Need some advice on my K5 build up

[3MAX]

I've been browsing here for quite a while as I get ready to do a build up of my own. I've got a pretty good idea of what I want, but still have a few remaining questions / decisions.

Here's my plan, starting with a stock '90 model, in pretty good shape -

383, Vortec heads, mild roller cam, headers
Rebuilt 700R4
14 bsf rear axle
stock 10 bolt front
4" lift
35" KM2's

The blazer will see approximately 30% towing with 4000-5000lbs, 30% camping & hunting 20% trails & offroading, and 20% crusing with the top off.

My main goal is reliability and towing power. This truck will see plenty of highway / interstate towing at 75 mph.

So here are my questions (feel free to give advice on anything I've missed as well).

1. Keep the TBI or go to carb? I'm more comfortable with a carb, as I have no experience with TBI, and I'm somewhat intimidated by the thought of customizing this system to keep up with the 383.

2. 4.10 or 4.56 gears? I want to be able to tow at 75mph, and I will not be running the 700R4 in OD while towing.

3. Detroit Locker or selectable locker in rear? (The front will be getting a True-Trac).

4. What brand lift do you suggest? I'm really leaning toward a full "off the shelf" system rather than using blocks or a shackle flip in the rear. My rear spring bushings are shot, and I don't mind giving up some flex in order to have a higher spring rate for better handling while towing.

I plan to purchase all my parts and everything available before I start the tear down. Once I get started, I'll post the build up here.

Thanks in advance for the help.

 

[munepit]

Welcome to the club! Pay the $25 bucks. Best money ever spent. Keep the TBI. You will never have to mess with it. 4.56s for towing with a 700R4. With the 35s it will be great for towing. Go with a Detroit in the rear. Might make some chirping, but no need for a selectable in the rear.

Make sure to pay, and post pics!! We love pics. Good luck with the build!!!

 

[shovelbill80]

what's the tongue weight of the trailer? imo 4,000 lbs is a decent weight for a lifted K5 with 35's. i'd buildt it more for towing than anything else. 2" spring lift with 33's and 4.10 would make for a nice combo with a nice 383 i think. i didn't know a lot about TBIanything till i got here and did the research. i'm looking forward to doing my '90 350 a bit for torque and MPG. check out this site http://www.tbichips.com/jaredproject.htm
don't 14bolt sf come with 4.10 already? good tranny cooler should be mandatory.

 

[tRustyK5]

I've been browsing here for quite a while as I get ready to do a build up of my own.

2. 4.10 or 4.56 gears? I want to be able to tow at 75mph, and I will not be running the 700R4 in OD while towing.

3. Detroit Locker or selectable locker in rear? (The front will be getting a True-Trac).



Thanks in advance for the help.

Welcome to CK5

2. Even with 4.10's you'll be turning 3000 rpm at 75 mph...and IMO towing at 75 is unnecessary and borderline dangerous. I'd aim for a towing speed not exceeding 65 mph and stick with the right lane. At 65 with 4.10's and not in OD you'd be turning 2560 rpm...it's a good rpm with 4000lbs or so behind you.

3. Detroit is quite civilized on the street unless you drive like a retard. Specifically in the rain...

Rene

 

[K85 Octane]

you will be posting and reading non-stop
member upgrade if you can
and ratio calculator is soooo cool, love it
http://www.grimmjeeper.com/gears.html

 

[sandypants]

scrap that engine just get a new 5.3, better power twice the millage! and reliability is perfect! you know a 4l80 would be a good choice too!
4.10 will be perfect. detroit will be just fine once you get use to it. really wont be a big deal.
skyjacker is a little bit stiffer i think they would work well for you

 

[3MAX]

Thanks for the responses and the links guys.

I guess I should have been a llittle clearer in my initial post. I know I asked for any advice on this project, but the items I listed so far have been decided. I've done a lot reading and weighing my options before settling on the setup of a 383, 14bsf, and 35 inch tires. A newer LS series motor would be nice, but I don't want to spend the extra $$ on it and time involved in making it fit.

It looks like most recomend a Detroit for the rear, and I was leaning that way already, especially for the $$ difference of a selectable locker.

I do like the idea of keeping the TBI - Just a little nervous about jumping into it with no experience. The information at TBI chips is great though.

For those that have upgraded their TBI system to fuel a 383 or modified 350, how hard is it to source parts, and how much $$ is involved?

As for gear ratio, anybody got experience towing with 35's with both 4.10 and 4.56's? After looking at the gear ratio calculator, I'm leaning toward 4.10's.

I'd like to hear if anyone has experience with different brand lifts as well.

And by the way, I went ahead and purchased a membership. I had planned to wait until I started my build so I could post pics, but I've already gained way more than 25 bucks worth of information. Thanks for a great site.

 

[tRustyK5]

I used my old K5 as a tow rig for a few years. Carb'd 355 with a mild cam (260HE if I remember right) SM465, 3.73's and 35's. The trailer I towed was an older 21 foot camper trailer, weight was around 5200 lbs loaded with our junk.

It towed pretty good, 4.10's would have been a little better. The biggest pain was the gear spacing on the SM465. We'd often tow through the mountains here, and on long hills I couldn't maintain speed in 4th so I'd have to slow and drop it into 3rd. I had all the power in the world in that gear but 45 mph was already pushing 2800 rpm which tended to work on my nerves. A gear between 3rd and 4th would have been perfect.

I think with the 700R-4, 4.10's and 35's it'll tow pretty good. The 383 will help as it'd have a bunch more torque than my 355 did.

I'm not sold on the TBI stuff personally, not on a modded larger engine anyways. I see a lot of guys burning chip after chip after chip and still having issues. You may be more tech savvy than average though, and if that's the case it might be fine for you. I'm going carb with the 454 i have sitting here though. For my purposes a good Q-jet will be more than fine, and easier to deal with.

Rene

 

[shovelbill80]

And by the way, I went ahead and purchased a membership. I had planned to wait until I started my build so I could post pics, but I've already gained way more than 25 bucks worth of information. Thanks for a great site.

i'm brand new hear too, but i like your attitude about the value of this information and camaraderie.

i'll just mention.....make sure you get a tire with a heavy sidewall. towing 2.5 tons with a short truck can make it interesting if not set up correctly. as mentioned, 75 is a tad quick too . i'm reading/learning the trick with TBI is to use a sensible cam that'll work with the computer. build the motor to run optimum for the way YOU plan on using it. low down torque is your friend, build that......big HP at 5000 rpm makes as much sense as an elevator in an outhouse for what you seem to want to do. all imo of course, Bill

 

[3MAX]

build the motor to run optimum for the way YOU plan on using it. low down torque is your friend, build that......big HP at 5000 rpm makes as much sense as an elevator in an outhouse for what you seem to want to do. all imo of course, Bill

I agree with you 100%. The motor will be built for torque, not HP, and I'm only concerned with power from idle to 4500 rpm. I've seen too many folks that try to build big HP, only to find that it's usless in their application.