I have a 350 that has a set of 305 heads( #376450)with 350 valves.It also has a ultradyne 276 cam 454 lift,and trw 2256 forged pistons.I have a performer intake.I plan on headers and probably a 650 carb. Any ideas about what my compression would be? Will the 305 setup be OK? What kind of hp ?I'm not going to race or rev above 5000rpm. Just cruise.I bought the engine with little time on rebuild.I plan on putting it in a 68 Camaro.

This is said to be an old school trick to bump up the compression on a 350 - with flattops and stock bore 350 - I don't expect the compression to be a cause for worry using 305 heads

Many times if the block is not decked, the piston even though aftermarket flattops will end up down in the hole somewhat

I would say maybe between 9.5 :1 perhaps 10:1 maximum if the block is stock deck & bore

A friend of mine did this on a .060 overbore 350 and his detonated quite easily - but the truck ran like a hotrod

If you are worried about compression and regular pump fuel issues - you can use colder range plugs and less advance on the distributor - or just use premium pump gas

Ithink you should be fine

OK, my 2-cents here!

305 heads are like 53 to 58 cc's so with a 350 flat-top pistoned motor, you had better check the CR. with the headgasket and quench you are at using them!!

I say this b/c the old 295 and 300hp/350 motors were 10 to 10.25 to 1 CR'ed back then with 64 cc double-hump head chambers and 4-notch flat-top pistons that were generally like .025" down in the hole with .020" shim headgaskets!

I won't build any motor much above 9.5 to 9.75 to 1 CR. if I'm gonna use cast-iron heads on it b/c of poor gasoline octane now!! UNLESS I cam it so that I can!!!

My 406 SB is 9.5 and my new 496 BB is 9.8!! But my old junk301 was like 10.25 or so!!

I guess what I am poorly saying is to cc your heads so you will know what they are when you input the info into a CR. program!!!!!!!!!!!!!!!

pdq67

Ive seen 2 different 305 cast iron heads, one being around the 76cc version and 1 set being a bit more closed chambered around the spark plug; maybe 70cc...
Consider your compression ration, and desired gas octane you wanna run...
Outside of that, the part # is the only difference unless you use the aluminum versions...
Early heads came with similar cc chamber volumnes alike the 305 heads

Off the top of my head I believe a 450 casting is about 59-60cc. They tend to cause a 4" bore small block to ping easily due to the chambers overhanging the cylinder bore. A little work with a grinder to round the sharp edges of the chambers works wonders here. Those heads also have 1.84/1,50 valves. Depending on your deck height and head gaskets, compression should be in the neighborhood of 10.0-1. I think you are going to run into some pinging problems with that relatively short cam unless your really sharp on the tune.

I'm kind of leaning to a set of Edelbrock performer rpm's, any comments on how they may do? 64 or 70cc?