I want to put a ramjet setup on a 283 (using a '730 ECM and SD tuned port harness) in a '65 impala but I'm worried that with a new set of vortec heads that the compression ratio would really drop. Being that a 283 has a similar bore to a 305, I am now wondering if that would work. My goal is to get a decent set of vortecs on this engine and the most bang for the buck.

What are the differences between the 305 and 350 vortecs? Is it just chamber size or are the 305 valves smaller as well? Are the 305 vortec heads as easily available as the more common ones? Does anybody have any alternative suggestions?

Thanks

 

I would guess that 305 heads have smaller ports as well. The people at Pace Pontiac will be glad to help you out if you call them. The other alternative is to mill the sht out of a 350 head. I don't like using domed pistons, because it messes up the combustion event.

You could use some decent 350 heads and put a blower on it instead of that ramjet and you'd be just about right with the comp ratio then.

 

The 305 L-30 Version of the vortecs has lots of potential.
Apparently it has same or simular ports as the L-31 heads.
The chambers are different. More like the 305 tpi heads (081)
the valves are 1.84x 1.50"

If You decide to go with the 305 vortec heads you'll want to upgrade to 1.94x 1.50 valves and do some porting work.
this should get the flow up to at or near the L-31 head
I think either head is usable. The 350 heads can be milled down
to get a good cr on a 283. 55/58cc.

 

Stock chambers on 283's are 60cc. All the Vortec's I've measured out of the box have come to 61cc's but they're advertised as 64cc. I say go for the L31 head.