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383 overbore

Stumper

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Another one of those loaded questions. Is a 0.060” overbore enough to cause concern in a 68’ 383 motor? Motor runs a purple cam with oem heads and about 10:1 compression..
 
It depends on the wall thickness, cam, and a few other things. In general, thicker is better, so go with as little overbore as possible. The sonic checkers are affordable, but I'm not familiar with their accuracy. Need someone that has checked it both ways- sonic and with a gauge.
 
We could use some more information here, to give a coherent reply.
What are your concerns? Are you worried about an overheating problem, or blowing out a cylinder wall? Worried about detonation? Are you thinking of buying this motor, or maybe the car it's in? Or maybe trying to determine value? Help us out here so we can help you.
 
exactly
is the motor already .040?
usually not
I've gone .070 and used low compression 440 pistons
BUT
go as little as you can unless you are running in a pro super stock class where every inch counts
 
Another one of those loaded questions. Is a 0.060” overbore enough to cause concern in a 68’ 383 motor? Motor runs a purple cam with oem heads and about 10:1 compression..
Heres a loaded answer....Maybe
 
we do need more info,like racing or daily driver?Is this engine built or being built.
 
The engine is built and in a car I am looking at. Current owner said it was 30 over when he took it down and he went another 30 with it. Car would be an occasional cruiser, not raced. My concerns are “all of the above” in answer to the questions. Running hot, wall integrity under load, needing to run lower timing due to preignition, etc. As mentioned the cam is a mild purple grind, 10:1 compression. I believe forged pistons. Stock heads and valves. I’m just not familiar with the 68’ 383 motor. If it were a 440 from the period I would be comfortable at 60 over and this build and use. Not sure with the 383?
 
For the application mentioned I would not worry a bit. Is there a chance there is a thin spot...yes. Will it cause problems.... IMO...unlikely

10:1 could cause problems with a small cam resulting in detonation. Doubtful .060 is going to be a contributing factor. Most engines fall short of advertised compression ratings though unless someone actually measured. I would ask more specifics about the cam...at least find out what MP cam is in there.
 
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I agree with curious. I think getting an actual 10/1 with the pistons available today for a 383 isn't easy. Still, that is what I would be concerned about, not the sixty over for your use. I would try to find out what cam and what pistons were used.
I would want to make sure the car has an excellent cooling system, both for potential thin spots, and to combat detonation .
 
.......... with oem heads and about 10:1 compression..

Hmmmm. How do I say this....

Its not 10:1 compression ratio.

Get the piston part number and I'll show you how I know.
 
I already questioned the compression and asked for cam specs. He told me in conversation that the pistons were flat top and with a 60 mil overbore unless the block is decked a lot and or heads shaved down it’s not going to be near 10:1, I know that. I’ll see what detail I can get.
 
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