Stock flexplate, converter and driveshaft hp + tq limit?

[1974scamp]

Hey guys,

ive got an got an aluminium headed 408cui in my 74 Scamp, about 10 to 1 compression, comp XE275 cam, air gap, holley 750 dp, msd ignition... nothing too crazy.
Last year my second hughes 2500stall converter failed and ive thrown in the stock converter with the stock flexplate, which came in the car when i bought it with a 318cui.
Car drives great since then with no issues and actually i really like the stock converter.
Trans is a built 904 with reverse manual vb, rear is a 8 3/4, clutch style sure grip 3.23
Now i have a set of mickey thompson street ss 235/60r15 drag radials and another 3rd member with an eaton true track and 3.91 in the basement which i would like to install this summer. I already istalled a driveshaft safety loop just to be sure, but should i worry about the stock flexplate and converter with the drag radials?? Car is driven on the street.

What would you guys say whats the hp and torque limit of a stock flexplate, converter and driveshaft?

Thanks for the help, Laurin

 

[66Valiant528]

7260 or 7290 joints ? Traction breaks things that are weak. You can put a better flexplate in when yours breaks! Frankly I think the 904 is the weak link. I used to break converter necks and wipe out front pumps.

 

[1974scamp]

Sadly u joints are also the small 7260...
Dont know whats exactly been done to the 904 but its fully built by a well known trans guy over here in Europe with billet parts from A&A so i think thats gonna be fine

 

[Brooks James]

Not sure if it's accurate, the tech who shortened my stock 70 Dart driveshaft on a /6 to 360 swap said the driveshaft would hold 450 hp

 

[transman]

Sadly u joints are also the small 7260...
Dont know whats exactly been done to the 904 but its fully built by a well known trans guy over here in Europe with billet parts from A&A so i think thats gonna be fine

Don't worry about how much HP/TORQUE a 904 can take. My ex employers race car had a Steve Schmidt pro-stock engine in his BA/A race car. The transmission was a 904 full of HP parts we manufactured for the high performance transmission industry. The car of course was the test mule. At one time the NHRA record for the class. I believe it was 6.9 seconds @ 201 MPH.

 

[33IMP]

Just my opinion only!
I don't think you can hurt the driveshaft with a stock converter. However, I would upgrade to at least the 7290 joints. If you plan on more gear ratio, and/or more converter, I would upgrade to the 1350s. It shouldn't be that much more than the 7290s.
It ALL depends on how hard it launches on good drag radials.
Edit: re-read the first post. I would at least do 7290s before I put in the 3.91s and drag radials.