Head Clearance Results

B

Bill Batson

Member
A couple weeks ago I posted a problem I was having with an 8BA which I had milled the heads .050 and had significant valve interference when I place the heads on the block with out a gasket and turned the engine thru 720 degrees. Claying the head to valve and piston to valve clearances using Russ/40s method and also the aluminum ball method with the gasket in place showed the driver's side head clearances were .010 to .015. The passenger side valves were all around .040 clearance and the pistons were about .060 average.

Based on advice from Pete, Ford3, Ol'Ron, and scooder I proceeded to flycut the driver head .040 and the passenger head .010. I used Ron's suggestion to come in at a 5 degree angle which worked great and based on Virgil's picture of the cut away valve in head, this should work good with a minimum material removed. I also used Bassman/NZs flap wheel suggestion to knock down the edge of the inverted dome in the heads to match the gasket.

One problem I had was I did not have access to a "shell mill with a small radius on the tip" as Ron suggested and the flycuts had a sharp 90 degree angle which looked like a crack producer. I took my trusty dremel tool and a "House of Balsa" cut off wheel and was able to radius that corner a small amount. That cut off wheel is almost a perfect fit to the valve pocket size and I even massaged the cut depth a small amount on some of the valve after reclaying the heads. I now have .048 - .051 over all valves, spark plugs clear easily, and the pistons have .060 to .065 clearance. Based on the great information in JWL's book, I wish that was a little closer but I'm happy with the results. As Bassman told me - if its just a muck about engine (it is) it should be fine. Thanks very much to everyone that sent me a reply. It sure helped. Attached are a couple of pictures of my shade tree work.

Bill

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Thanks for the follow-up. I see you used clay and aluminum. Which do you think gave more accurate reading? How did you cut the valve clearance? did you have a mill or something the average Joe would have in his shop?

Which head gasket did you use?

thanks
Gene
 
Gene

The clay and aluminum ball methods both worked good and gave very similar readings but I would say I had better luck with the aluminum. I believe the reason was in the quality of the clay I used. It came from Michael's, the craft store, and seemed to stick to both the valves/pistons and the heads so when they were separated it pulled the clay apart in some places which had to be redone. I'm sure there is a better type of clay to use or maybe a trick of lightly oiling one surface so it doesn't stick to both.

I was able to use a Bridgeport mill which belongs to a friend of mine. He helped a lot especially with setting the head at 5 degree to reduce the size of the cut as Ron recommended. I was surprised how easy this went once the head was leveled and clamp in place. Also, the dremel tool with the cut off wheel I mentioned was surprisingly good at removing a little more material where needed while being very controllable. I believe a determined person could make some rather accurate flycuts of .010 or even .020 with the dremel. The trick would be to have a way to gage how close each one is to the others.

I used copper big bore gaskets from Speedway (not cheap) this time which is around .080 new and .062 torqued. This should match the shims I used when I checked valve/piston clearance with the clay and aluminum foil.

Thanks for the interest
Bill
 
Bill, that is one very fine job you did there. I was a bit worried about the flap wheel exercise, as it would be easy to nick a sealing surface. Looks like a great job though. I saved the photos you posted, as they show the right way to do it. Thanks for the "after" photos, as it is exciting to see your great results.
 
As above, always good to have the feed back and follow up.
Looks proper job. Nicely done.
When I clay heads I oil one surface, head side usually. Then cut the clay on the pistons/valves.
Sorry I should a mentioned that before.
Martin.
 
Nice, as you noticed the combustion chambers are not very uniform and it takes an effort to do this kind of work and it will improve the efficency of the stock engine as well.
 
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