since i already have dual exhaust i am planing of putting headers on just after gear swap, i was thinking about 3" exhaust and ideas? another Question i have is after the gear swap would you put headers on or go with a different intake and carb

Jim, whats on it now for intake & carb?? think I heard it had a Holley from other post?? If it's got the stock intake, dump that & go for after mkt. Exhaust, you have to watch you don't go "too" big, as the engine needs "back pressure" to make horse power on street engine!! One of my car club members yrs. ago put 3" on his street rod, it ran like a DOG on 3 legs. after alot of tries else where, he tore it off & put the 2 1/2" on & the car just LIT right up!! OK don't know what Alta. like for emmission insp. but here in Ont. we have to make sure it's got all the original "crap" on it, so make sure you have EGR. AIR pump etc if they check out there

agreed with pete.

it has a holley carb not sure what one but i imagine its just a replacement . so i should change the intake what would you recommend. would my stock exhaust be ok, it was just done 2yrs ago i think its 2 1/4

Edlebrock "air Gap" or performer or a Offenhauser but make sure you get a "dual plane" manifold for a street use car. I'm still assuming this 400 is a US block & not a Chevy 400??? Dual plane is two levels under the carb base. When you look into manifold where carb sits one side will be a little deeper than the other side, this seems to work better on the street!!! I'd say leave you exhaust the way it is,no sense throwing $$$ away. I've got 2 1/4" on my 64 Catalina, still running stock manifolds [ cause no body makes a header to fit the body style] without pounding the "crap" out of them to get a "fit" a set of "mid" 3's gears out back, mid range CAM & you should have a "decent" performing car. You should find out what size Holley's on it, some guys go with the "bigger is better" but an over carburated engine won't RUN worth a CRAP!!!!!

bigjames wrote:

---

it has a holley carb not sure what one but i imagine its just a replacement . so i should change the intake what would you recommend. would my stock exhaust be ok, it was just done 2yrs ago i think its 2 1/4

---

I wonder how much "faster" a intake will make a stock 4200-4400 lb car go?

 

Carl, "at least ' 20sec. "quicker" in the 1/4 mi" Honestly I don't know but the throttle response will be noticable, & maybe a bit of fuel milage gain. What you want to achieve here is to get the engine to run in it's best "power" zone, get it to "Breathe" The US Pontiac 400 had a very poor Intake on it.

take measurements if your looking at an air gap. they are quite a bit higher than most intakes, resulting in hood clearance issues. thats the intake i,m running in my avatar picture. great intake though. the performer is also a good intake.

she does have the us motor and 6x in on there too so your saying just leave the exhaust and not get headers? i just want to open her up a bit without doing a engine rebuild Thanks so much for all the responses i really appreciate this!!