327 into a 302?

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Comic Book Super Hero
Apr 23, 2009
Greensboro, NC
tried searching but had to sift through too many 302-2 oil pan threads, so I just cut straight here...

few weeks ago, I found the crank in my small journal 1964 327, was grooved to far, and would require it to be ground past .040 to clean up. It's a Frankenstein engine (64 block .040 bore, forged small journal crank, forged flat tops, vortec heads), and someone had suggested making it into a 302...

I'm not a performance #'s person, and knowledgeable on stock engines, but going into conversions, I'm over my head. from what I've read on a couple of old forums, I'm getting mixed opinions on what is needed to make this happen... one said just swap the crank, another says pistons need to be swapped out for 302 pistons, another says the rods will be about .050 too long, etc..., I'm a bit of a cheap bastid, so swapping slugs out at $50 is a little hard to swallow, and I'm not a person that has to have it exactly as GM would've made it... I've been looking at some 283 complete engines, and thinking of swapping what I'd need into the 327, I just need info from you engine guys in some not too technical measurements, to know what all I need to make it work.


pontiac guy

Master Mechanic
Oct 28, 2016
Royse City, TX
283 crank into your 327. You don't need a different rod. A 302 is a good old school build and can make good power. It won't out perform a larger displacement SBC built similarly though. There's no replacement for displacement. Except forced induction of course.

My friend did one in his 57 that was really stout. If you are trying to do it as cheaply as possible, and you have the 283 already then go for it. But cranks are so cheap these days I'd replace it rather than go down in displacement.

Plus, the factory 302 had a really big cam, like .5xx lift and duration in the 300s. Unless you have all the parts already your 302 won't really be exciting, or cheap
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Comic Book Super Hero
Oct 22, 2017
if you're gonna build the 302,you gotta keep in mind it lives to rev.it shines in higher rpm's. unless your running a HIGH stall/stick & deep geared rear it's no fun on the street. a friend of mine tried this in high school with a some kinda crank from PAW(dating myself now)with bearing spacers.with no converter/gears it was a high compression over carb'd turd.


Nov 15, 2014
Des Moines, Iowa
Solid lifter. Forged bottom end. Wing that b*tch to 8k.
Last edited:


Sep 14, 2014
Elderton, Pa
Rods used in 302's were the small journal standard production rods with press pins, early '68 used the large journal standard rods with press pins, late '68 & '69 used large journal free float rods. All cranks were forged. Some where there has to be some '60's tech articles that made it to the web going over pre Z28 302/301 builds.


Know it all, that doesn't
Supporting Member
May 22, 2011
Central NY
Forget torque, learn to love rpm, and lots of it. Good engine, really needs a light car and LOTS of gear. Like 4:10 or even 4:56 with no overdrive. Not a bad thing, but so different than what we've become accustomed to. Many think they will like it then realize they just can't deal with it.


Comic Book Super Hero
Thread starter
Apr 23, 2009
Greensboro, NC
I appreciate the replies so far. I'm not trying to build a correct 302, just trying to work with what I already have, and something I might be able to pick up fairly cheap... (283's are pretty cheap at auctions around here, last one I went to early last year, 2 complete ones went for about $100 each...)

originally I was thinking I could swap just the crank, and it sounds like it may be all I need to do. the pistons I have are already .040 over, and the walls are in good condition, so I just needed to know it the 283 rods needed to be swapped over as well...

btw, I personally have seen this motor (with worn out double hump heads) hit 8500 rpm, and sang like a choir.... what originally led me to wonder about the crank was oil pressure loss after getting up to operating temp.... mechanic I got it from had it in a 68 camaro, and told me he'd hit 10k several times...


Apr 25, 2009
You can't just swap in a 283 crank.
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