350 heads on a 305

[C10man]

I have a 100% stock 305 and I was wondering if I could put 350 heads on it to wake it up a little. also what would I need for the swap (ive heard one of the exhaust manifolds are different)

 

[chengny]

There is no such thing as a "350 specific" cylinder head. The cylinder heads on all SBC's are interchangable among the various CID capacites and can be bolted to any block.

Exhaust manifolds will bolt right up.

The only real interchange issue: Vortec type cylinder heads vs. the intake manifold.

Vortec heads are drilled so as to bolt directly on to any SBC block. But you can't easily install a non-Vortec intake manifold on the Vortec heads. The bolt pattern and bolt hole angles are different and require modifications.

So anyway, all things being equal, just pulling the heads off your 305 and replacing them with a set from a 350 will not improve your engine's power or performance.

On the other hand, if your currently installed heads are shot - and the set from the 350 are tight and have bigger valves - well then ... yes you will see some improvement.

 

[Driver4r]

Little known fact relating to vortecs(if he goes that route). 906 & 062's are only found on 350's.

 

[chevyk10]

Biggest problem with going with a 350 head vs a 305 head is the 305's generally have a much smaller chamber size. So you would lose compression in that case.


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[bucket]

Right. People often used 305 heads on a 350 to gain some compression and a little power (only worthwhile if you have no money to spend but already have a set of them). The opposite will lower the compression.

 

[HotRodPC]

I would NOT consider this as a viable option. 305's already have a very low compression. And with a tired motor already, you'd be looking at a compression ratio at best in the low 7's and probably more like the upper 6's. You're 4.5hp Briggs and Straton lawn mower engine will have more power. (OK, a lil exaggeration, but not much)

As far as using 305 heads on a 350, depending on what type of improvement you're looking for, YES, a 305 head can certainly make an improvment to a 350. The 305 heads use a small combustion chamber so this will raise raise the compression ratio and give you more power. But, the 305 head runners are piss poor small so you will run out of air at low rpms. You could consider it a truck motor used for towing where all the power is at the bottom end and the top end just sucks and is gutless. I'd run a 350 with 305 heads and a 2bbl carb no problem and expect to be able to carry a good load and have fair mpg, but not expect any performance over 3800-4000 rpm.