How much hp/tq is really necessary for auto-x'ing a GM A body??

[Nicks67GTO]

Im 1-2 years out from building an engine for my 67' GTO. I know the go to move in my situation is to scrap the traditional 455 Pontiac and go for an LS type of setup. Its not totally out of the question. Im trying to gauge what kind of hp/tq is really necessary to have fun and be competitive with my fully street trimmed GTO at a carcraft or goodguys type of auto x event. Lets assume its 3800 lbs. Its a 5 speed car.

So what kind of power is necessary and what is complete overkill?

[chaz75]

good question.

[Twentyover]

To be competitive, more than hp than you can make. There will always be someone who an spend more money and time making his car lighter, more hp, bigger tires.

To have fun- not so bad, maybe a couple hundred hp. Remember that these are low speed events, really tight, so hp isn't a big a factor as mad skillz driving.

[Nicks67GTO]

The thing with excessive hp/tq is that at a certian point its unuseable and somewhat counterproductive in terms that it might actually slow you down with blown off tires or accidental power slides in a corner because you gave it just a bit too much.

If I can pull a street happy 450hp and 550 ft/lbs with a flat-fat tq curve out of an iron headed/iron intake 455 on the cheap, Im thinking that will be fine for events. Yeah the old Poncho is going to be nose heavy but im an amatuer and its all just in good fun anyhow. Does that seem reasonable?

[MonzaRacer]

12.5 hp and 15 lb ft of torque

[SSLance]

It's more about having the power in the right place than just massive amounts of it. My 383 puts 400 ft lbs to the rear tires between 2000 and 4500 RPM and coupled with the T56 makes not only a great driver but pulls like mad out of the autocross corners as well.

[SparkyRnD]

I would think 350-450 tuned hp would be perfect for most autocross courses, and that is just the tip of the iceberg. Tuned suspension that is dialed in, great (but not overpowered) brake system, very sticky tires that hold the weight of the car well, a properly sized steering system, and a ton of seat time. If any of those are off, the hp won't matter much. Look at how many cars have tons of hp/tq (well above the 500 mark) and watch how many of them spin out on the shorter courses. Huge hp/tq numbers are great for straightaways, drag racing, long road courses and the like. Lower power in the power curve is better for short autocross. Just have to look at what you will use your car for and find a comfortable medium that allows you to enjoy both, without overpowering or underpowering.

On Project Sabre, we went with a stock engine along with a medium cam upgrade, relatively conservative tune and headers. No power adders at this time, and nothing radical. The 6.0L makes great torque to get the beast moving, and the hp numbers will be good for keeping it moving adequately. I know that I will get beat in many flat out races on long courses and drag strips, but I'm building the car for fun driving, touring, running curvy roads and short autocross racing. I hope that the set up devised will keep the car very competitive in autocross courses, and fun to drive on anything larger / longer.

[ho428]

You can drop a lot of weight off the Poncho front with Aluminum heads, intake and radiator. A glass hood and headers, aluminum calipers and hollow sway bar helps even more. You'll never get it light, but you can shift the center further back.
Your hp and tq goals can be met easily with the 455, especially if you switch heads. Get a good baffled oil pan.

[Sales-TCI-Eng]

I would think 350-450 tuned hp would be perfect for most autocross courses, and that is just the tip of the iceberg.


^^^This

Our '68 Camaro weighs just under 3800 lbs with Sal in it and it makes 358WHP through a 700R4.

-Jason

[Tomswheels]

^^^This

Our '68 Camaro weighs just under 3800 lbs with Sal in it and it makes 358WHP through a 700R4.

-Jason

I agree with both, 1HP per 10 lbs is PLENTY for most autocross courses. The key is putting it down, and not overdriving...

[tazzz25906112]

I'd be a whole lot less worried about HP/TQ and focused on suspension setup, weight balance of the car.... Start with overall suspension mods (evaluate what you have and where you want to be) and then look at your drive train... The weight balance on that car would likely be a whole lot better with an aluminum LS stuffed in the nose and a meaty set of tires to plant it all ....

[Roadrage David]

Aluminum heads manifold ecetera. close to a sbc in weight with bbc performance. you cant beat pontiac torque. 530 hp 577 lbs T alu heads ecetera
leaf spring suspention mini tubbt. clockt at191 mph http://youtu.be/NFaA51l1HmE http://youtu.be/7Dp0PngisVI http://youtu.be/zn3K6d_e7bw http://youtu.be/LkLQXSygmQM

[High Plains Mopars]

Overall weight, weight distribution, spring rates, shock rates... all more imortant that horsepower in autocross.

[struck by Lightning]

I'd be a whole lot less worried about HP/TQ and focused on suspension setup, weight balance of the car.... Start with overall suspension mods (evaluate what you have and where you want to be) and then look at your drive train... The weight balance on that car would likely be a whole lot better with an aluminum LS stuffed in the nose and a meaty set of tires to plant it all ....

+1 ...... weight, sticky tires and suspension are key. I have the tendency to over drive the course in an effort to compensate for my heavy truck at 4,670 lbs (4,895 with me in it) with 57/43 weight ratio.

[Rod]

Great question! without sounding like a jackass, the answer is as much as necessary, OK heres why, tracks always change and are different there are no absolutes, what ever you build the drive-train should be able to transmit it to the ground allowing you to drive the car to the limit of track and car,,, I know you wanted a number, so I say between 300 and 700, when I had 300hp I only did 2 goodguys the first year and that was ok, when I did more autocross tracks I needed more on some tracks, then I upgraded to 360hp and had to add some suspension upgrades to get it to the ground and I needed more because I added some big track days, now at 405hp and lighting up the car with Carbon Fiber I also had to revamp the suspension again

[Ron Sutton]

Hey Rodney,

What engine is in your car?

[Rod]

Hey Rodney,

What engine is in your car?

LQ9 with a cam

[72BBSwinger]

Weight distribution is huge on power management, Next is tire size and compound, a set of the new Rivals in 335 rear and 295 up front would take 550hp around pretty damn good. If a guy is stuck with some 295/35/18 in the back probably be fine with 450hp. If you have a touchy throttle foot you might want as much rubber that will clear the wells.

[Nicks67GTO]

You will need 600-700 hp to the ground! I also agree torque curve needs to be flat. Also, I agree that an aluminum LS motor will be cool. Of course an aluminum 400 Chevy would work as well. Big brakes, bigger sticky tires, light-weight car, stiff chassis, etc, etc.
Conrad


700 RWHP and an aluminum small block chevy engine? Thats never going to happen.

[Nicks67GTO]

Great question! without sounding like a jackass, the answer is as much as necessary, OK heres why, tracks always change and are different there are no absolutes, what ever you build the drive-train should be able to transmit it to the ground allowing you to drive the car to the limit of track and car,,, I know you wanted a number, so I say between 300 and 700, when I had 300hp I only did 2 goodguys the first year and that was ok, when I did more autocross tracks I needed more on some tracks, then I upgraded to 360hp and had to add some suspension upgrades to get it to the ground and I needed more because I added some big track days, now at 405hp and lighting up the car with Carbon Fiber I also had to revamp the suspension again

No that completely makes sense. I have a new frame im going to box and add an SC&C stage 2plus setup to. Ive got a 12.7:1 PS box and im going to probably be limited to a 275 rear tire because its a real 67' GTO, ive got all the numbers matching stuff for it and at this point im not going to cut it up. If youre running well with 405hp in a lighter first gen camaro i would think that my 450hp/550tq estimate would be a good shooting point. I intend to stick as much tire in as possible but for me the auto X stuff will be a once in a while fun time. Never anything serious. The chassis improvements will benifit me on the street as well, many days this car is my DD. In fact its in the parking lot right now!

[Nicks67GTO]

Weight distribution is huge on power management, Next is tire size and compound, a set of the new Rivals in 335 rear and 295 up front would take 550hp around pretty damn good. If a guy is stuck with some 295/35/18 in the back probably be fine with 450hp. If you have a touchy throttle foot you might want as much rubber that will clear the wells.

Im probably limited to a 275 tire because at this point im not willing to minitub it. I intend to maybe relocate the battery into the trunk and eventually end up with aluminum heads, intake, radiator etc. This will however be a fully functional, PS, PB, AC Daily driver type of car so it may be difficult for me to get an awesome weight distribution. I suppose every little bit helps.

[Rod]

this car is my DD. In fact its in the parking lot right now!

I'm with you, My Camaro is my Daily Driver also and my race car, grocery getter, parts hauler all at the same time

[Tomswheels]

Great question! without sounding like a jackass, the answer is as much as necessary, OK heres why, tracks always change and are different there are no absolutes, what ever you build the drive-train should be able to transmit it to the ground allowing you to drive the car to the limit of track and car,,, I know you wanted a number, so I say between 300 and 700, when I had 300hp I only did 2 goodguys the first year and that was ok, when I did more autocross tracks I needed more on some tracks, then I upgraded to 360hp and had to add some suspension upgrades to get it to the ground and I needed more because I added some big track days, now at 405hp and lighting up the car with Carbon Fiber I also had to revamp the suspension again

I guess us Mopars just need less HP (Im at 270 at the rear wheels) due to our superior torsion-bar setup. :box2:

[69*Goat]

You probably already know this, but the 455 is a "Big" journal Pontiac , which some say is the same as a Big block chevy.... Long time to spin up. If you are looking at selling the 455, you could get a pretty penny for that thing, and build a stroked 400, which is a small journal Pontiac...spins up quicker. My combination puts 525/HP-580/lb Trq at the crank, which has been dyno'd at 475/525 at the rear wheels.

This is plenty.

[Nicks67GTO]

You probably already know this, but the 455 is a "Big" journal Pontiac , which some say is the same as a Big block chevy.... Long time to spin up. If you are looking at selling the 455, you could get a pretty penny for that thing, and build a stroked 400, which is a small journal Pontiac...spins up quicker. My combination puts 525/HP-580/lb Trq at the crank, which has been dyno'd at 475/525 at the rear wheels.

This is plenty.

Ive got an un-molested 67' block laying around for such an ocasion. Ive actually thought about going with a 4" stroke for 440" and easier revs plus for whatever reason, ever since i was a kid, ive always thought of the dealer installed 390 hp 4" stroke 428 as the baddest engine pontiac ever produced. I'm not sure why??

[69*Goat]

Jim Butler is the man to talk to regarding stroker kits. If you want to not worry about vacuum you can use a Summit 2801 Flat Tappet cam. I had this cam in a stroked 400 that I had in my Can AM. That land yacht was quick!!! If you want to go full roller on the valve train, the camshaft in my signature is outstanding, but you only get 13" of vacuum. Spend your money on head work. SD Performance can CnC Port and polish them for some sweet results.