Minimum HP and TQ

[William Quantrel]

Have read endless posts on hp/tq numbers, what transaxles can take or can't, and how power is too much.

Is there a minimum HP/TQ number a 40 should have? I recall reading many years ago reading about an RF40 owner had the audacity to run a 306 with 350 hp. The nerve of that guy...

Also, was there not a forum member here with a FMS 302 with 345 hp? Was that you Mr. Jones?

Is this number of HP too low? Not enough???

Many of you have 450-600 HP with similar TQ numbers. After living with such a high powered engine in your 40 would you say it is or has been too much? Would or rather COULD you drop down to 400 HP/TQ after driving 500+?

 

[Ian K]

Have read endless posts on hp/tq numbers, what transaxles can take or can't, and how power is too much.

Is there a minimum HP/TQ number a 40 should have? I recall reading many years ago reading about an RF40 owner had the audacity to run a 306 with 350 hp. The nerve of that guy...

Also, was there not a forum member here with a FMS 302 with 345 hp? Was that you Mr. Jones?

Is this number of HP too low? Not enough???

Many of you have 450-600 HP with similar TQ numbers. After living with such a high powered engine in your 40 would you say it is or has been too much? Would or rather COULD you drop down to 400 HP/TQ after driving 500+?

Firstly, build it the way you want to.

Secondly, there is no minimum HP/torque. It all depends on what you plan to do with it. Many feel that HP in the 350 - 400 range is more than sufficient on the track due to the 40s low weight. IIRC, even the Wyer Gulf cars only had 425 - 450HP, and they hit over 200 MPH on the Mulsanne.

Thirdly, the key is matching the engine (with whatever HP/torque numbers, RPM limits, power curve) with a transaxle that can handle the power and has the proper gear ratios to handle the power, RPM limit, power curve, etc. to, again, and I cannot stress this enough, accomplish what you want to do with the car.

I think matching engine specs and capabilities to transaxle specs and capabilities is more important than maximizing the engine's power output.

Ian

 

[Ian Anderson]

I'm running a Morgan (Rover type) 3.9 litre V8 in mine Ali block saves weight
At registration it was weighed at 1150kg

The 256hp that mine gives out is plenty for a road based car - it is enough to scare me silly! Enough to break the rear out at donnington track and enduse a spin, enough to drift it around Tetre Rouge on the Le mans circuit!

It's geared to do 170mph at max power (6600rpm)

Damp road and floor it in 3rd and the tyres spin. Dry road and it does the same in 2nd without trying too hard.

Off ramp from one motorway to another - leave a 40mph queue in 5th and floor it and be at 110mph before I get onto next motorway - (possibly 250m) - no gear change just pulls like a donkey!

How fast do you want to reach the point of the accident -- I bet my 250hp will not be that far behind!

That said for a 24 hour race I'd not fancy spinning the Morgan unit that hard for that long!

Ian

 

[Doug S.]

How quickly do you want to burn up tires, WQ?

Whatever power you can't hook up goes up in expensive tire smoke. Despite the fact that the "mid-engine" design of these cars helps them to develop traction, to some extent, their light weight works against it.

Most of the advice I've seen is that 350ish HP is adequate for spirited performance. If you want to do track work, here's the best advice I've seen so far (I'm paraphrasing):

"...don't spend your money on huge horsepower/torque; rather, spend the $$ on items that will lighten the car and buy the biggest brakes you can afford. They'll never catch you." If you're racing the car, big brakes allow you to power further into the corners, while others without the braking power are slowing down....and, the big brakes would certainly be a safety factor on the streets, where these cars can be hard to see in a rear-view mirror b/c they are SO short (they are called "40's" for a reason).

Lighter weight will help you accelerate faster with whatever horsepower you choose (up to the point where your tires break loose, then you're just in everyone else's way), will help the car handle better, and will allow the car to be stopped more quickly.

That's just MHO, others obviously vary, as there are mega-HP builds here on the forum.

If it were me doing it (and it isn't.....YET), I'd spend the $$ for an all aluminum alloy block/heads/intake/water pump, etc, to lighten the car up.....and those BIG brakes the advice I mentioned focused on.

Cheers from Doug!!

 

[roaldin]

How much is enough?

More.

Tim.

 

[Steve26]

I'm running a 400ish H.P. 302 with a 930 transaxle and it's plenty fast to scare anyone but is not hard to handle at all. It will do almost 60MPH in first and rapidly approching 100MPH in second if you want to do that or you can go 60MPH in fourth at a quiet very relaxing pace and talk to the person next to you. I'm not sure why the wheelspin Ian is talking about is going on? I have much more H.P. and similar weight and don't ever have any wheel spin "problem". I'm running BFG TA's (junk) 295 15 50s with a LSD in the tranny and if I get the wheels spinning I meant to. Very fun to drive and easy to live with at 400 H.P.
Steve

 

[Ian Anderson]

I'm running a 400ish H.P. 302 with a 930 transaxle and it's plenty fast to scare anyone but is not hard to handle at all. It will do almost 60MPH in first and rapidly approching 100MPH in second if you want to do that or you can go 60MPH in fourth at a quiet very relaxing pace and talk to the person next to you. I'm not sure why the wheelspin Ian is talking about is going on? I have much more H.P. and similar weight and don't ever have any wheel spin "problem". I'm running BFG TA's (junk) 295 15 50s with a LSD in the tranny and if I get the wheels spinning I meant to. Very fun to drive and easy to live with at 400 H.P.
Steve

Hi I have UN1 and open diff. 255-60-15 Kumho Tyres so less tyre and ability topspin 1 tyre

Ian

 

[Jimmy P]

They once asked many a billionaire "how much money is enough?" And the answer given most...."just a little bit more." I guess, as has been said....you can never have enough but IMHO 400-425 is enough for me. It suits the car. I believe many a person said the 289 Cobra was a much better car then the 427 becuase it was just much more fun to drive and throw around. I've always used that as a barometer for cars.....more power does not mean a better car. Each to his own.

 

[René]

my goal is to get a car that is 2 to 1,
meaning the car has for every 2kg, 1hp or say 500hp per ton.
thats enough to give the thrills and enough for most to scare yourself/others once in a while

 

RCR gt40. 302 crate engine allum head roller cam quick fuel carb.
On the dino without a header 328 hp @ 6200 rpm, 332 ft-lbs torque. 016 aaz transaxle 160 mph at 6000 rpm.
It's way more car than I expected. Ist gear is way to low maybe good for a parade. 2nd roll on the gas and hold on. It's almost a crime to have this much fun.

 

[Jack]

That combination with a 930 gearbox, or the new Griffin would be perfect for a street car with occasional track time. IMO, of course.

 

[Seymour Snerd]

my goal is to get a car that is 2 to 1,
meaning the car has for every 2kg, 1hp or say 500hp per ton.
thats enough to give the thrills and enough for most to scare yourself/others once in a while

That is almost exactly the typical Superformance GT40 with Roush 427W figure. See GT40 Specifications. However, the one I like is 5:1 (lbs/hp) which about 15% less scary than your number. They're both obscene and dangerous.

 

[Rick Muck- Mark IV]

I would venture to say the owner of the twin-turbo GT that was claimed to put out 1200 HP would have wanted more if he could have gotten it. That car is also now totaled after very few miles......

I find 450 HP to be more than enough for most situations. Your results may vary. The Safir GT40 (P1116) i sheparded in the 80's had an iron head 351 single Holley 4V that certainly had no more than 350 HP on a good day and it was a ball at Watkns Glen!

 

[William Quantrel]

I'm running a 400ish H.P. 302 with a 930 transaxle and it's plenty fast to scare anyone but is not hard to handle at all. It will do almost 60MPH in first and rapidly approching 100MPH in second if you want to do that or you can go 60MPH in fourth at a quiet very relaxing pace and talk to the person next to you. I'm not sure why the wheelspin Ian is talking about is going on? I have much more H.P. and similar weight and don't ever have any wheel spin "problem". I'm running BFG TA's (junk) 295 15 50s with a LSD in the tranny and if I get the wheels spinning I meant to. Very fun to drive and easy to live with at 400 H.P.
Steve

Sounds like a tall 1st gear. Much clutch slipping to get it off the line?

With your 400 hp do you spin through 2nd at all or does it hook up?

What is the tq on that 302?

Your 930 is a 4 speed?

Not sure how much spirited driving you do but is the car tail happy at all like a Vette or Mustang or other rear wheel drive car?

If you could magically turn a power dial and add hp/tq, would you?

I ask because I am pondering a 363 with 500 hp or a Roush 342 with 480hp that has its tq higher up in the rpm.

 

[William Quantrel]

They once asked many a billionaire "how much money is enough?" And the answer given most...."just a little bit more." I guess, as has been said....you can never have enough but IMHO 400-425 is enough for me. It suits the car. I believe many a person said the 289 Cobra was a much better car then the 427 becuase it was just much more fun to drive and throw around. I've always used that as a barometer for cars.....more power does not mean a better car. Each to his own.

If the tq was higher up in the rpm would this make for a more manageable car to drive? Or are you saying that at your 425 hp and tq you have found a sweet spot?

 

[William Quantrel]

I would venture to say the owner of the twin-turbo GT that was claimed to put out 1200 HP would have wanted more if he could have gotten it. That car is also now totaled after very few miles......

I find 450 HP to be more than enough for most situations. Your results may vary. The Safir GT40 (P1116) i sheparded in the 80's had an iron head 351 single Holley 4V that certainly had no more than 350 HP on a good day and it was a ball at Watkns Glen!

Sheparding a GT40 - our hearts weep for you!

That 351... was the tq up around 400?

Was it the tq that concerned you in slower corners or was that engine a perfect balance between power and drivability?

 

[Jack Houpe]

I would think 400 HP to be a good number for a street GT40. I almost detuned my engine shortly after installing it as it was much more HP than I could handle but then I bought Avons which erased much of that fear. Notice I said MUCH not all. So far I haven't broke anything in the car or myself.

I have a dart aluminum block 427 with AFR 225 heads, solid rollers and TWM throttle body injection, making 600 on the dyno.

 

[William Quantrel]

I would think 400 HP to be a good number for a street GT40. I almost detuned my engine shortly after installing it as it was much more HP than I could handle but then I bought Avons which erased much of that fear. Notice I said MUCH not all. So far I haven't broke anything in the car or myself.

I have a dart aluminum block 427 with AFR 225 heads, solid rollers and TWM throttle body injection, making 600 on the dyno.

Hello Jack,

Handsome looking SPF in red.

You drive with Avons on the street? Aren't Avons track tires?

Do you have 15 inch wide rears?

 

[Rick Muck- Mark IV]

Hello Jack,

Handsome looking SPF in red.

You drive with Avons on the street? Aren't Avons track tires?

Do you have 15 inch wide rears?

THe Avopn Cr6ZZ tires are DOT "street" rally dry tires and fine on the road, they are very good at the track, decent in the rain and even wear pretty well.)

Safir P1116 was never dyno'd but would postulate that the torque was no more than 350 either. It had a milder hydraulic cam (pre roller cam) and mid size Holley (can't recall model) but went as fast as I cou;d point it around Watkins.

 

[René]

nice specs Jack, more then enough hp