Promaxx Heads
03-01-2025 | 04:30 PM
#22
Registered
Joined: Feb 2009
Posts: 8,356
Likes: 1,515
From: NW Michigan
317’s made great NA power. 750 + on my 565’s. 87 on gps in a straight bottom 12 m ftn
edit: BTW - That was Tks to Valako. His name should be on the valve covers!
Last edited by getrdunn; 03-01-2025 at 04:37 PM.
03-01-2025 | 08:11 PM
#23
Registered
Joined: Aug 2019
Posts: 1,226
Likes: 416
From: BC
317s really perform. The Weingartner test of 290vs317 head to head wss very revealing. They both shared higher HP as the rpm curve went up. He even dropped milled down the 317s to the 290 chamber size to make it an even test.
Part throttle cruise with vacuum and less flow...will likely favor the 290s, certainly in smaller (454) BBC displacements.
03-02-2025 | 02:50 PM
#24
Registered
Joined: Feb 2009
Posts: 8,356
Likes: 1,515
From: NW Michigan
What are you running for a cam?
317s really perform. The Weingartner test of 290vs317 head to head wss very revealing. They both shared higher HP as the rpm curve went up. He even dropped milled down the 317s to the 290 chamber size to make it an even test.
Part throttle cruise with vacuum and less flow...will likely favor the 290s, certainly in smaller (454) BBC displacements.
317s really perform. The Weingartner test of 290vs317 head to head wss very revealing. They both shared higher HP as the rpm curve went up. He even dropped milled down the 317s to the 290 chamber size to make it an even test.
Part throttle cruise with vacuum and less flow...will likely favor the 290s, certainly in smaller (454) BBC displacements.
Valako wedged my intake ports and opened up some crucial areas. I think mine wound up close to 350 cc but they outflow the 340 cnc by a substantial amount. You’d think they’d be lazy even on 565’s but definitely not. Peak hp @ 6k. Amazing how much torque and throttle response in my heavy boat but has a slippery bottom to help.
the oval port 290’s be my pick up to 502 ci depending on application. Light boat vs heavy boat - hull design etc etc. My old 454 builds on roids had the dart oval ports and worked awesome.
03-13-2025 | 05:07 AM
#27
Thread Starter
Registered
Joined: Oct 2002
Posts: 2,056
Likes: 92
From: Bowling Green, Kentucky
Need help picking head gaskets. The block was decked and I did not have the machinist do a smooth finish. As a matter of fact it seems rough. The heads are very smooth. I purchased some cometic mls .040 gasket and now realize that a rough surface is problematic with a MLS style gasket. The short block is assembled and I don't want to go back. From the research that I have done it seems like a copper gasket with the seals seems like the best selection for the situation, a rough surface deck and very smooth head?
040
040
