Author Topic: nozzle drip still on a big cammed motor  (Read 2829 times)

Offline floivanus

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nozzle drip still on a big cammed motor
« on: July 03, 2011, 10:21:16 PM »
I've got a 350 in my 68 camaro with 10.5:1 compression, vortec heads, 292 duration cam with .510 lift.

I'm wondering how far I can go with the bypass air, I'm already pushing an eight of an inch with it (.118") but I can't get the idle speed much past 550 without starting to get nozzle drip happening at idle.

I've also got another question, I got on it near a red light the other day, let off and got on it again and experienced a massive bog (car is an auto with a 3200 stall, 3.73 gears and a turbo 400)


Offline Cliff Ruggles

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Re: nozzle drip still on a big cammed motor
« Reply #1 on: July 05, 2011, 04:11:10 AM »
What is the carburetor number, and how is it set-up?......Cliff

Offline floivanus

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Re: nozzle drip still on a big cammed motor
« Reply #2 on: July 05, 2011, 09:38:44 PM »
I'll have to get the carb number in the morning. off the top of my head the application is a 72 chevy truck with a 350 auto trans (no APT, and I haven't modified the baseplate)

I'm running 75 jets, 44 rods with the softest spring (I know, I might be better off without the rods and power piston right?) POE relocated below air flaps the idle mix holes were enlarged to .075" IFR enlarged to .040 IIRC and stock upper air bleeds (haven't touched them, i believe they are .050" or so). Fast acting choke pull-off (1.2 seconds) choke assembly deleted. I can remove a small vacuum line and no increase in idle speed, remove the pcv hose and there is a noticable increase of course. Vacuum advance run to a full manifold source 16 degrees initial 34 total.
This is just what I honestly can remember, just moved and lost my note pad for my tuning somewhere in my humble mess.

Offline Cliff Ruggles

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Re: nozzle drip still on a big cammed motor
« Reply #3 on: July 06, 2011, 03:23:02 AM »
How much vacuum does the engine make at idle speed?

Is the vacuum advance timing staying in when the trans is placed in gear?

The 1972 carb would have the huge main airbleeds.  75 jets and 44 rods are actually a pretty lean set-up for what you are doing.....Cliff

Offline floivanus

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Re: nozzle drip still on a big cammed motor
« Reply #4 on: July 06, 2011, 09:30:44 PM »
depending on which gauge I use (snap-on or mac) I'm either making 8 or 9.5 inches of vacuum at idle, and each read around 15 inches going down the road.

I've got the softest advance can I can find (B28, points style distributor, all in with 12 or 15 inches of manifold vacuum) so, actually The vac advance does kick in fully around 1500 or so rpm.

According to a wide-band display I'm usually right around 14.5:1 going down the high-way, so yes lean but not dangerously, almost ideal. some surging once in a while.

and yes, float height is set right at a .250" so I know it isn't caused by that, I adjusted it several times already, your float and accel pump are on the car, marked improvement in quality over stock units.

Offline Cliff Ruggles

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Re: nozzle drip still on a big cammed motor
« Reply #5 on: July 07, 2011, 04:41:53 AM »
Manifold vacuum to the advance may not work, unless you obtain an adjustable canister. 

In most cases we use ported vacuum instead, so the timing doesn't fall out at idle speed and make tuning difficult.

Sounds like more tuning is needed, including richer on the primary side jetting.....Cliff