I've been in the tech area alot lately at a local track. They have a pretty much strictly stock class there. The rule says must run an open chamber heads. One of the gray areas has been a 305 head on a 350. This is what the track says. The 305 chamber fits the cylinder on a 305, but on a 350 it overlaps the cylinder, and makes it a closed chamber. Is that so? I know a double humped head is a closed chamber head, but some of the guys being dq'd say that the 305 head isn't a closed chamber head, but rather a small chambered head. The track says that's the case on a 305, but it becomes a closed chamber on a 350. The track also says a 350 head such as a 487 won't run good at all on a 305. Is that so? Also some of the guys that run 350's are alledging that the some of the guys running blocks with a 305 number on them and a 305 head could be boring them out to 350. Now I know that the catings in those 2 blocks are different and the cylinder walls would be too thin, but some of them are claming that some of the 305 blocks can be bored out to a 350. Is this true?

I've seen things like this before. 78-86 GM passenger cars with a metric frame are supposed to be automatic, a no disc brakes on the back. That's what most people say anyway. Well, my friend has a 78 Monte Carlo that come stock with a standard tranny in it. The Floorboard is prepared for it and everything. My neighbor has a Buick Grand National, and it has stock disc brakes on it. By the way, that's a V6, and it will fly. Could possibly an early 305 have been just a smaller bored 350?

A 305 head on a 350 is just a smaller combustion chamber. These heads will raise your compression ratio at the expense of more quench area, smaller valves and smaller port "Windows". A 350 head on a 305 will lower your already low compression ratio and you won't be able to pull a fat girl off a tricycle.

NO WAY can a 305 be bored to 4" 350 bore. You may possibly come across a mis-cast block no. ( I've seen quite a few oddities ) but no big bore jobs on 305 blocks.

no chevrolet motor i know of can be bored more than .060 except the 283's. 305 had 2 high compression heads #416 and #601 both 1.84 1.50 valves. #601 had 53cc chambers but the #416 had 58cc and an intake flow of a 350 head. i took a set of #416 heads, had the intake valve seat cut to 1.94 from 1.84 and done a gasket match port job and bowl blended it. i put them on a 358 it gave it 11.3 to 1 compression. believe it or not i could retard the timing and have no detonation on pump gas. and i know for sure because i kept a close on the plugs.but the #416 is a better chamber design for a 350, i think.

#416 heads, huh, what would be the full casting number on these heads. i have put 305 heads on my 350, just looking to up the compression ratio. i was just wondering if i had a good set of 305 heads???????

An open chamber head is an open chamber head. The way it fits the bore has nothing to do with the chamber design. .




Once again, this is incorrect information. The 305 head IS an open chamber head. It is an open chamber head on a 305, and I could bolt it on a 400 SBC, and it would STILL be an open chamber head. What it does it boost the CR of the 350, the same way a closed chamber 350 head would. It simply does this by having a smaller chamber volume, while remaining open. I'd suggest having a good look at the rulebook for that track/class. If there is a rule specifically for the 305 head on a 350, you cannot argue. If there is not, and it simply states that you must run a stock, open chamber GM head, the 305 heads should pass tech