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Old 10-20-2019, 05:40 PM   #1
3739ford
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Default Location of tinfoil to check CR

Can someone tell me the location/s on the piston to put the tin foil balls to check CR. The picture below I was just fooling around and guessing.
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Old 10-20-2019, 05:48 PM   #2
V8COOPMAN
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Default Re: Location of tinfoil to check CR

I've used the little balls of aluminum foil to check for head clearance, but I'll be damned if I understand how you're going to compute COMPRESSION RATIO using the balls. Can you elaborate? DD
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Old 10-20-2019, 08:00 PM   #3
3739ford
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Default Re: Location of tinfoil to check CR

V8Coopman, I meant raise the CR by milling the heads if need be. I want .045 clearance and wanted to make sure I was measuring in the right places.
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Old 10-20-2019, 08:11 PM   #4
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Default Re: Location of tinfoil to check CR

I stick about 10 or twelve balls around the bottom half of the piston (the top half is in the transfer area and doesn't count). Let's face it; aluminum foil is cheap and easy to get.

BTW, I like the fact that you are taking this route, no matter what others say. In my opinion. the most effective thing you can do to get the maximum efficiency from a flathead is to get the "squish" right.

Oh, by the way, put a couple of balls on top of the valves. I have never had a problem there, but better to be safe than sorry.
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Old 10-20-2019, 08:34 PM   #5
3739ford
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Default Re: Location of tinfoil to check CR

Thanks Tubman, I may not get the terminology just right, but that is what I need the Fordbarn for. I will use more tinfoil balls as you are right readily available and cheap. The initial results are favorable with head gasket I'm at .045 on three cylinders and .046 on one with using one ball on bottom of piston.
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Old 10-20-2019, 08:38 PM   #6
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Default Re: Location of tinfoil to check CR

A old Bonneville racer that I knew used a small marble size ball of “Bondo”. Would let it harder and you would have a perfect casting.
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Old 10-20-2019, 08:54 PM   #7
tubman
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Default Re: Location of tinfoil to check CR

"3739" - It sounds like you are on the right track. Do you have stock heads or aftermarket ones? I find it strange that the "squish" appears to be right on. On the last two engines I build, I used second-hand Edmunds heads (I like them for reasons that are not important here), and both sets need to be milled between .025 and .050 and to get close to the "squish" figures you mentioned. I'd recheck you measurements (unless you have a set of "re-conditioned" heads). Otherwise, it looks like you lucked out.
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Old 10-20-2019, 10:02 PM   #8
3739ford
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Default Re: Location of tinfoil to check CR

I have a set of EAB heads from I believe a member on here, or HAMB (been so long ago I don't remember name). They look to be in excellent condition. I'm using copper big bore head gaskets and were surprised at the readings. I have only put on the right head, hope to get to the left side this week. I also have EAB cam, going with Rochester 2GC carb also for now. I keep slowly looking for duel carb intake I have two 97's to rebuild. If I don't have to do anything to the heads it will be the first thing on the "Nemesis" build to go my way.

I was running out of daylight today these short days are the pits when the to do list is long.
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Old 10-20-2019, 11:08 PM   #9
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Default Re: Location of tinfoil to check CR

3739-


What pistons are you using? Nice that they're coming out that close!


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Old 10-21-2019, 04:22 AM   #10
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Default Re: Location of tinfoil to check CR

I'd tend to use 5 balls, four just inside the outer edge and one in the middle. this will give an indication whether the dome shape matches the heads. for example French pistons have a pointy dome and the middle will have the least clearance.

I acknowledge that one ball might not get touched as it might be in the transfer area, but I'd do it anyway.
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Old 10-21-2019, 07:53 AM   #11
3739ford
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Default Re: Location of tinfoil to check CR

I'm using 3 5/16 pistons from Egge.
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Old 10-21-2019, 11:51 AM   #12
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Default Re: Location of tinfoil to check CR

I have a plan to do the same build you are.....please keep the thread updated...Thanks...Mark
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