Cummins Motivated 1983 Suburban Re-Build...

samedi 5 avril 2014

Howdy Folks-



I can guarantee I’m not as interesting as the girl from Texas with the pink bumpers and over 10,600 replies to her intro. However I will tell you why I cut the body off my truck with a sawzall…



I’m in the middle of rebuilding an ’83 Chevy Suburban that I bought 6 years ago. The reason I bought it is because it already had a 1995 12 valve Cummins and NV4500 between the frame rails. You’re always taking a chance when you buy someone else’s modified vehicle, but the original build was done well and it has been a reliable and entertaining daily driver.



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The Suburban was originally a ¾ ton 454 truck with A/C & power windows- fully loaded for 1983. The body was still presentable, but it was starting to rot from the inside out. Although I think it can be cool to have a $12,000 drivetrain in a $1200 truck, I live in the North East and I’m tired of using a torch when I should be using a wrench. I found a straight and rust-free ’89 Suburban (it was raised in Georgia) with barn doors, 3rd row seat, dual A/C and dragged it home. This finalized my choice to remove and scrap the original body, and got me thinking about what I wanted to do with the truck while the body is off- swapping the transmission, rear end, driveshaft, fuel lines and brake lines are all a hell of a lot nicer to deal with when you’re looking at the top side of the frame.



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Part of the reason I’m here on Competition Diesel is that I came across this 2009 post by “onadiet”:



http://ift.tt/PG0YjS

“95 6bt, 4GSK, lazer cuts, stock injectors, 17*, 16cm exhaust housing, 24mpg on the high way and 19ish average. All in 83 Suburban with 6inch front 8inch lowering kit.

Not the best MPG but it was fun!”



I had to read it twice, but I realized he had to be talking about my truck. I bought the truck in Maine from a friend of the guy who had originally built it in Ohio. Because I never spoke to the guy who put the truck together, I didn’t have any information about how the injection pump was set up. Here I am now, 6 years later, looking at a post I randomly came across that has my P7100 set-up specs. Pretty cool.



So that’s how I ended up posting here today. For those that are interested I have a fairly detailed outline of where I’m at and where I’m going with my re-build…

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This truck is my Hot Rod / Tow vehicle. I have a 31’ 1975 Air Stream travel trailer and a 10k gvw trailer I use to for dragging my other projects around. When I bought it, it had a stock turbo w 16cm exhaust housing. A few years ago I installed a 3 piece exhaust manifold, Industrial Injection 62/65/14 turbo and 4” down pipe. I didn’t touch the pump because the power was always good, but finding out now that it has laser-cut delivery valves probably explains why it’s always been smokier than I wanted. If anyone wants to trade my laser-cuts for their 181dv’s let me know…

Engine:

My goal is a clean 400hp/800tq at the rear wheels and anvil-like reliability. I want to tune for maximum power, torque, mpg and minimal smoke at under 40lbs of boost so I can reliably run the stock head gasket and bolts. The truck weighs 5600lbs wet, so I don’t have to make huge power to get to the hp/weight ratio that I want. At this point, I’m thinking that fueling to 325hp and going to 400hp with water methanol injection might be a practical way to get there. It’s a 1995 manual trans engine, and has the 175hp P7100 injection pump. I will probably start with a #5 or #6 fuel plate, stock 215hp injectors and 181dv’s. From what I’ve seen of dyno results, it seems like if you have enough air you can gain about 75hp/150tq from a water methanol injection system. In combination with the 62/65/14 turbo I already have, I’m guessing I could be around 350-400rwhp range with this set-up.

Transmission & driveshaft plan:

I found a brand-new NV4500 transmission that was spec’d for a 3500HD cab & chassis truck for $900 including freight. This trans has an extra-long cast iron tail housing with an integrated driveline parking brake. This is perfect because it will allow me to do a low-buck rear disk swap using GM 4x4 front rotors and calipers, but still have a strong parking brake. The other bonus is that the trans output yolk is sized for a 1410 u-joint. I can swap to a one piece driveshaft vs the two piece shaft with smaller (1310 or 1350 I’m not sure) u-joints I have now.



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Rear End:



The existing rear end is the GM 14 bolt, semi-float with 3.73’s and a Detroit Tru-trac limited slip diff. This axle has performed well and I can’t say enough good things about the Tru-trac lsd. I decided to build a new 14-bolt full float rear end for a few reasons: Going to the full floating 14b allows me to go from a 1350 to a 1410 u-joint, low buck disk brake swap that drops 50lbs of drums & makes the brakes easier to service, it came with the 3.21 ring and pinion I wanted, it has a strong following with all the off-road guys so you can get all kinds of trick parts for short money. I’m building it with a Tru-trac diff and rare factory 3.21 gears that came with the axle as I bought it for $350, originally from a 1977 GM truck.



Here’s the plan with the 3.21 gears:



Most of the time I drive the truck without a trailer, and when I do tow I pull between 6,000 – 8,000 pounds (project car or travel trailer). With a 3.21 ring and pinion and 275/65-18 tires, I can comfortably tow in 4th, (2100rpm @ 60mph) and cruise in 5th for optimal fuel economy (1650rpm @ 65mph, 1900rpm @ 75mph). 1st gear and reverse will still be plenty low for moving a trailer around. The transmission is strongest in 4th and the 3.21 gears will make it more versatile for the driving that I do- (1775rpm @ 45mph to 3150rpm @ 90mph) - highway on-ramp work, towing, passing folks who think their Honda is fast…



-More to come after I get back to work on the truck in two weeks.




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