New misfire - sticky valves?

[JMFL36]

Hi guys. My '34 developed a misfire yesterday when I was out for a 20 mile drive. It is noticeable at all speeds, under load and not. I checked all the plugs and none were fouled. It seems to be more noticeable on a cold start and less so when the motor warms up, but never goes away. I notice a bit of smoke from the filler tube which smells like exhaust, so I suspect I may have a sticky valve. I drizzled about 6 ounces of MMO down the carb under fast idle, but still have the misfire. Any advice on what to check next would be appreciated. Here is a link to a 30 second video of the motor running.

https://photos.app.goo.gl/1698PpxL9Xg7jNNX7

Thanks in advance.

[rbone]

One thing I have done to narrow down the problem is to one by one remove plug wires with the engine running to see which cylinder(s) is acting ugly.

[drolston]

That miss sounds regular; like one cylinder missing. Removing plug wires as suggested by rbone should affect the idle on all but the bad cylinder. And eventually, it should show up as a wet or sooty plug.

[Ggmac]

Do you have a vacuum gauge ? If so see what its reading , see if low and steady or it fluctuates . Check for a leak at the vacuum wiper connectors , and vacuum brake , next i would eliminate each cyl one by one and see if itll tell you which one . Next Id do a compression check on that cyl and on each side of it . If everything is okay idstart looking at fuel or electrical . Your vacuum should be a steady 19-21 if a healthy motor . High mileage may be 16-19 but always a steady needle . A bouncing or dropping needle indicates a sticky valve or dead cyl ( plug , wire , vacuum leak , etc . Good luck . Im a little far from you but willing to help .

[JMFL36]

Thanks for the tips guys. I just ran a compression test on all cylinders. All cylinders reported in at around 75 PSI except for #7 which reported in at ZERO. I guess that's the culprit. Any advice on how to un-stick those valves?

[drolston]

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With the piston at the top of the compression stroke so the stuck valve is off of the cam, go through the spark plug hole and squirt some penetrating oil around the offending valve and hopefully onto the valve stem. Then, after a while, with a screwdriver or rod to the top of the valve, lightly tap with a mallet. With an engine that has been recently in service, the valve should drop right down. Then run some more MMM through the carb while jazzing the throttle up and down.

In the future, add about 4 ounces of MMM to each tank of gas.

[JMFL36]

Should I also add some MMO to my oil?

[Mart]

Pull the plug in that cylinder and you can observe the exhaust valve directly below the plug hole. If that one is sticking open you will be able to see it.
You could remove the intake. You can see the valves in there and might be able to manipulate them up and down.
Squirt some penetrating oil anywhere you can that might get around the valve stems. (down the port for instance).
If you take another movie hold the camera sideways. It comes up bigger on the screen.

Fwiw the only time I experienced sticky valves was in a Y block. I was trying to be clever and was burning some very old fuel. In that motor it manifested itself by bending the pushrod.

Mart.

[51 MERC-CT]

Take a peek into #7 plug hole, you may or may not be able to see something like this.
A burnt exhaust valve spotted after chasing the source of some of the same symptoms.

[drolston]

Originally Posted by JMFL36

Should I also add some MMO to my oil?

Modern oil is so good that I do not add MMO to the oil. Without leaded gas, where MMO is needed most is in the fuel to give a little lubrication to the valve shafts. I do include one quart of Valvoline VR-1 in each oil change to provide some zinc to those flat tappets.

[topfuel724]

Had 2 sticking exhaust valves #4 and #5 in a 8BA recently. With the exhaust valves in the open position sprayed the stems and guides through the spark plug hole with "Brake Clean" and also MMO. Let them set for a couple of days and tapped them down with a brass punch making sure that the cylinders were on the back side of the cam. I believe the sticking was caused by old gas. Topped the tank off with non-ethanol fuel and some MMO. No sticking since.

[Als48]

You might try starting the engine at night and looking at the plug wires and distributor cap in the dark. You'd be surprised how much arcing shows up that way.

Al Hook

[Tinker]

Originally Posted by 51 MERC-CT

Take a peek into #7 plug hole, you may or may not be able to see something like this.
A burnt exhaust valve spotted after chasing the source of some of the same symptoms.

Had one of these on my 36. Compression was around 30lbs, Bruce L thought that was high from the culprit picture valve. Replaced it with a nice gentleman's help here sending me a good used valve setup.

Exhaust valves are usually the culprit. They receive all the heat and carbon. But sometimes it's the intake valve being burnt from a lean situation. Usually you can figure that out, if it is firing (electrical solid) then it back fires or pops out the carb.

yes you can do a mmo dump down the carb from time to time. It will not hurt. Cheap. I do it just because, once a year as regular maintenance. Seems to work for me so far. I wouldn't say it if it didn't.

When I first read this, the first thing I thought was electrical. But the compression test rules that out. Best of luck!!!

[Tinker]

If you want to waste a couple bucks and explore your tech side. You can buy something like this. Engine snake camera. (I'm not recommending this one, there are plenty of these types of things nowdays so look around). Doubles as a home colonoscopy (kidding!!! yikes). Again I don't recommend this one. hahaha

https://www.amazon.com/Inspection-Fa...42732349&psc=1




.

[JMFL36]

Thanks for all the advice, guys. Much appreciated. I ran several more compression tests and #7 is definitely the cause of the misfire. I got sporadic compression readings anywhere from 75 to 0 from #7, while all other cylinders reported consistently around 75. I also noticed my plugs, all of them, were somewhat black. So I am suspecting there is some carbon buildup on that exhaust valve stem. I need to lean the carb out once I get everything back together. But first my plan is to spray some brake clean through the plug holes around all the exhaust valves as wife cranks the motor. Then let it sit for a few hours and repeat until I get good compression out of #7. Then repeat one more time, but with MMO instead of brake clean this time. Sound like a reasonable plan?

[Mart]

I don't know about brake clean, wouldn't you want something that will add lubrication rather than wash lube away? I don't know.

If it is the exhaust valve, you could put something on it and lean on it while the engine is cranked. Make sure it is moving up and returning when it is supposed to.

[JMFL36]

Mart, I want to try and clean what I suspect is some carbon on the valve stem first, then lube with MMO after. Make sense?

[JMFL36]

I happen to have a scope-cam and took a short video of what I found today while soaking the valves with PB Blaster. Here's a link to that video -
https://photos.app.goo.gl/Sro1BG9P1i9JLNbM9

The sticking valve is the #7 INTAKE valve. When I crank the motor the valve lifts as it should but does not return. With just a little pressure I can push it back down into place. I then hand-turned the motor till the valve was just a little open, and using a 90 degree awl I was able to lift and lower the valve with very little resistance. I can also spin the valve fairly easily.

So I'm assuming I have a broken valve stem or spring. Sound right?

[drolston]

Any valve that can be pried up that easy has something broken. Probably the spring.
Take the intake manifold off to confirm. Then the head has to come off to fix whatever is broken.

[KiWinUS]

Horseshoe clip may have come out.

[Mart]

Would have to go with Kiwi. The guide appears to be moving.

Pull the intake manifold. Should be an easy fix.

Could be collets out of place or valve broken near the collet end.

Intake off inspection required.

Good use of the video capture.

Mart.

[51 MERC-CT]

Definitely something broken or out or place. Time to dismantle.

[JMFL36]

Just took off the intake and here's what I found. Guess I was lucky that it landed and stayed where I found it. The rest of the valve assembly looks good. Anyone know where to get a new C-clip?

[51 MERC-CT]

Originally Posted by JMFL36

Just took off the intake and here's what I found. Guess I was lucky that it landed and stayed where I found it. The rest of the valve assembly looks good. Anyone know where to get a new C-clip?

Vanpelt---


http://www.vanpeltsales.com/FH_web/e...prices-pg3.htm

[JSeery]

Or about anyone who sells flathead engines parts.

[Ggmac]

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Originally Posted by JMFL36

Just took off the intake and here's what I found. Guess I was lucky that it landed and stayed where I found it. The rest of the valve assembly looks good. Anyone know where to get a new C-clip?

Let me check tomorrow. If ive got part of a set ill send you some .

[Tinker]

It's nice to see a conclusion to a problem. Thanks for following through the whole project! Nice work!


You might take up any offers on a used/good clip. At least you'll know what the steel is made from.


I'd probably wonder why the clip failed. They are hard to get out on most engines in normal settings. Guides are stationary. Repeated valve sticking putting force on guide movement (there is only force from the spring, nothing from a sticky valve would force a 40/60lbs spring down to release the clip to let a 1/8" gap horseshoe to pop out), spring pressure? not installed correct previously, or a bent valve. Maybe look at how it happened also in conjugation to replacing the culprit.


.

[Mac VP]

It appears that the spring retainer has also come loose. Under the circumstances, the entire valve assembly is suspect. You could try to reassemble the this particular valve assembly, checking each of the various components for flaws, but if it was mine, I’d simply replace that assembly so I didn’t have to worry if some other piece of it would continue to act up. Further replacing of manifold and head gaskets plus all the retorquing would be a real drag to have to go through.

[Frank Miller]

Originally Posted by Mac VP

It appears that the spring retainer has also come loose. Under the circumstances, the entire valve assembly is suspect. You could try to reassemble the this particular valve assembly, checking each of the various components for flaws, but if it was mine, I’d simply replace that assembly so I didn’t have to worry if some other piece of it would continue to act up. Further replacing of manifold and head gaskets plus all the retorquing would be a real drag to have to go through.

I agree. The guide may have a defect that let the retainer come loose. At first I thought it just did not get fully installed but then I wondered if part of the guide did not break.

[JMFL36]

Mac VP, the bottom spring retainer is still in place and looks good.

Frank Miller, I was able to inspect the full guide circumference by turning the guide with a needle nose pliers. The retainer groove in the guide looks good with no damage all the way around.

I suspect (hope) that the retainer clip was not completely seated when installed, and worked its way out over time. The motor was rebuilt by a previous owner and has seen little mileage since the rebuild, under 1000 miles.

So my plan is to just replace the clip and not pop the heads. After a couple hundred miles I'll pull the intake again and do another close inspection of that valve assembly.

Ggmac, it would be great if you have a couple spare clips you could send me. Much appreciated.

[Terry,OH]

Make sure the recess in the block, the retainer clip fits into, is clean and clear of obstruction so the retainer fits inside the recess.

[Ggmac]

Originally Posted by JMFL36

Mac VP, the bottom spring retainer is still in place and looks good.

Frank Miller, I was able to inspect the full guide circumference by turning the guide with a needle nose pliers. The retainer groove in the guide looks good with no damage all the way around.

I suspect (hope) that the retainer clip was not completely seated when installed, and worked its way out over time. The motor was rebuilt by a previous owner and has seen little mileage since the rebuild, under 1000 miles.

So my plan is to just replace the clip and not pop the heads. After a couple hundred miles I'll pull the intake again and do another close inspection of that valve assembly.

Ggmac, it would be great if you have a couple spare clips you could send me. Much appreciated.

Ive found 5 that are homeless . Pm your address and ill get them to you . Itll be a couple of days till i get to the post office .
Gary

[Ggmac]

Originally Posted by JMFL36

Mac VP, the bottom spring retainer is still in place and looks good.

Frank Miller, I was able to inspect the full guide circumference by turning the guide with a needle nose pliers. The retainer groove in the guide looks good with no damage all the way around.

I suspect (hope) that the retainer clip was not completely seated when installed, and worked its way out over time. The motor was rebuilt by a previous owner and has seen little mileage since the rebuild, under 1000 miles.

So my plan is to just replace the clip and not pop the heads. After a couple hundred miles I'll pull the intake again and do another close inspection of that valve assembly.



Ggmac, it would be great if you have a couple spare clips you could send me. Much appreciated.

Parts sent . Pm with details . Good luck

[JMFL36]

Update. Thanks to Ggmac, got a few horseshoe clips in the mail yesterday. Borrowed a pickle fork (valve spring depressor) from a friend. Today I put the clip in. It was a snap (pun intended). Got everything back together and she fired up on first crank. Runs quieter than before the clip came out, so it must have been misaligned for awhile before popping out. Problem solved (fingers crossed). Thanks to everyone for all the tips and advice, and a special thanks to Ggmac for the spare clips!

[Tinker]

Originally Posted by Mac VP

Further replacing of manifold and head gaskets plus all the re-torquing would be a real drag to have to go through.

Every once in a while you could pull both. Gaskets are a good thing to have. I agree with you to not figure out an issue because you don't want to buy gaskets, seems weird.

[Ggmac]

I glad it all worked out . Getting back on the road with a simple fix is always a good feeling .