85 Grand Prix LE with a pontiac 400

[slick85gp]

I was just curious if anyone has ever seen some one stuff a pontiac 400 or any pontiac block into this type of car i was curious if any of you think it could actually be done if you do could you give me some tips and tricks i would really appreciate thanks alot guys

 

[SafariWagon]

Check out the engine swap section. Lots of people have done the swap. Basically engine mounts (the ones that bolt to the block not the frame) Are the hardest component to come by. You need ones from a 301 Pontiac powered car. Only in 1978-1980 lemans or Gran prix. Or buy one already done.........http://mankato.craigslist.org/cto/1564103093.html

 

[shotgun]

301 engine mounts are the ticket. I may have a set left, sold most of them off.

Exhaust does become an issue depending on how much power you are planning on making.

Cutlass below (same chassis) has a destroked 455 in it and seems to do ok.

 

[Bonnewagon]

Do it! The body can handle it, even the 7.5 rear as long as you respect it. I had a 70' GTO 400 in my 81' Malibu for years with a Saginaw 4 speed and 7.5 rear with S-10 type part time posi and Crane HMV278 cam. I wasn't gentle but I wasn't insane either. Nothing ever broke. An automatic would be even gentler. 301 mounts/perches and Firebird 400 head pipes fit right up. I believe Hooker made headers for the 400 in an A/G body but they may have discontinued them by now. The 400 is a lot heavier and I used Firebird front springs to hold it up. Tons of fun to drive.

 

[gto78]

Do it! The body can handle it, even the 7.5 rear as long as you respect it. I had a 70' GTO 400 in my 81' Malibu for years with a Saginaw 4 speed and 7.5 rear with S-10 type part time posi and Crane HMV278 cam. I wasn't gentle but I wasn't insane either. Nothing ever broke. An automatic would be even gentler. 301 mounts/perches and Firebird 400 head pipes fit right up. I believe Hooker made headers for the 400 in an A/G body but they may have discontinued them by now. The 400 is a lot heavier and I used Firebird front springs to hold it up. Tons of fun to drive.

I wish mine would have held up, I went through 4 rearends with my 400/400 combo. Finally the 8.5 rear has been indestructable.

I've spent years looking for headers that fit the car and have no success. I can only find SBC headers. We bent up a pair of headers made for another car and made them fit after some denting.

The engine swap from removing teh 301 and installing the 400 caused the front end to just about bottom out. I installed sprint car circle track springs with a 900 LB spring rate. The springs match the weight of the engine perfectly. It sits a little low still and doesn't bounce at all. When you push down on the car the front end is like a brick, it doesn't flex much it's beautiful. Also it handles really nice and rides great I love it.

 

[adam6640]

To;
GTO78, any chance you could post some pics of your 79 grand am ?

 

[pontiacgp]

a sprint circle track car does not use coil springs... the use two torsion bars

 

[gto78]

To;
GTO78, any chance you could post some pics of your 79 grand am ?

I have a few pictures in the "photos" section. They're not that good of a pic, haven't had too much time lately.

As for the "Sprint" circle track springs.... I don't remember the specific "Class" of racing the springs were designed for when I bought them, that was 10 years ago. All I can remember is they were made for late model vehicles that are raced on a circle track or road course. The place that sold them mainly sold springs that were in the 1200 LB to 1800 LB spring rate, and had a limited number of 900LB rate springs. The factory Grand Am springs were somewhere around 300LB rate and when not installed they were around 6 inches taller. The ones I installed fit in perfectly, just a little compressing (maybe 1/2") and when I let the weight of the car settle on them they only drop about another 1/2".

 

[84GP455]

I put my 455 in my GP back in 1991 way before it was popular with little modifications and it's still taking a beating to this day!

 

[MrHarley123]

This swap is very easy to do. I currently have a 400 stroker(461) under the hood of my 79 grand prix. You have to know what year block you have first of all because their are different motor mounts for the blocks built before 1971 or 72. You then can figure out other small details. The block mounts are very easy to get from butler performance out of TN. Headers are another story. You only need headers if you are going to race it. The stock manifolds will be more than good enough for a mild street build. If you really want them order headers for a 68-72 gto and bang them into place or a set of 3 tube headers will also fit. Shorty headers are also an option from summit, or you can order factory headers from ram a.i.r. restorations. You can contact me on any pontiac questions on this swap for a g body. It was a ruff road for me to get my car completed but well worth it. I can also help you with any performance mods also.