Compression ratio
 

What is the max compression ratio would you'll recommend for a single power big block will be using grumpy Jenkins head 496 to 572 cubic inches not sure I would like to make 600 to 650 hp opinions please

Iron heads 9.6 is my cut off point and ran in several different single and twin apps with no issues. Plus 1.0 for aluminum. Opinions will vary. Btw. That's no part of being easy on engines either.

Our 500 ci 3.80 stroke engines are 9.5 CR with Valako/Dart I.E. 308's ported to 320ci. We run 92-93 pump gas and have never had any signs of detonation including totally inspecting the recent complete rebuilds. The timing is locked at + 40 degrees and we have a very smooth valve train w/55mm cam cores. Total package gives us 780 HP @ 6800 RPM. Water conditions being reasonable, we regualrly make extended runs at 6000+RPM.

With 9.5:1 I run 89 with iron heads

What cube motors and I gotta ask, what cam specs Ben Perfected or BlaqueBaha to see those numbers. Impressive

If I recall around 500 CI valako worked over heads. He does an incredible job with those castings. I can't remember cam specs but were posted a while back I think in one of the FF threads. I'd have to guess decent size considering. Nothing like hearing some wicked BBC's turning near 7k.

these comp #s are a great starting point, but the real deal is to know your VE at operating RPM. I would that a 9.6 at 125% VE over a 10,0 at 95% VE of equal CID. Meaning the combination of parts in the build will ultimately determine your running CR and fuel requirements. Cam valve timing event, induction system and air flow volumes and speed, exhaust scavenging and so on. my point is static CR is no more then a good starting point.

Sorry if my above sentences don't flow very good! I'm on some good Flu meds tonight.

I ran 9.7:1 for a few years on Valako ported/wedged Merlin iron heads. 92 octane and sometimes a dash of 89, 454's 600HP 6500RPM's no problems.

Flu??? Who takes Vicodin for the flue... Just playin. Anyway well said regarding your post. That kinda goes back to the importance of well thought out cam selection. While Static vs dynamic CR are entirely different however often misunderstood by many. Cam dictates actual working dynamic CR. That's where a good cam guy is priceless.

Abones - Hope you get better. Lot of that going around.

for fun and laughs, define reasonable water conditions and stop being modest and post the speed at those 6000 rpm extended runs, boats' incredible

28P Bravo 1 props.... 90+ MPH in 2' or less water.....balls are getting smaller :eekdrop:

If running locked in timing it will be a bit less than a mechanical or digital curve... The lighter the boat the less difference mind you

Good point. The OEM's have been going to higher compression for years, once they figured that out. Engine Management is the big factor. I remember having old Pontiac 400's that were 7.6:1 static, that would spark knock.

Doing a little reading on comp. ratio and came across this , kinda interesting

https://www.uempistons.com/index.php...ors&type=comp2

Wow, I never caught 3.8" stroke in your comments. Did you race those engines in B-class?