Need some head clearance advice
 

I seldom post messages but have been reading all the your terrific wisdom for quite a while - guess I'm a lurker. I need some advice. I am nearly finished with my AV8 but after reading all the posts on head clearance issues I decided to check mine. Engine has not been turned over since assembly.

I have a 1951 8BA engine bored .080 over with Egge pistons, standard rods, an Isky Max 1 cam and I had the heads shaved .050. I assembled the engine some time ago and only recently became concerned about piston and valve clearance. I removed both heads and gaskets - placed the heads on the bare block without the gaskets and slowly turned the engine over by hand. Valves hit the head in several if not all cylinders but not the pistons. Heads were probably milled in the past and the .050 I took off was too much.

Can the valve chambers be safely milled .050 to provide clearance or should I start with another set of heads. I also wonder if NGK spark plugs will hit the valves now? I do have a set of 8RT but they have lower compression as I remember from all the posts.

Thanks for any help
Bill

Re: Need some head clearance advice
 

You need to know where you are with all measurements, before you decide what to do.
Go to my tutorial, and you can then come up with your plan of action. If you dont like the clay usage, you can use small aluminum foil balls positioned in place with grease, as some others suggest. I like clay.

http://www.flatheadv8.org/clayhead.htm

Find out where the problems are and then we can recommend a solution

Re: Need some head clearance advice
 

Thanks for posting that Russ. I am getting close to doing the same as Bill. Good to know info.

Re: Need some head clearance advice
 

Hi Russ. Thanks much for the reply. I had reviewed your excellent post showing how to clay the heads with a spacer of known thickness at each end of the head. I had planned to do this but thought I would see if the pistons/valves interfered using no gasket - as one of the barners stated if they don't hit with no gasket your good to go.

When I found the valves hitting I immediately concluded the chamber area over the valves should be taken down .050. That was a panic jump to a conclusion............

Your suggestion of proceeding with your method of claying is the logical next step. Knowing the exact clearance with a .050 spacer at each end will help determine the amount of alterations needed. I'll give it a try and post back what I found.

Much obliged
Bill

Re: Need some head clearance advice
 

"Can the valve chambers be safely milled .050 to provide clearance or should I start with another set of heads. I also wonder if NGK spark plugs will hit the valves now?"

Yes, there is plenty of meat both over the valves and the pistons.
As Russ says, MEASURE first. Check over the pistons also. When you are claying, do the spark plugs also.
You don't need projected nose plugs in a flathead . With standard plugs, you should be ok.

Re: Need some head clearance advice
 

Another point to watch, as I found out the hard way, is that when you take a significant amount off the head, you are changing the shape of the combustion chamber over the pistons. I solved this by following Ol Ron's advice and taking the reduced inverted dome out to the gasket line with careful use of a flap wheel. Not hugely accurate compared to doing it on a mill, but seems to work fine.

Re: Need some head clearance advice
 

you can have the heads fly cut, that's a circular cut into the head right over the valves to give them clearance,but you do need to know how much to cut, set head on block with no gasket and turn engine over till head rises as much as it will, stick a feeler gage between the head and block, see what the measurement is, that is the minimum depth the head has to be fly cut

Re: Need some head clearance advice
 

Thanks Pete, Bassman, & Ford3.

Pete, Glad to know there s plenty of material over the valves and I checked the NGK plugs - they are a short reach plug so that should not be a problem but I'll clay them also.

Bassman, I had forgot about your previous post concerning the flap wheel. I think that's a good idea as the piston area in the head has been reduced to about 2 7/8th inches in circumference due to the milling. Thanks mate, I'll trace the gasket opening and relieve the area.

Ford3, I have access to a mill and a person that knows old engine and how to make a Bridgeport sing, so the flycut will be used if the interference is significant. Thanks for the idea of slipping a feeler gauge in to get an initial idea of the problem.

I'll get some clay tomorrow and post what I find.

Much obliged
Bill

Re: Need some head clearance advice
 

I would have the area over the valves milled at a 5 degree angle. this will on;y remove a small amount of material for valve clearance..

Re: Need some head clearance advice
 

Bill This shows what part of the valve will be hitting the head ...

http://www.fordbarn.com/forum/pictur...pictureid=9192

Re: Need some head clearance advice
 

Roger on that.

Re: Need some head clearance advice
 

Good pic..

Re: Need some head clearance advice
 

Guys,
Once again, this thread illustrates the greatness of the Barn and how generous the contributors are with their knowledge. This is one of those threads to catalog for future reference.

Re: Need some head clearance advice
 

Vergil
Excellent photo. I use a tilt table to machine the head, I also use a shell mille with a small radius on the tip to reduce the tendency to cause a crack at the machined edge. Gota start posting pics again.

Re: Need some head clearance advice
 

Ron everyone would sure enjoy any picture that you post ... like this picture of the exhaust port you modified ...

http://www.fordbarn.com/forum/pictur...pictureid=3517

Re: Need some head clearance advice
 

I did that to all my engines, and believe it or not the center port flows better, so not a problem.

Re: Need some head clearance advice
 

Thanks Ron & Vergil.

I did as everyone suggested and both clayed and aluminum balled the valves and pistons - I'm a suspenders and belt kind of guy. I did this with a .062 spacer (same as a torqued copper gasket) at each end of the heads as Ross/40 shows in his great tutorial. This took me three days to do what was three hours of work and I needed a handful of Advil - I may have to admit I getting older. Very interesting findings.

The right passenger side head valve clearance was from .040 to .046 and the piston clearance .060 to .070. Now the left driver's side head clearance was only .015 to .020 over the valves and the piston clearance was from .050 to .065. Again this was with the head spaced .062 above the block.

It seems the difference between the left and right valve clearances was the result of new valve seat installed on the left side and not cut as deeply as the right ones. Probably was a machine shop error. I did some rough measuring of the top of the valve lip above the block and the left side valves tops were all significantly higher than the right side.

Now to fix the problem I plan to use Ron's flap wheel method to bring the inverted dome over the piston out to the gaskets diameter - now its at 2 7/8 inches approximately. I believe that would make piston clearance okay (>.050) using a copper gasket. Please correct me if I'm wrong.

What would be the best approach to increase the valve clearance. I suspect a .030 to .040 flycut at a 5 degree angle would solve the left side. Should the right be done the same amount? The AV8 will strictly be a fun time machine - no racing or hard driving.

Thanks ever so much for everyone's help - Fordbarn is one of the great parts of the internet.

Bill

Re: Need some head clearance advice
 

The valves tween left and right are at different angles, and therefore sit higher at the top of the block on one side. This is normal for a flathead, nothing wrong, don't fret. Just a muck about engine you say. Just clearance the side that needs it.
Martin.

Re: Need some head clearance advice
 

Scooder

Thanks much - that's exactly what is causing the difference now that I look at the engine. Would it be best to flycut .010 off the right head and .040 off the left head for valve clearance or the same on both sides? That would give me over .050 valve clearance once the gasket is torqued down. I believe the piston clearance would be good as is but can use all the advice I can get. Yup - this is just a run about engine that will probably be babied too much.....................

Bill

Re: Need some head clearance advice
 

Flapwheel was my doing. Ol Ron does it the proper way, with a die grinder. I'm just a bush mechanic!