914 V8's: What breaks first?, Drivetrain Options

[Dunc]

All you v8 conversion guys. I hear all sorts of opinions as to what breaks when you convert to v8 power. I would like some opinions:
1. Axles: I hear that these are the weakest link. Replacing them with 911 shafts seems to be the "fix"?
2. 901 transmissions. When they fail, what breaks? The case? Gears/shafts?
3. What level of hp/torque is the limit of a 901 setup.

Thanks.

Mike

[Bruce Hinds]

(IMG:style_emoticons/default/agree.gif)
CV joints are probably the weakest link. spinning one wheel in the gravel then onto pavement repeatedly will kill them just like poor driving in a V8 or high HP car will do the same when lifting the inside wheel in a tight corner.

First is a waste of time and geared too low for anything other than idling around a shopping center or starting off on a steep hill.

Drag racing or just a few burnouts can kill the ring and pinion.

HP is a product of torque and RPM - the little box was designed to handle a 300HP 6 at high RPM all day long, so torque at low RPM can be a killer. I drove the mountains of Colorado and California for 20 years like a madman with an overbored 327 and a cam that came on about 1800 and pulled like a mule through 6500. I was making about 340 HP but only a little over 300 ft/lbs.

Renegade rebuilt my 901 after about 15 years with some taller gears and said all looked well inside. It was until I side stepped the clutch one day and smoked the tires down a runway. That "did-in" the ring and pinion.

If you drive it like the road machine it was built to be, the little box will handle the v8 well.

[Dunc]

(IMG:style_emoticons/default/agree.gif)
CV joints are probably the weakest link. spinning one wheel in the gravel then onto pavement repeatedly will kill them just like poor driving in a V8 or high HP car will do the same when lifting the inside wheel in a tight corner.

First is a waste of time and geared too low for anything other than idling around a shopping center or starting off on a steep hill.

Drag racing or just a few burnouts can kill the ring and pinion.

HP is a product of torque and RPM - the little box was designed to handle a 300HP 6 at high RPM all day long, so torque at low RPM can be a killer. I drove the mountains of Colorado and California for 20 years like a madman with an overbored 327 and a cam that came on about 1800 and pulled like a mule through 6500. I was making about 340 HP but only a little over 300 ft/lbs.

Renegade rebuilt my 901 after about 15 years with some taller gears and said all looked well inside. It was until I side stepped the clutch one day and smoked the tires down a runway. That "did-in" the ring and pinion.

If you drive it like the road machine it was built to be, the little box will handle the v8 well.

Thanks Bruce:

I appreciate the advice. I currently have a 307 in the car...its doggy. What do you think of an updated Chev 302 setup? High RPM...lots of hp, but not so torquy like a 350. I take it you would not advise changing out the 901 transmission for a 915(?)

[Bruce Hinds]

Dunc,

Basically there were three common size crankshafts in the SBC series, other than the 400. I get mixed up on the 305 and 307. But torque being a product of stroke the 283 and 302 used a 3" stroke crank. The 327 and the 307(?) used a crank about 3 1/4" and the 305 and 350 used the most popular 3.48" stroke crank.

283 and 302 engines need to really rev to get the power out and then you get into the heavy duty valve train components, screw in studs, roller rockers and heavy springs. Everyday driving usually doesn't see those kind of revs(above 5500-6000) so you may not end up using the power after all.

I chose to use a bored 327(331) and controlling the low end torque with the cam, heads and exhaust. Here again, the big heads with 2.02 intake are probably great for making high RPM power, but everyday hot rodding the more popular 1.92 intakes will produce more even mind range power.

A lot of guys use the short tube headers too, they're great for making torque and creative exhaust set ups, but longer tube headers are better for the mid and upper range power and not having a crossover helps too. Without a crossover you'll have to work on pipe size to help quell the resonance.

Hope this helps.

[Dunc]

Dunc,

Basically there were three common size crankshafts in the SBC series, other than the 400. I get mixed up on the 305 and 307. But torque being a product of stroke the 283 and 302 used a 3" stroke crank. The 327 and the 307(?) used a crank about 3 1/4" and the 305 and 350 used the most popular 3.48" stroke crank.

283 and 302 engines need to really rev to get the power out and then you get into the heavy duty valve train components, screw in studs, roller rockers and heavy springs. Everyday driving usually doesn't see those kind of revs(above 5500-6000) so you may not end up using the power after all.

I chose to use a bored 327(331) and controlling the low end torque with the cam, heads and exhaust. Here again, the big heads with 2.02 intake are probably great for making high RPM power, but everyday hot rodding the more popular 1.92 intakes will produce more even mind range power.

A lot of guys use the short tube headers too, they're great for making torque and creative exhaust set ups, but longer tube headers are better for the mid and upper range power and not having a crossover helps too. Without a crossover you'll have to work on pipe size to help quell the resonance.

Hope this helps.

Thanks for your email Bruce. I am located on the east side, but occasionally I make it over to Kitsap County. Maybe we can chat over coffee some day.

From my reading, the 302 is a 4" bore with a 3" stroke...i.e. a 327 block with a 283 crank in it. What interests me about the motor is that Chevy specifically intended it to be a road racing motor...with a fairly broad power band. Not a motor for the Saturday nite drags. I have read that a modern 302 build uses roller lifters and roller rockers---the entire valve train, as you point out, must be very light weight to function at high RPM. In any event, I want to do a build that is balanced...motor, transmission, axles, brakes.

Thanks for your help.