Slant six on boost - upgrade the driveshaft?

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MadScientistMat

MadScientistMat

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1966 Dodge Dart with an A904 and a boosted 225. This combo may make up to 300 hp and 400 lb-ft at the crank at full boost if I go for that; may run it at less. I'm swapping in an 8.75" rear axle since I didn't think the 7.25" would survive too many hard launches. What are your thoughts on the what to do with the stock driveshaft? Shorten the stock part and stick a bigger U-joint on the back, or upgrade to something bigger while I'm making changes?
 
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Where did you get your numbers?
Dyno or a friend of a friend?
300hp and 400ft lb of torque?
 
I’d upgrade the slip yolk and trans side u joint to 1350’s. Dr Diff has them. You’ll have a hard time breaking them with that power level.
 
Max Wedges and Race Hemis used ball and trunnions and slip yokes. I think you're good.
 
Power numbers are an educated guess as to the most the combo could make if I really turned up the boost at this point, not yet dyno'd with this combination. Thanks for the responses so far - at this point just getting the stock shaft reworked is looking reasonable.
 
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I think the stock stuff is fine.

I have run a stock driveshaft and 7260 yoke at
much high HP than that. (500 HP Dyno) for years.

Be sure pinion angles are correct for your application.



Boy am I going to get Flamed on this Post!!
 
I had a driveline shop cut down a 904/ slant 6 shaft on a 8 3/4 install, he said 500 HP max
 
For years I ran Driveshafts out of 70's AMC Station Wagons with 904
Transmissions. Only 2 1/2 and 10 1/2 / 11 Pounds. Also a yoke that
is way shorter and lighter than the Mopar parts.

That = I did explode @ 510 HP. in my E/SA Demon. I may have got a defective one?
It put 6 large holes in the floorboards and the trans broke in two completely
right at front pump and it made a real big mess.

Actually lighter than the Aluminum shaft in the Superstock today.

It happened at Woodburn Or. in the lights and a piece came within an inch of my
opponents Windshield.

I do not run them anymore!
 
What tire will be on it? Any street tire, the stock stuff will be fine. With slicks or drag radials at 400lb/ft I’d upgrade the joints. The driveshaft will be fine.
 
Do you have a thread on your car or engine build?
 
U will be fine. No worries as u won’t have much torque off the line. By the time boost comes on u will be rolling 20-30 mph. Kim
 
Here's the build thread.

Dodge Dart thread on Grassroots Motorsports

This one is one year too new for ball and trunions; it has a conventional slip yoke. Thanks to all who responded; I think I'm just going to have a driveshaft shop swap the rear U joint and shorten the stock tube.

The other option I had been considering was seeing if modern trucks have any worthwhile aluminum driveshafts I could have cut down.
 
I know when I had the driveshaft made for my Duster, the shop said it was cheaper to get yokes for the 3.5" diameter driveshaft.
Standard 4x4 stuff.
A complete driveshaft cost me $350.
 
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