engine runs rough

[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]

Sponsored Links (Register now to hide all advertisements)

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.