71K5 - BP71K5's Just for fun build

[bp71k5]

Roll cage preparation

My wife gave me this beer sign a few years ago and I finally have a spot to put it. I had some time to do some cleaning and upgrading of the garage now that the top was out of the way. I added a bit of extra task lighting and moved my "office" out into the garage.

It's really cold now. I had to put some flip-flops on while I'm out there instead of my normal barefoot wrenching routine.

 

[bp71k5]

Roll cage preparation

I also picked up some 2" "DOM" ABS tube and some angles for a cage.

The plan is to mock up the cage in plastic and see how everything comes together to make buying the right amount of tube easier and make sure I can tweak the design before commiting to expensive steel tube.

The straight sections are ABS tube and the angles are non-metallic EMT. By cutting part of the bends away, I can get almost any angle I need and use press-fit joints to assemble it all and make changes when needed.

This is seeming like it will be fun.

 

[Jimmy4matt]

Using that sched 40 stuff is a great idea. I'll have to try that when I try to figure out cage layout. You may want to try to make an external factory rear tire carrier work. Mine had a 33" tire on it for decades and a 35" for a while and hasn't cracked or torn the body. You may be able to put a bigger reinforcing plate on the back side of the tailgate and reinforce the corner mount at an angle down toward the pass rear wheel opening and triangulate to the bed rail for greater load dispersement, if that makes sense. Big tires take up a huge amount of cargo space. I've been enjoying this thread since it started. You've had a lot of creative solutions. Keep up the good work. Merry Christmas.

 

[bp71k5]

Thanks, It's kinda fun seeing such big changes in the works.

I suppose if I can make the plastic version break down small enough, I can sell it on ebay for someone else planning a cage.

 

[Jimmy4matt]

...or just dig a hole, pull some cable through it, and bury it. Just kidding. Are you planning on doing some kind of frame mount or just body?

 

[bp71k5]

I'm probably going to start with just the body. Going down to the frame is a whole new level of fabrication that I can step up to later if needed.

 

[medicdave]

What are you drive shaft angles and lengths. Planning the same driveline, picking up parts a bit at a time, don't want to get a 1410 yoke for the 205 if I'm gonna need a flange and cv. FYI mine will be nv4500, 203/205, 4-5" lift in a 90

 

[bp71k5]

Both shafts are custom so I wouldn't buy anything until everything was setup.

I'll have to go measure exactly but the front shaft is about 4" longer than the rear after I moved the rear axle back 1.5". There's too many variables to know for sure how long they will need to be until you get there.

 

[medicdave]

Sounds like a plan. Did you have to run a cv shaft in the rear with the 4"lift?

 

[bp71k5]

The rear shaft is 31.5" from center of ujoint to the other ujoint. The front is 35".

I might be able to run a standard shaft in the rear, but I wanted to rotate the rear pinion up out of way a bit and keep any vibrations down at higher speeds so i went that way. I've also got about 6" of lift in the back so less would make it easier.

 

[AJs72K5]

The rear shaft is 31.5" from center of ujoint to the other ujoint. The front is 35".

I might be able to run a standard shaft in the rear, but I wanted to rotate the rear pinion up out of way a bit and keep any vibrations down at higher speeds so i went that way. I've also got about 6" of lift in the back so less would make it easier.

I'd suggest a CV in the rear with it being that short, and with the lift. I think the ujoints on a standard shaft would be pretty close to binding on you.

Smart idea on the pvc mockup btw.

 

[vtblazer]

I might be able to run a standard shaft in the rear, but I wanted to rotate the rear pinion up out of way a bit and keep any vibrations down at higher speeds so i went that way. I've also got about 6" of lift in the back so less would make it easier.

Best case scenario as I understand it, is to have both ends of the shaft at the same angle.
Find the angle of the t-case yolk & match the pinion yolk to it.

You do want some deflection, having a dead straight drive-line will cause vibration.

X2 on the CV joint for the rear too.
My rear drive-line is steep but with the CV, it's never made any vibrations at speed.

 

[bp71k5]

This also brings up another issue going on right now.

As I've been driving the truck around, I've discovered that the gearing is a little too steep for the motors power band.
When I shift into a higher gear from about 3000rpm, the rpm drops about 1000 rpm or more leaving me at 1900-2000. That's a little low when I'm trying to speed up and I find the motor lugging sometimes, especially if I shift any earlier than 3000 rpm.

Also, to use the overdrive on the tranny, I need to be traveling at 80mph+ and that's just not working.

So...I guessed wrong when going with 4.10 gears. It's close, but I -need- 4.56 or 4.88.

So if I'm have to regear, I might as well go d60 right? I found a buyer for my old axle and found a used d60 I can build up.

Edit: The question I forgot to ask was whether the pinion joint on a d60 sticks out the same amount as a d44? I'd guess it's eitehr the same or longer, which could mean I have to shorten my front driveshaft?

 

[Yukon Jack]

The pinion of the Dana 60 sticks out a little more than the Dana 44. Too bad about the gearing issue, but sounds like you have a good plan for stepping up to the Dana 60.

 

[Greg72]

Brian,

A stroker BBC could probably overcome your current gearing issues....plenty of low-end TQ to climb right over that gear spacing issue you've got!

I've got an extra roller cam 496BBC that doesn't have a home anymore. It would do the trick for ya!

 

[bp71k5]

it's not very nice to tempt a guy who obviously has issues with this stuff. I just got back from a road trip with Scott that will keep ,me busy with parts for a while.

 

[4X4HIGH]

Brian,

A stroker BBC could probably overcome your current gearing issues....plenty of low-end TQ to climb right over that gear spacing issue you've got!

I've got an extra roller cam 496BBC that doesn't have a home anymore. It would do the trick for ya!

So what's the deal here? You aren't going to stuff it into the burb now that you sold your trailer?

 

[Greg72]

So what's the deal here? You aren't going to stuff it into the burb now that you sold your trailer?

The Burb is for sale.... no point putting THAT much motor into an otherwise stock and original vehicle. It would just about double the sales price of the truck too.

Seems like a shame to keep it wrapped in plastic in my garage with nowhere to go. Do you think it would be a better motor for the K5 than the 502BBC??

 

[vtblazer]

The Burb is for sale.... no point putting THAT much motor into an otherwise stock and original vehicle. It would just about double the sales price of the truck too.

Seems like a shame to keep it wrapped in plastic in my garage with nowhere to go. Do you think it would be a better motor for the K5 than the 502BBC??

Awe crap...now you got me thinking I need it.

 

[4X4HIGH]

The Burb is for sale.... no point putting THAT much motor into an otherwise stock and original vehicle. It would just about double the sales price of the truck too.

Seems like a shame to keep it wrapped in plastic in my garage with nowhere to go. Do you think it would be a better motor for the K5 than the 502BBC??

Wow, what promotes the sale of the burb?

Swapping an engine isn't that difficult, why not install the 502 and see how you like it then swap in the 496 and see if you like it any better.

Once you've decided which engine you like best for your needs then sell the other engine. It would be bad to sell an engine not knowing if "it's the one you should have kept". Also this way you can guarantee that the engine you sell actually runs (gotta watch out for them damn engine builders you know).