The Stovebolt Site Forums The Shop Area Engine Shop 305 heads / 283 block

Will the heads from a 305 chevy fit and work okay on a 283 block?

They will bolt on. What are you trying to accomplish?

This chart and the accompanying diagram can be a big help. I'd suggest the 57-58 CC 305 heads as a good option for the 283. Bigger combustion chambers will give really lousy compression numbers with a small displacement engine like the 265 or 283.

http://www.fastnuf.com/Headguide.html

I used the 462624 heads on "claimer" round track engines with extensive modifications that allowed me to outrun engines 100 cubic inches bigger than mine.
Jerry

They will bolt on but the 305 is 4" bore block and the valves may be shrouded by the 283's smaller bore. The 305 heads also have thin decks and large chambers. Find some 283 heads and have them rebuilt with bronze valve guides and hardened exhaust valve seats. Mine ran about $450 to have done with all new parts.

Think again- - - - -the 305 has slightly under a 3 3/4" bore, with the same 3.48" stroke as a 350. The 305 and 350 crankshafts are not interchangeable, however, different balancing. The head casting number I recommended has a 58CC combustion chamber, almost identical to the high compression 283 head. Put 1.6" exhaust valves into the 305 head, do a pocket port job, and they will run rings around any 283 head. They're also 50-something years newer and a lot easier to find.
Jerry

I stand corrected on the bore size but I'll stick to the 283 head recommendation.

Stick it wherever you want it- - - -I've won a LOT of races with that combination.
Jerry

That's a poor recommendation, whether or not you stick with it. 305 heads are fine to use on that engine.

Think again- - - - The 305 and 350 crankshafts are not interchangeable, however, different balancing.


However.


I just dis-assembled a 305 and a 350. The cranks both had the same part number on them...... Just saying.

The rebuilder I worked with in Nashville bought a balance machine specifically to check those cranks- - - -the balance was definitely different between cranks from 305's and 350's, and there was an annoying vibration problem if one from the wrong engine got swapped by mistake. Producing about 200 rebuilt engines a week will teach ya a few things about "matching part numbers".
Jerry

If the 305 and the 350 have the same stroke why would they need to be balanced differently? "Although I don't know much, I am less confident about what I think that I know." (Mark Twain should have wrote that right there!)

For one thing, over 1/4" difference in bore size, resulting in a noticeably different "reciprocating weight" when computing the bobweight used to simulate the weight of the parts attached to the crankshaft. The usual rule of thumb is to clamp a weight onto the rod journal equal to 100% of the reciprocating weight and 30%-40% of the "rotating weight" (lower third of the connecting rod, bearings, etc., plus a fudge factor for oil trapped in the assembly. Then the crank is spun and weight is added by welding or removed by drilling the counterweights, similar to balancing a wheel.

One interesting bit of trivia about inline 6-cylinder crankshafts is that they can be spin-balanced without bobweights because of the 120-degree separation of the counterweights. For a tight-winding inline 6 race engine, I computed the bob weights anyway, but for a low-RPM street engine, it really wasn't necessary. A 4-cylinder, V8, or V6 crankshaft will jump out of the machine if that is attempted!
Jerry

Yes, balanced differently but still the same crank. I also ran a Bear balancing
machine. Bob weight will be different for every engine. Have a good one.

Roger Grooms ran the best engine building business in the southeast for 30-something years. They had a bulletin board featuring several of their reman engines that ran more than 200,000 miles. Little details like spin-checking crankshafts to separate the 305's from the 350's, and a couple of dozen other nitpicking details made that kind of reputation possible.

Then Roger retired in the late 1990's and sold his business to a bunch of Yankees. Quality control and engine reliability went down the tubes. The last Grooms engine I installed had to be replaced on warranty- - - -twice!
Jerry