What Size Jets for Holley Carb?

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Sep 20, 2004 | 04:31 PM

Motor City Vette

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From: Las Vegas NV

What Size Jets for Holley Carb?

I'm looking to get some more power from my car and I'm thinking about changing the stock jets on my Holley carb, but I'm not sure what size to go with? What size jet would you suggest? I don't use my car for racing (it's a driver), but I do want more power. Here's some details about my car that might be helpful:

* 1970 L46 (350/350 and 6k redline)
* Holley 0-1850s 600 cfm (with the stock jets)
* Muncie 4-speed
* Hooker headers/sidepipes (not sure if the exhaust system matters or not when selecting Jets)

It seems like switching out the jets would be a relatively inexpensive and quick way of getting more power.

Thanks.

Sep 20, 2004 | 04:50 PM

lars

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From: At my Bar drinking and wrenching in Lafayette Colorado

You need to determine if you're currently running too rich or too lean. If you don't have a mixture problem, changing jets isn't going to do anything for you - the purpose of changing jets is to correct an identified problem.

Sep 20, 2004 | 04:50 PM

Brettmc

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From: St Louis MO

Get a new carb....that 600 vacuum secondary is way too small...you should run at least a 650 double pumper up to maybe a 750 dp...then you'll see a tad more power.

Brett

Sep 20, 2004 | 06:17 PM

Motor City Vette

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From: Las Vegas NV

Quote:

Originally Posted by lars

Thanks...I seem to be running pretty good (not too lean or rich). Is a 600 cfm carb "good enough" for my engine? According to my math (which isn't very good!), I don't think I would be getting anything by going to a 650cfm or larger carb. Does this sound about right?

Engine Size (CID) * Max. RPM / 3456 = cfm
350 * 6,000 / 3456 = 608 cfm

Last edited by Motor City Vette; Sep 20, 2004 at 06:24 PM.

Sep 20, 2004 | 06:32 PM

The Dude

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From: Calif.

Quote:

Originally Posted by Motor City Vette

It's spot-on using that formula. However there's no such thing as "too much" carburetor, provided it's tuned correctly.

Holleys come out of the box "calibrated" for best operation at sea level. (I don't know how they can say that since every engine combo is different.) But they are pretty often darn close right out of the box--a little fiddling with the mixture and idle speed and you're good.

What makes you think you need a jet change? What are the symptoms? Is it stumbling at part-throttle cruise? What?

Last edited by The Dude; Sep 20, 2004 at 06:34 PM.

Sep 20, 2004 | 11:48 PM

Vetterodder

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From: Fountain Hills AZ

Quote:

Originally Posted by lars

If you want better performance, consider a double pumper and in something a little larger.

Sep 21, 2004 | 12:51 PM

MotorHead

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From: Who says "Nothing is impossible" ? I've been doing nothing for years.

Engine Size (CID) * Max. RPM / 3456 = cfm
350 * 6,000 / 3456 = 608 cfm

That's the old math the new CorvetteForum C3 math is:

Engine Size (CID) * Max. RPM / 3456 = cfm
(350 * 6,000 / 3456) x 1.23355263158 = 750 cfm, douple pumper with mechanical secondaries.