Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: cris85 on January 19, 2011, 08:49:54 AM

Title: 350 pontiac
Post by: cris85 on January 19, 2011, 08:49:54 AM

hello, i'm french!
my English is not very good!
i have two firebird!
a 1968 firebird convertible 400/th400 and a 1978 firebird with a 1970 350 pontiac engine!
i need help finding the right calibration of my carb , it's for the 1970 350 pontiac engine.
i have edelbrock intake, an aac k2801
(Intake Duration at 050 inch Lift,
214 Exhaust Duration at 050 inch,Lift 224
 Duration at 050 inch Lift   214 int./224 exh.
Advertised Intake Duration      272
Advertised Exhaust Duration      282
Advertised Duration      272 int./282 exh.)
dual exhaust, cr 9.5, power brake, th350

i have a 1968 rochester quadrajet 7028264.
i want a street application!
can you help me? ( idle tube, idle down channel  restriction, ...)
regards
chris

Title: Re: 350 pontiac
Post by: Cliff Ruggles on January 20, 2011, 04:40:02 AM

Chris, do you have one of our books?

Without typing many pages here, it is well explained in our book......Cliff

Title: Re: 350 pontiac
Post by: cris85 on January 20, 2011, 07:29:10 AM

yes, off course, i have your book!
but i want your opinion.
i make it:
idle tube:0.37
idle down channel:0.55
upper idle: 0.50 ( air horn)
down idle: 0.70
idle bypass:0.80
mixture screw: 0.96
primary met.:i buy it on your sit
sec met.: i buy it
main jet: 0,73

i try it, but i'm not sure, because the car start very well, i can adjust idle very well but after, she make a bad reaction: when i accelerate gently, i have hole! i think she takes too much gas !!!
i want to install back the original primary and secondary met. and jet?
thanks

Title: Re: 350 pontiac
Post by: 65WildCat on January 20, 2011, 04:48:33 PM

[when i accelerate gently, i have hole!]

Make sure you secondary air flap spring tension is not set too loose...

Title: Re: 350 pontiac
Post by: cris85 on January 21, 2011, 01:35:23 AM

i'm sure the secondary air flap spring tension is not set too loose!
the problem is not when I accelerate hard, but when I accelerate just a little!
I try to post a video

Title: Re: 350 pontiac
Post by: Cliff Ruggles on January 21, 2011, 02:59:19 AM

It may be slightly lean.  Have you performed the "tip-in" test as described in our book?......Cliff

Title: Re: 350 pontiac
Post by: cris85 on January 21, 2011, 12:21:32 PM

I have not done  the  "tip in" test, what is  this number page?
for information, I made only one lap to settle the wealth
thanks

Title: Re: 350 pontiac
Post by: 65WildCat on January 21, 2011, 12:36:10 PM

Tech Tip - Tip In Procedure - Page 99

Title: Re: 350 pontiac
Post by: cris85 on January 21, 2011, 01:26:44 PM

ok, thank you all already, I solved one  of the problems, the hesitations came from  the  depression  of the igniter! but how to prevent  this?
it smelled strongly of gasoline!
and I have no acceleration pump, no small jet fuel! it must be just the float level!

i make the tip in test, but i do not see anything  special

thanks

Title: Re: 350 pontiac
Post by: Cliff Ruggles on January 22, 2011, 04:07:16 AM

No accellerator pump shot, common problem these days. 

Did you install one of our rebuild kits with the tuning changes?

Our kits contain upgraded components, the accl pumps are much better than the factory parts that carburetor used.

At a minimum, install one of our SR kits, and set the float to exactly 1/4"......Cliff

Title: Re: 350 pontiac
Post by: cris85 on January 22, 2011, 04:42:07 AM

thanks cliff!!
ok for the kit, i think it's only float level problem!
but the vacuum advance, how can i do ?

Title: Re: 350 pontiac
Post by: cris85 on January 24, 2011, 11:14:06 AM

no news?
it's impossible to connect the vacuum advance!!!
how can i do?
thanks

Title: Re: 350 pontiac
Post by: Cliff Ruggles on January 25, 2011, 05:37:01 AM

Set the float to exactly 1/4".

Is the accellerator pump working or not?

The vacuum advance port on those carbs should be in the front of the main casting, drivers side, just to the right of the fuel filter housing.....Cliff

Title: Re: 350 pontiac
Post by: cris85 on January 27, 2011, 02:56:13 AM

thanks cliff!
I know where is the location on the carburetor, thank you!
the concern is that the suction created is an adverse effect, and sucks when it's connected intermittently (sucks, stop, sucks, stop) and the advance does the same! and the engine is running, stop running, stop!
idle, it goes. the middle was the problem. and bottom, that's ok!
is it a problem of spring in the ignition?

Title: Re: 350 pontiac
Post by: Cliff Ruggles on January 27, 2011, 06:23:38 AM

There shouldn't be any vacuum at that port at idle speed.  The throttle plate angle is too high.  It may need more idle fuel, or more idle bypass air, or both......Cliff

Title: Re: 350 pontiac
Post by: cris85 on February 14, 2011, 11:45:01 AM

thanks cliff!
at the iddle, it's ok!
how fine the good idle bypass air hole?

Title: Re: 350 pontiac
Post by: cris85 on February 27, 2011, 02:21:28 AM

i put this in my other car ( firebird 1968 400 th 400, original ignition) and the vacuum problem doesn't come back!
the 1968 firebird run very well!
why does it run bad with the HEI ignition in the 1978 firebird???
thanks

Title: Re: 350 pontiac
Post by: Cliff Ruggles on February 27, 2011, 04:12:49 AM

Much lower compression engine and larger cam in it.  This produces less signal at idle and low speeds......Cliff