motor job redo 400 or take 455 from motorhohe

[chuckynmisty]

ok i posted this same question on the other site but i will ask here also. took old 400 out of 81 trans am was not started in 4 years. have 350 in it now so its driveable. question should i redo the 400 or take the 455 out of 70something motorhome was told as its from a motorhome going into a car it would have alot of torch would not need alot done to it . was also told could twist body of car. your thoughts please and thank you

[chevman57]

455`s were put in the cars for many years so i wouldn`t worry too much about twist. Although if it`s going into a T/A you might consider installing frame connectors to eliminate the unibody flex.
Terry

[trifive]

This may not even be close to what you are talking about but I will post this just for info.

I had a 70 Something pontiac grandpre, with a 400 engine with an automatic trans, The Transmission failed so I went to a buddy's house and got one out of another car I think a gto, the drive shaft had to be shortened or lengthened i don't remember which, but the trans was free and I was broke as usual, I don't know if it was a 350 or 400, but I did notice that with the differant Transmission that the speedometer read wrong, gave wrong speed I guess it was due to the differant trans gearing.

And I know you were asking about engines, but just thought I would share.

Otis

[walt bauer]

455`s were put in the cars for many years so i wouldn`t worry too much about twist. Although if it`s going into a T/A you might consider installing frame connectors to eliminate the unibody flex.
Terry


I agree. Pontiac used the 455 in T/A's from '71-'76.

[ndpolston]

dont have much to offer other than im sitting on a 400/400 out of a 79 camper special pick up that i havent done anything to yet except to get the chevy book on motors and read it.

[mokicruz]

I've ran Pontiacs for years they all have a lot of torque . The head design makes a faster and more complete burn than the other manufaturers. Like chevman57 said frame connectors are sold by most hot rod shops . The differential is a 7.5 and the suspension is pretty lite duty on the 81's . I would save the 400 for a stronger body and frame. Bruce Fulper's SS/D was an 82 and it ran in the 9's. He rebuilt the Diff once a year he said. The best power for the 80's would be a new 5.3 or 6.0 Aluminum head Engine. They have great power and get good mileage plus make it lighter on the nose end. The frame took a lot of work on Bruces car to stay togather going that quick. It all depends on what you want to do with it but it will feel nose heavy with the 400-455 .

[D.S.]

It all depends on what you want to do with it but it will feel nose heavy with the 400-455 .

There's really not a lot of difference in weight of Pontiac engines from 1955 on..

Most iterations had an overall length (to the edge of the water pump pulley) of 28.25 in, an overall width of 27 in, and a height (not including air cleaner) of 31 in (718 mm × 686 mm × 787 mm). Later 455s had a two-inch (51 mm) higher deck height, and were slightly longer overall. Dry weight ranged from 590 lb to 650 lb (270 to 295 kg), depending on displacement and year.

[mokicruz]

Your right but he has a small block chevy in it now it sets closer to the firewall and is Lighter.

[chuckynmisty]

Your right but he has a small block chevy in it now it sets closer to the firewall and is Lighter. the front end is still set up for a big block. with this 350 in it i feel the front end is to high and i had to put higher seats in it so i'm looking strait down the hood and not feel like i'm looking up it.

[chevman57]

Well have you decided to install the 455 into it yet?
Terry

[dseale4888]

I would drop the 455 in it and do like Terry sugested.
Dave

[chuckynmisty]

first i got to bring the car north so i think over the winter i'll get the 455 ready to come out then spring clean it up crome it out but ya i think i'll drop it in

[Thadd]

Just a question..Did the 81 have a 400 Pontiac or a 403 (6.6) Olds motor???

[Cruzr55210]

I'd go with the 455 just for the cubes. Especially in a Firebird, I've seen factory installed 455's. Nothing beats cubic inches when you already have the engine. Torque rules!!!!!