Wayquick4u

I just swapped from TPI to carb when i put a 383 in my 85 vette. Its 383, afr 190's, 224/230 .510 hydralic cam, victor jr intake, holley 750 double pumper, 1 3/4 longtubes. It made 450 at the flywheel on the dyno.

The car has terrible off idle acceleration and backfires occasionally through carb off an idle. the car runs awesome over 3000 rpm and pulls extremely hard. but if you floor it at 1500-2000 it stumbles until the rpms get up. Where should i start on tuning this carb?

The ODB

First thing,
swap the Vic Jr intake for an Edlebrock RPM.

I would adjust the connection between the throttle shafts so that the primary blades open further before the secondary starts to open.

next I would work with the accelerator pump circuits. May need to back off on squirter size and increase the duration.

next I would consider installing annular discharge boosters (from a Holley vs) into the primary side of the carb.

Wayquick4u

My vette runs high 10's on the bottle, i picked up 15 flywheel horse on the dyno from rpm to the victor jr, its definately staying

ack all those adjustments are beyond me, i wouldnt know how to do any of that

lukerene

mate,,,buy one of those holley tune up books,you can get them for $20 it is the best thing you will ever buy,,,,you will be a wizard in a day,,,all the graphs are there,,the flow rates,,you will be suprised,,dont get the how to hot rod holleys book ,,,they work fine as is,,,just a few small changes,,,thats my oppinion,,,those 750dp,s will run a big motor,,so holley reckons, this is comming from the guys who make them,,,good luck, they are interesting,.always an article by smokey yunick, or bob gliden in them if you want to go all out racing,

Polecat

What model number of Holley do you have. Is it falling on it's face? Are you sure you are getting either enough fuel or too much at first?
Need to check WOT runs too to be sure your secondaries aren't to rich. I had to back my new Holley from stock 71/80's to 71/77's.

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350 4 bolt main, Speed-O-Motive 383 stroker kit, re-sized rods ground for clearance,TRW Forged pistons,10.7:1 compression,HPC Coated RPM intake, Holley 750 cfm carb,World Products Sportsman II heads,2.02/1.60 valves, Comp Cam 1.6 roller rockers, Comp Xtreme 284 cam,240/246@.050 with .540 lift,Crane pushrods,ATI damper,Proform HEI and MSD6A box,HPC coated 1 5/8 headers, 2.5" exhaust with 40 series mufflers,TH350 with Hughes 3000 stall, Powertrax NoSlip Locker, 4.11 gears.

[This message has been edited by Polecat (edited May 10, 2001).]

FastBroker

It's stumbling from the manifold runners/plenum being too big for low-rpm operation, ie, air/fuel mixture slows down a LOT. Has to live with it for top-end power. Can be tuned-up a little, VERY rich, but never fully cured. Those big tube headers are not helping low-end either, but if he wants/needs 15 more hp at the cost of low-end torque and driveability, he got what he wants.

[This message has been edited by FastBroker (edited May 10, 2001).]

The ODB

Sorry but that doesn't sound like very valid testing to me.
First what did YOUR CAR run at the TRACK on the motor only with the Vic Jr intake?
Second, what does it run (on motor) at the track with an RPM intake?

If you can honestly answer both of those questions, then you will change your opinion about the Vic Jr staying on there for the little 15 flywheel HP.

I told you exactly how to fix your problem, and you know how to do the tests yourself. Lots of information is out there in print and on the net about working with Holley Carbs.
The rest is up to you.

[This message has been edited by The ODB (edited May 10, 2001).]

JB Camaro SS

In order to cover up the flat spot you need to increase accelator pump shot. Make sure you have the pink cams and increase squrter size to 37 both primary and secondary. This is only a starting point you must fine tune from there. Also make sure total advance is around 36-41 depending on compression. The victor jr manifold is race only, but with a 3000 converter, 373 plus gears, heavey pump shot, and a lot of timing it will work on the street. You make the call.

lukerene

VICTOR JUNIOR,, good for ski boats, constant R.P.M outfit or all out race ,, go down a bit in manifold,,even one of the old 780 vacumes will run a large small block,,easy to drive, good on fuel,,goes like a rocket,,its up to you, some good advice from the other guys also,,mentioned,,good luck

The ODB

caution on increasing squirter size... larger squirters will decrease the duration of the pump shot. In this instance he probably needs to increase duration because the engine is so slow to respond.

Damon

If it's backfiring you're running lean, not rich. Too rich it just feels like you stepped in a bucket of cold oatmeal.

You need to bring the squirter size up quite a bit- especially on a single-plenum manifold with a lumpy cam. I'd go with JB Camaro SS's suggestion as a good starting point for both squirters and pump cam. Might want to bring the primary jets up a few steps, too.

One other thing- if you are running an automatic and have too tight a converter you will NEVER fully get rid of the hole. If you have a manula then what are you doing flooring it at onlyt 1500 RPMs? You're way out of the cam's powerband. Unfortunately, the low RPM soggies are a fact of life for a 10 second ride!

Damon

ODB- seriously, man, you need to calm down. Those mods MAY or MAY NOT help this gentleman's situation. BUT there just isn't enough information in this post for you to draw a conculsion about that yet.

You're confusting the situation and leading this guy way off into the weeds.

SIMPLE STUFF FIRST!

BadSS

Absolutely work with the carb first. Gotta get what you got right before making a determination to swap out stuff. Properly tuned,, including a proper ignition curve,, and cam phasing,,, a 383 with 10:1 compression with a 224/230 cam should have little to no stumble / hesitation EVEN with the std Holley boosters and Victor Jr,, especially if it dynoed 450 flywheel.

A few folks gave a good suggestion about buying one of the Holley "HP" books. The one(s) by Dave Emanuel seem to have very accurate info and will get you started in the right direction.

kevin v

you can probably clear that up with a pump cam change. if it's a new carb it probably has a pink cam on the primary. take it off and throw it away. very lazy pump cam.try the dark green one. it's very quick and agressive in the first part of the throttle, which is where you need it. if that does'nt totally get rid of the problem then start going up in squirter size. you should'nt really need more than a .031. this is all assuming that you've got enough initial timing in the engine as well. if you don't have a local speed shop to get holley parts from try calling the carb shop. their down south from you in ontario. 909-947-3575
what kind of torque did your motor make and at what rpm?

super83Z

the carb may need tuning also but I am going with ODB on this that intake is in the 2500-6500 RPM range it is not a low revving intake with the large runners on that thing it is going to stumble at low RPM's. Even though most people don't like the cam the RPM cam has a duration of 234/244 and that is recommened for a dual-plane intake. His duration is 224/230 I think this would make a difference

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I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package with 64cc aluminum heads, dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, ASCD SS hood, 16" IROC rims.

future mods:
completely done over suspension, black paint with flames, Hurst shifter, dakota digital gauge package, procharger supercharger.

The ODB

well it is possible to tune the carb to work with the vic jr,
but considering that adjusting the secondary linkage or swapping boosters was beyond his immediate ability, then I think the intake swap should be done first. Besides a dualplane will give much better overall results on a streetdriven car.

by the way, the 'soggies' are due to the camshaft and intake manifold and have nothing to do at all with the horsepower output or the E.T. potential.

kevin v

you guys read to many hot rod magazines. he's got a 383ci motor with a high velocity
190cc cylinder head and a small cam. a victor intake is not going to hurt that motor down low like you think. he just needs to dial in the pump cam/squirter combo. i've seen smaller engines with that manifold take full throttle down low without a hiccup or a backfire. although they would'nt set your hair on fire they still accelerated cleanly.

super83Z

No I don't it is just that the Engineers who designed the intake say that it is not for low revving motors and small cams


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I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package with 64cc aluminum heads, dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, ASCD SS hood, 16" IROC rims.

future mods:
completely done over suspension, black paint with flames, Hurst shifter, dakota digital gauge package, procharger supercharger.

super83Z

Sorry I just checked my Edelbrock catalog and that intake is actually rated for 3500 RPM-8000RPM



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I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package , dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, ASCD SS hood, 16" IROC rims.

future mods:
completely done over suspension, black paint with flames, Hurst shifter, dakota digital gauge package, procharger supercharger.

kevin v

that's funny. i had the victor-e(which has even more plenum area) on a 406 that had a camshaft 276,284 @.050 with an even bigger 850 carb and i could stab the throttle off idle with zero stumble or back firing. not to mention the motor made peak power at 6800rpm. those rpm ranges they give are not absolute. 3500-7000 for a victor is for what size engine? 302,327,350? do you see what i'm getting at. the manifold isn't the problem. it's his tune-up in the carb for the combination of parts he using. if he gets it right there's no reason he should'nt be able to stab the throttle from an idle and burn the tires for days.

BadSS

I know Kevin V and I are not the only guys out here that have no problem tuning in a carb on a Vistor Jr!!!! I've tuned in a Vistor Jr on a 9:1 305 with a 224/224 108 cam and 750 DP with no "soggies". I've had more mis-matched crap brought to me to tune in than I can shake a stick at,, this isn't even close to being bad!!!!! And if the thing dynoed 450,, with that cam (assuming a 110 spread),, it should have no problem leaving without hesitation,, even with a torque converter as low as 2200 rpm. With the carb tuned in and the ignition curve right,, this guy should have NO - NOTDA - hesitation what so ever.

I'll admit,, I probably would not have picked a Vistor JR for this combo myself,,, but I sure wouldn't tell anyone to swap intakes before they got the carb and ignition curve tuned in. I keep saying ignition,, because without the proper advancement curve in the distributor,,, it won't matter which intake or carb you have.

super83Z

I would agree that that cam would work out better because I said it isn't designed for small cams and that cam is on the big side



------------------
I WOULD RATHER PUSH A CAMARO THAN DRIVE AN IMPORT

1983Z28 350w/ edelbrock performer RPM power package , dynomax shorty headers, 700R-4 with shift kit, 750cfm carb, edelbrock 3" exhaust system, ASCD SS hood, 16" IROC rims.

future mods:
completely done over suspension, black paint with flames, Hurst shifter, dakota digital gauge package, procharger supercharger.

gtabadboy

I have a similar problem with my car. Towards the end of the track the car dies off on me as if im losing fuel. The fuel pressure is at 6psi but I also tested it all the way up to 9 psi. The problem was still there. The timing is at 10 degrees initial and 36 total timing at 2500rpm. I need to adjust my carb but know how to do nothing except the air/fuel ratio. The carb is only about a month old. How can I adjust it? Some people suggested rejetting. The best ET is only 13.6 and look at the mods on this 383 stroker. Help

Jester

The Vic Jr is a good choice for that motor. Keep it.

Poping through the intake off idle is either an insufficient squirter or too much play in the pump arm. easy enough to fix.

F-BIRD'88

Yes check the accel pump linkage, should move fuel
as soon as you move the throttle, no lag.

Experiment with different cams but get bigger discharge nozzles.

The lower your stall speed the more shooter you'll need.

should be between .031 and .047"

You will need lots of initial timing but with the same 32 to 36 total. don't be shy here. 16/20 deg initial.

Getting 15hp at the peak does not mean that intake will make your car the fastest. The dual plane will be a lot more flexable
but the Vic Jr is probabily the best of the single planes for flexability. Just need to tune the carb.

If you converter stall is below 3000, consider getting a 3500
converter, this will keep your motor in its best power band
and make it faster and easier to live with overall.

jwfirebird

iTrader: (2)

you need to buy a jet kit from a perf shop or mail order,take the bolts out of the rear of the carb(for the bowls)and remove the jets.replace w/ bigger ones, make a run, keep going up until your et stops droping then go back to the last set you had in there. you should also get reusable gaskets so you dont have to keep replacing them. normaly you need to change jetting w/ every setup change or mod.
another tip: be ready to catch the gas when you pull the bolt out.

gtabadboy

I bought the holley jet kit assortment 64-99 jets. What jets should I start off with? Should I just change the jets in the rear or do I do the same with the primaries? Thanks

jwfirebird

iTrader: (2)

first you should set the fuel presure to 8psi, then check what jets you have in the carb if youve never changed them i think it comes with 70 prim. and 76 sec. or close to that. id say go with 74 prim. and make a run if it helps go bigger till it doesnt help.when it doesnt help go back to the set you you used before then raise your secondaries the same way. you have to play with it and make runs. every setup is different so you have to see what works for you. with that cam and intake your going to need alot of secondary jetting. check the plugs often black crap=rich, if it looks burnt=lean, kinda gray with no crud=good.

gtabadboy

Thanks for your help. Im going to try it Saturday.