hey everyone, im starting to plan a 496 build for my 73 big block car. the engine thats in the car now is a 402 from a 71 chevelle, ls3 i believe, at least i know it has oval port open heads. it runs great, but doesnt have the power id like. PO said it was rebuilt in the last few years, im guessin it was a fairly vanilla non performance build

currently i have a perfromer 2.0 intake and a holley 670sa carb. ive got about 3/8" space under the stock hood w a 2" drop base and a 3" air cleaner.

by my measurements if i went w a performer rpm or air gap when i built the 496 i would need a bit more hood clearance, less than 1/4 inch. i might get it by trying different style aircleaners and bases, or a shorter cleaner, but this will bring the lid down even closer to the carb vents and choke tower; and honestly i think the airflow is probably pretty restricted now even if it meets holleys critera for space above the vent tubes etc.

should i plan on using the performer, or will it give up too much compared to the rpm/air gap? am i missing any manifolds that are close in height to the performer that are worth looking into? i havent found much good said about the torker II so its off the list atm. the few tests ive found online show it doing no better and often worse than the performer.

is it reasonable to get an air gap and mill 1/4" off the carb mounting surface? i have a buddy w a mill who can do this for free.

should i consider one of the holley carbs without a choke to improve airflow? bet thatll be a PITA when its cold, but id do it for the airflow improvement if it seems the benefit would be decent

i dont race, this is simply a hobby car fair weather driver. i wont be changing the hood or installing a scoop. i like the cars' looks as it is

budgets no real concern, im thinkin 5kish. i plan on slowly collecting the parts and building the engine myself; ive got a few friends who have done this in the past, a good machine shop nearby, tons of time, and i like to read the books..

im thinkin oval port iron heads to save a few bucks, i see them around here reman'ed for under 1K per pair

any help appreciated

 

loose the spacer, you have no spare room to work with,
you need a min. of 3/4" from top of breather to your bowl vents.
don't go crazy on the Cam, or you loose good vacuum which you need in a Vette.
you did not mention which hood your running, I assume a BB oem hood.

 

by spacer do u mean between the carb and manifold? if so theres none there now

3/4" is about what i have from the vents. actually a bit more since the air cleaner lid is dished. if i lay a straightedge across the cleaner w the lid removed i have the 3/4 inch. yep, i dont want to be any closer

when the day comes the cam will be fairly mild... i really havent given a specific one any thought yet. its a ways down the road

im using the stock 73 hood, which i believe is the same height for both small and big blocks made that year

thx!

 

A lot of 496 awnsers here.

http://www.chevelles.com/forums/forumdisplay.php?f=13


BILL

 

you won't have enough room under a small block hood, with a Performer intake on a BB.
without modified Air Breather.
BB Hood gives you slightly more height mostly at the front of the breather.
I estimate about 1/2" height gain with a BB hood.
This is why I choose a oem Aluminum manifold, they have a much lower profile.
Check your heights carefully, it stinks to not be able to close the hood !
keep your choke on a driver, not worth the hassle cold.

 

I posted on your thread at TC but.... I'll reiterate it here for yourself and others..

Go here and order you a nice 468 (570hp) or 496 (650+) for much cheaper then you can build one....
http://www.vortecproperformance.com/...binations.html

Get an L88 hood. Run the RPM air gap intake with an L88/LT1 drop base air cleaner and 3" filter. You will need to get a carb with the choke horn removed...or better yet get an HP style carb like a 950HP.

Air flow is the biggest problem in a vette. Anything you can do to improve air flow to the carb is a must....especially if you are talking 500+hp...

BBCs are a lot of fun when built/setup right....then you will start breaking everything from the flywheel back...