I own a 1965 with 327/365 engine (small journal block), which is disassembled for resto. Should I be concerned about an .060" overbore. Some people claim the thinner cylinder walls will be more prone to overheating- others say this isn't true. Who's right? Also, this motor has domed, forged 11.0:1 pistons, which are like new. Since the motor is apart, should I replace these with flattops, or leave the domed ones in. The car ran fine before the teardown with no apparent overheating, and no detonation/dieseling using hi-test pump gas. Is it true that an aluminum radiator (mine is a copper replacement) will provide better cooling.
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Re: 1965 Small Block Overbore
My understanding of our vintage small block is that a .030" overbore is okay, but anything beyond this and you should have the walls sonic tested. Depending on how much "core shift" there is in your individual block, the sonic testing will reveal if there's enough material to go beyond .030". Has the engine been rebuilt before? Has it already been bored? Does it have the original "30-30" cam? If it was a factory built engine, did it have two or one steel shim head gaskets. Need this info to address the compression ratio issue.
One other thing. The early small bearing rods are notoriously weak in the big end. You could spend a lot of money magnafluxing, grinding, replacing the bolts and shotpeening them, or for about $400 you could just buy a set of Crower Sportman rods and never have to worry.
Duke -
Re: 1965 Small Block Overbore
Joe-----
I'd recommend the smallest overbore possible. If the engine is currently at +.030", would an overbore to .040" be sufficient? +.040" pistons are a lot harder to find than +.060", but you can get them. If you had no problems with detonation with the existing piston top configuration, I'd use the same type if I could get them in a +.040" overbore size. This slight of an overbore will not raise your compression significantly.
However, if the heads are surfaced, that will raise compression and might put you into detonation. If the head gaskets that came out of your engine were the OEM steel shim type, then go with the Fel Pro stainless steel wire ring gaskets at .039" or .050" thickness and the effect of head milling will be cancelled out. I recommend these gaskets in any event.
An aluminum radiator of equivalent size will produce about a 30% increase in cooling capacity over a similarly configured brass radiator.In Appreciation of John HinckleyComment
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Re: 1965 Small Block Overbore
I once bored out a 283 cu in by 0.100 inch! Darned thing won a lot of dirt track races here and lasted a long time. 60 thousandths on a 327 is nothing to worry about. 40 is better of course and I would start worring at 80. If you want a bullet-proof block, sleeve every cylinder. It's expensive but it sure makes things stronger.Comment
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Re: 1965 Small Block Overbore
TRW made pistons for 265 up to .060 oversize and .125 oversize for 283 engines. they were just std replacement pistons not race pistons.Comment
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Re: 1965 Small Block Overbore
You and Dale mention 283s, and 265s, but the 327s have a larger bore, and weren't the 327 blocks so-called thinwall designs similar to the 221-260-289 Ford. As time progressed the industry learned how to cast thinner sections, so doesn't this limit the safe overbore of a 327 relative to the earlier small bore blocks?
DukeComment
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Re: 1965 Small Block Overbore
TRW also made up to .060 oversize pistons for 327.Comment
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Re: 1965 Small Block Overbore
Would you beleive 0.080 pistons? In a 327? GASP! Wow! An finally, a 4.125 inch piston and a new mouse casting producing a very unreliable and questionable 400 cu. in. motor, one of which has resided in my 4x4 for the past 22 years,been rebuilt 4 times, and still has a STANDARD bore! ( do however use a 5.7 inch rod and a few other tricks.)I have driven this small block an UNGODLY number of miles hauling Corvettes from California, Parts all over the country, and last but not least, daily transportation. My truck is recognized as "The Ugliest Pickup in America" with the floor totally gone due to rust. I love it and usually park it near the dumpsters when I attend NCRS functions. It used to run a dual AFB set up on an offenhauser intake, then a 1962 Fuel injection set-up but now the engine is fed with a numbers matching 62 340 hp intake and AFB with Corvette aluminum valve covers! At least the engine compartment is beautiful! You can generally overbore a 327 to 0.080 inch without problems.Comment
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Re: 1965 Small Block Overbore
Hi Dale:
I'll say this for you, you are not a timid soul.
jerComment
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Re: 1965 Small Block Overbore
Timidity.....Stupidity.....A VERY fine line separates the two!
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