I need a RR carb!!! Site sponsors? Anyone?? HELP!!!

[ZZ4Blazer]

Ok, I need a carb set up for road racing. I've asked around the forum, and bascially anyone old enough to have experience with carbs for help. All just basic little stuff that I've already tried, with little to no gain in performance.

Truck is 99% street driven. Will usually see a test and tune night a few times a year(1/4 mile), and I would like to hit some open track days since Im modding it to handle. But even on an open road in the middle of nowhere, my carbs killing me. I cant imagine trying to push it on a course where I can let it hang out some.

But my carb will not keep up with any kinda agressive driving, let alone trying to push it. Especially braking. More than 40% of the brakes and it will kill the motor. Bogs out of corners, etc.

Anyone know a good carb shop that specializes in this? I've searched around the net some and found a few. But no clue if theyd be any better than mine now.

Eventually I will go to EFI. But I dont have the cash for it now(kit, fuel system, etc) nor the time to tune it.

Any help would greatly be appreciated.

[hotrdblder]

call todd at pro systems, ask for a hp for road racing or bo law, and ask for same set up, a custom built carb is th emost important thing when building a motor

[another69]

Pro systems and PC (performance carbs) are a couple of shops that will set up a carb for RR, but I'm sure there are others. The new mighty sportsman from BG can be bought as RR if you want to buy new.

[ZZ4Blazer]

Thanks guys!!!! Pro systems was one of the first that I found and looked like I should investigate more.

Have any of you had personal experience with the a pro systems carb?

[hotrdblder]

i put a pro systems built carb on vinnys car, which is a 496ci and won the air ride autocross at year one this weekend

[Shaker455]

Have any of you had personal experience with the a pro systems carb?

Yes, I have had many first hand experances with both Pro-Systems and PC Carbs as I build new custom Holley's, Qjets and rework and modify existing units.

I have reworked many Pro-System 4150's as they modify the accel pump system in the metering block in an attempt to create what Holley has already done with a simple screw in part....a syphon break.

Unlike myself they use the cheapest parts and do not calabrate to your specs or live test on a "real engine" and no wet bench is going to give you real time results!

I just finished modifying a PC carb, the owner thought he would save a few hundered bucks and buy one of there calabrated units.

They had set him up with a straightleg 650, the owner came to me having tuning issues.

When he came over with the carb on the car the first thing I noticed was the idle was erratic...maybe a vacuum leak I figured..

Tested all the carb and inatke gaskets and could not find a leak...

Took the bowls off to see how they jetted it and found the brass well caps that they installed into the top of the metering blocks installed cockeyed!....the caps were not sealing the wells and were the cause of the erratic idle.

Upon drive testing I found the carb they selected him to be pulling 3" of vacuum at WOT and if the carb was sized right it should be zero.

I knocked out the inefficent straightleg boosters for new HP downlegs with a shear step for better atomization.

Resized the venturi to 750 specs, reworked the metering blocks, modified the baseplate by slabbing the shafts for airflow gains.

Teflon bushed the shafts to control vacuum laeks and reduce metal to metal contact.

Live tested it on my car days before he came back and tuned it live on his.

After tuning we went to the chasis dyno to varify HP, Tq and A/F.

Previously he had gone to a chasis dyno with the carb out of the box from PC and made 336HP & 290 Tq.

Our session produced 342Hp & 333Tq and the A/F was 12.8 at WOT

Engine was a 302 with AFR heads in a 65' Mustang modified for RR
Jeff

[hotrdblder]

well todd nailed the carbs i have gotten, i did not touch a screw on the last one for the 11-1 496, which ran 10.60 @ 131, but i guess he got lucky on that one

[Shaker455]

Hot,
In all fairness thses companys have to have some sucess stories or they would not be in business.

I just talked to a guy who's sending me another Pro-Systems 4150.

It has been sent back to them three times with the same issue....

[ZZ4Blazer]

Shaker455,

What would you recommend being in my position?

[Shaker455]

ZZ4,
I know we talked a bit last year and you had installed jet extensions...are they all removed now?

Tell me about your fuel system?

Tank, pump, lines, filtering etc.

Also lets have a detailed run down on your engine combo.

Still have that Pro-form 750 mainbody on there?

Unless you want an all new carb you may be able to rework yours

Floats and some other parts geared to RR may be key in your sucess

[ZZ4Blazer]

Jet extensions were removedas suggested with no improvement.

My biggest problem is on braking. It always kills the motor. Im sure I could find a way to learn to heel toe it to bring the rpms up high enough to keep it from flooding the engine, but the pedals arent even close to each other. And having lack of racing experience probably doesnt help either.

Anyhow, tank is a summit 20 gal cell w/foam behind the axle. Generic canister style filter right off the tank. Down the frame rail probably 12" to an Aeromotive 11203 street/strip pump. 1/2" line up to the Aeromotive 13204 regulator set at 5.5 psi. 2, 3/8 lines to the carb off the regulartor(one to carb one to nitrous noid) 1/2" return line to return port on cell. 1/2" return line is what aeromotice calls for for that regulator.

Motor is ZZ4 shortblock
fastburn heads, upgraded to beehive springs
Comp HR 282 cam, (230/236, .544/.555 lift w/1.6RR's)
AFR hydra rev kit
Edel rpm air gap intake, opened up a little to match the taller heads better
MSD 6AL, pro billet dizzy
1/2" NX nitrous plate
holley 650 dp w/upgraded proform 750 main body
PV matched to 1/2 the idle vac as per holley's instructions
Decent A/F's cruise and wot, tuning with AEM wideband

No real mods done to the carb. Other than trying a bowl vent crossover tube to rule out fuel spilling out the vents and flooding the motor. No improvement there either.

[Shaker455]

I've worked on many ZZ4's as I have buillt and tuned Holleys for guy's that race super modified limited class at the local raceway.

Okay, this is what I see so far adding to your braking problem:

Fuel filter is a pre-filter that usally has a 100 micron element which will allow dirt to go into the carb, you need a second 5 to 10 micron paper element filter up near the carb.

Increase your line size to 1/2" all the way to the carb.

Increase your fuel pressure to 6.5 to 7 psi max and reset your floats.

Your 650 metering blocks are a problem as well, in most cases they have emulsion tubes inside taking up fuel well volume and the main well passage to the booster is inefficent.

Take a look at the well caps on the top of your metering blocks the next time you pull them off and tell me if the two center caps are up level with the outer plugs.

I bet they are and this is a low performance deal as on performance blocks the caps are down low right above the passage to the boosters to prevent an air bubble to develope.

Also 4-corner idle is a good upgrade

Nos plates usally cause tuning problems so you may want to take it out and retune to see if it's causing any issues.

How's the engine timmed and what bushing and spring combo did you use?

[Skip Fix]

If it's flooding on braking what vent is on the secondary side metering block? A "whistle vent or none? Many Holleys have none from the factory. Hard braking alows fuel to slosh right up and out into the carb. Some old drag racers used to connect both vent tubes with a piece of fuel line and a hole notched at the top to prevent slosh.

[ZZ4Blazer]

I forgot to add I've got a small inline filter after the regulator on both the carb and nitrous line.

Line was kept 3/8 because thats what size the outlets on the regulator were. PSI was also set lower for the requirements for the NX plate.

I dont remember which bushing and springs I used, but idle is set at 14* and total timing is 35 or 36* by like 3200.

Rear block has the vent whistle, and I tried adding a once peice vent crossover tube to connect both vents to each other to see if gas was getting past it. No improvement with that.

[Shaker455]

ZZ4,
Fast burn heads are supposed to use about 4 degrees less total timing and with your combo I think you would benefit from having your mech advance come in eariler....2500 to 2800 rpm

I make a custom MSD bushing that allows more ideal intinal timing (18-20 degrees) that will keep your total in step with fast burn configuration.

I'm not a fan of NO2, look at the things you have to do to accomidate it....I don't see a use for it in road racing...

I suggest you take it out of the loupe and go back to basic tuning and nail down your combo.....I would be happy to help!

[ZZ4Blazer]

This spring before it was running again I swapped the springs to have the timing coming in sooner. Wasnt till bout 3600 before. My combo seems to like 34-35 degrees best. I've got an msd adjustment knob in cab to adjust timing when on the nitrous. Ive played with it some at the track and seems to have the best mph around there.

Nitrous is just for fun. 1/4 blasts/bragging rights, occational street race, etc. Wont be used for track days. Eventually will be a turbocharged combo.

[Shaker455]

Okay so what's your next step?

[ZZ4Blazer]

Now thats the million dollar question.

[Shaker455]

Okay, email if me if you need anything

[David Pozzi]

Most Holley carbs I've autocrossed or open tracked needed a simple lowering of the float levels. You can do more mods, but that's the first step I'd do. It's fixed our Holley and Demon double pump carbs.
David

[Skip Fix]

The Holley I autocrossed with with roadrace slicks never missed a beat. A buddy did have one he was autocrossing that had a crack in the main body that would intermittently seap. Took forever to figure that out, and a carb swap cured it.