I have a 85 firebird 2.8 v6 that i want to swap to a 350.What all would i need right down to the motor mouns.CAn i use the same tranny,700r4?Stuff like that.
Thanks

 

I did the v6 to v8 swap last winter. I had 2 complete cars though. 90 body\87 Formula guts.
You didn't say if you were going to carb or fuel injection; but here goes.
No you can't use the v6 tranny; not the same bolt pattern. It wouldn't be strong enough anyways.
You'll need:
front springs from a v8 car.
v8 fan shroud,
v8 radiator,
I can't remember if the frame motor mounts are different but they will have to be moved, the holes should already be drilled in the crossmember though. When you change the front springs would be a good time to move the frame mounts because there are 3 nuts inside of the crossmember that are really a pain to get to,
v8 motor mounts,
v8 transmission,
v6 transmission crossmember should fit, but I don't remember if the rubber mount is the same,
the driveshaft should fit,
the shifter linkage should be the same,
you'll need a v8 speedometer, I don't know what the difference is but My v6 cluster had a tag on the back with "for v6 only",
If you are going with fuel injection you shouldn't have to change anything in the gas tank, your electric fuel pump is in there(if you have EFI),
If you are going to carb you might have to drop the gas tank and put in a nonelectric pickup, use mechanical fuel pump on block,
you may have to move the fuel lines from one side of the trans tunnel to the other side,again depending on whether you are going to carb or FI,
I had to exchange the complete wiring harness from the headlight motors all the way back to the tail lights, but that doesn't mean you will.
I'm sure I left out something, but this should get you started.

 

I did an emissions-legal swap, which is much harder than a non-emissions-legal swap. You need to know before you start which you are going to do.

You don't need a V8 speedometer, you need a V8 tachometer.

You do need to switch the engine wiring harness, but not the headlight harness. I switched all the dash harnesses & equipment including the instrument cluster because I had them and didn't know what all changed (diagrams indicated differences, just easier to switch it all).

You'll need throttle and throttle valve (to the tranny) cables, as well as cruise if you have that. V8 front sway bars are larger than V6. V8 cars also have some bolt-on frame braces that V6 cars don't have. If you stay with computer control, you need the V8 ECM and all the sensors.

If you now have fuel injection but go to carb, you can keep your in-tank pump by putting a 3-port regulator in to lower the pressure to about 6 psi. The fuel lines are on the driver's side frame rail on V6, switch over to passenger side by going over the transmission on V8. The V8 cars have a clamp to hold the line up in the tunnel that V6 cars don't have. I fabricated lines to go across the front of the front cross member.

Don't forget a radiator fan. Power steering, AC, smog pump brackets and lines are all different. Exhaust all the way to the bumper needs to be changed.

If emissions legal, you need the V8 stickers under the hood.

The one piece of good news is the rear end is fine.

I also had a V8 donor car, and believe that is by far the best way to swap from V6 to V8. It isn't necessarily the best way to have a V8 car, though - getting a factory V8 car is the best way to do that.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

it hurts me that you're going to switch your 85 to a v8, same year as mine and all. j.k. o.k., to tell you the truth after i looked at a v8 swap i decided not to do it, for several reasons,
1. it would cost "me" to much money!
2. This is my first car, and my father was the original buyer in 1985 making it still a 1 owner
3. I wanted to do my best at keeping the car original.

Now, i thought to myself that if i did get a v8 i'd most likely go for a 350 v8, or maybe drop in a chevy ZZ4, no the best idea for that, to me was to get a 305 firebird with a bad motor, and hopefully a straight body, then gank the motor out, beef up the transmission, and drop in the crate. It'd be a lot less work, and going from a v8 to a bigger v8 will also save a lot of money. that's just my opinion. But don't think i'm telling you not to do the swap, or even discourage you, i was just giving my .02.