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Old 06-14-2010, 11:21 AM
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holley jetting

i have a 350 basically stock block with vortec heads and mild cam bored 060 over. i have a holley 600 on it to get rid of some quadrajunk issues i was having. has been running really rich so checked the jets and has #66 jets in it. swapped those out for some #62 and its still running rich although maybe not as bad. was going to go down another step to #60 but that seems like getting kind of small. any opinions ?

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Old 06-14-2010, 11:26 AM
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Quote:
Originally Posted by vetteran
i have a 350 basically stock block with vortec heads and mild cam bored 060 over. i have a holley 600 on it to get rid of some quadrajunk issues i was having. has been running really rich so checked the jets and has #66 jets in it. swapped those out for some #62 and its still running rich although maybe not as bad. was going to go down another step to #60 but that seems like getting kind of small. any opinions ?
Check the engine vacuum to see what power valve should be used compared to what's in it. 62 jets are small for most 350 cid SBC applications.

Other than primary throttle bushing wear and the occasional (easily repairable) main well leakage, there are no bad Q-jets- just bad Q-jet "tuners".
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Old 06-14-2010, 11:56 AM
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What is your vacuum reading at idle? First starting point I'd look at is the power valve. Both if it's good (they can break if you've had backfire thru the carb). Second issue is "IF" you have real low vacuum readings at idle (normally caused by big duration cams) ...would let the power system in the carb to be activated and run real rich. ...Good Luck!
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Old 06-14-2010, 12:02 PM
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i'll check the idle vacuum but no backfire and the cam is a xe262 so its not much of a cam. thanks for the input.
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Old 06-14-2010, 12:06 PM
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define mild cam...

rich, when? at idle? low rpm cruise? part throttle cruise ?
Wide open full throttle?

What is telling you its "rich"?
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Old 06-14-2010, 12:29 PM
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the black plugs and the smell in the garage.
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Old 06-14-2010, 12:53 PM
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You can try checking the fuel level in the float bowls for being adjusted too high, too much fuel pressure will run rich, the power valve I've already mentioned, ignition problems, etc.

I'd start w/the vacuum and check on the PV.
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Old 06-15-2010, 03:11 AM
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Quote:
Originally Posted by vetteran
the black plugs and the smell in the garage.
The main jets have nothing to do with this. You are playing with the wrong part of the carb. Put the #66 main jets back in. The fuel is not controled by the main jet size when you are in the garage. You have a idle circuit issue and or a ignition system or spark advance issue.

70% of all carburator problems are actually ignition problems.

Inspect the secondary side of the ignition system even/especially the new parts. Check the supply voltage to the distributor. Hook up the engine ground wire to the body.
Check the carbs power valve. Blow out the air bleeds in the carb with compressed air. Reinstall the PCV. Its part of the idle circuit.

clean out or replace the needle/seats and get a fuel filter. 6psi max fuel pressure at idle.

What cam? Big cams require special specific tuning adjustments.

Black plugs do not indicate a rich AFR, They indicate fouled out spark plugs caused by ignition missfire and or carb flooding. The smell of the exhaust does not indicate a rich afr. It indicates raw unburned fuel exiting the exhaust from missfire and or late ignition timing.
The size of the main jet has nothing to do with this. #66 are within the normal correct range for this carb. The correct tuning range is 64 to 67 primary main jet. none of which will make the plugs black. Ever.

Unless you can run along behind the car going down the road at 40+mph you cannot smell a rich jetted carb.

If you want to find tune the main jetting get a 02 sensor installed on the exhaust and read the voltage it produces as you drive down the road.
Not idleing. You can use a DVMM or AFR gauge to read the 02 sensor.
google it.

You have a (spark or fuel control) fault problem not a calibration (jetting) issue. google search vacuum gauge diagnostics and then get a vacuum gauge and learn to use it.

Last edited by F-BIRD'88; 06-15-2010 at 03:42 AM.
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Old 06-15-2010, 04:24 AM
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Is this an 0-1850? It's not one of the "S"-carbs. is it? (0-1850S)
(just checking because I had issues with the S-carbs when they first came out)
If all your plugs are fouling, I'd say it's either your float level or your PV.
If it's only a few plugs, I'd say probably ignition.
But if it is your PV, don't forget to put your 66's back in.

P.S. Yeah that xe262 is mild. Smooth idling.

Last edited by a1supersport; 06-15-2010 at 04:33 AM.
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Old 06-15-2010, 10:43 PM
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holley tuning issue

I've had a ton of trouble recently with sticky needle and seat assemblies. For whatever reason, the current formulation of gas does not agree with the Holley "Viton Tipped" arrangement that worked for the thirty+ years previous. Both of my carbs - a Holley on the Olds and a Demon on the 312 - have now been switched to the steel .130's and the trouble was solved.

The bowl fuel level has the effect of raising and lowering the air/fuel curve of the carb - and the sticky needle & seat makes this vary at random. And more likely rich than lean......
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Old 07-15-2010, 11:38 AM
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Quote:
Originally Posted by F-BIRD'88

70% of all carburator problems are actually ignition problems.
Isn't that the truth!! That, and 70% of ignition problem are actually carburetor problems ha!! Spend all day working on the timing and it's the carb, spend all day working on the carb and it's the timing.

Also one thing to look at is to peek in the carb while it's running. If there is gas dripping from the boosters on the primarys or secondaries then you likely have a problem with either the neadle/seat or fuel pressure.
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