how fast/slow will it go!
 

So Hears a quick question. A chevy 496 bb, 9:1 pistons, 544/547- 226/236-112 cam ( flat tappet) Edelbrock air gap rect port with 502 rect port heads. This is in a 1988 23 ft Scarab concept / bravo 1 with a 24/14 four blade. how fast should this thing be going? I'm hoping for close to 70?

Whats your normal WOT RPM? And do you know your gear ratio?



For a reference point......

24 pitch propeller with an outdrive gear ratio of 1.50 and a slip% of 18 you would have to spin the motor up to 5600 rpm.

This is a new combo im putting in. It ran 60 with the 496 bottom end with peanut heads and a stock intake (low rise dual plane) with a 510-224-112 sep cam ? wot was 4600. not sure on the gear. Might have to change up the prop so I can stay around 5400 max.

Hmmmm.....

Looks like newbie know a little bit....

I'd guess that you'll add 75-100hp and pick up about 6-7 mph.

Using the same numbers as before. If you can spin a 26 you would get 70 around 5200 rpm. Were you running the 24" prop with the 496 or are you just using this propeller as a baseline? If you are adding horsepower I would think you could come up a little in prop.

Go run it!!!!

I also think 6-7 mph is what you will get ,I think you would need almost 200 more hp to get over 70 but I am sure the boat will be much faster thruout the rest of the rpm range and thats a ton of fun also.Let us know where you end up.

My guess is 65mph.

Thanks for the input! I was running the 4 blade with the old set up. I tried a 25 3 blade but couldn't get past 4200 rpm. Pulled the motor today and had a pretty bad issue with blow by. Not sure what was up with the rings (only 50 hours or so) but with out a doubt loosing horse power. Fresh oil was getting "dirty" after only a few hours of running. Looks like the crank/mains and rods are ok, thank God!
Glad I pulled the motor instead of just popping on the new heads.
The new combo should put me close to 475/500hp. Here's looking for 70+.

Not sure on the whole pro slip thing yet. Is there a basic rule of thumb I could use when I get up and running?