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Discussion Starter · #1 ·
hello,

I'm new to the forum and to the car world itself. back in July i bought a 1981 esprit with a Buick 3.8/231 v6 (the car specified in my profile). i'd known since the day i bought it that i would eventually like to swap the engine for a more powerful unit, and i've done a bit of research on this for the past 5 months. after looking around on local craigslist i'd found a few examples of 60's pontiac v8 engines in mostly complete conditions that "claim to run" for under $1000. with the amount of time a swap should theoretically take (10 hours to put it in/take it out) at my mechanics rate of $50 an hour, combined with other variables, i came up with a number around $2500 for a complete swap.

the engine that i'm considering is a pontiac 400, and it may be this particular one ( https://seattle.craigslist.org/tac/pts/5350898971.html), but it may be a different one, as some of these have shown up around here for similar prices. i understand that these engines may not actually run, but i am planning to have it gone through and checked out, made sure that it runs.

what i would really like to know is what exactly needs to be done to the car itself to take the swap. i'm trying to compose a list to help my mechanic figure this all out. mostly:

  • will a TH400 fit in my transmission tunnel as-is? if not, what needs to be done?
  • will my stock rear end be able to handle the power of a more powerful (lets say for example, 350 hp) engine? if not, what rear end should i switch to?
  • will i need a new radiator to properly cool the new engine?
  • anything else that i need to change?
 
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Discussion Starter · #3 ·
UPDATE:

i found an entire car, this '70 Le-mans; https://seattle.craigslist.org/oly/cto/5378176004.html, and after doing searches for the individual parts i would need (engine, trans, rear-end, driveshaft,etc), i found that it would be the same price, if not more, than this entire car. i haven't gone to check it out yet, but am thinking of just swapping the entire drivetrain into my car. normally this would seem a bit wasteful, but it has been in an accident and i'm guessing that it has frame damage, otherwise, i would think that the owner would just fix the rest of the damage.. anyways, will these parts actually work in an '81 firebird? i'm guessing that i will need to shorten the driveshaft, but other than that, from what i've found, everything should fit, the rear-end, the transmission (SHOULD fit in my trans. tunnel), and the engine of course.

  • has anyone done a swap like this before?
  • from what i've found, the motor mounts in the le-mans should work in my car, correct?
  • i know i will have to move the battery tray from the passenger side to the drivers (i beleive pontiac engines had them mounted opposite side of buick/chevy engines?).
  • the transmission crossbar should be the same for both cars, if not, the TH200 crossmember should be the same for the TH400, just need to mount it in a different spot?
  • is this all correct? anything else i really need to know about?

any/all info is greatly appreciated. no work has been done on the firebird yet, and the lemans owner has not even been contacted.
 

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I would sure think hard about putting an LS engine in it. I've not done any research on it and won't be as cheap, but it would be way cool. Better mileage, reliability, horsepower, car value.. just something to think about.
 
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Discussion Starter · #5 ·
yeah, i thought about it but what i really do need right now is a cheap swap, had a few mechanics quote me $1000+ (probably closer to $2k) for my v6 to have the ignition fixed (no spark) and it just isn't worth that much, and i don't want to put any more time into that engine. But, this swap would only cost me about $3k in the end. that, plus the fact that i cant actually find any running, carbureted Buick v6's that i could directly swap in, is the main reason i'm doing it. i guess the question i'm asking myself is: why should i pay $2000 for 110 horsepower when you could pay $3000 for 350, and increase the value of the car at the same time?

but i suppose if i were to find someone selling off an LS corvette drive train for a similar price, i'll check it out.
 

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A vette LS setup wouldn't work, the transmission is in the back with a torque tube. Unless you have a busted camshaft or something, S1000 sounds rediculous to fix the ignition system on your engine. I bought a new "chinese" distributor for $36 on ebay for my car. The tranny in that lemans may not be the right length, that would need some research. The engine should fit with the right motor mounts. The rear end I don't think would work, I don't believe the lemans uses leaf springs. You might be able to weld on some brackets, but that wouldn't mean the width and other measurements would be right.
 

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Somehow, I missed this thread. Sorry !

Anyhow, I've read that all '71-'81 Birds came with an 8.5" 10-bolt rear. These are stronger than the 8.2" rears that came in most early '70's A-bodies. A FEW , like the 455HO cars came with a Chevy type 12-bolt. So, unless someone has swapped it out, a '70 Lemans should have an 8.2 rear.

Yes, you can replace the coil spring mounts, with leaf spring mounts. That's what we use to do, in order to put Chevelle 12-bolts into our Birds, for racing. But, if the rear is an 8.2, you're better off to keep your Bird 8.5. You can buy a posi unit and whatever gear ratio you want for it, should you ever wanna make the change. But, again, the Bird 8.5 rear is stronger and more desirable than the 8.2. :yes

In order to install a Pontiac V8, you'll need some motor mounts(the part that bolts to the block) which came in a '75-'81 Bird, with a Pontiac engine. These are unique to the Birds. Those for the other body styles, from these years, look similar, but will position the engine too high in the frame. I learned this the hard way. :(

Unfortunately, these motor mounts have become scarce, and many are asking ridiculous prices for 'em. I've seen some on Ebay for $150 & higher. :(

But, if you ask around and maybe place a want ad on some of the Pontiac forums, you can probably still locate some for under $100. Maybe somebody on this site has a set for a reasonable price ?

There is a left and a right. The numbers for each are stamped on each mount. The numbers are 496892 & 496893.

Then, the part of the motor mounts ("clamshells") that bolt to the frame are the same for several types of V8's. Not sure about the V6 tho. Anyhow, these V8 mounts must be bolted to the frame, in the correct position. Same mounts used on both sides.There are several sets of holes. I've read that the larger Pontiac engine will use the same holes as the 301, in the '81 model Birds. So, a '70-up Pontiac 400 should work, using 301 mount locations. Maybe some of the guys who have done this, can explain and/or show pics of exactly which holes to use for the frame mounts. :smile22:
 

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Discussion Starter · #8 ·
so from what i'm understanding;

  • i need firebird-specific (301) engine mounts,
  • i need to make sure that the TH400 out of the lemans is the right length. what is the right length; the same length as my current TH200?
  • if i want to use the rear axle from the lemans, i need to convert my car from leaf springs to coil springs (or convert that rear axle to use leaf springs), and make sure that it's the right length for the width of the car
  • i should use my stock rear axle because it's stronger than the one in the lemans (this seems odd, because why would they use a stronger rear end for weaker engines, especially a v6?)
 

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so from what i'm understanding;

  • i need firebird-specific (301) engine mounts,
  • i need to make sure that the TH400 out of the lemans is the right length. what is the right length; the same length as my current TH200?
  • if i want to use the rear axle from the lemans, i need to convert my car from leaf springs to coil springs (or convert that rear axle to use leaf springs), and make sure that it's the right length for the width of the car
  • i should use my stock rear axle because it's stronger than the one in the lemans (this seems odd, because why would they use a stronger rear end for weaker engines, especially a v6?)
(1) Any Pontiac 301, 350, 400, or 455 mounts, from a '75-'81 Bird.

(2) I'm not exactly sure of the exact measurements. But I've read that the TH350 and TH200 are the same. There are short and long tail TH400's, All the A-body TH400's will be short tails. But, someone could have swapped a short for a long. I do know that the TH400 has a larger diameter rear shaft. So, it will require a bigger front driveshaft yoke, For these reasons, you may wanna consider finding a TH350, rather than the TH400.

(3) Convert that rear axle to use leaf springs.

(4) These 8.5's are what are called "corporate" rear ends. They were used in LOTS of GM vehicles, therefore were mass produced--by the millions, probably. So, it was a money saving deal. Most all '71-'81 Birds and Camaros got 'em. I think they were also used in '73-'77 A-bodies, Grand Prix. and many others.

Then, for the 3rd gen Birds and most other GM cars, they switched to a smaller, weaker 7.5" rear. These were 1st used in the Vega, and probably Astre, in the mid '70's. They were also used in other low powered vehicles. The site I'll link next says that the 7.5's were actually used in some '81 F-bodies. Most sites do not agree with that. So, you need to take a look at the rear in your car, to make a positive ID on it.

http://www.chevydiy.com/history-and-identification-of-chevy-10-and-12-bolt-chevy-differentials/
 

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Discussion Starter · #10 ·
i've been looking around for some 75-81 pontiac v8 mounts, and i can't seem to find any whole sets, at least not for under $200. would it be possible to have some custom made, perhaps by a local shop? from what i understand, the problem is that earlier (70-74 mounts) will have the engine sit too high in the engine bay to clear the hood. could i possibly modify these earlier mounts to have it sit low enough? i've checked multiple firebird-specific sites, ebay, local craigslist, etc. should i try some diy/modification stuff, or should i just spend the $200 and get a legitimate, original set?
 

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No, don't pay $200 for 'em. :no There are a lot of guys who will sell some cheaper than that.

The Pontiac site with the most members is probably PY. And TA Country has a LOT of 2nd gen guys. A simple want ad on either site will probably find you a set.

Even tho these are getting harder to find, you should be able to find a set for $100 or less. I'm thinkin $50-$75 would be reasonable. I'll post and see if I can locate some, If not, I'll contact my engine guy. He can probably find some. He's an A-body guy, but knows a lot of Bird guys.

OK, I posted it on 3 Pontiac sites. Should locate a few sets. :smile22:
 

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My question is, why would you want to put a 301 into your bird? They are pretty anemic. If going to all the trouble to convert your v-6 car to v-8, why not a 400 or 455. Even a 350 would be a decent choice.
I believe he said he was lookin at a 400--not a 301.

"...the engine that i'm considering is a pontiac 400..."

But, I've read that the 301 mounts will also work on the larger engines. :smile22:
 

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OK, I've located 2 guys who think they have a set and will check when they get home. One of 'em said that if he has the correct mounts, he'll take $50 + shipping. I figure it should cost no more than around $10 or so to ship USPS. :smile22:

Another guy said he definitely has some, but ask what the budget was and didn't give a price. So, he may be a price gouger--don't know. But if the others fall thru, I'll PM him and get a price.
 

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Good luck! Unrelated, different setup.. My Dad and I tried the "swap" with a 1982 V6 Firebird back in about 1991. We put a 455 in it. So many problems.. Never could get the cooling system right because there wasn't enough room for any electric fans or a big enough radiator. We called it the Blue Money Devil. We never did get it running right. Still sits on my uncles farm in Polo, MO.. giant rust bucket. Big waste of time and money. Even has a 2-speed power glide in it that went to waste
 

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Yeah, those 3rd gens make it a bit more difficult. But it can and has been done successfully, many times. There are high performance alum rads and fans in all sizes, that will work in most any build.

But, the '81 Birds are still 2nd gen. So, most of the same parts that installed Pontiac V8's in any of the '77-'81 Birds, will work for the swap. :smile22:
 

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OK, this guy over on the PY forum has a set, and he'll take $50 + shipping. Here's a copy of our messages.

"

Pretty sure I have a set, will double check the numbers when I get home

$50 plus shipping

Thanks
Dave

OK. thanks ! Let me know if you do & I'll pass on the info. :)

Yea I do have them, double checked the numbers
"

So, I told him to get me his contact info and I'll get it to you. So, when I get it, you'll get it. :smile22:

[/QUOTE]
 
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