Engines HP

I am in the process or ordering a SPF Mk I and the question is, is the chassis capable of taking 650 HP since originally designed for 300+ HP with the 289 Ford? I know later they went to 302, 305 and 351 engines that got up to 400+ HP but that is not 650 HP.

thanks.
 

Mike

Lifetime Supporter
It's capable of taking 1200 but why? 450 or 500 is about all that can be put to the ground.
 

Doug S.

The protoplasm may be 72, but the spirit is 32!
Lifetime Supporter
Most often the advice I read is build for about 350 RWHP, put your $$$ into good brakes, and build for light weight and they will never catch you :thumbsup:

If I ever get to build one, I will save enough for an alloy block with as many alloy parts on it as I can afford...IMHO that would make for a better balanced car.
Cheers!

Doug
 
I would heed that advice as well. For a street car better to keep it around 300-350HP max.

Track car, not more than 425 will get you around while other similar higher HP cars will be wasting time trying to get all that power to the ground.
 

Rick Muck- Mark IV

GT40s Sponsor
Supporter
I am in the process or ordering a SPF Mk I and the question is, is the chassis capable of taking 650 HP since originally designed for 300+ HP with the 289 Ford? I know later they went to 302, 305 and 351 engines that got up to 400+ HP but that is not 650 HP.

thanks.

In a word, Yes. And a word of advice, NO!

There is an SPF vintage race car that has been on track with close to 700 HP. The driver now has about 525 as I understand and is going FASTER than the higher power version.

The MK IIs ran with 485 and on the SPF there is no chassis difference between the MK I and MK II versions. I concur that many guys are "dyno" racers and you really can't put more than 500 HP down with the available tires. My MK II has a Roush rated at 525 and it goes faster than I need to.....................
 
The only real place where hp can be unlimited is drag racing or top speed racing. I just got a 2010 shelby and it's 540 hp and it spins the tires every where. My 69 mustang has 700 hp ish and it does the same but it can get more power to the road because it's set up for drag racing. I would pee myself if my gt40 had 500 hp because it would be beyond my ability to drive. I know some of you guys are real race car drivers and my hat goes off to you. One of you will have to take me for a spin in my car so I can see what It can do at even 80%
 
I donno.

An age old question...and I'm not sure I agree with all of the answers. I don't intend to get into a "mine is bigger than yours" contest. But...

Yes, the chassis can certainly handle the horsepower. There are lots of examples of cars running near or more than 650 bhp. So, no, the chassis won't twist into a pretzel or anything like that.

Can you put the power to the ground? Can you use the power even if you could? Those are two separate questions, and the answer, IMHO, is it depends.

Putting the power to the ground depends on your suspension set up, your tires, your gearing, and I suppose your clutch. I have a track suspension set up, very tall gearing (in theory good for 210+ mph), and make 601 bhp at the flywheel. Do I have enough traction to put it to the pavement....yes, mostly. Out of first gear, and pointed mostly straight, I can stomp on it and not worry too much about losing traction.

Now, can I handle all of that power. Well, I'm not dead, so I suppose that the answer is yes. Realistically, I can't put the pedal to the floor for long when I'm on the street... no matter what gear I'm in (outside of first...good for about 65 mph). But I certainly wouldn't want less power.

I'd have to say that 350-400 bhp is NOT enough for anyone who has any experience in relatively high horsepower cars. It's just not. If you're used to driving a Honda civic, 350-400 bhp might be fun for a while on the street. But I think you'd get bored pretty quickly.

Contrary to what you might think, it might be enough for most people on the track where you can keep pretty good momentum going, and would be able to hit triple digit speeds rather often. Conversely, on the street, I find myself getting most of my thrills during rapid acceleration, rather than running at 100+ mph with any frequency. Hence, the need for horsepower. Besides, who want's to get smoked by any number of modern econo-boxes in the stoplight derby? I think my lawnmower makes 350 horsepower...and I'm sure that there are several minivans that do, too. Talk about being embarrassed!

So. How much is enough? I don't know, but I have a friend with a Kirkham that makes 750 bhp and has fairly standard Cobra gearing...I think he has enough. You so much as breath hard on the laud pedal, and your head gets snapped back. I've seen the car break traction while accelerating at 60-70 mph, and I doubt that the driver really had his foot in it. I briefly drove it, and it was scary fun.

In the final analysis, yes, the chassis can handle the power. Can you?....probably. I'll take flack for this, but unless you really just want to drive around and look cool, I wouldn't build one with less than 400 bhp.

What was that old Mark Donahue quote....?
 
Oh, and to be clear, I disagree about 500 horsepower being the "limit" of how much can be put to the ground.

In what gear? 1st...OK, I agree. 2nd, maybe. 3rd...I'm pretty sure I could use every bit of 500 horsepower in third. 4th and 5th...do I even need to ask?
 

Jim Craik

Lifetime Supporter
David, Where in CA are you?

I have P2264 in the Santa Cruz Mountains...

As for huge HP, don't do it...I have a 302 with 450HP in my MKI, way more than enough.

The high HP motors are huge, hot, heavy, noisy, blister the paint, block the rear view and I'm told the small blocks sound much better.
 
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Jim,

Let me egg him on. Pretty soon, nobody will even put a small block into one of these things. :)

To each his own, though.

We'll have to agree to disagree.

David,

I see you're in Cali...where are you located? If you'd like to meet up, I'll take you for a ride. I'll check my insurance, I may even let you drive...see for yourself.

Jim, My 393 is basically the same size as your 302...my view out the rear is no worse than yours.....ie, terrible.
 

Jim Craik

Lifetime Supporter
Ron, the top of my stock Roush air cleaner is a good inch below the lowest part of the rear window, I have no rear vision problem...
 
Jim,

A 351 Windsor motor (on which mine is based) only sits about 0.5 inches higher than the 289/302 Windsor that you're using. Any difference in the quality of our rear vision is due to our respective choices of induction, the location of our mirror, and the length of our back.

In my case, I'm a bit over 6'1", with much of my length in my spine. I placed my mirror where I got the best view out the rear. Still not very good. Next I'm going to shave my seat cushion down to nothing. Hopefully that will help...and I may be able to get my helmet on.

Regardless, I wouldn't base my engine choice on how well I could see out the rear...Who was it, Raul Julia in the cannonball run....just tore his mirror off...what's behind you doesn't matter.:laugh:

Ron, the top of my stock Roush air cleaner is a good inch below the lowest part of the rear window, I have no rear vision problem...
 

Jim Craik

Lifetime Supporter
Originally Posted by Jim Craik
Ron, the top of my stock Roush air cleaner is a good inch below the lowest part of the rear window, I have no rear vision problem...

Ron, this makes no difference how tall you are or where you put the mirror...

11159478_838360582897759_844095980140830490_n.jpg

I just walked outside and took this photo, My car has a Roush 342R crate motor based on a 302.... 45,000+ miles and still STRONG! The air cleaner sits on a Holley...

450HP 425tq, It is small, it is light, it sounds wonderful and honest Ron, it does not block any rear view:)
 
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As Rick said SPF Mk I and II chassis are the same. Put however much power you want in your SPF. My 500hp seems adequate, but to each his own. I'd be a little more concerned about the ZF or RBT if you have torque figures matching your hp. An RBT is pretty strong, but I wouldn't make a habit of burnouts with 600+ lb. ft.
 
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650 hp is in the territory where you'll be risking breaking even a ZF transaxle. Break a ZF and you'll be writing a big check. If you need an even beefier transmission than a ZF you'll be writing a big check as well, and have a monster heavy transmission hanging out the back end of your GT40.

Big HP is fun and can be fast for sure. Mark Donohue apparently said that you have enough horse power when you can leave two fat black lines from the exit of every corner to the braking point of the next. I wouldn't know about that, but I've driven a few cars with very big hp and it's not all it's cracked up to be. In fact, it can be dangerous if the power modulation isn't very controllable or refined.

400hp is a s-load in a 2,500lb car....that's as much as I can control or use at any time....relatively safely.

Just my $.02.
 
Jim,

For the sake of originality, I'm running IDAs with low profile tea-strainer "filters". Whether they were on your motor or mine, rear vision would be "compromised."

Mike,

I think my 393 still sounds like a MK I...it's a (relatively) high compression all solid roller built to rev to 7.4K...it'll scream with the best of them.
 
More factors here than you could shake a stick at. Firstly I think 500 real HP is about all thats needed for a road/ occasional track car , secondly is how that HP has been achieved. I personally would stay away from stump pulling tourquers in favour of engines that spread their power over the widest rev range. Also there are many a mismatch between HP/torque and gearing which can leave a 600hp car getting stuffed on the track by a well sorted 300hp combination.

Bob
 
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