Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: boondocker on May 18, 2012, 11:43:37 AM

Title: Black Smoke on deceleration
Post by: boondocker on May 18, 2012, 11:43:37 AM

Hi, I rebuilt my quadrajet (Cliff's HP kit), it's a '77 olds qjet and the car runs fantastic. I noticed when I rev the engine there's no black smoke, but when I let of the gas I get a puff of black smoke. I also noticed my plugs are black...seems real rich and I've tried adjusting my front mixture screws to no avail. Any ideas would be appreciated.

Title: Re: Black Smoke on deceleration
Post by: Cliff Ruggles on May 21, 2012, 03:30:42 AM

What are the engine specs, and how did you set the carb up for it?.....Cliff

Title: Re: Black Smoke on deceleration
Post by: boondocker on May 21, 2012, 05:07:59 AM

engine_info = '72 Oldsmobile 350R, Rebored .30 over (355), forged flat top
pistons
heads = 7A rebuilt, comp magnum pushrods, HE rockers
exhaust = Dual FlowMasters with Headman headers
intake = Stock
rear_ratio = 2.73 non-posi
carb_info = Qjet '77 olds carb_number = 17057252 APU
cam_specs = Comp XE-262 (olds)
.475/.480 lift, 218/224 @ 0.50, @110
purchased CR - HP carb kit with the following:
Electric choke (set at mid way)
Jets .073
Primary Metering Rods .043
Idle tubes .037
Natural Power Piston spring
CR choke pull off and link (didn't adjust)

Title: Re: Black Smoke on deceleration
Post by: Cliff Ruggles on May 23, 2012, 03:35:17 AM

Any other modifications to the idle system.  Lacking control of the idle fuel indicates either not enough idle fuel, or too much. 

Is there any "nozzle drip" from the boosters at idle speed?.....Cliff

Title: Re: Black Smoke on deceleration
Post by: boondocker on May 23, 2012, 11:02:50 AM

Thanks Cliff,
I didn't explain very well initially, the black smoke appears when i rev the engine and then let off, doesn't appear when idling...in fact the idling and overall performance of this engine is awesome...can't keep the tires from spinning.

Title: Re: Black Smoke on deceleration
Post by: boondocker on May 23, 2012, 11:37:02 AM

Just checked...No leaks, also, no modifications although I'm using an aftermarket breather assembly...I get smoke with or without the breather in place

Title: Re: Black Smoke on deceleration
Post by: boondocker on May 23, 2012, 11:49:44 AM

...could this be a timing issue?

Title: Re: Black Smoke on deceleration
Post by: Cliff Ruggles on May 25, 2012, 04:32:37 AM

Unlikely as the engine performs well.  Might not need all the accl pump shot you are getting.  Try moving the link to the outer hole in the arm......Cliff

Title: Re: Black Smoke on deceleration
Post by: boondocker on May 29, 2012, 11:19:42 AM

We'll I got a chance to move the pump lever to the end...and low and behold it fixed the problem!
No wonder they say your the "best in the business", thanks Cliff for the great setup!
Dave ;D

Title: Re: Black Smoke on deceleration
Post by: Cliff Ruggles on June 05, 2012, 03:52:12 AM

Good news!...and thanks....Cliff