Diveshaft queston.
 

Hi guys im going to be a senior in high school. im rebuilding my 72 GMC C20 after it damn near burned to the ground in march :smoke: :gmc2:. So it is nearing time to put in the motor and trans. Im going to be running a 450HP Corvette motor. this beast was built in a race shop in texas. it a 350 not stroked, its running like 11:1 compression. The trans ive decided im just going to reuse the 350 that I had rebuilt shortly before the fire (nice right). Now that was hooked to the original 350. Im at the point that if I blow the trans oh well :gi:. But anyways back to my question: will the original drive shaft handle that kind of power or will I twist and/ or break it? :gmc2::flag:

Re: Diveshaft queston.
 

If it were me I would ask your tranny guy what he recommends on your tranny cause if it can't handle the power and your drive shaft can't you will twist it. With 450hp you are going to run the **** out of that truck. I recommend a new driveshaft especially if it's 40+ years old. But ask the trans builder what he recommends he had it apart so he will know

Re: Diveshaft queston.
 

Is the original shaft one piece or two piece?

If it were me I'd ask a local drive shaft builder for his advice. He should be able to make you a nice new one piece to handle the power for about $300.

K

Re: Diveshaft queston.
 

Probably twist like a piece of salt water taffy. If, you truly have 450HP.

Re: Diveshaft queston.
 

I think $20,000 to $25,000 should just about do it. Then again after all that some newer Camaro, 500 horse Cadillac or Dodge charger will just blow you doors off. 11to1 comp requires racing fuel and it won't be very streetable.

It'll sure sound nice though.

Re: Diveshaft queston.
 

When you grenade the stock TH350 then you will need yet another driveshaft for the different length TH400 to handle that much power. You might be OK with stock tires, but if you can actually hook up you will have some issues. A Powerglide is the same length transmission so you could go to that I guess. I would not waste a lot of time and money having a custom made driveshaft made for a TH350 with that much power unless you have the transmission built to take it.

Corvette 350 motor-what year? I do have a '91 Corvette TPI motor in my '83, but it is still fully Corvette with stock aluminum heads and stock everything-never even had a valve cover off. If you are getting 450 dyno HP out of a 350 there is probably not much left of the original motor (unless you are using a 200 shot of nitrous). Always puzzles me to hear somebody has a Corvette motor, but changed the heads, cam, intake, carb, pistons, and crank. Who cares what the block came out of at that point? A 4-bolt truck block is probably stronger for a lot of those years.

Anyway, good luck with your build. As noted you will need race gas to feed that and you will probably have to upgrade your cooling system.

Re: Diveshaft queston.
 

I have more than 400 ponies coming out of my 350 and my stock driveshaft is just fine.

However... mine is not a Corvette engine. ;)

Don't get hung up on the HP.

Gary

Re: Diveshaft queston.
 

[QUOTE=MARKDTN;7251240]When you grenade the stock TH350 then you will need yet another driveshaft for the different length TH400 to handle that much power. You might be OK with stock tires, but if you can actually hook up you will have some issues. A Powerglide is the same length transmission so you could go to that I guess. I would not waste a lot of time and money having a custom made driveshaft made for a TH350 with that much power unless you have the transmission built to take it.

Corvette 350 motor-what year? I do have a '91 Corvette TPI motor in my '83, but it is still fully Corvette with stock aluminum heads and stock everything-never even had a valve cover off. If you are getting 450 dyno HP out of a 350 there is probably not much left of the original motor (unless you are using a 200 shot of nitrous). Always puzzles me to hear somebody has a Corvette motor, but changed the heads, cam, intake, carb, pistons, and crank.
QUOTE]

it was dynoed at 450 HP and like 550 Foot pounds of torque. ill need to double check the torque but that is what i can remember. i bought it off a buddy who had it in a lifted jeep wrangler. it broke the yoke and then the rear end after he fixed the yoke. and yes ill need to run premium fuel with octane booster for best performance. it wont be my daily driver. right now im driving an 03 Silverado. Finally ill need to call AAMCO and see what they say about the trans they built for me. also no N20 and its naturally aspirated. he was running a 770 CFM Holley Truck Avenger carb on it. its even got an alternate firing order.

Re: Diveshaft queston.
 

I'm going to stick my neck out and ask why in the Wide World of Sports you would want an engine like that in a pickup truck? If you don't run octane booster ALL the time it will detonate and destroy itself. It will be hard to start, may break starter noses, no vacuum for brakes probably, won't idle, and will be hard to cool. Why would you not buy a crate 350 and put that in? Then you would have something that you can drive and enjoy. My .02

Re: Diveshaft queston.
 

It can run 92 octane pump gas you just need to change the timing. It runs BETTER with octane booster. Also I have a high flow water pump for it.

Ok I just got off the phone with AAmco and they said that the turbo 350 they built for me should handle 450hp as long as I use an aux cooler (already have) and a stall converter (I am planning on getting) probably 2300 rpm. As for the driveshaft his coment was that driveshaft is better than most stock ones today. Input???
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Re: Diveshaft queston.
 

If it's the original drive shaft definitely take it to a drive line shop and talk to them.

Re: Diveshaft queston.
 

I'd get that in writing.

Re: Diveshaft queston.
 

I have no idea why he would say that.

Back then it was a steel tube with a yoke stuck on each end.

These days they are a steel tube (usually) with a yoke stuck on each end.

There are some carbon fiber/aluminum composite/metal matrix shafts in use, which are lighter and still handle the load, for more premium applications.

I stand by my original comment (except I probably wouldn't go see the shop owner you just talked to).

As an aside, my Chevelle is about 950HP and has gone 9.80's @ 3950 lbs. I ran the original shaft for many years and it was fine when I took it out to replace it with an aftermarket shaft. I have it stored as a backup in case anything ever happens to the new one.

K

Thanks for the input guys! I'll pay a visit to a shop that handles driveshafts.
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Re: Diveshaft queston.
 

Save your money. The stock shaft will take much more than 450 HP. I know because this engine, by spec not imagination is over 600 HP and 650 Ft-Lbs of torque and the stock shaft in my truck has lasted 15,000 miles with that beast trying to break it!

Re: Diveshaft queston.
 

I personally wouldn't run a TH350 behind that much motor, I'd find a TH400.
But that's just me.

Re: Diveshaft queston.
 

Couldn't agree more! TH400 is a much stronger trans.

Re: Diveshaft queston.
 

I do believe the 550 ft/lbs of torque is more important in breaking things with the weight of the truck.A built th350 would handle it with good sprags/discs/bands etc... Does the 3/4 tons run the 1350 series u-joint? if so run it! Be wise put a driveshaft loop or 2 on the driveshaft.You can repair alot.Hard to get a driveshaft out of the neighbors house/body/pet/

Re: Diveshaft queston.
 

I have no idea how would I know? Also couldn't I just change the U Joints?

Re: Diveshaft queston.
 

The end caps on the 1350 u-joint are bigger( 1.188" o.d. from the interweb) If not the safest the cheapest would be to replace the factory joints.