To plane or not to plane

Dick Deegan

Dick Deegan

Well-known member
Good Morning All;

I am doing some work on my '30 Coupe which involves changing the head gasket. The engine has only about 3,000 miles on it after a rebuild.

I have checked the flatness of the head with a very crude straight edge - a long steel ruler - and it looks reasonable.

The head is a 5.5 Snyders head.

My question is, in your opinion, should I have the head planed with so few miles on it or not?

BTW, I used Gord's head puller to pull the head and it worked great.

Dick
 
Dick, IMO if the head is flat (no warpage) leave it be and re-install with a new gasket. If it ain't broke, don't fix it.
 
I guess to help understand the question, why did you pull the head? If you only have 3,000 miles on the engine did you have a problem, if so what? Was the gasket leaking things like that?
 
John;

The gasket wasn't leaking. I have a problem with the intake valve on #3. When the engine was rebuilt the valve lash on this valve was too tight and compression low. I reset the valve lash to the correct amount, but the compression has continued to deteriorate. I pulled the head to lap in the valve and hopefully to put things right.

Dick
 
I've been told the straight edge is a good a way to check as any. I doing the same thing with an exaust valve on #1 so my heads off also. I'm just going to clean the old material off the head and deck and replace it with a new gasket. If it didn't leak before, It souldn't leak when replaced.
Pete
 
Dick,

I doubt that the steel ruler you are using would be adequate. We use a straight edge made for checking heads and blocks. Buy one, borrow one, or go to a machine shop and have them check the head, if your are concerned. When you check it, you can look for light coming under the straight edge and if you see some, check it with feeler gauge.
 
Jack '29 Sport Coupe said:
A machinist surface plate would be ideal. JMHO

Jack
Click to expand...

Yes, A good doall granite machinist's plate would be fine. You can either put it face down and try rocking it corner to corner or try to shove shims or a feeler gauge under it. Bear in mind that it's only a Cyl head and a .001" shim may go under at the edge. This is within spec and shouldn't be a cause for concern. Before I did all that, I would try the recomended gasket with a reccomended sealer and the reccomended torque sequences and pattern. Model A heads seem prone to leaks if not done with great care. Just my $.02!
Terry
 
Another common item to check flatness is an ordinary flourescent light bulb. They are straight and they don't bend ! You can line many things up with them.
MIKE :)
 
my susgestion is to have the valve faced or buy a new one, even have the new one faced, you will be surprised how warped even the new ones are
 
Thanks to everyone who replied to my query.

I have looked at the head with a slightly better straight edge and it looks fairly good, so I am going to reinstall it unplaned.

Also, I am going to take the suggestion that a new valve be installed and I will lap it in. The intake valve that I removed did not have much contact with the seat for some reason. The seat looks good.

Thanks again for all the good advice.

Dick
 
When installing the new[or old] valve, try pencilling the face to see where the contact area is before using any compound on it.. I'm not sure what you meant by not having much contact area.. The contact should be roughly in the middle of the valve face and .060"- .080" wide..
 
Patrick L. said:
When installing the new[or old] valve, try pencilling the face to see where the contact area is before using any compound on it.. I'm not sure what you meant by not having much contact area.. The contact should be roughly in the middle of the valve face and .060"- .080" wide..
Click to expand...

I usually grind valve seats to have about .032-.040" seat area. Too wide and a piece of carbon can more easily lodge in there and keep the valve from sealing, especially with the low pressure on Model A springs.
 
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