Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

edelbrock 1904

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dwelch:
i have been running this 1904 for about 2 years now on my 81 malibu hot rod.blueprint engine bp3503ct1 385 hp @5200rpm turbo 350 3:73 open. when i bought this carb.i got a kit from cliff with a couple idle tubes and a set of 74 jets(73's were in it).opened up the new tubes a couple thou.and restriction to .054. this q-jet seems to be on the money.idle at 900rpm 16 inches of vacuum, cruse at 2400rpm @21inches of vacuum. lean into it at 2400 and it's gone. no hesitation. stomp it all the way at 2400 and it's has no hesitation,just gone. cam specs are hyd.roller intake .495 ex..502 dur at .050 is 221intake 226 ex. lobe sep.110. looks like a torque cam. i have never had a carb. that worked this well and has the manners this one has. so now your probably wondering why i have some issues. i get no action from the tip in method. i get no action from the idle mixture screws. nothing. this carb. runs perfect like is now but i have been wondering if something has been left on the table. i tune by the seat of my pants feel. wideband says 13's and plugs are pretty much white. don't go by plugs very much anymore(too many additives).just use the wide band to see if things are close.i'll check idle screw hole size this month. would really like to get some response from idle screw adjustments. once again i cannot say enough good about how well this carb. works. sorry for the long rant.

Cliff Ruggles:
How much timing are you running at idle?

dwelch:
locked at 34. thats what blue print suggested when i bought the engine.they did not recommend the locked dist.i do not run vacuum adv. performance is instant,no hesitation,no barfing or bogging. for such a fantastic operating both at idle and part throttle,and wot.i am at a loss why there is no change in the idle adjustment screws or tip in. try to get a change at 800 rpm idle,but nothing doing. i was thinking maybe a 48m pri. rod might change tip in,i run the stock 50m now. i am very happy with the performance of this carb. right now i'm retired and have some time to mess with it. very quick with the 3:73's. i have several perf. dist. but this one on it now works so good that i'll run it for a while. really have not changed anything since the install a few years ago.

Cliff Ruggles:
WAY too much timing at idle and why you have no control with the mixture screws.

NOT ENOUGH timing at light load so why you don't see control with the APT system.

Running a "locked out" distributor on a street driven vehicle is "stone age" and not a good idea.

Also a good way to bust the nose off the starter on an engine re-start fully heat soaked.

Nearly as bad is running a super quick advance curve distributor w/o a vacuum advance, which will also result in some tuning issues and lower than idea A/F for "normal" driving.

Can't really help out with tuning suggestions for the carb and I've never seen a street engine that needed, liked, or worked well with 36 degrees timing locked out and no additional timing from a VA for "normal" driving.......Cliff

dwelch:
totally forgot about the locked initial timing. just changed oil and went for a cruse. at 2400 rpm i'm at about 55 mph. engine smooth running,i'll lean into it enough to knock the vacuum down to about 5 inches and it's gone. there is no hesitation or bog. it's instant. same mph same rpm and this time i floor it and it goes to zero vacuum,barks the tires and then barks them again in the 2-3 shift. at first i did not think the cam was not quite radical enough for locked timing like my vette was. cam in vette has around 6 inches of vacuum at idle and shakes the windows in the house. was a pill until i locked the dizzy at 34. now it's very tame to drive now. no starter issues,even when hot (180),i'm talking about the malibu. i would love to have someone dial in an advance for that vette engine but we spent about 3 hours with numerous springs weights and cans. locked was the best for that engine. as far as street manners,this car is a joy to drive. no heat problems,no loading up,just nice idle and off idle. i credit the q-jet for that. "stone age"hell Cliff i'm stone age(lol). apt two turns,idle mixture screws,2 turns. wide band 13:1 through 13:9. go more by feel than the wideband. this engine likes locked. some of my friends engines did not. most with a lot of overlap liked locked.

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