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driveshaft loop install.. how far back

18K views 22 replies 13 participants last post by  cv67 
#1 ·
im going to the track this sunday, and now that i have sticky tires, i need to run a loop since i have a stick.

so how far back does the loop go from the x-member, is it 6"?

thanks

aaron
 
#4 ·
Here's a pic of the loops that BMR Fabrication sells. But they come in black unless you specify red. I installed one of these on my 70 Chevelle, and what I like about them is that they're contoured specifically for our cars, since the arms are angled perfectly to follow the angle of the reinforcement boxed rib on the Chevelle floor board where the floor is the strongest. Which I believe is also the perfect distance away from the front U-joint. The main hoop also fits the driveshaft tunnel perfectly. It makes for a much more precise fit and a cleaner install than those universal type loops made by Lakewood and Competition Engineering do.

http://www.bmrfabrication.com/A-Body.htm

 
#8 ·
I like the concept of the loop that bolts under the trans mount. Does anyone have or know of anyone's experience with it doing what it needs to do if a joint actually breaks? Thanks,
 
#9 ·
I liked it too, so I bought one (although I cannot remember where I bought it from, and I've misplaced the receipt, so I couldn't even tell you where) but I went to put it on my car, and learned that it's only good for the Chevelle stock sized 1310 series U-joints. I have 1350 series U-joints, and that loop that bolts to the transmission mount has a diameter that's too small, so it won't even clear the 1350 U-joint, nor the 1350 series transmission slip yoke. It looks like it would be good if you have the smaller 1310 U-joints though.
 
#10 ·
Wish I would have seen this when I posted about a loop,(thats a nice unit) had a lakewood & fabbed ,bent to conture of the body brace ,loctite all bolts ,& renforced. yes 6" max from u/joint center 2"wide band is the NHRA rule in the 2007 book
 
#12 ·
I easily made one.I bought just the 2" loop from Jegs,I think it was around 10 bucks.I then took a piece of 1/2"bar stock about 3" wide by about a foot long.Welded the loop on the top of the end of the stock.There are 2 holes,one behind each other on the crossmember,a couple of inches apart,parallel with the tailshaft.One was 1/2 " drilled the other one out to 1/2".Drilled the stock and bolted it into place with two 1/2" hardened bolts.It's a bit of an overkill as strong as it is,and it's a little heavy,but the best part is I didn't have to drill any holes in my virgin floors,and it's easily unbolted out of the way.:thumbsup:
 
#14 ·
Not that I know of. My guess is that if the tech inspector can reach the loop, and he grabs onto it to try and wiggle it, and it feels solid, then he won't have a problem with it as long as it's relatively close to the front U-joint. And I can't see them trying to crawl under there with a tape measure to enforce the exact distance specified by the NHRA rule book either.
 
#18 ·
Aaron,
No more than 6" back from the tailshaft is the rule. It will be tough to get it that close with a universal loop because of the way the floorpan is on a 68-72 Chevelle. Just get it as close to the 6" - 8" range as you can and it will be fine. At Island, they have nver looked under my car. He just asks me if there is a loop and I say yes.
 
#19 ·
Put it as close as you can within reason. The tech inspectors at many tracks are not going to look under the car. I have been running my car at many northeast tracks and they are checking for the obvious things. My car has many SFI certified parts in it and none of them have been recerted since new. I had a balancer that was certified in 94, but when they see an aftermarket one on there it's good enough. My car has never been checked for a driveshaft loop at Maple Grove and it's not within 6" of the joint because it didn't fit there.
 
#21 ·
Years ago, when I had the old motor dyno'd on a Dynojet, it put down 315 RWHP. Car ran a 13.2 back then. Your sig says you have 303 RWHP. If you can get any sort of traction at all, you should be high 12's to low 13's. Your car is not as heavy as mine. I'll see if I can make it Sunday. Who else are you going with? We could meet up at my house and go from there.
 
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