My uncle asked a buddy of his if my Quadrajet carb was good enough for my new combonation (its in my sig). This guy has supposedly been racing for 20 years or something and said right away : "No, because those carbs only flow 4xx CFM" I've been reading these boards and know that some of you state flow of 750-800. I don't want to spend $400 that I don't have on a new carb that won't help me. My carb setup is as follows: DR/K secondary rods/hanger, #570 primary rods, and #74 primary jets, filed down secondary "stop" so they open 90*. Will this be adequate for my 350 with mods? I think I'll be putting out 360-400 hp. I used a voltmeter and the o2 sensor last night to check the air/fuel ratio as described in the tech article because I thought I was running really lean. the article says something to the effect that "part throttle doesn't matter because the computer keeps it in the desired range" but I was having a problem with the headers glowing at 2000rpm for a minute or two. Well I ran the car like that again and the voltmeter said .645V-.800V for most of the time. Yet the headers still glow. Is this a normal range or rich for part throttle? It's obviously not running lean(which is what I thought). So Does this narrow it down to timing conclusively? I've been told to set it at 8-12* adv. Its at 4-6* initial right now. Its hard for me to believe that is all thats wrong. Thanks for reading this rambling, multi-question post.
sincerely,
John

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• 84 Firebird w/ T/A gfx
• 350 4bbl (LM1)
• Automatic
• Non-leaking T-Tops (new rubber all around)
• Working headlights (new parts)

Mods: 14" K&N open element, 160* stat, ram-air hood, Accel cap & rotor, MSD Super Conductor Wires, 24mm solid rear & 36mm hollow front sway bar w/ PST polygraphite bushings & endlinks, Spohn SFCs, WS6 springs, SLP 1 3/4" Jet-hot coated headers, Hooker 3" cat-back, Catco high-flow cat, Comp Cams High Energy 268 cam, AFR 190 heads, Weiand Action+ intake, Comp Pro Magnum 1.6:1 Steel Roller Rockers, Moroso Oil Pan with trap doors, windage tray and crankshaft scraper, poly graphite motor mounts, K&N oil filter and Mobil 1 synthetic.

http://www.homepagez.com/350thirdgen/

[This message has been edited by johns84bird (edited September 26, 2001).]

[This message has been edited by johns84bird (edited September 26, 2001).]

 

1st, the q-jet will flow adequately for your setup. Check the mag articles "Stroke in the Desert" on this site. "20-year racer" and "q-jet expert" are almost mutually exclusive (people on this forum excepted).

I don't know about your O2 readings, but what distributor are you running? Sounds like you have a non-CC q-jet, you'd better have a non-CC distributor as well. As for timing, total timing is more important than intial, although both should be addressed for best driveability. Shot for about 36 degrees total (vacuum advance disconnected), all in by at least 2500 RPMs, maybe even less. The initial timing will then be dictated by the amount of mechanical advance the distributor has in it.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

it is a computer controlled quadrajet so I guess I don't have vacumn advance. does the computer control that? If so I guess only a prom would change the total advance part right? I don't know how to tell if the distributer is cc. I guess it is cause its an HEI with wires going to it and some electronics inside under the rotor. I still have a great deal to learn about the general mechanics of my ignition and fuel systems. Thanks for your reply
John

 

Computer controlled systems suck. You can bandaid it with a new chip, but you're better off just ditching it for a non CC carb and dist.

A non CC Q jet can be adaquate, and made to run decent, but you're still better off ditchng it for a Holley or something similar. Especially with all the money you have in that motor..ignition and induction isn't the place to start skimping.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

[This message has been edited by Jester (edited September 27, 2001).]

 

If the distributor doesn't have a vacuum advance can hanging out the side of it, it's computer controlled. IF it's computer controlled there is no way to adjust the timing curve since the ECM does all that electronically. However, stock timing curves are not THAT bad and usually a simple 4* advance over the stock setting will get you fairly good performance.

The key with computer controlled stuff is that all the various sensors must be hooked up and working correctly. Having sensors lying to the ECM is a great way to kill performance. If ther's a "check engine" light lit, then it's even worse. If you don't have time or inclination to make the CC stuff work correctly then replace the CC carb and distributor with non-CC units and begine tuning in the conventional way.w

 

Damon,
Thats very true! we got it working almost properly tonight! No more header glow, missing or roughness but it is now running rich and has fouled my new plugs. It was a combonation of the egr valve not being tight on the manifold (damn weiand bolt holes were too shallow for everything), timing not being advanced enough, a couple of key vacuum hoses connected incorrectly, low coolant (duh!) and carb tuning issues. But its all good now (I have to replace the airhorn gasket and purge valve tomorrow and adjust the float level) It should be fine after that and then on to emissions testing! wish me luck! You guys are great.
John

P.S. I made my uncle's friend eat his words by showing him it worked fine and also furnishing an arsenal of text including lingenfelter's book showing that q-jets are rated at 750 cfm.