[cas]

what kind of horse power would I expect from a stock rebuilt 71' 455 with 6x-8 heads?

motor isn't rebuilt yet. came from 71 big pontiac. been sitting for years.

[68gtoMN]

depends on how much $$ you want to throw at it. I'll say that with a mild/medium build, you could see 415ish

[goatless]

Need more info. Cam is key.

[cas]

Sorry for the vague description. I'm just wondering. Now I have a 76' pontiac 350 originally a 2bbl now a 4bbl setup and it's decent and moves the car but won't really break the tires free. especially after I put a 10 bolt posi in over the winter.

I was thinking if new heads would pep it up , but was told that it's not worth the expense.

I do have a 455 that has been sitting for quite awhile. Would need a total rebuild, but as always money is the concern. If I did a budget rebuild, if there is such a thing and put the 6x-8 heads on the 455.then where would that get me.

not sure what heads are on 455. I think they're original to block. Motor came from 71-72 big pontiac

[north]

I had a 455 with 6X heads and T400, it was bone stock (mid seventies Qjet and distributor) in a 69 GTO with muffler shop duals and it pulled almost 200 horse on the chassis dyno, I swapped a set of 71 GTO heads (96?), intake, carb and distributor and a 068 mellings cam and ended up at 250. A stock 350 horse 400 auto GTO pulls about 240 on that dyno and a tuned 455 HO with full but performance exhaust is about 290 just to put things in perspective. Also my 69 Lemans with a 2bbl 350 and T400 pulled only 145.

[north]

to convert to gross just multiply my above numbers by about 1.35 to get a ball park number.

[cas]

So with North's info I'd be lucky to get 200 net or 270 gross HP. I must only have about 120 now lol

[PontGuy]

I have been in a similar place with my 69 Lemans vert with a mildly built 350. The engine actually pulls nicely at higher RPMs, but it does not have quite enough on the bottom to spin the tires. I am starting a major refurbishment of the car and decided to go with a 455 to wake it up. Nothing really special, a 462 with '71 400 heads and a relatively mild cam. My goal is not to get a ton of extra horsepower, but I want a lot more bottom end torque. The car just has to be able to burn rubber and pull hard to be "right"! Not sure if this is what you are looking for too, but all the extra cubes should get you there. The additional HP whatever it is would be a bonus.

Walt

[cas]

Walt, seems we're on the same page. I'm not looking for anything crazy, just enough a$$ to break them loose. Car pulls ok at higher RPM, just not enough torque. Was hoping for a bolt on fix, but I guess I'll have to wait for the 455 sometime in the future.

[PontGuy]

I've probably got more experience experimenting with Pont 350's than anything else since I used to use them racing dirt track on a budget "back in the day". We were limited to 360 CI so the 400s were out, and the bigger engines probably would have overheated like crazy anyway. Found the Pont 350s were about bullet-proof which was a big plus. Tried all kinds of heads, valve sizes, cams etc. Was able to build engines that had great mid range and top end power, but the bottom was always a bit anemic no matter what I did. Of course bottom end torque is really not important for dirt track racing so it was not a problem. By the way I was very competitive running the Pontiac mills against the top Chevy and Ford guys which all of them found surprising. It was lots of fun but way too much time and work and I wanted to stay married so I had to give it up.

But the bottom line.. I don't know of a bolt-on fix that would give the 350 the bottom end grunt that we are both looking for.

My new 455 is still sitting in the crate and it looks like it will still be some months before I will be ready to drop it in. Can't wait to see what it does!

Walt

[goatless]

The way to give that 350 more bottom end (or at last feel like it) is to put a steeper gear in the rear end.

The beauty of the 455 is that it'll have tons of torque just about any way you build it. Even with highway gears it'll still roast the tires any time you want.

[cas]

good luck with it.

what's a good source of info for me to get to learn about the pontiac motors and heads? seems cofussing to me

[b-man]

I built a 455 for daily use some years back, using all factory Pontiac parts or repros of them.

It had stock 114cc #66 1971 455 heads (8.2:1 compression) and a '66 Tri-Power setup along with repro '67 GTO HO exhaust manifolds. Cam was the Crane 'blueprint' 068 cam (one step above the 067 which came in most stock 'standard' 455 4-barrel engines), which is said to not be as good as the OEM Mellings version. I put some good used stamped-steel RAIV 1.65:1 rockers on it too.

This is about as stock as it gets for a 455. The Tri-Power setup was mostly for looks, a well-setup Q-jet on a stock iron intake would easily equal it in performance or at least come very close to it.

Horsepower at the flywheel was estimated at 328. The 1/4-mile MPH (101.85) and car weight with driver (3980) along with the ET (13.899) were entered into the calculator on the SD Perfomance website to arrive at the 328 HP figure.:http://sdperformance.com/calc_hpet.p...=3980&check2=1

Horsepower according to the ET was considerably lower at 293, but ET is a better measure of traction than horsepower. The car was very traction-limited and geared quite tall (2.56 open rear with 235/45-17 street radials).

[cas]

Here 's a belated thanks for all the replies back in 2009. I don't know why I never got back to this post.
Anyway as of yesterday the 455 is in the machine shop getting checked out, I got the cam out and called the manufacturer for specs, Erson.

Ill get back with the info I found out

[Darth Menace]

[cas]

Very funny, I know, it's been awhile. I guess i could start a new thread. Now i. I'm looking for all the info i have written down over the years.

[Darth Menace]

I know how it is. I resurrect old posts from myself or others, beats starting new ones and having people complain you could have used the search function (I am not meaning on this forum). I do love going back and getting the info on a project maybe you put off for too long, and it is all still waiting for you. I wish I had the same help on the Viper forum as I have here. Post some pictures of the 455 when it is up and running

[b-man]

[PontGuy]

Wow, seven years since this thread started!

I haven't been very active on the board for a while- enjoying my cars but have had no issues/problems to discuss for a long while. That's a good thing.

My 455 went into the Lemans six years ago, a few months after responding here. I dressed it out with a Cliff-built Qjet, rebuilt points distributor, factory intake, RARE manifolds and Pypes exhaust with Dynomax mufflers. Once sorted out it has been 100% reliable. 5,000+ miles since with nothing but oil changes and an occasional tune-up.

I intended to keep the original peg-leg rear but found I could hardly step on the gas without roasting a tire, so upgraded to a 12 bolt 3.07 posi and put 60-series rubber out back. No HP numbers to report but I took it to the track once for testing. Even with the mild cam it ran a 13.6 in the 1/4 with limited traction and fuel flow problems in 2nd/3rd gear. Driving around town it is almost stock sounding so nobody can tell what it is capable of. Its great fun just "cruising" in the 'vert and shocking people every now and then.

Build that 455, you will be glad you did!