350 Heads on a 305 - NJFBOA - Home of New Jersey's Camaros and Firebirds

Koll · 04-17-2005, 07:07 PM

In an attempt to get rid of thoes swirl port heads, I have a set of 350 heads off of a 327 (dont ask). Ofcourse they are going to allow for more air/fuel and more exhaust getting out. Would they be too big? I might be comming into a 350 engine so this idea might get scrapped quickly.

GP99GT · 04-17-2005, 07:25 PM

from what ive heard the stock 305 heads flow like crap (i think thats what i heard anyway) so it would probably be worthwhile. as for overflowing the engine, i dunno, your intake/exhaust is probably restrictive enough to eliminate that.

ar0ck · 04-17-2005, 07:58 PM

IMO, I would pick up a set of Vortech heads with an TBI intake, plop them on the 305 for a little while, then carry them over to a TBI 350. You'd make some good numbers with them on a cam'd 350, and I dont see why you couldnt make some little extra ponies off that 305.

The Fixer · 04-17-2005, 09:10 PM

Vortecs and other SBC heads can't just be bolted onto a 305. Don't forget, the 305 has a 3.74" bore, while the 327s and 350s have a 4" bore. That's .26" that'll be shrouded, which will kill performance more than the 305 heads. You need something with a 58cc chamber; Vortecs are close at 62cc, so they can be machined to work, but I wouldn't bother if you're going to build a 350 in the long run. Leave the 305 alone until it blows up.

Koll · 04-17-2005, 09:18 PM

There you go gettin all technical.
I suppose the best way to find out is to put them on and see if if there is any change.

Fasterthanyou · 04-17-2005, 10:25 PM

Don't bother with the 305. The 4" bore is your FRIEND so get heads on a 350, don't try and save the 305, it's just a wasted effort.

Koll · 04-18-2005, 08:27 AM

Quote:

Originally Posted by Fasterthanyou

Don't bother with the 305. The 4" bore is your FRIEND so get heads on a 350, don't try and save the 305, it's just a wasted effort.

I dont have a 350 tho. just heads

Koll · 04-18-2005, 09:46 PM

Ohhh I just thought of this. Would that extra .26 difference......well are the valves gonna clear the block?

Batman · 04-19-2005, 06:04 AM

You'd have to check valve clearances but if they are small valved heads they may work. Another thing to consider is if they are old 327 heads and you have an 86 and newer engine (not sure what you got) you need a different manifold or have to modify some bolt holes on the stocker. Plus 350 heads are going to make your compression ratio drop to around 8.5:1, whatever you may gain in air flow you just lost in compression. Stick with the 305 heads or Ebay a new set of 305 heads, they are cheap as hell (can get a pair for about $100 used).

The Fixer · 04-19-2005, 08:15 AM

Quote:

Originally Posted by Koll

Ohhh I just thought of this. Would that extra .26 difference......well are the valves gonna clear the block?

That's what I was talking about, and why I said you shouldn't bother. Your chamber would be slightly mushroom shaped, which is definitely not good.

NJSPEEDER · 04-19-2005, 09:29 PM

the 350 heads will have bigger valves that will clear easily. the only thing that you are missing is a cam to match.
heads are nice, but they are a waste if you don't have a cam to work with them. the additional volume won't be taken advantage of.
the heads will help you, but alone the benefit will be minimal. get a cam and do both swaps at the same time. that way you are taking it apart once for all of the benefit instead of 2 disassembles to get to the same point.

later
tim