Author Topic: Before buying the book..  (Read 2048 times)

Offline 99 advantage

  • Newbie
  • *
  • Posts: 1
Before buying the book..
« on: December 01, 2014, 09:22:00 PM »
I'd like to get an idea of how many more rpm's is possible in my jet boat.
Here are the specs.
454 Gen VI
bored .030
4.25 Stroke
Forged crank
Forged flat top pistons
Comp Cam xm284hr hydraulic roller
.547 lift intake and exhaust
Duration 284 intake 290 exhaust 230 intake and 236 exhaust at .5 lift
Peanut port heads :(
750 cfm Quadrajet #17059280
Weiand Plus intake

The carb was rebuilt 3 years ago before the engine was built. The carb was rebuilt to stock for a 454.
Before rebuilding the engine, It was getting a maximum of 4800 rpm's. Since rebuilding It's getting 5000.
I'd like to know about how many more rpm's is possible using some of the modifications in Cliff's book.
Thanks.

Offline Cliff Ruggles

  • Administrator
  • Qjet Hero
  • *****
  • Posts: 5435
Re: Before buying the book..
« Reply #1 on: December 18, 2014, 05:27:44 AM »
Difficult question.  Those carbs are not emission calibrated, but still respond well to some additional fuel at full throttle since this new fuel contains less energy.  I would try a slightly smaller metering rod for the secondaries, and see how it responds.  If things improve, go smaller again, till you see no improvement or it goes the other way.

We can custom machine any size secondary metering rods that you would want or need to do this.......Cliff

Offline 429bbf

  • Qjet Hero
  • *****
  • Posts: 539
Re: Before buying the book..
« Reply #2 on: December 19, 2014, 04:57:42 AM »
in the late 70;s my best friend and i tried the same thing, we had 2 engines and 3 carbs  11.5 427 chevy and a 11.0  460 ford they were installed in a pickle fork boat with an arnison drive.carb 1 predator 2 quadrajet 3 holly. heres the results.carb 1 was the worst it had a decent mid. range but thats about it . carb 2 quad had excellent low,  mid . power but we could not get the rpms over 5000 on ether engine (now mind you we weren't the most knowledgeable on carbs but we were very good at making things run)it seemed in our testing that the only way to get over 5000was to feed it a lot more fuel and that was done by installing a big 850 double pumper. it took its toll on the fun because the lake was only about a mile across and it would empty a 6 gallon plastic tank across and back,so the end result was install the quad and save some money for beer. fwiw