BeefTip

Ive been looking at several cars lately to play around with. I have found a 78 trans am with a pontiac 400 in it(not the olds 403).

I know absolutly nothing about these motors. Does anyone know anything about it...good or bad or whatever.
Do they take to mods well?

cbr954rr

iTrader: (1)

these are very good engines if done correctly,they are basically like a big block chevy,you dont want to rev them much more than about 5500 rpms.they are torque monsters,there torque peak is around 2800 to 3000 usually.go to butler performance for more info on building one,their only real downfall was poor oiling at high rpms and spinning rod bearings,thats why i say not to spin them high like the ls1s.ive owned several old pontiacs,they are a lot of fun you can easily get 4 to 500 horse and 5 to 600 ft lbs out of one.also check out high performance pontiac magazine,lots of info in that mag,hope this helps.

ZONES89RS

iTrader: (25)

cbr954rr is right on track, there are stroker kits and the works for those engines, the heads flow pretty good, the 6x heads from way back in the late60s/early70s were a good set to use. The can make big block cubes in small block size.

ulakovic22

iTrader: (12)

Pontiac's are good motors, but IIRC they are all the same block and it's a 10.2 deck height. There is no small block/big block. Stroke the hell out of it and use some aftermarket aluminum heads and you'll make some good power.

steelcity6

My buddy builds nothing but pontiacs and he is right they make gobs of torque..the 6x heads didnt come out till 75 i believe the aftermarket for it is kinda non-existant though.He just rebiult a 455 with a good street cam and it pushes his landbardge 73 grandprix are well..but he gets tired of me sayin:" you wanna make that car fast put a cheby in it"

bb5401000

iTrader: (2)

You can bore the 400 block and drop in a 455 crank to make it a 455. They'll handle plenty of power but the rods are the weak link. Eagle and a couple others make good forged rods so you can rev 'em up if you want. Another popular thing to do is to stick BBC rods in 'em with a stroker crank. You're risking it taking the stock rods past 5500 rpm (I think they're cast).
As far as heads go, the Edelbrock Performer RPM is the most popular with this motor. They'll make over 500 hp out of the box with either the large or small chambers. There are plenty of outfits that do good port work on them as well if you want to make more power. 6x heads are harder to find (but out there) and by the time you get them machined and ported you've just bought a set of Edelbrocks.
The stock rear main seal is a rope seal. You can get a setup from Butler or Indian Adventures (I think) to convert it to a rubber seal.
Try the Pontiac forums for more info. Those guys are fanatics about their Pontiacs.

RARON455

iTrader: (35)

all of these guys are right, I can attest to the knowledge of Jim Butler at Butler performance, He got alot of my money when I built my 462.
The one little tidbit of info that these guys have not listed, (and they know as well as me) Is you need to expect to pay almost double for all the PONTIAC parts to build it when compared to a small block chevy.
My 69 was a 10 second daily, with the 462 my only complaint was the overheating issue EXTREMELY common with iron headed high perf pontiacs.
I had a 400 in my first bird and it would run hot as hell too. I ended up fixing it by putting lincoln fan on it, there were alot of other tricks involved too.
I love pontiacs, but there are some things you NEED to know.

93ls7z

iTrader: (2)

400 has 3 inch mains and the 455 has 3.250" mains.

bb5401000

iTrader: (2)

Thats right. You can have the 455 journals machined to fit, or you can go with an aftermarket crank.