holley 3310 jetting and power valve advice - Chevelle Tech
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post #1 of 36 (permalink) Old Oct 6th, 19, 11:21 PM Thread Starter
 
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holley 3310 jetting and power valve advice

I am trying to dial in my holley 3310 on a 30 over 396 with builder forged pistons (not zero decked so prob 9.7 to 1 comp) stock 702 heads and the cam in picture with exhaust manifolds and 2 1/4" exhaust (not Ideal).
The issue is black sooty plugs that foul and cause performance loss pretty quickly.
Carb is set as built with 72 jets on primary, stock plate on secondary 6.5 pwr valve. lighter yellow spring in secondaries, mixture screw want around 1 3/4 turns out and that gets around 10-11 inches vacuum.
I am at 3445 ft elevation.
So do you guys think the jets or the power valve is causing plugs to foul?
I was thinking lower jets to 70 or 68 because small chamber head inefficiency, manifolds flow, and a bit too big cam for the manifolds, and also elevation...
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post #2 of 36 (permalink) Old Oct 7th, 19, 12:26 AM
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Re: holley 3310 jetting and power valve advice

The one thing I suggest checking before doing anything else is the float levels.
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post #3 of 36 (permalink) Old Oct 7th, 19, 12:32 AM
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Re: holley 3310 jetting and power valve advice

68 jets is next after the float levels check; or needle and seat replacement...
3310 carbs are pretty foolproof

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post #4 of 36 (permalink) Old Oct 7th, 19, 1:09 AM Thread Starter
 
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Re: holley 3310 jetting and power valve advice

Float level in primary was good and secondary was maybe 32nd inch too high but now lowered and good. The needles and seats seem to be holding fuel back once adjusted as there was no trickle out the sight plug when idling.
I'll get a set of 68 jets and give that a go.
Thanks
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post #5 of 36 (permalink) Old Oct 7th, 19, 8:06 AM
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Bob
 
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Lean the primary jets down till it surges at a 50mph cruise rpm.
Then go up 2 numbers see how it feels and install new plugs
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post #6 of 36 (permalink) Old Oct 7th, 19, 12:27 PM Thread Starter
 
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Re: holley 3310 jetting and power valve advice

Ok,
thanks Bob.
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post #7 of 36 (permalink) Old Oct 7th, 19, 12:31 PM
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Re: holley 3310 jetting and power valve advice

What does your ignition look like? You need to get that right first.

always and forever. what's the initial timing, how much mechanical advance at what RPM? how much vacuum advance? hooked up to manifold or ported vacuum. Onmce you know the answers to these questions we can sort the carb.

Do you have a PCV hooked up? and a breather?

Apparently you have a 3310-x carb, not an original 3310?

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Last edited by Tom Mobley; Oct 7th, 19 at 12:51 PM.
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post #8 of 36 (permalink) Old Oct 7th, 19, 12:55 PM
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Re: holley 3310 jetting and power valve advice

Tommy, sorry, but when I posted it somehow merged into your post instead of making a new post.???

oddball deal.

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post #9 of 36 (permalink) Old Oct 7th, 19, 2:03 PM
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Re: holley 3310 jetting and power valve advice

Quote:
Originally Posted by Tom Mobley View Post
Tommy, sorry, but when I posted it somehow merged into your post instead of making a new post.???

oddball deal.
I've been told that two Toms don't make a right....

Our carb advice is usually almost identical so maybe even the computer is confusing us.

No worries!

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69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #10 of 36 (permalink) Old Oct 7th, 19, 3:51 PM
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Re: holley 3310 jetting and power valve advice

Quote:
Originally Posted by Tommy the Cat View Post
What does your ignition look like? You need to get that right first.

always and forever. what's the initial timing, how much mechanical advance at what RPM? how much vacuum advance? hooked up to manifold or ported vacuum. Onmce you know the answers to these questions we can sort the carb.

Do you have a PCV hooked up? and a breather?

Apparently you have a 3310-x carb, not an original 3310?
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post #11 of 36 (permalink) Old Oct 7th, 19, 4:45 PM Thread Starter
 
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Re: holley 3310 jetting and power valve advice

Yes 3310-2 and not original

Initial is 22deg idling at 700rpm with vac unplugged.
at 2800rpm its at 40deg
at 3300rpm its at 44deg.

Manifold vacuum plugged in raises it to 37deg and 850rpm
at 3000rpm all timing is done and stops at 55deg total.

It seems happy timing wise no rattling with 4th gear and low rpm load, no light load low rpm bucking and plenty of pull and responsive all through rpm range until the plugs foul and the noticeable miss shows up.

I very rarely hear any rattling with this engine/car/rear gear combo but did have the bucking at low rpm syndrome from timing coming in way too quick, that was really annoying to drive.
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post #12 of 36 (permalink) Old Oct 7th, 19, 5:43 PM
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Re: holley 3310 jetting and power valve advice

Have you checked that the power valve is good? What is vacuum at a steady cruise?

That's a lot of timing. Have you ever verified your balancer indicates correctly?

70 Camino...Roller

69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #13 of 36 (permalink) Old Oct 7th, 19, 6:04 PM
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What plugs are you running? Gap? What is the ignition system, and what coil?
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post #14 of 36 (permalink) Old Oct 7th, 19, 9:25 PM Thread Starter
 
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Re: holley 3310 jetting and power valve advice

Tom,
Balancer was good last time I checked.
Power valve is good.
Cruise vacuum is probably in the 16 to 18 range but never really paid attention to it to be honest.

Kerry,
Plugs are AC R43XLS gapped 40thou
Hei with MSD module (same place in distributor as regular gm module) with the builtin rev limiter from 10 years ago or so when they came out.
Hei stock coil.
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post #15 of 36 (permalink) Old Oct 8th, 19, 12:33 AM
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Tom
 
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Re: holley 3310 jetting and power valve advice

My math says you should probably be around a 70 jet but two jet sizes isn't enough to foul plugs. You're pulling fuel from somewhere. Have you made sure there's a weight ball/needle under the squirter? Is your transfer slot square on the primary at idle? Are your secondaries open at all at idle?

I would recommend going to a 10.5 or 8.5 power valve if your carb were working right but right now that would exacerbate your problem so leave the 6.5 for now.

70 Camino...Roller

69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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