The Stovebolt Site Forums The Shop Area Engine Shop 283 to 302 (301.59) CID engine build

I've seen this issue discussed on several Chevy sites...and Ive seen it turn into cycber-nastiness from the vastly varied opinions.

Firstly, I know its cheaper to go buy a GM crate motor, than to assemble a 302. If I wanted a modern replacement with a warranty,
that's a direction to consider. I'm looking for a retro orange beast for the '46 truck. Perhaps a 3-duece nostalgia look ?

Secondly, I have an extra 283 laying around.

At first mention of a Chevy 302 to the common person on the street, you get the same reply...."NO, 302 IS A FORD MOTOR."
(The third reason I want a 302 CID, instead of a generic off-the-shelf 350)

I know Chevy made them for the Trans-am series, which was limited to 305 max. displacement...
I believe 68-69 Z28 had this option. The common direction to achieve 302 is de-stroking the 4.00 bore 327 with a 283 3.00 stroke crankshaft,
the other way is to bore a 283 from 3.875 to 4.000, for a total of 301.59 CID.

I've heard the arguments....that you cannot take a 283 to 1/8" over. I've I seen others say they did it for years, back when they could not afford a 327 block.
I know CERTAIN years of 283's CANNOT be taken that far out...but I've read the early blocks were thicker between the cylinders. (pre-63 maybe??)
Coming from building many old air-cooled motorcycle engines...I understand the heat issues that could develop, and the inevitable destruction that would follow.
Half the world says these early truck blocks were hardy, stolid creatures. The other half of the world says to stay away, and gain power from modern large cube blocks.
I've seen the small journal/large journal discussions...and the 4bolt main advantage discussions...

Anyway, the block I have is a #3849852 ('58-'61 Casting) Dated May '58. Which should be one of the blocks usable for punch-out.
The heads are junkie Triangle casting from '58. (1.72"/1.50" non-hardened seat, 59cc/9.25:1, no acces holes)
These, Ive read, are similar to the poochy 305 that Chevy built later...and will be tossed into the scrap pile.

Now to the crux of the biscuit:

I've located a source for 302 Z28 pistons...a tad on the expensive side...but, oh well. They are 11:1 comp, which
is too much for pump gas, yes? I'm going to go with big valve heads, but was wondering if I went to 70cc chambers over the 64cc,
if it would get me into the 10:1 range?
(I don't need to spin past 6500...I'm not looking for 500 HP with a blower.)
I want a nasty orange and aluminum Chevy motor, maybe in the 350/375HP range...
parked in front of a 700R4. Loud and bulletproof.

Anyone have first -hand experience with 302 displacement that could verify and/or add to this topic????
Suggest combinations??

Thanks in advance-
Luke

If your mind is set on a 302 I'd start with a 4"bore block. then get out a piston catalog and check out wrist pin height specs. This will affect your final compression ratio.

Why bother? Bore the 283 .060 oversize ( 292 cubic inches), use Speed-Pro hypereutectic flattop pistons, and a set of 58CC 305 heads retrofitted to use 1.6" exhaust valves, and do a little pocket porting to open up the exhaust flow a little. Run a 268 degree duration Comp Cam (part # 268H) and a set of Comp anti-pump-up lifters. With the right carburetor you'll have a 6,000+ RPM capable engine with the same throttle response as the 301/302 Z-28 Camaro engine without the outrageous cost. The short stroke crankshaft makes the little engine wind up fast, and the extra 15 cubic inches or so gained by going to the 1/8" overbore isn't worth the cooling problems you'll encounter with the overbored 283 block. If you just have to have 301 cubic inches for some silly reason, find a small-journal 327 block and put a 283 crankshaft in it.

I've built approximately 200 dyno-tuned 301/302's for circle track racing over the past 40 years, so I'm not blowing smoke like some of the self-appointed experts on the forums I've seen.
Jerry

Your the exact person Ive been looking to talk to...a voice of experience. May I send you a private message to continue this conversation, or keep it here for others to learn from?

Sure, I'm good for either approach. The really well-built round track engines would live very comfortably at 8K RPM, but that kind of race prep gets into machining and blueprinting that drives the cost into the $12K range or so, which isn't necessary for a street engine.
Jerry

Awesome!

Using my block/heads seems like the logical/cheapest approach.

I don't mind throwing some money at this thing, but wasting money for 15 CI's is a valid point. Spend it elsewhere.

A typical aluminum intake/600 CFM carb set up?

There's another approach to building a short stroke tight-winding engine. Find a 350 4-bolt main bearing block, and a 3.1" stroke crankshaft for a 75-76 Monza 262 cubic inch V8 Casting # 354431. You'll end up with 311 cubic inches with a standard-bore 350 block. Use a set of 6" long large-journal H beam connecting rods and a set of Speed Pro hypereutectic flattop pistons for a 350. It might be necessary to adjust the compression height a little by machining the top of the piston level with the top of the block- - - -it's been awhile since I've built one of those engines and I don't remember if the compression height comes out exactly right.

Use the same 58 CC 305 heads, and a good cam, with either a Quadrajet carb jetted for a 305 or a small-CFM Carter AFB. You'll have a very responsive street engine that will respond well to a low-geared rear end with some awesome acceleration.
Have fun!
Jerry

Jerry,

Having trouble locating these Speedpro Hyper flat tops...
I'd be looking for 3.935", yes?
I found the Sealed power cast flat tops (#235NP60,
but I don't think these are the pistons you suggested.

-Luke

Keith Black option?

KB pistons

Little more money perhaps?

Yes, that bore size is right. I don't have a Sealed Power/Speed-Pro catalog handy at the moment but several manufacturers make a H-E piston. They're much stronger than regular cast pistons, but they're about half the price of forged ones. The other advantage is an almost zero heat expansion rate which means they can be fitted to a much closer skirt clearance than forged pistons. Forged pistons need .004" or more clearance, and they're noisy. A hypereutuctic piston can be fitted to .0015-.002 clearance and run hard without tightening up in the bore. I have built 400+ HP engines and run them hard on circle tracks with no problems, using that type of piston.

Edit:
KB makes good pistons, but they're a little spendy. Keep shopping for Sealed Power or Speed Pro, but KB is OK if the others are hard to find.
Jerry