u joint durability?

[Jim Comet]

So I am putting together my 66 Comet that will have about 550-600hp. The original big block drive shaft has 1330 ujoints and my new front and rear yokes are 1350. This will be a foot brake bracket car. I would prefer a non drilled joint for strength but there does not appear to be any available with this cap 1330-1350 size setup. Do you see any problems with running a Spicer 5-648x conversion u joint at this hp level? I would upgarde drive shafts but the money pit is hungrier than my wallet right now. Anyone racing with 1330 joints? Should I be concerned? Thanks for your advice. Jim

[57 lima bean]

Raced my car for years with 1330's.Foot brake with an auto...no issues.

[TomP]

My Fairlane uses that U joint at the front because it has a Mark Williams 1350 slip yoke but runs the stock 1330 series Crown Vic driveshaft and the rear U joint that comes in it.

[manofmerc]

On my 67 comet it runs 6.80-7.00 460 power with the same setup you are speaking of c-6 with a transbrake no problems so far .I do have an ford motorsport yoke and I had a driveshaft shop build my drive shaft so I have solid u joints and a bit thicker tube .Good luck Doug

[Falcon67]

Footbraker here too.  Stock driveshaft, 1330 front, converter joint in the rear to hook up the 9" yoke.  I haven't looked at them in 18 years.  Car has run as fast as 7.0x over the years.  As above if crossing under the 7.0 mark, have a local build a good driveshaft.  If I pulled the 570 HP motor out of the dragster and dropped it in the Falcon, the next thing would be to replace the stock shaft. 

[Barry_R]

Back many years ago I ran the conversion joints without any problems in a 12 second car.  I was "instructed" to clock any grease fitting so it would be "under compression" as the driveshaft was loaded.  I stepped up everything after I acquired a nitrous habit so I cannot attest to u-joint durability at higher power levels - - because it broke pretty much everything between the flywheel and the lug nuts......