BlueChevyZ

iTrader: (1)

I'm looking for someone who is knowledgable in Holley carbs to tune my combo,
Needing help with fine tuning my carb, I'm no expert, and before I mess it up to where I cant drive the car. I have a 383 stroker that was built by T&L Engine Development, a little about the motor, it has a hydraulic roller cam, was a custom grind, spec'd at 236/242 @0.50 .555lift, (only info they provided) Dart Iron Eagle heads, Edelbrock RPM airgap intake, 10.3-1, it dyno'd at 486hp @ 5800, 478tq @5100, idle at 950 with 9"vac, 12* timing with 32* @3600, the engine is in a 84 camaro Z28, roughly 3400lbs, with a built 700r4, 2600 stall, 3.42 thru a 7.65 10bolt rear,
My problem is I have the off idle bog when accelerating, carb specs from AED, 70 primaries, 82 secondaries, powervalve 4.5, primary squirter .031, secondary squirter .035, I have been searching/reading up on all the info that I can find here. I adjusted the timing recomended by AED, to 18* and 1000 rpm for idle, but I still have the bog, my vacuum is @ 8-10" at idle, in gear it drops to about 5 and flucuates to 8-9", I did the easy cruise and monitored the vacuum at a speed of 30 to 40 with a very light pedal to maintain that speed and the vacuum reads 12-15", the engine will load up pigrich while stopped, fuel pressure at the fuel log is 6psi and sometimes fluctuates to 5psi, mechanicl pump, and the level is barely right at the site hole, and yes it has a primary powervalve a 4.5, the secondary is blocked off, the MSD diz has the black bushing, & 2 heavy silver springs, have adjusted the timing to 18*, and according to MSD's website, that gives me a total of 36* @ 3500, this helped very little, the bog off idle is still there, and any time I stomp the loud pedal while cruising it has a slight hesitation.Once the motor clears it's throat, it runs like a raped ape.

I tried adjusting the idle up, but in doing so I cant adjust the idle adjustment screws, any suggestions before I totally screw up the adjustments.....

89gta383

iTrader: (5)

What carb is it and what size? If they dyno'd it I am assuming they dyno'd it with their carb and not the carb that is on the car now?

Do you have a jet kit and some spare squirters?

Have you set the mixture screws at idle with your vacuum guage hooked up? You want the highest vacuum that you can get when turning the mixture screws in and out. I think you start with 1 full turn out from all the way in and start from there. I haven't touched a holley in years. Too much EFI stuff around here.

Hot Rod, Car Craft and other mags have had good carb tuning articles in the past, do a search on google for one, (hot rod: holley carb tuning) and you should get good results.

Unfortunately, carb tuning is something you need to get under your belt. You won't blow up the car, because it sounds like it is rich at idle. The 70-82 jets sound oK for WOT. I used to drill a hole in the primary throttle plates to help with the idle on a big cam with a low vacuum signal, but my carb was a 3310 holley and carbs have been updated since then.

mrr23

a couple things come to mind. first the power valve may be opening too late/soon. second squirter isn't reacting fast enough. with the vacuum in gear near the PV opening point of 4.5", it might be slightly opening and allowing too much fuel in causing the richness. it's something i'd have to be there and mess with. if you wanna bring it to me one day i'll mess with it.

BlueChevyZ

iTrader: (1)

they are gonna tune it at the dyno day tommorrow