Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Dialing in your rebuilt Quadrajet carburetor => Topic started by: PonchoVia on March 04, 2019, 08:15:43 AM

Title: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on March 04, 2019, 08:15:43 AM
17058276 Previously installed Cliff's kit, 73 jets, 44 rods, float level 17/64.

Engine Pontiac 400 0.040+, 96 heads, performer intake, comp 262 cam, HEI with centrifugal coming in at 1000, all in at 2900. I've been using manifold vacuum for advance. 2004r, 9 inch 3.25.

Had an issue with idling like crap but driving perfectly. Called Cliff to order a choke pull off, turns out I   didn't need it. Recently installed AFR/wideband found my idle problem was WAY too lean, mixture screws did next to nothing to correct.

Cliff is NOT A FAN of these cams and said has always had idle issues with them.

He suggested just to open idle tubes to .038, down tube restriction to .050, idle air to 1.0, and using the recipes in the book opened idle bypass to .070 and mixture screw holes to .10, cut 2 rounds from spring they seat.

CAR IDLED GREAT!! I   adjusted rpm, mixture screws with vacuum gauge and achieved 17" of vacuum from the cam that says it is good for 17.5".

THEN found the vacuum line to the vacuum ball for interior controls wasn't even hooked up!!

Corrected that leak, corrected for idle mixture, engine still runs better than before, but can barely achieve 16" of vacuum.

I   assume this means that I   need more idle air? Am I   just not supplying enough of what this engine/cam combination needs?

I'm thankful to have the idle I   have now, but the OCD in me is flaring up big time. I   am using these issues to try to understand the black art of carb control.

AND one more question...

I'm unclear how/where to measure the secondary flaps to determine optimum opening. I   see the spec is 1.271 (memory?) is fully open. from the back of the opening to the ...... upper face of the open secondary? I    can't make out where from the pic in the book.

Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on March 04, 2019, 07:18:36 PM
A low compression 400 CID engine and 262 seat timing cam will not need a lot of cfm, so really no need to modify the stop for the air flaps on that carburetor.

Idle bypass air is used to lower the throttle angle to keep the main system off line at idle speed or no nozzle drip. 

Not sure why that engine combo would want a lot of timing at idle speed, might want to try ported vacuum to the advance instead of running a lot of timing at idle.   With some set-ups doing so will actually help idle quality and provide stable idle in and out of gear as well.

I really wouldn't worry about engine vacuum at idle speed as much as idle quality, control with the mixture screws, and RPM drop/idle stability when the trans is placed in gear.

I've tuned at least a half dozen low compression 400's with that cam in them and never once found that I had to use a lot of timing at idle speed to make them happy.  Matter of fact tuned one not that long ago that had 7K3 heads (functionally identical to your #96's) and it was fine with 14 degrees initial timing and the tach barely moved when the trans was placed in gear.

It had a near identical carb on it as well, and I used .038" idle tubes, .055" DCR's and .110 idle bypass air, all airbleeds main and idle were left at the stock sizes.........Cliff
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on March 04, 2019, 07:33:00 PM
Thanks for your time. As usual, you were right. Car idles so much better.
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on March 10, 2019, 04:05:44 PM
All the settings are good except....

Car starts up perfectly on the choke, idles at 1500, but once it warms up, it occasionally sticks on the last step of the fast idle cam. I   know its that because I   can adjust idle speed with the choke screw.

I   must have made a mistake installing the choke but damned if I   know what it is. Im not real clear on how all the choke components work together.

I   loosened the choke and disengaged it, I   can start the car relatively easily but no fast idle, and I   don't get it hanging on the cam, runs great.

I   had installed your electric choke 3 years ago, had no issues until I   went back into the carb recently.
I've been hooking the choke loop on the tang inside the housing and setting the 'rivet' on the second mark passed the center.
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on March 11, 2019, 04:51:38 AM
Make sure the choke element is heating up. 

Engine heat will eventually allow them to work some and open the choke a bit.

Dead cold turn the choke CCW until the flat just barely closes.  That will be the quickest release time.

Also lubricate all the parts involved with the choke and fast idle cam.  Also verify the fast idle cam isn't rubbing on anything and lifts freely clear across the range of motion. 

I've seen a few that needed some minor adjustments made to the part that is pressed on the center shaft to provide adequate clearance for the cam to move up and down......Cliff
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on March 11, 2019, 07:58:32 AM
Thanks, will do.
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on March 12, 2019, 06:11:39 PM
Carb idle tip in likes about 12.5 on my afr gauge.

But APT tip in took 5 rounds to begin being happy. Afr shows upper 13's to low 14's. i know You don't care for afr tuning but I'm a bit concerned about maybe being too lean.

Is 5 rounds out on apt too many?
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: tayto on March 12, 2019, 06:45:46 PM
Keep in mind if your cam has a lot of overlap your O2 could be lying to you. I do like the idea of knowing what my AFR is when the carb is setup right for future troubleshooting.
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on March 13, 2019, 02:57:56 AM
Tune for results not for a particular A/F ratio.  Don't forget about the distributor.  Vacuum advance is a BIG player for tuning in the "normal" driving range and allows much leaner A/F ratios to be burned, increasing engine efficiency, improving power, engine performance and increasing fuel economy.......Cliff
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on March 13, 2019, 08:56:06 AM
I   had forgotten to mention that I   did take your advice and switched from manifold to ported vacuum for the distributor advance.

So I   think I'm ok.

So just to be clear, 5 rounds out on the APT is not a concern?
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on March 14, 2019, 04:56:07 AM
I usually end up around 4.5 to 5 turns up.  This is putting the metering rods tapered section between steps high in the jets.  Fine as long as the hanger arms are EXACTLY even, and you are reducing travel distance which speeds up enrichment ever so slightly........Cliff
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on March 14, 2019, 05:21:56 PM
Would that not indicate a need for 1 size larger jet? And put the rods back down a bit?
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on March 15, 2019, 02:02:14 AM
No, the APT tunes light part throttle.  The jet size should be determined first as it controls heavy and full throttle fuel delivery......Cliff
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on March 19, 2019, 11:26:27 AM
OK, lets move back to the choke.

I   think its close to being correct.

question is, there is nothing else other than gravity to move the fast idle cam down as fast as, and as far as the choke mechanism will allow?

Im pretty sure I   had the screw that holds the choke assy to the body of the carb too tight causing a bind in the mechanism.
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on March 21, 2019, 04:44:51 AM
That screw needs to be tight.  If you find that it is binding thing up you may have issues with the choke shaft parts.  I've had to "tweak" a few where the part is staked to the center shaft to create some distance for things to work like they are supposed to.......Cliff
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on June 27, 2019, 12:47:40 PM
Making changes to this engine which creates carb question.

Called Jeff at Kauffman and changing #96's to Kauffman 74cc D ports. 310 CFM.
Kauffman is having a custom grind done for a new roller cam. Should be 10.2ish compression.

Still want the quadra-jet. (its fun to send modern Mustangs, Camaros and Corvettes home from the autocross).

Still keeping the 200-r4, and the 3.25 for now.

Carb setup. 17058276 Previously installed Cliff's kit, 73 jets, 44 rods, float level 17/64.

Will I   need to change this carb recipe? My mind says yes but more air will pull more fuel so I'm not gonna guess.

My AFR shows good to barely lean with the old config at light throttle. WOT is pretty fat.11's.
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on June 29, 2019, 04:17:52 AM
What are the cam specs?

Unlikely you'll need to do a lot of tuning far as jet/rods, but the idle system must be set up for the CID/cam/compression so it's happy.

The new set-up will be more efficient as well, so most likely you will not be adding fuel.   My 455 with over 11 to 1 compression and KRE 295cfm heads uses basically the same carb and its fine with 73 jets, 44 primary rods and 44 secondary rods.  Just a tad "fat" at WOT but better than being too lean.....IMHO.....Cliff
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on August 23, 2019, 02:02:15 PM
OK, finally have all the info for the setup:

462 cid, Kauffman Aluminum D port heads, 85cc, 310cfm 4.25 stroke forged crank, H-beam rods, Ross -6cc pistons,
Cam is comp roller from Jeff. 232-238@.050, 113lsa, with 1.65's will be .590's lift.
Ram Air exhaust manifolds, Edelbrock RPM intake. calculator shows 10.45

Gonna be pulling a lot more air thru this carb now compared to an 8.5 400 with 96's.

again, autocross car, auto trans, 2600-2800 stall, 3.25 ford 9inch

recipe still recommended? or any changes?
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on August 25, 2019, 04:35:08 AM
It will be fine.  Pretty similar engine combo as I'm running with the same basic carb.

I use 73 jets, our custom 44 rods, DA secondaries and same idle set-up as I recommended earlier in this thread.

You may need to go to a larger N/S assembly, and fuel delivery system for that power level.  Not sure what you are using now, but to keep up with that kind of power takes a "garden hose" for fuel delivery!......Cliff
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on August 25, 2019, 05:31:18 AM
I purchased A low profile Carter fuel pump to run the quicker Camaro pitman arm
Will that pump keep up?
I
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: Cliff Ruggles on August 26, 2019, 07:51:09 AM
Those pumps are known to give nose bleeds.......when you run out of fuel at the top of first gear and your nose bounces off the steering wheel!!!!....LOL...
Title: Re: Tuning Idle Pontiac 400 with 17058276, Comp xe262h
Post by: PonchoVia on August 26, 2019, 11:04:37 AM
hahahaha! oh shoot!