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Carb set up help.

5K views 19 replies 3 participants last post by  bygddy 
#1 ·
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.
Thanks
Dave
 
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#3 ·
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.
 
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#7 ·
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?
 
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#8 ·
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?
 
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#10 ·
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...
 
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#9 ·
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.
 
#11 ·
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 boxes......is 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?
 
#13 ·
True, but having to pull the Rad, and front of the motor down only to have to do it again would suck....as 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?
 
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#17 ·
Comp wants you to use something a little better for this camshaft.
They recomedn their medium size 986-16 spring.

I use a stock diameter high pressure single spring with similar seat and open specs.

This Summit racing Spring is similar to what I'm using
SUM-174000
Others are Lunati 73943
Isky 235D

Pioneer 810107-4
Pioneer Automotive 810107-4 - SummitRacing.com
You need to order 4 units to get 16 springs
They are packed as a 4 spring set pack.
..

Crower Performance Valve Springs 68304-16

Comp valve spring shim kit #4753 You need this to correctly shim the deep exhaust spring seats
to get the installed height right.
Should pick up the cam this weekend. And after I figure out heat for my garage I will likely pull the tranny, then get the heads off and go from there. Yes I will upgrade the springs then if you think its a must. Think maybe I will splurge on arp headbolts this time around lol....
 
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