I have a 1981 Trans AM Turbo in need of a new engine.Is a Chevy 350cu/in better than a 400cu/in for it?

Question

I have a 1981 Trans AM Turbo in need of a new engine.Is a Chevy 350 or a 400?
Someone has been telling me that the 400 has heating up issues. And is a 350 with a roller cam going to out perform a 400?
and which is the more reliable and easier to mantain of the two?
Thanks

Answer 1

A 400 and a 350 are the same engine. The 400 jsut has a bigger cylinder or piston hole. If you want some advise, use a 350 "Four Bolt Main with 350 heads. Have the "Intake Valves" bored over to the 400 "Exhaust Valves" size. This increases the amount of fuel to be compressed per stroke. Then use a 1979 Z-28 Cam. Use a Low Profile Cast Iron Intake and use a Quadra-jet Carb. Use a Cyclone steel/chain and gears. A standard shift is more powerful.
The 400 overheat and crack easier. The Exhaust Valves will tolerate more heat than the intake valves. A 308 Limited Slip Rear/End Gear is the best for in town and highway. I would also use coil springs on top of the leaf springs to stop the sagging of the rearend of the car. A Bendix Clutch is the best. Hope this helps. Herbert West III

Answer 2

the 350 and 400 are not the same engine lmao


the 400 is a siamese cylinder engine, and due to this the water jackets are larger around the cylinders and bulge outwards on the sides of the block, also they are externally balanced unlike all other sbc engines
and the cylinder heads have extra holes in them that all the other sbc heads do not have


the 400sbc is one of a kind unique but it it the same bellhousing bolt pattern as all the chevy v-8 engines 1955-'95

they dont have a coolling issue if the water pump and radiator are not old and are in good shape, this is a common myth started by ppl who are too cheap to replace their old parts with new ones when they are in too bad of shape to keep an engine cool

if you can find a 400 then get it, if not then go with a nice 350 or 355 or maybe even stick a 307 crank in the 350 block and have a 327,

you will need a better rear axle ratio most likely, as all these cars usually had a crappy ratio such as 2.73 and 3.08, this kills performance really bad, so you will have to watch what cam ou put in the engine depending on the axle ratio

your t/a should have had the pontiac 301 in it, if so then you wont be able to bolt a sbc engine to the transmission you will have to find a chevy transmission,

some th350 trannies do have 10 bolt holes however so they bolt to all the gm engines, 90 degree ones anyways, thats 3.8L rear wheel drive, and all the straight sixes and all the v-8s's

i have a really good running nice shape 400sbc in my 77 pickup i might sell it is still stock factory untouched and i daily drive it, i would sell it complete minus the brackets and pullies for 500 bucks,

good luck

Answer 3

Pontiac 400 can put out some great numbers but parts are a little more expensive to find, especially performance parts. If budget is a concern then go with the 350, if it isn't then keep the T/A all Pontiac, and when you are ready to sell, you will have much better luck.

Answer 4

bigger is always better. i have a 400 sb in my car (78 regal) that is bored and stroked to 421ci and have no problems of overheating. the main difference in the motors is hp. an torque output. if both motors are built the same the 400 is going to kill the 350 on the dyno. just watch the red line with the 400, it has a longer stroke than the 350. (3.48, in the 350. 3.75 in the 400) .

Answer 5

Thats a good question. 400 CID motors are getting more rare. I would suggest going with a 350, as they are cheaper and parts are a dime a dozen. Also you can make serious horsepower with a 350, if thats what you are looking to do.

Answer 6

IMO-I would go with a small block 400 IF U can find one & IF U can find a machine shop that will drill & ENLARGE the CENTER ports on the Intake manifold & maybe the heads.BUTT U need 2 find SOMEBODY that knows (CHEVY) smallblocks & has done that B 4.

Answer 7

400's have thin cylinder walls and are prone to overheat. Just 20 years of experience talking

Answer 8

i could have it towed on your storage the place you may artwork on it at your spare time, i could drain all the previous gas out and put in sparkling and alter the gas clear out as this could be assorted your undesirable working issues, additionally substitute the plugs and wires and distribuator cap and rotor, as for the brakes i could get it domicile and do an entire brake activity on it and flush out all the previous brake fluid and put in new fluid and that way you would be waiting to work out if the calipers are frozen.