Originally Posted by Longbob
Originally Posted by chlinstructor
Originally Posted by Longbob
Originally Posted by chlinstructor
Originally Posted by Jahrs
Originally Posted by chlinstructor
My 1975 Pontiac Trans Am with the Factory 455 and Hurst 4-Speed would bury the 150 mph on the speedometer.

Don’t know what top Speed was, but no one ever out ran me on the Hwy when I had it.


Me and a buddy out ran a factory 455 t/a in a Gremlin. Red light to red light.


First off, let me clarify that my Trans Am was a 1974 Model. NOT A 1975 Model.

And that T/A driver y’all raced was probably laughing so hard at a Gremlin trying to race him that he forgot to shift gears. 😜
Had a cousin that put a 454 Chevy big block in his Chevy Vega and took a lot of folks money street racing way back then.
So looks can be deceiving. 😬


Anyhow.......
My 455 engine was not stock. Blew the original engine at 30,000 miles racing a Corvette out on the Interstate.

I had a local guy that drag raced Top Fuel Dragsters Professionally rebuild it for me. Cost me $3K back in 79.
He over bored it, shaved the heads, added a 3/4 Racing Cam, balanced and blueprinted the engine. Also added EDELBROCK Racing manifold, Holley 650 Double pumper Carb, Hooker headers, and a pair of Thrush Straight-through glass pack mufflers. And, I added a set of traction bars and wider tires for the back, as it was tough to get traction out of the hole with the 4-Speed Manuel transmission and an engine making 450 horses.

I had two buddy’s at the time with T/A’s and Firebirds.
On had a 78 Trans Am with the 455 and the other had a 75 Firebird with the 400 engine. And another buddy with a 69 Barracuda with the 440 engine. Another buddy had a 1978 Corvette Pace Car, and another had a 69 Chevelle SS with the 396 engine, and another friend with a 1971 Mach 1 Mustang with the 429 engine.
We all hung out together and spent every Saturday night we could at the local drag strip. My car with the rebuilt engine would run in the low 13’s on the strip.
None of the friends I mentioned above ever beat me on the Legal Drag Strip or on the street.
And I never got beat street racing either in my hometown.
I took the 455 decal off the hood scoop and won quite a bit of $$$ racing on the street, from folks that would cruise Main Street looking for a race on Friday nights

And, also, I should have proof read my original post before posting. I’ll blame it on the small onscreen keyboard on my iPhone. 😬
Again, My Trans Am was a 1974 Model. NOT A 1975 Model. Sorry for the confusion, but the Specs EdM posted are for another model. Not the one I owned.
Pissed me off because I knew they weren’t the correct specs for my T/A. Sounded like was being condescending before I went back and reread his post.
My fault, not his. So I guess I owe him an apology for acting like a [bleep]. 😬

Here are the the correct Specs for the 1974 Model.

Engine type Pontiac Big Block V-8 455 SD
Displacement 7.5 l (455 ci / 7456 cc)
Power 314 ps (310 bhp / 231 kw) @ 4000 rpm
Torque 529 Nm (390 lb-ft) @ 3600 rpm
Power / liter 42 ps (42 hp)
Power / weight 189 ps (187 bhp) / t
Torque / weight 318 Nm (235 lb-ft) / t
Transmission 4 Speed Manual (3.08 ratio)

Wished I had kept that car. Only 212 were produced with the 455 SD engine and Manuel transmission.
One with only 9,500 miles sold for $111,000 back in 2015 at a Barrett-Jackson’s Vegas Auction. 😢

https://www.sportscarmarket.com/profile/1974-pontiac-trans-am-sd-455


What is a 3/4 racing cam? What rear gear and tire size?


It may have been a term that was used here regionally.
I just remember it as s term the local hot rod crowd and mechanics I hung out with used.
I can’t remember the brand and version of the camshaft that my mechanic used in the engine build. Wished my memory was that good. 😬
That’s what we referred to back then as a Cam you could still use on the street, and for normal every day driving, but was much more high performance than a stock camshaft.
A racing cam back then made your engine’s idle way too rough when you were sitting at the red light before it changes.
An engine with a full racing cam always sounded like they were about to sputter and die at idle RPM’s. They made your engine sound like it was about to run out of gas, until you got above idle RPM.
And if I recall correctly, the rearend gear ratio was a 3:43

I can’t recall the tire size. I know I put on set of air shocks so they wouldn’t rub on the fender wells.
Seems like the tires were Goodrich. I also put a set of Custom Crome Rocket brand Spoke wheels on it. The type that had like 5 big spokes. Not those bicycle type spoke wheels you see on cars in “da hood”.
Heck, that was 42 years ago. Lucky to remember my name on some days. 🤠


I get it about the memory fading thing. Same thing for me just walking into another room. I have heard some use the term "3/4 racing cam," but it really doesn't mean anything because a "racing cam" isn't absolute. I guess someone is trying to guess it is somewhere half way between a stock camshaft and low vacuum lumpy stick. We build high performance engines for the street and race cars that are on the literal edge. Camshafts are normally referred to by lift, duration, and lobe separation. Even with these we have to be concerned with valve to piston clearance, ramp rates, spring pressures, hydraulic/solid/roller lifters, base circles, degrees advanced, etc.... That is why it makes it difficult to say what is 3/4's of that in my opinion.

The 1974 455 was a square bore (bore and stroke were more or less equal). This was more of a torquer motor rather than a high revving engine which bodes well to the tall gear you had in the car and taller tires it appears. I am surprised that the engine builder put a 650 cfm carb on that many cubic inches especially after adding another 8 to 10 with the larger bore. It would make it a stoplight to stoplight beast, but wouldn't breath well at the upper RPMs. It would take a lot of RPMs for that beast to push the aerodynamics of a 1974 Firebird anywhere close to 145 or 150 mph in my opinion.




Thanks for the clarification LongBob. I knew it wasn’t the correct or proper terminology for the Camshaft, but that’s just what stuck in my mind from 40 something years ago. Wish I could remember the exact Cam mfg and model, but it’s been too long.

And if I recall correctly, about 5000 or 5500 was redlining on that original SD 455 Factory Engine.
It could have benefited greatly from a 5th or overdrive gear for top end speed. Like I mentioned, that’s how I blew the original engine.
They were nothing like the small block Chevy engines of that era that you could push the RPM’s way up there, without worrying as much about engine failure.
Seems like a lifetime ago and my driving habits have changed significantly. In fact, I’m probably one of those that others bitch about when they pass my old farm truck for driving too slow. 🤠

Last edited by chlinstructor; 02/09/22.
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