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Ok maybe its a stupid question but I am trying to decide what to order here.
I bought my dream car: 1968 coupe, 454, M-20 4-speed in quite good shape with NOT the original engine. The engine was way under powered and when we pulled it apart it was very VERY worn.
What I am doing to it:
- Wilwood Brakes
- Sharkbite Coil over suspension
- New steering, bushings, brake booster/MC, brake & fuel lines, radiator, and all the components around.
- M-20 will be gone through to make sure its solid (feels great now)
- Staying with my 3.55 rear end.
- Interior back to stock
I am trying to decide if 600hp is too much for a C3 with the specs listed above. I will not be racing it. This is just to build the car I've always wanted. I do want it to be EXTREMELY fast, but I am concerned that the bigger HP might be unusable.
I would love to hear from your experience.
Thanks everyone!!!! Here is a picture just before I started the winter tear down.
What kind of upgrading would you recommend?
I haven't done the rear suspension yet so I will be back there playing around anyway.
My new big block should make 600+. I've got an upgraded driveshaft and half shafts with solid u joints. Safety loops on both the driveshaft and half shafts. I have a Dragvette 6 link which I wouldn't consider a requirement but it does remove the half shaft as the upper link. I'm gonna try to make the stock diff and stub axles live for awhile, but I'm prepared for upgrades in short order. The clutch is also on the list for upgrades. I may bite the bullet on the clutch during the engine swap.
For 98% of the people in the world, 200hp is more than they can handle. Take away ABS brakes and then it is 99%.
Build the car for what you want, to handle what you want and you will be fine. Respect the power in your hands and you won't have any problems. 600-800hp sounds like a good number to me.
After building a few cars, I would go with a LS motor if you want horsepower.
The advantage is longevity and you can program the throttle (gas pedal) for economy mode as you get older. I'm not a fan of computer controlled cars, but sometimes it makes sense.
I have 540hp in my 85 with a 6 speed - no traction control. It's a handful in the rain / cold days even with 335's in the rear.
I have 400hp in my 71 - I think that is a good number based on the structure and tire size. With a 5 speed it's a pleasure to drive and delivers good gas mileage. (I drive it a lot). (3:55 and 5 speed)
Torque is what you will feel on the street, unless you are racing I would look for a good torque motor. You will probably have to upgrade the drive line.
One of the best conversions for less money would be a 5 speed and 3:55 or 3:73 rear. Gives the best of both worlds and keeps the car drivable.
Last edited by BLUE1972; 12-21-2017 at 11:19 AM.
Reason: hate auto spell
I would value your opinion,
What hp number would you top out as "safe" on a stock c3 rear if the driver is cool with it, meaning not just trying to break something,
I would value your opinion,
What hp number would you top out as "safe" on a stock c3 rear if the driver is cool with it, meaning not just trying to break something,
Thanks
Horsepower doesn't kill a gearbox. It's torque or shock loading.
An 800 hp race engine at 8000 RPM is putting 525 ft-lbs of torque into the rear end. No big deal for our stock differentials.
A 400 hp diesel engine at 2000 RPM is putting 1050 ft-lbs if torque through the rear end. Half the horsepower of the above example, but twice the twisting force. Not a recipe for differential longevity.
And any horsepower "rating" of a gear box can easily be overcome by a heavy spinning flywheel.
IT's the F = MA, the more mass, the greater the force it takes to reduce the RPM (negative acceleration) of the flywheel. The reason racers went to AL flywheels was to allow the engine to rev faster, less mass.
What also should be mentioned is tire size. If you stay with 205 70 R15" you will not brake anything, but have great burnouts.
If you go to 245 55R15" things may brake as you will have less tire slip and more load on the rear and drivetrain.
ScottJamison:
With out reading any of the other comments my answer to the question is there such a thing as too much horsepower? You can look at it two different ways. Yes and no. Yes, there is such a thing as too much power if you can't put it to the ground or No, there is no such thing as too much power just not enough traction.
Either way you look at it you need to be able to put the power to the ground otherwise it is useless and unsafe. You should be ok with around 600 horsepower. I had around 500-550 with a 4 speed and even with 215/70/15 BF Goodrich tires I didn't have too much problem with traction (sometimes I would lose it on the 1-2 shift and have to pedal out of it a little)....went 12.30s @ 118MPH with the 215/70/15 street tires. 4 speeds and high horsepower motors are a blast!
The previous incarnation of my motor included a 10.5 pound aluminum flywheel with a twin disc clutch. Absolutely loved the light flywheel feeling. As long as you have a deep enough gear in the rear or tranny for takeoffs lol. Going to use a light flywheel with this iteration also.
I would value your opinion,
What hp number would you top out as "safe" on a stock c3 rear if the driver is cool with it, meaning not just trying to break something,
Thanks
I'm really not sure. I would say as long as you don't put a drag radial on it, it will live a long and happy life on the street with 500-600 hp. On the other hand, if you've got 400 hp on a drag radial going to the strip every weekend, it's probably not going to last. I tend to roll into the throttle and I don't do much dig racing, so parts tend to last. With the C3, I would take every precaution with the driveshaft and half shafts because when they break it can really do some damage.
As much as i think an old school 4 speed wiuld have a cool factor i might be way better off with a th400
I'm running an "old school" four speed in mine (the original M21). I pulled enough weight off the car that I no longer needed the extra gearing of my 5 speed, so I pulled it out. The four speeds are also lighter than a 5 speed or a TH400 (which I currently have in my '51 Chevy PU).
Go for it! IF!!!...you get one of the frame builders for pro-stock and or pro-mods to build the frame. If you harness that many ponies to a from St. Louis GM Corvette frame, can I have your O/U shotguns, vintage tube powered stereo gear and your collection of '40's era New Mexico Navajo rugs?
Regards.
Anxious on the Post Oak Savannah.
For me, 1hp per cubic inch makes for a nice street motor. I'm looking to go 383 sb with 400 ish hp, built with the most bottom end. Hooked to an auto in my case, tempered by the rear end ratio, probably 3.36. Semi sensible, semi affordable, I hope.
12-20-2017, 10:29 PM
