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bygddy 11-03-2012 04:16 PM

Carb set up help.
So continuing my budget beater 350 vette build, as a couple people had suggested I picked up a used Performer rpm for 50$ a couple weeks ago, yest I got a used b&m 20413 holeshot converter from a friend that is stepping up to a 4500 so having been in his car I know it works well. And today I picked up a used 750dp, 4779. I had a 650 dp and traded it for the 750 as the guy is class racing 358 dirt modified and the 750 isn't legal.
So what I'm trying to determine is a decent baseline for the Carb, squirter size etc. It has 30cc accel pumps now, 70/80 jets, and 28/37! Squirters.
Its going on

350, stock bottom end, 4 valve relief flat tops
416 heads, 1094 headgaskets
Lunati 224/234 , 465/488
Performer rpm
Headers to 3.5spiral flows as sidepipes, 3" all the way down the sides
TH350, 3000 stall
411 gears
Timing at 18 initial, 38 total, vacuum advance hooked up to manifold.
Runs on 94 exclusively with zero pinging
Lumpy 77 Vette.
Have a qjet on it now, but when i install the converter and intake this week I will be switching to the Holley so looking for a good baseline and i will creep up on it till the snow flies.

vinniekq2 11-03-2012 08:00 PM

When I used a 750 I think my jets were 71/79,power valve was changed to match vacuum. squirters were stock.It worked quite well.I had an open plenum manifold.

bygddy 11-03-2012 09:54 PM

Your completely right, In the garage now actually, lunati 10001, 214/223, 443/465, oops.....
Does that make my current timing curve a little more realistic?
I'm running an after market L88 hood and have lots of Clearance, as it sits now with the performer, the qjet, 1" Carb spacer, and a non dropped base air cleaner I still have at least an 1.5" clearance.
Will def order squirters this week, I have a jet kit and a bunch of Holley stuff laying around, just no squirters for some reason.

idontdrivericeieatit 11-03-2012 11:13 PM

Fbird is right I bought used double pumper both the arms were bent had fix that and another thing u need do is look at the air gap intake and u will see where they have cut small slot out of the divider on the rpm it is best to do that to it will make little more power

bygddy 11-03-2012 11:31 PM


Originally Posted by F-BIRD'88 (Post 1606698)
Get the accellerator pump cams set.

Los of room for sure, with a L88 hood.

The holley and RPM manifold should run pretty good,
Getting the amount of exhaust heat riser flow volume up to the
manifold plenum to heat the holley carb just right is critical.
Full open unrestricted flow is too hot for Hot August Ottawa cruising. Makes the carb too hot.
full blocked is too cold for cold Ottawa winter driving ( if quick winter warm up matters)

One side of the intake manifold heat passage blocked off and one side restricted with a 1/4 to 1/2" hole at the intake gasket, is a good compromise for summer/winter driving. Getting this just right makes a good difference and takes some work.
Full blocked off heat riser passages is best for hot summer and max power.
(I prefer to fill the {twinned} exhaust heat /egr passages in the exhaust ports of the
416 heads with molten aluminum (old melted down pistons)

You can try the Qjet carb with an adapter, on the rpm intake too.
I recomend a divided/split style plenum Qjet adapter/spacer
(Not 4 hole) Now you will have two good carbs for your RPM manifold.

The felpro 1205 intake gaskets have the heatriser blocked off, that's what I'm using now,, Is this good enough or should I do more? Not worried about cold weather really, its a little cranky when its below zero like this morn, but it warms up OK and then is fine. And as soon as snow hits it will get parked and taken apart till springtime for paint.

bygddy 11-03-2012 11:33 PM


Originally Posted by F-BIRD'88 (Post 1606701)
Sometimes the accelerator pump linkage arm gets bent , on used double pumpers.
Needs to be bent back to shape to get proper fuel shot action.

It seems as the second the throttle moves the pump arm moves so i belive its ok,what color cam do you reccomend?

bygddy 11-04-2012 09:18 AM


Originally Posted by F-BIRD'88 (Post 1606829)
The blocked riser is a ok for summer driving when its hot.
Incorrect manifold temp ( too cold for the day) will effect throttle response
and best jetting. so..... its up you you.
cold manifold cold day wants richer jets and more shot as the fuel vapourizes slower. (or a hotter manifold)
hot is opposite. (leaner jets smaller shot) Its up to you to realize this and tune, retune for the day
or find the happy average. (one side with limited flow, other side blocked seems to work, ok)
Its all about fuel vapourization....liquid fuel does not burn.

Before you install the carb, flip it over and preset the pri and sec throttles idle position/ transfer slot exposure evenly
Throttle response and "drivability has a ton to do with the idle --off idle transition circuit.
If this is out of wack no amount of fooling with jets and shooters will get it right.
This where the proform-holley 750 HP carb body upgrade comes in, with its swappable tunable idle and high speed air bleeds
as well as smooth air flow design.
Its all about dialing it in for YOUR MOTOR. These 750 carbs can be dialed in very very sharp.
Its up to you to do that.

The squirters are fairly inexpensive so I'm going to order a 31 and see how that works. Currently the primary transfer slot is squared up, and the secondary is closed up. I will be pulling the HEI apart and limiting advance as you suggested to more of a 15-16 curve so i can get a liitle more aggresive with my initial, then switching to ported source for my vacuum so things don't get real stupid at idle. With such a mild cam and more initial I hope I will be OK running on the primary idle circuit and leaving the secondary closed up?

bygddy 11-04-2012 12:26 PM


Originally Posted by F-BIRD'88 (Post 1606845)
With such a mild cam and more initial I hope I will be OK running on the primary idle circuit and leaving the secondary closed up?

This is wrong. The holley carb idles using both the primary and seconday throttles.
It idles on all 4 barrels at once.

set it up so all 4 are even. You want even "4 corner idle" Thats the beauti of a holley. Don;t fugg it up by closing the sec throttles at idle.
That is not how a holley works. Don't shoot your self in the foot.

From that point the idle speed is fine adjusted by base idle timing, PCV system air flow (PCV valve choice) and fine adjustment of the throttle(S) position at idle.
Closed sec throttles will create the primarys to be too far open.
You want balanced 4 corner flow at idle.

recurve the distributor after you find the best idle timing, throttle position
PCV flow balance.
The throttles ALL 4 throttles must be in the sweet spot at idle for the idle and idle transition to work correctly and smoothly.

99% of the holley problems are tuner error, not carb design problems
That goes equal for Qjets and Edelbrocks too.

Q jets and edelbrocks are different.

Well there's something else I learned today, I was always under the impression you only used the secondary idle circuit if it was needed. Before I install it I will adjust accordingly. Thanks! I replaced the needle and seats today just because these were unknown and i had new ones in stock, I also have a multitude of pv's, should i replace and what size would u suggest?

bygddy 11-04-2012 12:30 PM


Originally Posted by F-BIRD'88 (Post 1606865)
Did you blueprint the balancer timing tab yet?
True TDC....using a piston stop

Check for vacuum leaks.... PB booster,, trans vac modulator, carb base, intake,,, corvette vacuum operated acessories (head light doors) ( A/C...heater duct control)

the intake bolts WILL NEED retorqing. (by hand)

I run a cold manifold...but I don;t drive in the winter. ( and my engine combo is much more radical and racey..
(its very drivable and smooth 'cause I spent the time to dial it all in.)

On your car....I would start with one side blocked off and one
side with a 1/2" hole in the intake gasket so you have a "warm manifold"... A warm manifold is easier to tune correctly. A Hot manifold, too hot is a pain..(full open heat risers).. a cold manifold is harder to tune for especially this time of year.j

Its all about finding the sweet spot.

Yah, in had verified with a stop my tdc awhile ago, all was good there. This is about as much cold as the car will see, bout 5 and it seems to run fantastic with the riser blocked. No vacuum leaks, headlight leaks were many when i first got it home and that was the first thing I addressed.

bygddy 11-04-2012 12:44 PM


Originally Posted by F-BIRD'88 (Post 1606846)
Your best idle timing is going to end up between 14 and 18deg with that 214-224 442-465 cam.
Correct throttle idle position ON all 4 barrels at idle is CRITICAL.

Do not confuse the timing curve I recomend forr a hot-racey cam, on all cams or your cam.

Idle circuit is ubbber critical.... shooter pump shot tuning is soo easy once the idle circuit is correct

and near impossible when the idle circuit is fubared. (incorrect thottle positon)
Don't shoot your self in the foot.

Vacuum advance tuning comes in last after every thing else is dialed in.

Thats funny and bang on correct, I creeped up on the initial until it pinged just a tiny bit on 92, switched to 94 and even on the hottest days it had no evident knock and made best power at 18. Only then, after reading a bunch of your stuff on vacuum advance did I try that, and even using manifold instead of timed it seemed to have much better tip in, cleaner idle for sure, and no detonation. I had pulled a plug to look for anything weird as I have zero tune up time on the qjet and the plugs looked clean, no peppering, goldish colored so I reinstalled. It actually runs amazing as it sits. And its suprisinhly very quick. I just want more, I'm determined to put it in the 12's using stock bottom end and hand me down or swap meet parts next spring. That's why I'm trying to stay away from solid cams or roller stuff etc etc. I'm def going to swap cams in the spring, and hopefully just some summit long slot rockers. My machine shop guy said he wrote down all the measurements I told him you said I needed. So i will dig out my paperwork and see what it says. That will help determine my cam choice, but again, budget hyd flat is likely. Stock pushrods, pinned studs and go from there. The guys I hang out with think this stuff is pure stupid, everyone wants a roller cam, alum name brand heads etc etc..and think what I want to achieve is impossible without spending huge money.....difference is, i have so little money in it, I'm not afraid of hurtimg it at all....makes it lots more fun lol...

bygddy 11-05-2012 04:01 PM

Hey f-bird, things got a liitle bit more intresting today, one of the guys I hang out with has changed directions on his 406 build, so he offered me me his XE284 cam and long slot rockers for 200$. They are new in this something I can use in my current set up? Heads are good to 550 I'm told according to my machine shop guy after I asked your appropriate measurements. Whether they will flow that is of course another subject....sticking with my welfare build this sounds like a decent deal to me if it will work....the converter i got is the b&m 20413, and 411 gears....and as above the 4779 Carb....power interrupt switch, lock timing at 34-36, 3.5 pv, 70-80 jetting, does this sound like a street slug or something that's actually going to get me the damn 12sec et I want so bad for very little cash? I have no issue shifting the thing at 6500 till it eats itself....assuming the heads flow enough to warrant it.....what's your and anyone else's input?

vinniekq2 11-05-2012 04:37 PM

try it,its not a big investment.

bygddy 11-05-2012 05:11 PM


Originally Posted by vinniekq2 (Post 1607565)
try it,its not a big investment.

True, but having to pull the Rad, and front of the motor down only to have to do it again would it is I need to drop the oil pan this time and replace the front cover, never pulled the pan on one of these but indont think there is much in the way?

vinniekq2 11-05-2012 10:02 PM

why do you have to pull the pan?

bygddy 11-06-2012 06:50 AM


Originally Posted by vinniekq2 (Post 1607758)
why do you have to pull the pan?

I have had exactly zero success rate with getting the timing cover to seal with leaving the pan on.....and I don't wanna deal with leaks after words....

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