jet size

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Mar 29, 2010 | 08:58 PM

painterman52

Thread Starter

Racer

Joined: Dec 2004

Posts: 336

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From: crystal lake Il.

jet size

I`m putting a 650 holley double pumper on a 383 with a cam that is 230/236 @.50. It was on a 350 with a 227/230 cam. How many jet sizes should I go up?

Mar 29, 2010 | 09:08 PM

marz

Burning Brakes

Joined: May 2006

Posts: 774

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From: Round Rock Texas

Quote:

Originally Posted by painterman52

I`m putting a 650 holley double pumper on a 383 with a cam that is 230/236 @.50. It was on a 350 with a 227/230 cam. How many jet sizes should I go up?

First off you need to trade that 650 for a 750 for added power for that 383. But, if you want to keep it you need to get a jet kit and go up two sizes at a time until you get it to where it is not running rich or lean. That motor will want some fuel. But, the 750 will give you more air and that motor will want more air and fuel. Let us know how you come out. Check the air/fuel mixture as you adjust.

Good luck.

Mar 29, 2010 | 11:08 PM

lars

Tech Contributor

Joined: Aug 1999

Posts: 14,379

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From: At my Bar drinking and wrenching in Lafayette Colorado

A carb doesn't know what size engine it's on. Set the carb up to its stock specs and tune it from there based on the observed needs of the engine.

Contrary to popular belief, a small carb on a big engine receives a stronger metering signal and will run rich. You don't randomly jet a carb up because a big engine "needs more fuel." Start with the stock baseline and tune from there, otherwise you'll be chasing your tail.

Lars

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