Opie the Animal

Hello I'm putting a 450 horsepower engine in my court vet will I need to change anything else besides the brakes will it hold up its a 1975 C3

eboggs_jkvl

It probably will get better answers if this thread is in the C3 forum.

Sorry,

Elmer

TedH

What is the condition of the balance of the drivetrain (transmission, driveshaft, rear diff, half shafts and trailing arm assemblies)? If any are marginal, that 450hp engine will reveal them through breakage/failure.

If it were me, I would have the driveshaft and half-shafts rebuilt. Also, have the differential blueprinted/refreshed. Finally, have the rear t-arm assemblies rebuilt with focus on the spindles/bearing assemblies.

What is state of your suspension system (springs, tie rods, strut rods, shocks, ball joints, etc.)? I'd refresh them also.

Over the course of the first 10 years of ownership of my C3, I addressed all of the above. I have 0% concern over their ability to stand up to a 400hp/400tq engine. Weak link would be my aluminum differential. Your differential from '75 is cast iron and much stronger but still, 450hp will test its health considering the HP from 75 was about the lowest from the C3's.

7t9l82

Where do people come up with this stuff? If everything is in good condition 450 hp is no issue for these cars. They did build them with L-88 's you know.

calwldlife

450hp does bring in some issues like
clutch
pressure plate
universal joints
drive shaft
rear end
tranny

the hp is at some parts limits

suggest you look at the recommended hp ranges of the parts you have,
minimum the clutch

lars

Any C3 will easily handle 450 horse with street tires. Why do you want to change the brakes..? I'm running 500 horse/500ft-lbs with stock drivetrain and drum brakes (I'm running an RST twin disc clutch, but the rest of the tranny/driveline is stock). No issues or problems. I don't push the gas pedal down when I'm applying the brakes, so it stops just fine.



Lars

calwldlife

any?
ok then.

lars

Any C3 on street tires will handle it. If the driveline is in good condition. Other than my clutch, my driveline is all stock with new, good quality components. No problem at all. None. And I hammer it every time I drive it and race it.

Lars

calwldlife

street tires and a CLUTCH

lars

Only because I'm pushing 500 ft-lbs of torque and I want light pedal feel. The OP is planning on a mild 450-horse upgrade, which likely has 400 - 420 ft-lbs of torque. That means the stock components (in good condition), will hold up just fine. The stock LT-1 small blocks put out 370 horse, and the stock 454 big blocks in the C3 chassis/drivetrain put out 500 ft-lbs of torque, so the OP's 80-horse increase over a stock C3 Vette, in a small block putting out less than 500 ft-lbs, is negligible and irrelevant to reliability. No problem.

Lars

Edit:
As an example, I built a 700-horse/650ft-lbs supercharged 383 for a guy with a C3. He ran it for a year, nailing it hard, with no reliability issues, even on big street tires. We upgraded the halfshafts after a year, only when he decided to re-do the rear suspension. There was no damage or indication of failure when we pulled the stock components out of the car. These cars are tougher than most people realize, and many failures are due to worn or damaged parts - not because the power has been increased a little bit.

Opie the Animal

Thank u guys for all the responses u helped out a lot 👍

AboveTheLogic

Sweet, I'm gonna go out and dump my clutch some more

My engine puts somewhere north of 400 ft lbs and I'm always afraid of breaking something just because I don't want to have to fix it. I had driveline failures occur in the past with my old midsize Jeep Cherokees and Datsun Z-Cars so I'm overly paranoid.

This is why I stayed with 255 width tires all around when I bought new wheels. Some folks have asked why I didn't go with a staggered size and wider tires in the rear. For me, rear wheel spin is good clean fun and keeps the driveline from breaking, as long as I don't let any wheel hop happen (which hasn't happened yet).

scottjamison

I didn't see any mention of the transmission.
(I may have missed it, who knows).

For my engine I had to switch out my M-20 4-speed because it would not handle 580ft-lbs of torque.

calwldlife

gm felt the need to up u joints
and other drive line things for LT1 and BB.

op should have "good parts"
he should look at ratings.
qualifiers about this and that doesn't change that.

jb78L-82

My 2 cents on this question is that as others have stated, as long as the drive train is in good condition with up to date heavier duty ujoints, all "should" be well.

However, as mentioned previously, the transmission type does make a difference. The Saginaw wide ratio 4 speeds as well as the M20 wide ratio, were never intended for big gross HP motors, like the M21/M22 close ratio 4 speeds. In addition, the close ratio Super T-10 with the aluminum case like in my 78 L-82 4 speed was rated to about 350 gross HP, not the 450 Gross my rebuilt L-82 355 has now-the Super T-10 in my car is the weak link. As my builder who did the bottom end of the motor and is an expert on GM engines, transmissions, and rear ends told me back in 2014, as long as I don't drop the clutch at 5K RPM's with my super sticky ultra high performance summer only 255/45/17 ZR tires, the transmission will be fine and has been. I always roll into WOT, rather than mash the go pedal. All good so far entering driving season #5.

Outside of the 427 L88 corvette, the highest Gross HP C3 corvette rating was 435 Gross HP. Once you pass 500 Gross HP, things could start to break, in my opinion, if everything is not perfect. Just my thoughts!

stingraymaniac

I'm pushing 550 hp now and 515 torque, changed my rear end to 3:55 gears
Spicer solid u-joints and new clutch, the only thing that has problems so far is the rear tires

Opie the Animal

Yeah I didn't have 454 is in them how much horsepower did that kick out

Opie the Animal

​​​​​ so all stock and you got 500 horses and everything is all good ????? U didn't change nothing

Opie the Animal

handle how many horses

cv67

Dont worry about numbers its too easy to get tied up in the internet then keep yourself from getting what you want.

Get some decent Ujoints, try it out on street tires. Bet it holds up just fine
Most breakages are due to sheer abuse. The guys that are always breaking stuff....take a look at thier driving habits theres a correlation.
Drop the motor in!