Engine Swap Help

I'm new to this site and joined in hopes to have a few questions answered. I recently purchased a 1988 Firebird with a 2.8 in it. It has a bad vibration at high RPM's. Its an automatic trans. Does anybody know what the problem could be?? And second i would like to drop a 350 in it, would it line up to the Automatic Trans (with overdrive) that i have now or would i have to get a new trans as well?? Thanks for your help!

The 350 should line up with the current Trans just fine; just in case, what transmission do you have? Also make sure the Trans can handle the additional power of the 350.

Actually, I don't think your transmission would bolt up to a 350. The transmission you have is setup to bolt up to a 60 degree engine. If you were to try to bolt it up to a 350, which is a 90 degree engine, then the bolt patterns wouldn't match up correctly. Plus, you would probably be better off if you swapped out the tranny. That way you wouldn't have to worry about how long it will hold up until it gives out. Since the transmissions that come on the V6's aren't as strong as the ones that come with the V8's.

I'm new to this site and joined in hopes to have a few questions answered. I recently purchased a 1988 Firebird with a 2.8 in it. It has a bad vibration at high RPM's. Its an automatic trans. Does anybody know what the problem could be?? And second i would like to drop a 350 in it, would it line up to the Automatic Trans (with overdrive) that i have now or would i have to get a new trans as well?? Thanks for your help!

check the driveshaft and u-joints for the vibration...

My 85 had a 2.8 with a 700r4. The bolt pattern on the bell housing wouldn't line up on a small block. Think you'll have to find a tranny out of a v8.

Thanks everyone. Reading other posts it looks like the 3.1 and the 3.4 will line up to my current trans. I don't know what trans i have, is there an easy way to find out?? I just know its an automatic with overdrive.

As for the vibration i will look at the drive shaft and the u-joints. I was also told it could be the Harmonic Balancer or the torque converter.

I really like the car and would like to restore it. It looks really good now although time has taken its toll on the interior and is starting to on the body. I'll take some pics and put on here when i get a chance.

u can change the bell house easily enough..
i was pretty sure 700r4 bolt to small block..
my friend has a 305 and his tranny is a th200 the same tranny thats in chevettes .. i found that amusing.. really weak trans..

also its a 3rd gen v6 before 90s so im pretty sure those v6s are identical to v8s only the have 2 cyl lopped off... run the casting numbers? figure out exactly what u have.. maybe look at sum interchange books online otr whereever... im not entirely sure if they are the same as blindxeyed was saying.. the if ur tranny is a 700r4 u should be able to handle 375 hp without problems and i dont think ur gonna get that hihg with out a performance engine.. or sumthing special.. my oppion atleast

The THM700-R4 for the 60 degree engines will NOT bolt up to the V8s. Nor can you simply change the bellhousing, as it's "integral" with the case. The unit from a 4.3 V-6 WILL bolt up to the V8.

ok ok... but im still right 700r4 will bolt up using an adapter plate ;) .. never done it but appently its not worth it.. so mrpbody is right..

also its a 3rd gen v6 before 90s so im pretty sure those v6s are identical to v8s only the have 2 cyl lopped off... run the casting numbers? figure out exactly what u have.. maybe look at sum interchange books online otr whereever... im not entirely sure if they are the same as blindxeyed was saying.. the if ur tranny is a 700r4 u should be able to handle 375 hp without problems and i dont think ur gonna get that hihg with out a performance engine.. or sumthing special.. my oppion atleast

All V6's from the 3 gens up to mid 1995 fouth gens (the 2.8, 3.1, and 3.4) are all 60 degree blocks. So the tranny from those won't be able to connect to a small block.

Whats the word on the 3.4 V6?? Is it a reliable engine? Is there a big diffrence between it and the 3.1 V6? I had a 3.1 in a grand prix and that thing was awesome. So i'm thinking about putting a 3.1 in it.

Thanks for the info guys

i didnt mean to question ur knowledge of v6's i heard from sum ppl the they are the same except for 2 cyl.

what im saying is that the 700r4 transmission will bolt up to a small block it has bedone on many cars and continues to be done.. thats all nothing more.. if u still dont believe me i can show you

Whats the word on the 3.4 V6?? Is it a reliable engine? Is there a big diffrence between it and the 3.1 V6? I had a 3.1 in a grand prix and that thing was awesome. So i'm thinking about putting a 3.1 in it.

Thanks for the info guys

IMO, there's nothing wrong with the 3.4 V6, it's an extremely reliable engine. Except for the fact that it doesn't generate alot of power as its 3.8 predecessor. In fact, over the course of this next year that I'm taking off from school. I plan on rebuilding my entire engine, put on tranny oil cooler and a shift kit, an aluminum driveshaft, and completely upgrade my entire rear end by getting posi and rear disc brakes. Oh, and I left out the fact that I'm going to slap on some twin turbos. Alot of people would think I'm dumb for wanting to do this, when I could get all that money and put it into a V8. But seriously, how many people have actually seen a souped up 3.4? Probably not very many.. if any.

But back to your question. Yes, there is a huge difference between the 3.1 V6 in your Grand Prix, than that of 3.4 in the Firebirds. That 3.1 is designed specifically for FWD vehicles. As the 3.4 in the Firebird is for RWD vehicles. That 3.1 has DOHC, as the Firebirds 3.4 has 1 camshaft and uses pushrods. I could go on and on. But all in all, the key difference you'll notice is that the 3.1 has DOHC. If you were to try to put a 3.1 like the one out of your Grand Prix into a Firebird, then that would require ALOT of custom fabrication, and in the long run, just wouldn't be worth it.

And in case you're a little confused right now. There were 2 different types of V6's. Most GM fwd vehicles back in the late 80's and early 90's that were V6's came with DOHC (such as 3.1's, and 3.4's, and possibly the 2.8's as well.. not sure). While also at that time, there were 2.8's, 3.1's, and 3.4's in the V6 rwd vehicles, but they had one single camshaft that used pushrods, rather than the DOHC in the FWD vehicles. So yes, a FWD and a RWD vehicle could have the same size engine, just not the same exact engine. A Firebird could have a 3.4 V6 (Pushrod), while a Grand AM GT could have a 3.4 V6 (DOHC). The main difference is that the Grand AM GT was FWD had about 40 more HP than the 3.4 in the Firebird. That's the only disadvantage to the 3.4 in the Firebird.

Let me know if I lost you, I'll try to explain it a little more clearer. I just got off work and my mind is just rambling off.


i didnt mean to question ur knowledge of v6's i heard from sum ppl the they are the same except for 2 cyl.

what im saying is that the 700r4 transmission will bolt up to a small block it has bedone on many cars and continues to be done.. thats all nothing more.. if u still dont believe me i can show you

Oh, no man. I believe you, I've seen it done. I was just letting you know what V6's were the 60 degree engines. Thats all. And pretty much the only V6 that I've seen that's nearly identical to a small block is the 4.3 V6 that comes in s10's. It's basically a V8 with 2 cylinders chopped off. Everything on it is identical to that of a small block.

Thanks for that info, it was very helpful. I'm ok with cars but i'm definately not a car wiz and I thought a 3.1 was a 3.1. lol I was not aware that the motor could be the same size but worked diffrently. So I need to make sure I get a motor designed for my car and just not any old car. Now I know you explained the 3.4 in the firebird is much diffrent from the 3.1 in the grand prix, but what about the diffrence between the 3.1 in a firebird and the 3.4 in the firebird?? The reason i'm asking is because i'm having a tuff time locating a company that offers a 3.4 motor for the firebird, but they do offer a RWD 3.1. Would that motor be built the same as the 3.4?? And power wise is there going to be much of a diffrence?

Thanks again for your help. I'm learning a lot, although i can see i have much more to learn. lol

Thanks for that info, it was very helpful. I'm ok with cars but i'm definately not a car wiz and I thought a 3.1 was a 3.1. lol I was not aware that the motor could be the same size but worked diffrently. So I need to make sure I get a motor designed for my car and just not any old car. Now I know you explained the 3.4 in the firebird is much diffrent from the 3.1 in the grand prix, but what about the diffrence between the 3.1 in a firebird and the 3.4 in the firebird?? The reason i'm asking is because i'm having a tuff time locating a company that offers a 3.4 motor for the firebird, but they do offer a RWD 3.1. Would that motor be built the same as the 3.4?? And power wise is there going to be much of a diffrence?

Thanks again for your help. I'm learning a lot, although i can see i have much more to learn. lol

There really isn't much of a difference between the 3.1 and the 3.4 in the firebirds. They're both in the same 60 degree block family. The only difference between the two is obviously the cubic inches, and the intake. The 3.4 is basically a bored and stroked out 3.1. Not really much more to it than that. I'm not sure as to how much Hp and Torque the 3.1 generates. But the 3.4 generates 160 HP and 200 Touque at the flywheel. So if I were to guess, I'd say that the 3.1 makes anywhere from 120-140 Hp, and somewhere between 160-180 Torque. But I'm just guessing at that, so someone please correct me if I'm wrong. If you're looking into buying a 3.4, then you can probably find a reasonably priced one on eBay. ebay's your friend, it's always the first place I look when I wan't to buy a part. Good luck and let me know if there's anything else I can help you with.