Is there any published information on the power limits of the stock Firebird drivetrain? What is the maximum hp you would feel comfortable with putting in the engine bay without modifiying the transmission, driveshaft, or rear end?

The reason I am asking is because I am finding an unusual amount of Pontiac blocks for sale, and I might build one soon to replace my 305, but I don't want to build too high for the stock components.

I understand that gearing can make a huge difference in the answers, but just for ballpark figures, what is safe?

I don't understand why you would not want to mod the trans. A good shift kit is very easily installed, and a cheap mod. Then it depends how you drive it? If you drive it like you just stole it parts will fail. I am prob around 4 to 450 hp. Trans is built, and a trans cooler. HD u joints Auburn posi. Cheap insurance! It seems very solid. I do use it. but not constent abuse.

Well, I run a 4-speed (not sure if M-20 or M-21), so the trans cooler doesn't apply, but I figured I would work with what I have with minimal mods (college student budget). From what I saw on other forums, many seem to run with stock transmissions, so I figured I could too. Though I have been on this forum for a few years, I still consider myself very new to the hobby. I actually haven't driven my car yet (cracked 383, replaced with 305, still not registered), so I don't know how I will drive it. It's also my first manual trans car so I truly have no clue on my driving style.

Perhaps I am thinking too far ahead? Probably, but learning now will help me make better decisions when the time for something bigger comes around.

Not worth worrying about. Stock Muncie's will take more than you can afford to build. Rear end too. I say that because it costs alot of money to make serious power. So unless someone dies and leaves you a buttload of money that you want to throw away into your car...forget about it. Buy a block cheap, buy the best parts you can get cheap and build it yourself and you'll still be into it for $3-$5K. That'll be a mild build. Maybe around 350HP if your real lucky.

See what I mean?

Torque (and traction) is what kills those parts, not horsepower.

No worries on street tires. They wil NOT hook up.

I am between 400 and 450 also on a muncie 4 speed. My engine builder said the weakest link in the drivetrain is the 10 bolt.

Scott Roberts took his '68 to 10.47 @ 128 MPH with the stock 8.2 rear (added an Auburn posi, but stock axles). 406 CID, TH400 (TransGo "Stage 2" kit), 2,800 "stall" converter, 3.70 gears, "150 shot". The rear axle is the weak "link", true, but it's NOT the same as the Chevy 8.2, MUCH touhger.

A small block won't make NEAR the raw power (low-end torque, which is what "kills" parts) of the 400 Pontiac, so you should be fine. They still used the BW T-10 behind small blocks LONG after Pontiac abandoned them for the Muncie.

Jim

A manual trans (Read "Driver")will also put more strain on the rear end than a auto transmission.

Back in the 90s my daily driver was a Olds with a 350 chevy and a Th350 and a 10 bolt in the rear, it did at best 14.6 and had around 400 HP with a more or less stock Th350 only a shift kit was installed, used it every day for over two years without any problems.

The engine did die late at night during a vacation, racing another guy for nearly two hours (still remember my X ask what that smell was, I did replay NOTHING... 2 minutes later we where standing on the side of the highway with two cracked heads..)
I think I got the most expencive taxi ride ever that night...

Yep.
Found that out from 79-83.

455 block/#12 hds-11.5 cr/240-250 @ .050 cam, etc.
HP...???
Not in exact order;

Muncie input shaft bearing.
Trans mount.
U-joints.
One leaf on rear springs.
Couple of wheel studs...twice.
Oh ya, cracked windshield and A-pillar from body twist(no frame connectors.)
Once crack started, w/s would crack another 1/4"-1/2" on launch.
Passengers thought it was cool though.
All i can think of right now...

Oh ya, the last time i changed rear end fluid, the cross shaft had egg shaped the case along with a couple big cracks!
Axles had a twist at the spline end.

Thanks for all this info, guys. It will still be a while before a different engine goes in, but this is great to know. So, a mildly above stock 400 build (what I would like) shouldn't be anywhere near the car's limits unless I really abuse it, which I don't plan to. Excellent!

Well nobody really plans to. It just sort of happens sometimes. Sort of like having kids.

The drivetrain components are like birth control?

Ain't that the truth. It's really hard to have a lot of horespower under you and not use it.

"Well nobody really plans to. It just sort of happens sometimes. Sort of like having kids."

"The drivetrain components are like birth control?"



Yeah, you know once you put it in, you spend the rest of your life going round and round waiting for the inevitable breakdown.

Unless you back off the throttle in time

I don't believe in letting off until aftter I cross the finish line. The 13 minutes of BS isn't worth the 13 seconds unless you do.

Agree Firebob, but sometimes racing against a slower car, have to let off to keep from breaking out early and losing.

I was hoping when I lobbed that one up there, someone would spike it hard!

You guys make me so proud.

Keep 'em comin' (no pun intended - no really, it just came out that way. Shoot there I go again, no pun intended that time either.)

Remember once you let the smoke out you can't get it back in!

I aint talking bout no bracket racing. It's heads up all the way for me. Win or lose, I always cross the finish line.
(I had to go back and look at the thread title. I forgot what we were talking about)
I'm done.