I was just sort of daydreaming earlier, and I had a thought about one day putting a real Pontiac motor in my 86 Trans Am.

First, is this even doable? I know of one guy in my neighborhood who put a 400 Pontiac in his 86 Grand Prix, so its obviously possible to replace a SBC with one, but thats a G-Body, obviously.

The problems I can think of right now are mainly exhaust related. Does anyone make headers for this engine swap? What about proper motor mounts? Transmission would require either a BOP TH-400 or TH-350, correct?

Im sure im leaving a lot out here, but please post any additional problems you can think of, as well as any insight from someone whos done this successfully. Thanks in advance.

 

Putting a 400 Pontiac in my 87 Camaro. As for headers, I got an e-mail from Dick Duclow... Indian Adventures. I believe its www.chiefmanyhorses.com. Will be ready after the first of the year. I believe they are making the mounts too. You will need the BOP tranny and get an adaptor for the torque arm. Also Will need to shorten drive shaft I believe. Making my own 2 1/2 exhaust ( I work at a tube bending factory ). The stock gears will not handle the power you'll be putting out, will need a 12 bolt or Ford 9. The other problem is goin to be taction, will need to get the power to the ground.
Here are my engine specs:
71 400 +.060 0-decked
BBC 6.800 Eagle rods
custom Ross +030 455 pistons with 1.540 compression height
crank cut to 2.199 on rod journals
block filled to freeze plugs
6x4 heads milled to 81cc for 9.5 compression
HO Racing cam with 542/558 lift and 244/252 duration 114 ls
Harland Sharp 1.65 roller rockers
Holley Street Dominator intake with 2" spacer
Holley 800 4150 series double pumper with 1/2 fuel lines
th350 going to narrowed 12 bolt with 4.56 gears running 16x32 inch slicks

 

I agree to some extent with what Bob is saying....

However....

I don't see how you would need a new rear end.

The 2nd gen f-body ONLY used a 12-bolt rear end in the VERY first year of production, 1970. They offered a 396, 360hp big block in the Camaro, and a 400, 370hp V8 Pontiac motor in the TransAm. ALL the other years, 1971-1981 ONLY came with a 10-bolt rear-end.

The 10-bolt rear ends in the 2nd gen are not THAT different from the ones in the 3rd gen. The only differences realistically are in the manner that they bolt to the frame.

For example, in 1971, they offered the 455 Pontiac V8 putting out 480 foot pounds of torque. The car came stock with a 10-bolt POSI rear-end.

Chances are, you're going to get ahold of a Pontiac 400 with the 6x heads. This, with a Summit Racing catalog will put out around 300-350 horsepower, depending on how much you want to spend. This will bolt up to your stock rear-end (axl) with no problems. I suggest swapping in a TH-350 however. You can do this by purchasing one of those TH-350 conversion kits for the 3rd gen.

The only thing I'd suggest, if your TransAm doesn't already have it, is getting a posi rear-end.



Todd,
1997 Pontiac GrandAm SE
1987 Pontiac Fiero SE/V6
1984 Pontiac Fiero 2m4 SE/WS6
1981 Pontiac TransAm WS6

-----SOLD----- (well... junked)
1982 Pontiac TransAm
1976 Chevrolet Camaro LT-350

 

The Th-200R4 has a BOP bolt pattern allready drilled into it. So you can use that tranny with no problem, I like the over drive option, or you could do like I did and buy a BOP adapter plate, for $56 from Summitt, and have your 700R4 bolt up to that motor. Talk to Spohn performance about any traction concerns...

 

LMAOOOOOOOOOOOOOOOOO please dear *** please tell me your joking right? the 3rd gen rearends SUCK!!!!!!!!! plain and simple ......there totally different from the 2nd gen 10 bolts...


2nd gen 10 bolts use a 8.5 inch ring gear =strong

3rd gen 10 bolts use a 7.5 inch ring gear =weak panzy rearend
trust me...anybody whos ran a decent amount of hp through a stock 7.5 10 bolt 3rd gen rearend will agree,there weak. plain and simple end of story.

ive blown 2 up so far,one with a built 350,the other with a near stock 350. once you exceed around 300hp 300 tq with a 3rd or 4th gen rearend..they dont last long..they pop easy..and dont dare running slicks..]

82ta you forgot mention or dont realize pontiac motors have a assload of tq that 400 will put out probably around 450 ft pnds if not more..depeending on how built... rearend go boom...

KUDOS to bob8748 sounds like you got the hot ticket. i want to do a real poncho swap my self..since i have a transam..

 

desktop dyno... for what its worth, has me about 530 hp with 480 lbs torque... rear end goes boom.
Ford 9 or Chevy 12 bolt
nuff said

 

Evil T/A, MOST Pontiac 400s put out a mere 180 horsepower and had only 325 lbs of torque. That's 100 less addition foot pounds of torque than your run of the mill 305 LG4 V8.

Also, I doubt that the rear ends in the 3rd gen are THAT bad. I see many 3rd gen Turbo T/As running around at Moroso every Saturday night, mostly all with stock rear ends. The rear ends in the 3rd gen usually outlast everything else in the car, including the engine.

 

:nono:

I don't know about the rest of you but I've NEVER seen a "run of the mill" 305 that cranks out 425 lbs. of torque! I believe you are mistaken with those numbers. Try MAYBE 225-250 lbs. of torque.

 

I believe that's exactly what he just said, although not very clearly... should have been "less than 100 additional ft-lbs" or some such. Actually, most 305s in these cars are rated at between about 240 and 255 ft-lbs. which corresponds to the 400's 350 ft-lbs being a good bit less than 100 additional ft-lbs compared to a typical 305.

People have this strange idea about a motor's torque output... like somehow it's directly related to the weight of the cast iron the block is made of, or the mass of the vehicle the motor came in, or something. In reality, torque is directly proportional to 4 things: CID, stroke, cylinder fill %, and thermal efficiency. No matter whose cast iron you use, no matter how bad-a$$ desktop dyno says your torque will be, if you take 2 motors of the same CID and stroke, and at any given RPM you fill their cylinders to the same %, and you extract the energy produced by the combustion of the fuel to the same percentage (compression ratio is the main determining factor that varies from one engine to another), the torque from the 2 motors will be the same. It doesn't matter whether they're Chevy small block and Chevy big block, or Pontiac and F*rd, or 1966 and 1996, or any other combo. And since the relationship of CID and stroke is within a relatively narrow range for virtually all production motors, you can usually even leave the stroke out of the comparison.

For virtually every gasoline automotive motor, the maximum attainable torque in ft-lbs is about 1.2 times the CID. The RPM at which this occurs varies as a function of cam and heads and various other things, and there's lots of ways of coming up with less than that, but that's a pretty universal rule for the peak attainable torque from practically any car motor.

 

Stock Pontiac 400... 380hp

 

All this talk about "BOOM" the rearend exploding is a crock! I've ran 11.20's@119 MPH with slicks even. I have a 3:73 with a powertraxx locker and housing welded. No I don't run it every weekend. How many LT1's have you guys seen with six speeds running low 12's at the track look under them most are 7.5's(unless they're rich enough to afford a $1300 rear after making mods,high dollar insurance and a car payment). I have used them in Monte Carlo SS's,S/10's and 3rd gens with a Powertraxx locker the diff has never broke on them(at least while I had them one kid managed to frag his gears but the locker was reusable).


These rears get a lot of disrespect with the right parts and an automatic they are quite durable.

 

A few, very very few, 400 Pontiacs had that kind of HP rating, which was of course published under the rating system in effect at the time, whereby some Chevy 327s had 375 HP. Yeah right. So since the factory put that number on a few 400s, does that automatically mean that every 400 out there is guaranteed to produce that? I don't think so. If they do, then I'm going to go get some large-journal 327 2-barrel from 68 or 69, and demand my 375 HP from that too.

OBTW I have had my share of Pontiacs too, I am quite familiar with them. My first car was a 59 Pontiac 389, it ran real good. I also had a 64 389, it was Catalina so it had the POS "Slim Jim" trans, and a 67 LeMans with a 326/PG, that got regularly spanked by the Chevelles with 327s.

Let's lose our romantic fondness for our favorite brand of car and come back to Earth when we give advice.

 

jharms, that's exactly what I said. A FACTORY 305 LG4 on average put out 240-245 lbs of torque
during it's lifetime.


Bob8748, the Pontiac 400 was used for MANY MANY years, in particular, the one you're looking for was used from 1970-1981.
In 8 of those 11 years, the engine put out 180 horsepower. Only ONE of those years put out the horsepower rating you say. Going with what you just said, I could say... "Stock 350, 360 horsepower" which would NOT be true.


And flyin89, that's exactly what I'm trying to tell them. You're right!

 

Actually, 82-TA, the '70.5 Camaros (and '71 i think as well) DID have 350s that had 360hp. It was the original LT1, which had about 11:1 compression, aluminum heads, the whole bit.

RB83L69 - Not trying to argue, but there were csb 327s that had 375hp. It was one of the optional Corvette motors for '65, and it was fuel injected.

Not argueing with anyone, just stating some facts.

And if you want to see a good build for a Pontiac 400, take a look at Edelbrock's website, they have a build on one that makes a ton of hp/tq.

 

So you're trying to say that a 327 with that crappy mechanical Rochester FI and a 151 cam had more HP than a 350 with better heads, a Holley 3310, and a 346 solid lifter cam with .040" more lift and 35° more .050" duration?

Yeah right. You obviously weren't there. Yes, I remember the 70½ LT-1 cars quite well, I was there. The 70½ Z28 was so much faster than the 65 Vette, it wasn't even a race.

The factory "ratings" of motors in the 60s are utterly unreliable as a guide to what those motors will actually produce. I would be willing to bet a substantial sum of money that some of them cannot be duplicated in the real world, even with modern piston rings, synthetic lubricants, etc. to add those critical couple of tenths of a percent here and there. The 375 HP 327 is a perfect example. So GM somehow forgot how to do that over the course of 5½ years and the addition of nearly 10% more cubic inches? I think not.

And yes, you can build a Pontiac 400 that has impressive HP and torque. Absolutely, no question of that. Does that mean that every Pontiac 400 has impressive HP and torque? I think not.

 

Just to back that up I had a 1978 Trans Am (looked just like a bandit) 400 pontiac motor (lord knows they came with everything chevy to Olds) 2:56's it ran a whopping 16 in the quarter. there are 4 cylinders that would eat that slug nowadays. Add gears stahl,headers,hell a 6 speed it would still be a slug. If you want to make it run your gonna be going into the motor. That means chasing down Ram Air heads or equiv.(just like chevy guys for the double humps 10 or 20 years ago) buying cams,pistons,Intakes(yes I know some people say pontiac made the best cast iron intake)Carbs. What have you done? You now own a car that every engine part is more expensive and a motor that hasn't been made in over 20 years. The Chevy engine is lighter,more economical,parts are more readily accessable and Just as powerful CID for CID.

 

AirAdam, yeah, I knew about the 360hp sbc, that's why I was mentioning it. It was to show whoever it was (forgot his name) that just because they made one engine with 360 hp, that not ALL versions of the same motor put out that kind of power.

 

By the way, I just wanted to add that, while YES, swapping in a more powerful SBC is 100 times cheaper than going with a Pontiac Motor. I WILL say though that I think the idea of having a Pontiac powered 3rd gen is awesome (so long as it's going in a Pontiac of course).

Kinda hipicritical of me though, I'm dropping a 350 small block chevy into a 1981 Pontiac TransAm that originally came with a Turbo 301 Pontiac.

 

"Kinda hipicritical of me though, I'm dropping a 350 small block chevy into a 1981 Pontiac TransAm that originally came with a Turbo 301 Pontiac."




You could be shoehorning that 350 into one of your Fiero's!

 

Yes, I agree the Chevy is a lot cheaper and there are a lot more aftermarket parts available, but I'm a Pontiac man. And for what its worth "nothing" on my engine is stock. And yes its going in a 87 Camaro.

 

C'mon you guys! "average" Pontiac 400? Comparing a total smog '78 with 2:56 gears to the combo Bob is putting in his car? What about the SBC camaros in '78? They were even SLOWER, and weren't saddled with 2:56 gears. Does that mean all SBC's are toads?

I had a '69 GTO with headers, an Isky 280 hydraulic cam and ported heads, that was putting out 412 RWHP on pump premium in 1980. Otherwise, that motor was (.030 over) stock, right down to the Quadrajet and dual snorkel air cleaner.

You can't argue that SBC will be cheaper to hot rod, and there is more plentiful parts, information, and R&D on them. But didn't we get these cars to stand out from the crowd and have a little fun? Maybe you guys should look into Honda Civics with wings...

 

Hey TA
The 69 GTO is a great ride. Buddy had a 69 Judge in the late 70's early 80's. Awesome power and stock from factory, wish I had that car now. 400 4 speed. Would be worth a fortune. A lot of people dont realize the torque and power these older Poncho 400/455's put out. And to put this in a light weight, gutted F body...

 

Since were talking 400's, how much lift can stock 6X heads take? My brother has a 400 in his 76 Firebird and we are thinking of swapping to a XE-268 with .480" lift or so.

 

the stock valve springs can only hold around 450 lift, will need to change the springs. Also... anytime you change the valve train geometry the 3/8 bottleneck studs will no longer work with 20lbs torque to set valve lash, will need to use poly locks, I have a set of comp cams locking nuts I can part with. Best bet (what I'm doing) is to use BBC 7/16 rocker studs, part #135-7101 ARP studs from Summit with lock nuts.

 

On another note, You want 6x4's not 6x8's. Even using 6x4's If they are stock you will not get good performance. The 92cc heads will only give you about 8.1 compression. For that cam you will need 9.5:1 (If not 10:1) any more and you risk detonation. I had my 6x4's milled to 81cc for 9.5:1 with zero decked block, You also have to mill the intake side so manifold will line up. Now... while the heads are off you can install Harland Sharp 1.65 roller rockers (which actually check about 1.72) that would change your lift to about .550, but you need to elongate the pushrod holes in the head for clearance. Hope I aint scaring you away from the swap