Just curious if anyone knew the ACTUAL amount a horsepower a 1970 455 puts out? I look online and get anything from like 280 to some guy sayin that with simple upgrades (exhuast, and heads) he was near like 490 I believe. Quite a difference, haha. So I was hoping that maybe someone on here had actually dyno'd a stock(ish) 455. I'm building my T/A and found an engine builder who said he can sell me a rebuilt 1970-75 455 for 1,800 shipped. When I mentioned my hp goal of 425, he said he could do that for about 2,900 shipped. Either way sounds like a steal to me, just curious tho if it would be worth the extra 1,100 dollars as I'm just starting on this one and have PLENTY of other things I need to upgrade/replace. I mean that 1,100 dollars could be my new trans, or my rims AND slicks lol. Thanks for your help everyone!

 

The problem with the hp ratings in the early 70's is that they changed the way they were being rated. A 1970 455 in stock form probably put out about
280 rwhp.

I made 456hp at the flywheel and 512 ft-lbs of torque with that other combo I gave you info on in your other post.

There is money to be saved if you are saavy.
Get the block bored and honed locally, as well as the assembly balanced. You can bolt the heads on yourself as well as the accessories.
The heads don't need to be ported or anything special. Just make sure to get heads that will put you at 9.5 to 1 compression with whatever piston you choose. If you run a zero decked block with trw L2359.30 you need 95 cc heads. Make sure the heads are the 2.11/1.66 valves.
Run a RA IV cam and whatever headers you can afford.
With 3.42 gears and crappy street tires I ran 13.3's in mine.
If you want to go faster then you can always spray but becareful with that if you run stock cast rods, I wouldn't recommend it.
If you know how to adjust valves a solid cam will do wonders.
Hydraulic rollers are nice but expensive.

Recipe:.....once again

455 30 over
6x heads milled to 95 cc
RAIV cam
Headers to 2.5 inch exhaust
performer intake with holley 750 DOUBLE PUMPER
TH400/TH350, you choose
3.42 gears out back.

 

I have almost the exact car as you. I have a 1980 Trans Am WS6. The factory 301 broke it's crank (awww, too bad!) and I built my 455. It's a 1972 block, bored .030 over, nodular crank, 1971 #96 heads, edelbrock performer intake, and wolverine 236/244 cam. Now, if I were to do it over, I'd have gone with a better intake and spent time and money to get the shaker to fit, rather than getting a manifold that fits. Thing Performer RPM or Victor. Also, the Wolverine cam is no longer available, but that's ok. Plenty of cams out there. The RAIV isn't bad, but I'd move up to more modern technology. That cam is older than most people driving today! Try Bruce Fulper at Rock-n-Roll Engineering or check the recent builds on High Performance Pontiac. A good carb is a must (Mighty Demon 825) and good fuel supply system (Holley blue electric pump). Headers of course and a stall. 3.42 gears are good, but 3.73's aren't bad either.

Overall, you should be close to 500 horse with the right cam and good breathing heads. If you can swing it, get the Edelbrocks. They're great and make the power. Have fun!!

 

Hey thanks for the feedback. And 30thanniv, thanks again for your "recipe" lol. I was just curious about stock becuase the engine isn't all the car needs and I've been lookin into headin to collage so I thought I could shave about a thousand off the project and use it elsewere. Then after collage (lookin at UTI so it's roughly a year, plus I'll have some more experience) workin it up. I Just put in an order for a carport so I'll have year round "car time" lol. Prolly doesn't mean alot to you guys, but something about rolling in rocks the size of my fists just makes workin on the cars a little less enjoyable lol. Thanks again! And BAD2000TA, what kind of trans did are you running? I know the 80's were all autos so that is my one weak spot. Found TCI's streetfighters, but they are only rated at 450 hp, and for only N/A. The thought of some nitrous has been in my mind with this car (nothing huge, maybe like 50 or 100 shot TOPS) but still, that just makes it that much more of a problem lol. Thanks!

 

Good thing you're going to collEge.....but anyway. If you're still interested in the orginal horsepower, or at least rated hp, then first off what kind of 455 was it. I don't believe the 455 was availabe in f-bodies until 71, but I could be off a year. Where was this engine orginally from. I do know that in Trans Ams, the 455HO was rated at 320 in 71, and I think 310 in 72. Flywheel power is anyone's guess, unless they dynoed a bare motor.

 

transmission: the stock turbo 350. But, it'll need a rebuild soon.

 

HAHA it means a lot to me! Those rocks were a killer when we were installing the ram air kit on my car.

 

Hey BAD200TA, just curious what kinda front sprins your using? I've heard a few people say I'de probly need to change em, and seeing as you have what I'm doing what did you do?

 

Hey dude can you shoot me a PM. I think your making a mountain out of a mole hill, either that or this is your first project and you are going to spend alot of money you needn't. I know I don't know you, but since you asked I feel an obligation to help you and make sure you don't make the same mistakes I made .
The springs will be fine as long as they aren't worn out. The car will have more weight transfer on launch with 301 springs. Sort of a drag springs type effect.

 

I don't think they use Dynos back the day it was rated as Gross HP (calculated HP) changed in 1972 to today it's rated as Net HP their is like a error gross to net. 340 netHP=430 grossHP
For 70 not sure if originally in a Bird but GTO's and and larger.
70 WA 455 360HP
70 YC 455 360HP
70 YH 455 360HP
70 WG 455 370HP
71 was
L75 455 325@4000/ 455@3200
LS5 455 335@4800/ 480@3600
455 for 72
LS5 455 300@4000/ 415@3200
for 73
L75 455 250@4000/ 370@2800
LS2 455SD 290@4000/ 390@3600

 

Don't forget, in '70 compression ratios were still up, but in '71 they all dropped for all GM engines (some Ford and Mopar engines retained higher C/Rs into '71). Then in '72 (as mentioned before) the ratings went from gross (FWHP w/ no accessories) to NET (FWHP w/ accessories). Therefore for a given GM engine, you'll see the highest HP rating in '70, then a drop in '71 due to lower C/R, then another drop in '72 due to NET ratings.

360-370 sounds about right for a high C/R '70 Pontiac 455. Low 300s in '71 and the only thing over 300 after the NET ratings went into effect was the '73 SD-455 @310.

 

I am still running the factory WS6 front springs, but had to put in new leafs when I brought the car. I just ordered replacement WS6 spring for the 1980 Trans Am. They work great. The car is exactly very smooth riding. I sometimes prefer the ride over my 2001 WS6. But, nothing like hear a four barrel kickin' in!! WAGH WAGH WAGHHHHHHHHHH!!!!!!