I specified flat top pistons when I ordered my o/haul kit for a customer"s 1940 "A".Appears that the pistons/sleeves are slightly overbored from stock,no problem.The pistons I received are pop-ups[domed]and the pin height appears to be the same.Will everything clear?If so,will I have to worry about detonation?
- Thread starter Ken-Mt
- Start date
Red Dave
Well-known Member
Hard to say. I've had to remove just a little from a head once because the high rise pistons touched the head. Didn't take much. I think it was because a previous rebuild job had planed the head.
The original compression ratio was pretty low on these engines. I doubt that detonation will be a problem.
The original compression ratio was pretty low on these engines. I doubt that detonation will be a problem.
The head has to be planed quite a bit before the domes will hit.Once I had the head planed .0125 ( and I think it had been planed once before) on an A to get it flat and there was still no problem with it hitting the domes. As far as detonation, you shouldn't have any problems with that even on 87 octane. Only way you would have any problems is if you could find some old Low Octane Pertroleum Distilate from WW1.
teddy52food
Well-known Member
Install one piston in the block and lay the head on without a gasket. Turn the engine over and if the head doesn't move , it is good to go.
Anonymous-0
Well-known Member
If you're going thru the efforts of assembling the pistons to see if they hit, try this die-setter's trick:
Place a layer of plastic food wrap on the piston top. Place a dob of mixed up Bondo on the wrap. Place another layer of plastic food wrap. Drop the head in place and roll the engine 2 revolutions to make sure both valves open/close. Let it sit for 20 minutes then open it up and removed the hardened Bondo. It can be cut and analized for machine clearance.
Place a layer of plastic food wrap on the piston top. Place a dob of mixed up Bondo on the wrap. Place another layer of plastic food wrap. Drop the head in place and roll the engine 2 revolutions to make sure both valves open/close. Let it sit for 20 minutes then open it up and removed the hardened Bondo. It can be cut and analized for machine clearance.
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