VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1941 216 Engine Miss

If anyone has a 216 engine miss they might want to try tightening their manifold bolts. I was told that by a 50+ year mechanic friend. I found 2 of my bolts were hand tight so I tightened them and my miss pretty well disappeared. Good luck.
John

You need to be extra nice to your mechanic. His knowledge of solutions to a variety of our mechanical problems and potential problems could save you a lot of money and sleepless nights.

Good luck, Mike

John,

I wonder if that miss wasn't merely an exhaust leak. Was the engine actually shaking or were you hearing a pitter-patter. It just seems strange to me that tightening a couple of manifold bolts could have cured a "miss. " Most times it something having to so with "fire" to a plug.

How in the world they get that loose in the first place?

In any case, Mike's advice is "right on."

Charlie

Hi Charlie, Well it didn't cure the miss, it's a little less but still there. I should have listened a little longer before I posted the info. The miss I heard is at the exhaust pipe not at the engine, and it was idling a little rough. The bolts maybe loosened over time with heating and cooling or got missed getting retorqued from the engine rebuild. Soon I will be doing a compression test then making sure the valves are adjusted correctly.
John

I had a miss in my 37 a few years ago, I thought I had a bad valve, but it turned out to be a leaky intake manifold gasket. It didn't work to just tighten the bolts as it needed a new gasket. I fixed that and now she runs smooth.

I did a compression test and all cyl were above 105 except for #6, it was 91. I then checked the valves and adjusted #6 intake, it was tight. It was a good exercise in getting back into the tools but the engine miss is still there.

Did you recheck the compression after properly adjusting the valve?
A good chance the valve is burnt.

Chev Nut, I will certainly recheck the compression & report back.
Can you tell me if I am correct in understanding why the valve might be burnt: since the valve was tight would this cause the valve to not completely close on the compression stroke then during the ignition stroke cause the valve and also the seat to get burnt? Thanks

That is a correct description.

A couple of questions before I do the compression check:
Would this be the miss?
Would this be the engine vibration I feel when I approach 50mph?
Would the fix be a valve job?
Thanks. John

If the compression is more than 10 pounds under the the other cylinders it could cause a rough idle and a slight miss when accelerating at low speeds, Usually gets "covered up" at higher engine speeds but would effect performance. See manual for proper compression testing.

Will not cause a vibration at 50 MPH.

A vibration at 50 and above is usually caused by a worn U oint, loose drive shaft bushings or a metal to metal contact from the drive train to the chassis.....in that order.
Also could be caused by a rotating part out of balance but that vibration more or less peaks at one speed and disappears as the speed increaes or comes back at a still higher speed.

Thanks for your advice ChevGene. I thought it would be 2 separate problems as well. I'll start with the compression test and then checking the U joint is next. John

I did the compression test 2 times today to be sure on #6 cyl and got 96 both times. It was 91 before I adjusted the intake valve. The rest of the cyl test 105 and up to 115.
Would this mean the valve is seating better but will need a valve job and reseating?
Thank you. John

First if it was an intake that was tight normally it would not burn. The exhaust would be more apt to burn.
If an intake is not sealing wel it will pup-pup-pup thru the carburetor.

It looks like it is time to consider a valve job. Don't let them talk you into hardened seats, they are not necessary. Regular grade gas did not contain lead when the car was new.
Tetraethyl lead was in ethyl (preimum)gas only years ago. That is why is containd red dye and the pump was a poison warning sign.

ChevGene, Since there was no pup-pup-pup through the carburetor can I assume then that this intake valve is sealing not too badly?
I'll put a valve job on my list and check for a worn u joint for that vibration.
Thanks again for your advise.
John

Hi Uncle Ed, I am going to replace the manifold gasket on spec. Does anyone know a method to torque these manifold nuts. 5 of the 8 nuts are not reachable with a socket. Also is there a tightening sequence?
A few weeks I checked the manifold nuts and found the last 2 only hand tight. Since I bought the car last summer I always noticed an exhaust smell while driving. I thought it was the old exhaust system, I had that replaced this summer. Thank you.
John

The center bolts are tightened to 15-20 foot pounds and the end bolts to 25-30. Work from the center out.
I doubt if the end bolts being loose had any effect on a leak as the later model engines did not even have nuts on the end, just guide studs.

I would have a careful look at the gasket that comes off to see if there are any black leaking areas. Also on mine the bolts were bottoming out on the threads. The manifold was a replacement and I guess the bolts wanted to go a little further in. The solution was to chase the threads with a dye. Normally I would loosen the nuts and bolts holding the exhaust portion to the intake part. Then I tighten them after the manifold is installed. I would also replace that gasket.

Hello old216, Just picked up the new gasket. Using a torque wrench is there a special socket or tool available to fit these manifold bolts & nuts? It's impossible to get a regular socket on 5 out of 8 of them. Thanks, hopefully this will help with my miss.

John

Hello Chevgene, Thanks for the tightening sequence, hopefully this will help with the engine miss.

John

I have never used a torque wrench on those bolts. I probably use a box end wrench.

Doubt if you could even get the average torque wrench on the center ones.

I only know two ways to use a torque wrench on those bolts. A universal joint on the socket or a crowfoot. Neither is 100% accurate but might be comforting to know you are close.

old216, The old gasket was blackened on all exhaust ports but the manifold looks straight, no warping. I cleaned the intake rings and installed the new gasket and manifolds. I think I can get close with the proper torque by using a open end wrench - copying the 3 I can get to with the torque wrench. Looking forward to firing her up.
Thanks everyone for their advice.
John

FWIW I never use a torque wrench on my manifolds for this very reason. So far I've been successful in not having the fasteners too loose. Snap-On used to make, I assume they still do, an adapter that fits on the end of their torque wrench that allows the user to torque difficult fasteners like those on the manifold. The problem with that is you then need to run a calculation to determine where to set the torque wrench to get the desired torque at the fastener.