sorta sounds like a race cam .

That's exactly what it sounds like and if I can't get if fixed that's what I'll tell people is in it!

[Tom Wesenberg]

If you have a severe air leak in the rear intake runner, then you will have no work from the last 2 pistons. A short in the distributor cap will also mess up #3 and 4, and I've seen this on two A's in the past few years.

To check for an air leak I use an unlit propane torch. When the propane gets sucked into the opening the engine will smooth out and speed up.

[Terry,NJ]

Loping or "Hunting" as the Brits say is when the engine surges and then slows down all by it's self. It sounds like verrrum, verrrum, verrrum. Although you're not touching the gas.
However, I'd like to say that my engine was running rough recently, too. Always remember, when troubleshooting, try the simplest and cheapest possible solution first. So I poured some MMO (Marvel's Mystery Oil) into the tank. It runs much smoother now. The valves seemed to be sticking.
Terry

[freak]

Does anyone know how to diagnose a sticking valve?

[Tom Wesenberg]

Originally Posted by freak

Does anyone know how to diagnose a sticking valve?

Use a vacuum gauge connected to the intake manifold. A slow to close or stuck valve will show up as a flicker on the needle.

A good ear at the intake of the carb or at the tail pipe might also help.

[freak]

Thanks but I'm scared to even run that test. What is the typical fix?

[Mitch//pa]

i also say check for a vacuum leak at the intake.. if 3-4 are not firing when you interupt the spark find out why. i am thinking if you had a sticking valve your compression would have showed up lower....

running on 2 cylinders yes it will lope

put an inline spark tester on and compare the spark intensity to the other known good cylinders..

[Tom Wesenberg]

Originally Posted by freak

Thanks but I'm scared to even run that test. What is the typical fix?

Scared to run which test? The propane is safer than crossing the street.

A good fix is a can of Sea-Foam in the gas, and another can in the oil.

Remove the spark plugs and spray penetrating oil on the valve stems.

If they are really stuck then you might have to remove the manifolds and spray the valve stems.

[freak]

I'm scared of the results not the actual test.

[Purdy Swoft]

With sticking or slow sticky valve action, you will lose power, big time. If more than one valve is sticky, you will hardly have enough power to take off without stalling . I had this problem once with my roadster. Ethanol adultrated gas will do it if it stays in the tank for a month or more. I drained and added fresh alky-rub free gas . I connected a temporary vacume line to the intake and stuck the other end in a bottle of marvel mystery oil. With the engine running fast enough not to stall, vacume will draw the marvel oil into the engine. It will smoke like a tar kiln but the valves will usually free up and the engine will again run smooth with power. I don't know if sticky valves are your problem but if they are this will usually do the trick.

If you are running an original distributor, the modern style cap may be the problem. The air gaps can't be adjusted with the modern style cap. Some of these caps have so little or no gap on some of the cylinders that the effected cylinders will have weak or no spark at all. In some such cases you can see the distributer cap jiggle as the engine runs. As a test, if you've got a good used spare rotor, grind a few thousants off the rotor tip and see how it runs. This won't give equal air gaps but will at least give some air gap to the effected cylinders.This may tell you if the air gaps in the cap is the problem. More air gap at the rotor tip gives hotter spark. The smaller the gap, the weaker the spark will be. Just a couple of thoughts that you can try.

[tbirdtbird]

we can't offer concrete suggestions that have any meaning until you give us a full compression test set of readings.

you want ALL plugs out and throttle full open. Spin engine sufficiently on each cyl. until needle stops climbing, usually 3 compression strokes or 6 revs of the crank. Much easier with 2 ppl, one in car activating starter.

You said this was sudden onset so I am not sure how that is carb all of a sudden or even stuck valves all of a sudden. You must go thru a proper diagnostic paradigm

what kind of work has recently been done to this engine

while plugs are out can you take a pic of each and post them (closeups) so we can see the burn color of the porcelain, check for carbon, etc. You may have bridging of a plug gap by a foreign particle. With the plug in place, it will still show a spark when you hold the wire away, but the spark never jumps the gap in this scenario (because there is no gap)

If a modern type dizzy with modern cap you could have carbon tracking which will give spark crossover and take out whichever cyls are being crossed.
Take closeup pic of inside of dizzy cap so we can try to look but this will be tough to see in a pic; hard enough to see it in person.

The point is a lot more info is needed.

Tom, the propane torch idea is just *superb* less messy than using WD40 and not as dangerous as using ether. dave

[Ed Saniewski]

Freak, did you test for spark between the spark plug tip, and the spark plug cable? You said you got spark when you grounded the plug, but try testing the plug itself. Ed Saniewski

[Tom Wesenberg]

You can check the spark plugs by swapping 1 & 2 with 3 & 4 to see if the miss follows the plugs.

[Mitch//pa]

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and swap the wires also
it should be fairly easy to figure out why they are not firing with all the suggestions posted

[Growley bear]

Originally Posted by freak

My engine has been running a little rough. It lopes as if it has a spark miss. The fuel system is very good all the way through the carb. I pulled wires 3 and 4 today (both at the same time) and it sits there and runs as it was with the wires on. I pulled the plugs and they look ok. I ran it with the plug connected and grounded and spark was present. It has a high compression head, autolite 3923 plugs and what I would call a modern style distributor cap. I have no idea where to get a cap for it since is isn't the original. I ran a compression test on #3 and it showed steady 100psi. I'm worried that a valve could be stuck. Any other ideas?

No compression with stuck valve. If any valves are stuck, they will be open. If any valve is not opening there is a larger problem. Did this problem begin suddenly or gradually?

Chet

[freak]

Originally Posted by tbirdtbird

we can't offer concrete suggestions that have any meaning until you give us a full compression test set of readings.

you want ALL plugs out and throttle full open. Spin engine sufficiently on each cyl. until needle stops climbing, usually 3 compression strokes or 6 revs of the crank. Much easier with 2 ppl, one in car activating starter.

You said this was sudden onset so I am not sure how that is carb all of a sudden or even stuck valves all of a sudden. You must go thru a proper diagnostic paradigm

what kind of work has recently been done to this engine

while plugs are out can you take a pic of each and post them (closeups) so we can see the burn color of the porcelain, check for carbon, etc. You may have bridging of a plug gap by a foreign particle. With the plug in place, it will still show a spark when you hold the wire away, but the spark never jumps the gap in this scenario (because there is no gap)

If a modern type dizzy with modern cap you could have carbon tracking which will give spark crossover and take out whichever cyls are being crossed.
Take closeup pic of inside of dizzy cap so we can try to look but this will be tough to see in a pic; hard enough to see it in person.

The point is a lot more info is needed.

Tom, the propane torch idea is just *superb* less messy than using WD40 and not as dangerous as using ether. dave

I'm going to run a full compression test tonight. Nothing has been done to this motor recently. I bought the car in September and haven't touched it.

[freak]

Originally Posted by Ed Saniewski

Freak, did you test for spark between the spark plug tip, and the spark plug cable? You said you got spark when you grounded the plug, but try testing the plug itself. Ed Saniewski

I tested the plug itself. There is spark at the plug tip.

[freak]

Originally Posted by Growley bear

No compression with stuck valve. If any valves are stuck, they will be open. If any valve is not opening there is a larger problem. Did this problem begin suddenly or gradually?

Chet

It was sudden. I am wondering now about a head gasket.

[Growley bear]

Originally Posted by freak

I tested the plug itself. There is spark at the plug tip.

Just because a spark plug shows a spark out in the atmosphere doesn't mean that it will fire when under compression.

Chet

[Growley bear]

Originally Posted by freak

It was sudden. I am wondering now about a head gasket.

If a head gasket is blown, compression will be 0 or almost. A gasket blown between two cylinders will also have an effect on the other two due to the nature of the induction system.

Chet

[Patrick L.]

You are removing one plug wire at a time, right ? I'm thinking that if #3 has 100# compression then there is nothing wrong with the head gasket and valves are not sticky.
If you still feel you have some sticky valves, then fill it with non-ethanol and a heavy dose of Sea-foam.
I'm agreeing with the fellas that there is an intake manifold or gasket problem, that is, if #3 and #4 have good spark.

[Growley bear]

Stock Model A intake manifold? Vacuum wiper motor? Tillotson? Zenith? The flow of fuel vapor and negative pressure in an induction system will follow the path of least resistance. The Model A intake manifold runners are all connected at the junction of the carburetor mounting pad. Any leak on either end albeit an intake or head gasket leak will limit the negative pressure at the upper side of the carburetor thus limiting the proper flow of fuel vapor. 1&2 affect 3&4 and vice versa. There needs to be a proper intake manifold seal on 3&4 or 1&2 will function although only well enough to allow the engine to run. A flow of propane from an unlit torch as Tom suggested is the best way to find any induction leak to the atmosphere. Remember that engine (suction) does not (pull) the mixture into the engine. Atmospheric pressure pushes it in. Therefore if there is a leak in the induction system that is the path of least resistance and the point at which atmospheric pressure is induced into the system. A very lean condition is the result.


Chet

[tbirdtbird]

if this happened while you were out driving then the more 'catastrophic' problems i doubt. i am still back to an ignition problem. do you know what carbon tracking is? I do not know how we all of a sudden jumped to a head gasket. slow down and get rid of the doomsday attitude!! (Smiley Face)

[Purdy Swoft]

I mostly agree with Tbird. The problem probably isn't anything Major. Loping is mostly a result of running rich. Model A's can sometimes have multiple problems, all at the same time. I've had experience with a few of the modern distributor caps some bad but not all. I wouldn't be too quick to mess with the head unless I was sure that the head gasket was the problem. I've only had one head gasket failure in 54 years . The repro steel clad gasket burned in two in the narrow area between cylinders 3 & 4 and did not involve the water jacket. This type failure can happen between cylinders 1 & 2 or 3 & 4 but not likely between 2 & 3 because the gasket is wider between 2 & 3 cylinders. When this type failure happens you will loose all compression between the adjoining cylinders but have NO effect on the water jacket . In other words, coolant won't enter the combustion chambers or the crankcase. No need for a compression gauge, a simple thumb over the spark plug hole while the engine turns will reveal whether you have any compression or not. If all compression is lost between the mentioned cylinders, my next move would be to remove the valve cover. If I didn't find a stuck valve in the open position in both adjoining cylinders my guess would be a burned in two gasket between the cylinders. If the problem is the gasket it would cause much worse running than just loping.

When I had problems with sticky valves, I still has some compression. The slow valve action caused by ethanol and sticky valves weakened compression to the point that the engine had no power under even the slightest load.

Your problem is probably as simple as incorrect GAV adjustment, 5/8 turn open after warm up is enough to cause loping. Running too rich is sometimes enough to cause the spark plugs to become so sooty that they don't function at optimum level. I would also take a good look at the modern distributor cap.

[Growley bear]

Carbon tracking in the distributor cap if tracked between the center and one wire lug will fire that one every time a spark is fired. If tracked between two plug wire lugs inside the cap, there will be backfiring almost as if the distributor was installed out of time.

Chet

[Growley bear]

As a side note; the Model A engine has a certain rhythm while it turns over before starting. With spark plugs installed and ignition OFF, turn the engine over with the starter and if a cylinder is low on compression you will hear a change in the rhythm of the engine.
As Purdy said earlier, pull the plugs and place your thumb over the hole if there is compression you will know it. At this point all you are interested in is if there is compression. The first method that I mentioned is very quick, easy, and doesn't require any tools. If the sound is erratic, then further checking will be necessary. Start with the easy and work toward the more complicated. If all cylinders have decent compression, (will blow your thumb off the hole), you could rule out a blown head gasket between two cylinders.

Chet

[freak]

Ok guys... Just ran a full compression test. Here is the results....

#1 105
#2 105
#3 30
#4 30

I early reported 100psi on #3 and I must have been on #2.

Head gasket?

[Mitch//pa]

okay now a whole new circumstance
yes i would say a blown gasket but a leak down will tell you for sure

[J and M Machine]

Head gasket.! You have to retorque a few times and don't forget the copper spray on both sides of gasket.

[freak]

Why do the gaskets fail? Is the head or block typically warped? Should I expect that one or the other (or both) need milled?

[freak]

Originally Posted by Mitch//pa

okay now a whole new circumstance
yes i would say a blown gasket but a leak down will tell you for sure

How do I properly do a leak down test? Also I don't have a tester but is it worth getting for this case?

[Mitch//pa]

freak here is a previous thread for leak down testing info

https://fordbarn.com/forum/showthread...ight=leak+test

[larrys40]

No just pull the head and fix it
While your at it inspect the valves and service if needed. If you don't know what you doing on the valves get someone to help you . If they have a good centered seat on them then you are probably ok. I would check the head for cracks and plane . Get it surfaced and replace head gasket and your back in business

Larry Shepard

[Mitch//pa]

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its probably not necessary in this case to perform the leak down but its good to know what its all about

[tbirdtbird]

leak down is nice but not mandatory. Compr test told diagnosis clearly. Blown between 3&4. Common. There ain't much gasket there!
Pull head. Have it surfaced to be sure (did car overheat anytime that you had it? You would not know if before you bought it.) Cheap insurance.

Get the Felpro copper (Felpro PN is 7013) NOT the silicone gasket which is junk.
Use a copper spray-on liberally, Permatex makes a good one, as well as others. There is K-W copper in a dauber can, forget it, you will never get the head off again.
Use proper torque sequence (it is in the Bratton catalogue maybe others)
Torque in steps, ie all to 20 lbs, then all to 40 lbs, then all to 55 lbs. Some use a final torque of 50 on the two nuts on the water neck to prevent cracking; your call.
Run engine for 10 min. Shut off. Re-torque right now while hot. Under no circumstances should you back the nuts off a half-turn doing this I do not know how this fool-hardy suggestion ever came to be. I do this for a living and I would get beat up by my clients if I messed up their head seal.
Run car on road for 20 min. Re-torque hot again.
Wait a day, allow full cool down, drive car for 30 min, then re-torque hot one more time. At this point you will take up very little on the nuts. We have always tried a 4th hot re-torque but are never able to take up any more.
Do not drive like a maniac while doing any of this.
This has been standard shop practice in this country since at least 1950 when I started working on cars. i have never seen a professional do it any other way. I have several racing buddies who do it this way. I have never had a failure. Should you elect to deviate from this method your results may vary!
I have never had a client's A in the shop that did not need a re-torque, never, because they were improperly torqued in the first place.

This is actually an easy fix, and inexpensive.
Good luck
Post questions if you have any

There will be naysayers to all that I have written. Procede at your own risk. Try to imagine how many head gaskets I have installed since 1950 on every variety car.

[Growley bear]

I don't know where the idea of backing the head nut off a half turn or so before a retoruqe was started either. I decided to try it on my A; I marked the nuts with a sharpie and first checked them without backing off, no movement. Next I backed them off and retightened ant they all save one stopped at the mark. That one barely split the mark in half, surely not enough to worry about. I have the silicone gasket with standard head and retorqued 4 times before I got it to seat. I check the head nut torque on a regular basis.

Chet

[Tom Wesenberg]

I agree that most likely you have the head gasket blown between 3 and 4.
In 1970 I bought a 1950 Studebaker Commander with an engine miss. First thing I did was check compression and got 100-100-100-100-40-40, so I guessed it must be the head gasket. I was surprised to find the last 2 exhaust valves were burned. I like to keep everything well matched, so I replace all 6 exhaust valves for a total cost of $7.60. I guess those were the good old days.

You can bring #3 to TDC firing, then use a rubber tipped blowgun to inject air into that cylinder and see where you hear it coming out. It will come out the carb, tail pipe, oil fill pipe, or #4 if the head gasket is blown between 3 and 4.

[Purdy Swoft]

If it has 30 pounds compression on cylinders three and four, the gasket isn't burned in two between the cylinders. If the gasket was burned in two between number three and four, you would have no compression on either cylinder.

[freak]

Originally Posted by Purdy Swoft

If it has 30 pounds compression on cylinders three and four, the gasket isn't burned in two between the cylinders. If the gasket was burned in two between number three and four, you would have no compression on either cylinder.

So what is your theory?

[Mitch//pa]

Originally Posted by Purdy Swoft

If it has 30 pounds compression on cylinders three and four, the gasket isn't burned in two between the cylinders. If the gasket was burned in two between number three and four, you would have no compression on either cylinder.

purdy i rarely disagree with your valuable input
but i dont agree that compression is always 0 when a head gasket leakage occurs between two cylinders..

[tbirdtbird]

on the outside chance it is a valve issue the head has to come off anyway.

[Purdy Swoft]

Not necessarily. If the valves stems are gummed up from using ethanol gas, valve action will be slow enough to cause weak compression without complete loss of compression. If the head gasket is burned in two between cylinders 3 and 4, number 4 cylinder will be down when number 3 is on compression stroke. I just can't see it holding any compression if the gasket is burned in two between the two cylinders. Maybe in the early stages of burn through, it may briefly hold a small amount of compression but not for long. I just feel that other things should be tried before jumping into removing the head. Running Marvel mystery oil through a temporary vacume line while the engine runs will free up slow sticky valve action. Just trying to help. Its a forum, we can disagree, no harm meant.

[Growley bear]

I think that Tom already pointed this out. An adapter can be fabricated to introduce a metered amount of air into one cylinder or the other. All spark plugs removed and with say # 4 on top dead center apply 30psi (don't just apply 110 psi as the engine might try to turn) to that cylinder and see where the sound of leaking is coming from. Out of #3 spark plug hole blown head gasket between the cylinders. If leaking air is found at tailpipe or carburetor then a valve is leaking. If it was my engine I would pull the head as what ever is wrong at 3&4 is probably not far from wrong at 2&3. Best to repair this at home or in the shop than have a problem out on the road.

Chet

[Purdy Swoft]

I agree, Toms test is good as usual. Sticky valves can give similiar symptoms . In the spirit of trying to help the guy ,I would do some easy tests before I removed the head . I have experience with bad gaskets, burned valves and sticky valves . A simple test with a temporary vacume line and some Marvel oil will be easy and inexpensiuve . This simple test will give quick results if the problem is actually sticky valves. If the guy jumps into head removal and gasket replacement, the chances are better than average that some of the old head studs will wring off in the process, no matter how careful a person tries to be. Sometimes you get lucky and no studs break. Most want to replace the old studs while they are at it, this is generally where the problems begin. Broken head studs are not good for the average guy at home. Many times the engine will have to be removed and then find a machine shop that will even take the job of removing the broken studs. I don't know what the real problem is. I just recommend exploring all avenues before doing something as major as removal and replacement of the head. The last engine that I had with partial loss of compression on the back two cylinders had two broken piston skirts and some of the rings had dropped into the oil pan. The engine was weak but would still run , it had a low speed miss but would still hit on all cylinders when RPMs increased. Removing the head in some cases may not show the real problem. Still just my thoughts.

[Tom Wesenberg]

Well, an intake leak won't cause low compression, so we can rule that out for the loss of power on 3 and 4. I would still do the simple checks first though. Try putting air pressure into #3 and see if it escapes. If it does, then the head will need to be removed. If it doesn't, then it might be a sticky valve that is slow to close and I'd try sea foam in the gas and oil, or spray some penetrant on the valves directly.

If that doesn't help then start soaking the head studs with penetrating oil and get ready to remove the head.

[freak]

The gasket was blown between 3&4. It had a copper gasket with a white material (asbestos?) sandwiched inside.

[Purdy Swoft]

Thanks for the heads up. Good luck.

[tbirdtbird]

Purdy, to back up, I mostly agree with you about MMO, and that sticky valves don't nec. mean the head has to come off for those, I was a bit ahead of myself there.
Having said that, the guy had his problem occur while he was driving the car. I am not sure that is when the valves would stick. I myself have seen blown gaskets with low readings like he got between to adjacent cyls. It doesn't have to be a major blowout; in the early stages it could be more like a 'leak'.

He wants to know why the gasket blew, and my answer is that it was never properly torqued in the first place; or that someone drove the car like hell and over-revved the motor/overheated the motor. There is so little gasket material in between those cyls to begin with I am surprised they don't blow more often.
If the car had been overheated at anytime that could have warped the head easily; these issues don't always show up right away. If i ever have any head off for any reason, it gets machined regardless. All this deal about checking with a straight edge and all is a bunch of BS. They can be warped at any angle and a straightedge is like using a crescent wrench to measure thousandths of an inch like somebody said they did on here not that long ago.
Maybe the copper spray was not used. Who knows. In any event, all the more reason to do a fresh install by professional mechanics standards, and not by myth, guessing, random Barn comments from folks who have never done even one, and Ouija board.

You and I and the other responsible posters here want the best job for this guy. Which is why we are here.

I hope this renewed discussion of possible stuck valves will highlight once againthe need to use MMO in the gas tank, and some in the crankcase as well. Thanks to the senator from Iowa, we all have to live with a gasoline fuel that is highly polluted and does really bad things to our cars, not that he cares; they just want the govt subsidy. Pure gasoline is not available to all of us. It is easier to get in some areas, like I think Tom W has access to it because he mentions 'good' gas every so often. And I can't figure out why it is only available in certain places.

I encourage the OP to carefully study the advice he has been given, proceed slowly and thoughtfully, gather the correct tools (he will need a way to get a torque wrench on #8 stud, me I use a crow's foot wrench which throws my reading off only a tiny bit), etc. I think the suppliers have a special offset 11/16 socket or extension to get around this problem. Bratton's PN 6082. And do not be afraid to ask questions as you go. Spray a good 3 coats of copper spray on both sides of the gasket, for heat transfer if nothing else.
Be sure your cooling system is not borderline. Run something to help you keep an eye on the temp, a thermoquail, an actual temp gauge, an infrared temp gun, etc , something anything to give some idea of what is going on.

You might consider a fresh set of head studs; the old ones are stretched. Use Permatex PTFE (Teflon) sealant (comes in a tube) (PN 80631) around the threads in the block since many of them go into the water jacket.

good luck. a blown head gasket is actually one of the cheapest and easiest repairs on an A, and will give good service if done right

keep us posted on your progress. This is actually a very educational thread for more novice A owners, and closure from the OP will help with that

[freak]

I'm taking the head to the Ford garage tomorrow. They have a full machine shop and the guy I talked to today says he has done many Model A heads. I'm getting it magnafluxed, pressure tested and surfaced. New gasket is on order. I appreciate the advice and will keep this thread updated on my progress.

[freak]

I agree with tbirdtbird... There is so little room between 1&2 and 3&4 it's amazing they don't blow out all the time.

[Purdy Swoft]

Tbird, as you know the thread started out with a loping problem ,then the symptoms started to include such problems as the rear cylinders having no change , no matter if the plug wires were connected or not. Then a repro modern distributor cap was mentioned as being used. At first it was stated that number 3 cylinder had 100 lbs compression. Near the end of the thread it changed to being that the back two cylinders had only 30 lbs compression. The symptoms were all over the place. I tried to address each symptom judging by like problems that I had experienced over the years. Somehow, I overlooked where he said that it had a high compression head. I guess I had too many symptoms to think over and missed an important key. I agree with your thought that the head probably was never torqued and retorqued as it should have been. I think that any model A head should be planed every time that they are removed because they will usually be warped to some extent. Old original heads will usually have cracks from stud hole to water jacket in some places. I was just trying to find a simple fix without having to pull the head. Being as the head had been replaced with a newer head, maybe the old studs were also replaced at the same time and won't be a problem. I still find it strange that the gasket wes burned in two and still had 30 lbs compression on both cylinders. Ive seen engines still hit on cylinders with less than 30 lbs compression but would have a low speed miss untill rpms increased.. I hope that a new gasket solves the problem but I wouldn't be surprised if other problems didn't still exist. It is hard to diagnose problems sitting at the computor. I may be a hard headed old coot but I would like to see that head gasket.

[freak]

I was going to post a photo of the gasket. It's too late tonight but I'll get it tomorrow.
It actually ran pretty good till the other day when it blew the gasket. I suspect it wasn't torqued well enough as well. The nuts cam off rather easy. Looking back I should have re-torqued it but didn't know that was necessary at the time. I'm used to modern cars where we have head gaskets for life. The A is a different beast and I'm learning.

[tbirdtbird]

Purdy, no harm no foul. I consider what you offer here to be some of the best advice on the Barn; to an experienced mechanic it is obvious you have been around the block a few times.

"It is hard to diagnose problems sitting at the computor" Ain't that the truth !!!!!!!!!

Modern cars and modern head gaskets usually do NOT require a re-torque. In fact in many cases you couldn't if you wanted to. The reason this is so is based purely on the way the gasket is constructed. Modern materials/designs are technologically superior to vintage cars (where my comments were addressed).

Having said even that, there is no such thing as a 'head gasket for life'! LOL. Don't we wish. I diagnose about 5 blown head gaskets in modern cars per yr, and a buddy of mine about the same. Last one was a Hyundai Santa Fe. Changing them in a modern car is a nightmare.

The OP is prolly onto something, he should have had to work hard to get those nuts loosened. When As come in here that I have never worked on I always check the torque and most are right about 35-40 pounds. Not even close.

[Tom Wesenberg]

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I also missed where it was stated anything about having a high compression head, and that makes the gasket and retorques all the more critcal. I always use the copper gasket and copper coat on both sides.

While the head is off, I would stick a thin air gun down each coolant hole in the block and blow while you move the nozzle around, just to see if you can blow out any rust or junk. You could remove the side water inlet and hold a shop vac hose to it to help suck out the junk while you blow with the air nozzle down the coolant holes. I would tape over the cylinders to keep any rust out of the rings.

[Mitch//pa]

sounds like you have a solid plan going forward keep us posted.
as tbirdtbird mentioned replace the studs and nuts

[marc hildebrant]

In College I had to replace the head gasket in my 1933 Chev coupe. Without any info except a head bolt picture and value, I replaced the gasket O.K. My mechanical skills were not good then...fair today.

Now a days, I would use the methods discussed by TBird and other's...

Marc

[Purdy Swoft]

My friend Tbird is right on.The head gasket that burned in two with me was the cheap steel clad gasket from JC whitney. It worked good for nearly eight years before the burn through happened. The gasket was completely in two between number 3 and 4 cylinders and lost all compression between the two cylinders. The car had been my daily driver so it got lots of use before the gasket failed. I do torque my heads after the first twenty minutes while the engine is still hot. I continue to retorque cold in sequence , often untill it will hold 55 ft, lbs. torque. The last two engines that I did, I used the BF grade 8 studs and nuts and they only needed 2-3 retorqueings to hold the torque. With grade 5 studs it will take at least 5 retorqings to hold.

As Tom says it is very important to clean out the water jacket . Whenever I do one on my engines, I turn the block upside down on the engine stand, place a tray under it and dig out all of the foreign matter that I can. I then wash and blow it out and repeat as many times as necessary untill I'm satisfied that I've got it clean as possible. The back two cylinders run hotter and is where problems happen with most engines.I was a bodyman by trade. The only time that I worked as a mechanic was on summer vacation between the 11th and 12th grade. I worked at an alignment shop but we did everything from front end work to tune ups and such.I've always been a car nut and did all of my own mechanic work since I was a kid. I know nothing about the newer cars with electronic ignition, computers and fuel injection. I now just keep our model A collection running, anything else gets sent to the dealership.

[freak]

Gasket pics...

[tbirdtbird]

great teaching pix if nothing else, thx for posting. This will be great thread for others in the future. To me there are two issues pertaining to proper torquing. Of course, you have to hold back the pressure that is in the cylinder, and there is precious little gasket there to help you do it. The other is heat transfer, and you can see the copper is discolored between 1&2 and 3&4, more so at 3&4. Without good clamping force, you will not get the heat transfer you need. Since 3&4 run hotter anyway, I suspect this is why the gasket always seems to let go in this location.

This is a 14-stud block, and it can be argued that more studs would have been better. If you look at the early V-8 as example, Henry went to 21-studs. Of course the heads were higher compression so he really had no choice; but you get the idea.

I noticed that there is a survey going asking ppl for their wish list for the new A blocks that will someday be cast and available for purchase. One of the items mentioned by a poster was more uniform cooling for the four cylinders.

There are a lot of things going on with an A motor that are persnickity to the A. That is why I often mention that a knowledge of modern engines will not necessarily get you where you want to go with an A. Actually, any engine has its own unique traits that need to be understood.

[Mitch//pa]

nice pics
i see burns on every edge of the gasket firing area front to back. maybe its from a torque problem but once you get this bear back together listen for detonation, or running to hot from a restricted radiator. make sure your timing is on as many different things can contribute to the failure. you have a hc head so be careful how much advance you run

[Tom Wesenberg]

Also when the heads and decks are ground, they need a certain amount of roughness to grip the gasket.

[colin1928]

That's the weak area when running increased compression
To prevent gasket blowing out in this area I lay a fire wire between the studs on all hi compression engines

[Tom Wesenberg]

Originally Posted by colin1928

That's the weak area when running increased compression
To prevent gasket blowing out in this area I lay a fire wire between the studs on all hi compression engines

What's a fire wire?
Any pictures of it?

[colin1928]

Tom this my fire wire does the same job as O-ringing a combustion chamber on a race engine where they use bigger dia wire but grove the block here I use 0.6 mm mig wire and just lay it down if you wrap around the stud like do just to stop it moving I chamfer the stud hole in the head slightly or just a straight wire will work
These gasket are only made for standard compression so you need this for the hi comp heads
I have run as high as 10-1 using the wire with out a problem
I fit to all engines with 6-1 or better
Colin

[tbirdtbird]

hmmm, you are also not using the copper Felpro # 7013 which is higher quality than the steel gasket......

[colin1928]

Yes I use the 7013 Gasket that is just an old stock gasket used as a template

[freak]

The head was magnafluxed, pressure tested and surfaced. I'm picking it up tomorrow. I have new studs and a gasket (gasket from Charlie Yapp). Right now I'm cleaning up the block and noticed there are 4 holes that look like a roll pin or set screw is in them. I've circled one in red, can someone tell me what they are for?

[Tom Wesenberg]

I think that is just a gasket wear mark around a water hole.

[freak]

They aren't through holes. They only are around 1/4" deep.

[tbirdtbird]

Hmmmmm....Tom, do suppose some misguided individual decided to reduce the diameter of the water holes to the head? In a similar vein that misguided ppl drilled holes in their dipper trays so they could 'drain out all the oil on an oil change' ?

Before I reassemble anything I'd get the dimensions from another block as to what is going on.

Measure the diameters and post them and then we can better advise you.
I sure wish Purdy were still posting

[freak]

I started another thread on this so some others with knowledge might notice.

[Tom Wesenberg]

Originally Posted by tbirdtbird

Hmmmmm....Tom, do suppose some misguided individual decided to reduce the diameter of the water holes to the head? In a similar vein that misguided ppl drilled holes in their dipper trays so they could 'drain out all the oil on an oil change' ?

Before I reassemble anything I'd get the dimensions from another block as to what is going on.

Measure the diameters and post them and then we can better advise you.
I sure wish Purdy were still posting

I don't have a block handy to measure the hole diameter, but the corresponding hole in the head is 1/4".

[tbirdtbird]

can you get us a better closeup pic?

Do all the altered holes have the exact same appearance?

Is this just rust buildup over the years that has narrowed these? In which case they def. need to be drilled out.....

we need more info...
tough not being right there....

[freak]

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I'll get a better shot tomorrow. I really think they are plugged with a set screw. I couldn't see good enough but I'll see if an allen wrench fits. This has me worried now.

[tbirdtbird]

can you use a small pick tool to poke around there? and a blow-gun?

[colin1928]

Those are called steam holes and should be block off if fitting any aftermarket Hi comp head
Most good heads do not have the corresponding hole (Winfield ect)
Blocking off both the head and block is common and prolongs gasket life
They are not needed if you have a working water pump

[freak]

colin1928 you were spot on! I got the head back today and there are no corresponding holes in it. Your statement that "Blocking off both the head and block is common and prolongs gasket life" appears to be the reason. Thanks!!

[freak]

The head was .002 out. I have everything ready but I ordered a new torque wrench because both of mine are cheap and I no longer trust them. Unfortunately I don't think it will be here for the weekend. How do you guys go about setting your stud height? I heard one thread showing past the nut is the rule. Should I set the head on the block with a spacer equal to the gasket thickness and set the height from there?

[freak]

I'm starting to think this blown head gasket is a blessing in disguise. My distributor was extremely hard to turn. It was probably only a short time before something snapped. I got it clean and lubed and it turns great now. Just painted the head and water neck today. Still waiting on my new torque wrench.

[tbirdtbird]

good work!