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Old 04-19-2020, 05:06 PM   #1
Scott52
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Default 8BA head measuremt help needed

After getting my car, 52 Ford Crestline, I have finally touched a part other than putting stuff on shelves and taking photos. I want to measure the head to figure out how much material has been removed from the mounting surface. I have been cautioned to do a piston to head clearance test before using that head and starting an engine. It seems that the spark plug entry surface to head deck surface might be a good place to measure. I am thinking about following John Larson's .050 milled from stock head. Any ideas on how to measure or what the stock number is?
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Old 04-19-2020, 05:14 PM   #2
Newc
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Default Re: 8BA head measuremt help needed

Hi; I always measure the diameter of the 'Dome' in the head. should be close to the stock bore of 3 3/16". Have seen used heads below 3" dome and mismatched pairs. Others will answer this shortly Newc
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Old 04-19-2020, 06:24 PM   #3
Scott52
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Default Re: 8BA head measuremt help needed

So you mean the opposite end of the chamber from the spark plug? So the original diameter would be 3 3/16 and because the chamber is tapered, the diameter would decrease as the material was removed from the head. I would probably have to go back to my calculus to figure out what diameter was equivalent to X material removed. (maybe just trigonometry) but I have long forgotten both. Can certainly give and idea of one head compared to another. I asked a fellow ford guy that was selling a couple pairs of heads if he could do the measurement that would give us four heads to compare to each other. He is in his 70s and was a former metal and auto shop teacher. Looking forward to meeting in person and seeing his restored 51 Shoebox. Maybe in a couple months when the virus issue subsides.
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Old 04-19-2020, 06:25 PM   #4
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Default Re: 8BA head measuremt help needed

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Old 04-19-2020, 06:46 PM   #5
tubman
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Default Re: 8BA head measuremt help needed

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Here's something I posted on the H.A.M.B a day or two ago. It has to do with head clearancing, and optimizing the "squish" to maximize efficiency (power and economy).

"The original heads will perform just about as well as fancy aftermarket finned heads if you get the "squish" right. The process involves using aluminum foil balls on the top of the piston and then turning the engine over by hand. You them measure the compressed thickness of the compressed balls and decide how much has to be milled (taken off) from the head to bring most of it down to a .045"-.050" clearance. You then have to cle(an up any close spots with a die grinder. I think I paid $25 a head ($50.00 a pair) for the last set I had done. An interesting aside here is that after I determined what the best "cut" on each head would be, the amounts ended up being different. .030" from one and .040" from the other on one set I did, if I remember correctly. I haven't mentioned head to valve clearance, because it has never been even close to a problem with a stock cam; you should put a foil ball on top of each valve thought, just to be absolutely sure."
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