Ok as many of you know im going to be purchasing vortec heads, performer rpm air-gap, and a xe262h, to replace my stock heads, performer rpm intake, and performer rpm cam.

Right now i have the edelbrock performer 1406 600cfm vacuum 2ndary carb. Is this carb going to be enough for the 350 after the above changes? Would it be benefical to bump it up to a holley 650 or 750 or should i just stick with what i have?

(Cubic inches/2) X (Max RPM/1728) = Carb CFM

example:
(498/2) X (6300/1728)= 907cfm

There ya go graemlins/beers.gif


Rassan

i read an article that you cant calculate it that way and the best way is to dyno it. And since i dont have bottomless pockets to dyno my options its best for me to ask those with experience, which is why i posted here tongue.gif

I ran a 625 cfm B/G road demon on a mild sb and it ran great. Tried it on my current engine and it ran well but I couldn't get the idle right. To much cam. Went with a 650 speed demon m/s and it runs just fine!

David

the 600 edelbrock will work fine for your combo, although i would much rather see you with a 650 holley. either a double pumper or vacuum secondary, both would work fine. the vacuum secondary would probably fit your combo better for the simple fact you are building a street car.

im using a 750 edelbrock on the 350 in my biscayne, and while it always ran good i would have rather had a 650 holley on it.

having had both i prefer a holley over a edelbrock any day. not that there was anything wrong with the edelbrock, but i am much more comfortable tuning a holley. in my opinion the holley design is just simple and more tunable.

yeah everything i see says go for a 650 holley.

is it possible to put a double pumper on a car that currently uses vacuum 2ndarys?

i read that i shouldn't use a double pumper on an automatic car, but hte double pumper will make the car really kick at WOT, what is the truth?

You can use the double pumper on your automatic car but it might require some foot control if the converter is stock.

Short answer: Either a 600 Edelbrock, or a 600 vacuum secondary Holley will be fine.

Mike

if you're not having any problems with the Edelbrock, then it will be fine. although anytime you can upgrade it to a Holley you'd be better off, IMO. unless you've got a 3.73 gear and at least about a 2500 stall, i would stick with the vacuum secondary carb. the main benefit of a dp carb is better tunability and that second acc pump, which i've always found out makes more difference in the first 60ft than on topend. but your motor has to be able to take advantage of the extra shot of fuel. and without gears and a stall most 350's just can't swallow it. basically, just stick with VS carbs until you're ready to start racing it alot.

IMO it will be a little on the smallish side; not by much, just a little. But it shouldn't be so bad that it requires immediate attention.

I'd suggest running what you've got and seeing how it does after the changes, before swapping it out. If it seems like it reaches a point where it winds up to some RPM and seems to suddenly get "stuck", then that might be an indication to get a bigger one. Although, that will depend on your gears; and also, with that cam and the small-tube headers I seem to recall that you have, it may very well be, that the engine won't ever reach that RPM in the real world, for other reasons; in which case the small carb might actually make the car go faster than a larger one, and use less gas and drive better on the street as well.

If you decide to replace it, try a Holley instead of the Carter; something about a 650. I'd also suggest manual secondaries, especially if you have a stick shift, or a real loose converter, or a real high-ratio rear gear, or you can resist the temptation to just slam it to the floor from a stop and instead can roll into it gently.

IMHO, double pumpers ( DPs) are best suited for high stall or clutch applications where the engine can see some rpm right away. In low stall applications, high gear etc, the vacuum secondary allows a controlled amount of air to the engine, which the engine has an easier time using while building rpms. Car weight would also affect the choice, a lighter car allowing easier rpm building and therefore able to use full carb cfm earlier.

I'd keep a known running carb on the engine until after the new cam is run in. It'll ensure an easy, quick start and allow you to run that cam in good without worrying about carb settings.

ok if i were to upgrade it wouldnt be until febuary probably. i ahve a 3.73 rear but i dont know what convertor is in there, all i know is that it is a b&m