From tbi to Carb and 305 to 355 power & time est.
 

I just recently changed my stock TBI 305 to a 350 Carbed engine. The track has not opened yet and I dont see my self getting it dynoed. Just wonder what I may run and how much horsepower may I have?

ENGINE: Chevy SB 355, 600cfm Holley, Edelebrock Air Gap intake, Vortec heads, compression of Pistons with heads 10:2:1, Comp Extreme Energy cam .487/.490 lift 274/286 adv.duration. Hedman Elite cermaic coated headers.

TRANS: 350 Turbo, shift kit, 2200 style converter, mega shifter, and other nic nacs.

GEAR: 342 with posi

Any replys would be great.

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Make sure you put a regulator on that carburetor set to 7psi, or you are going to flood out your carb. TBI fuel pressure is around 14psi, that is way too much for a holley

Thanks Formula2fast. I have a reg on it, its set at 5&1/2 PSI.Thanks for the reply man. It would be nice if any people with the same are close to my set up could tell me what they run r how much horse power they have.

My guess is lower 13's with that setup. I assume you are probly making about 275-300 at the rears and with that gear, you should get down there in the low thirteens.

Ive seen a few people with almost that exact combo run high 12's so there isnt any reason you shouldnt other than your carb is a little small. There are a ton of super chevy articles with the vortec heads, XE274 cam, and air gap intake making over 400hp on a 350. So thats where I would say you should be as well.

IROCaholic do u like the 670 street avenger carb? I was looking at changen mine for a bigger one. Thats one that I was lookin at. Its either that r a Demon 700. I'm not wanting anything bigger than that. I think a double humper is to big for my setup.

If you believe recent "revelations" about the SA carbs, a "670" SA flows about the same as a "normal" 600 CFM universal carb.

Do yourself a favor and get a DP, if you're getting another carb, anyway. With 2200 stall, a 355 can easily handle a 750 CFM DP ( http://www.holley.com/HiOctn/TechSer...nfo/P225A.html ). It wouldn't have any "bog" problems with an 850 DP, for that matter (just wouldn't need that much flow).

That is a good link that you posted and could be very helpful in selecting a carb. I originally went off of that chart when I first put my old motor together (almost same motor as he is doing), and ended up changing the carb from a 750 because it was just too much. I think a 750 is a bit much for his motor. If you do the math, and figure with his heads and cam, he should have 617cfm flowing. I would go with nothing larger than a 650. With a carb, it is better to be on the conservative side. He should only got up to a 750 or more if he is going past 7000RPM (which I highly doubt he will) or if he has a blower/turbo. A 650 DP would be just a hare over what he really needs, but would suit him best on the street. Go with carb number 4777. ANything bigger is also going to slow down his throttle response.

I see what ur sayn about the air flow. The thing is, is it going to gain me any power going from 600 to a 750 dumple pumper are just more gas being drunk. I've been told with my setup i could run real low 13's r high 12's. How much could I gain from the swap in time r power?

If you go too big, you will drop a bit of power and definitly lose some mph down the track. gas mileage will also be affected. It has more to do with air speed velocity into your engine than gas. If you have a bigger hole (venturi) but not the vacuum/airflow in the engine to take advantage of that extra air, you will be loading up your cylinders with more than it needs. It is better to have the smaller hole and accelerate the air faster.

Gas mileage is typically better with a smaller carb. Not always, depending upon state of tune, but typically.

The flow formulas give you a good idea what is needed for peak power. However, as experience tells us over and over, a larger carb (within the limits of the posted link) will usually give you a lower ET in the quarter mile. It has to do with the way the carb works as you're going up the torque curve.