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6.5 TD/NV4500 conversion into 73-87 full size?

S

sharbour

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West Linn, Oregon
Has anyone successfully done this? At first glance, it looks easy since the 6.2 was a factory option. However, it looks like there is no way to fit the 6.5 turbo exhaust manifolds without major interference from the frame rails and A/C box, according to some posters. My goal is to use as many factory parts as possible. I'm gathering info, this will be my winter project next year.

The donor is a 1993 Chevrolet K3500 longbed. It has the mechanical injected 6.5 TD, NV4500/BW4401 drivers side drop transfer case and 4.56 gears with 31" tires. Runs and shifts like a top, same power as my 350TBI at half the RPM, but almost double the mileage.

The transplantee is a 1991 K5 Blazer, 350TBI with SM465/NV241 and 4.88 gears with 35" tires and a 6" all spring lift front, 2" spring/4" shackle flip kit back.

What's the most straightforward way to do this? I haven't been able to find much info about this type of conversion without other major mods. I want to keep the body/chassis changes to a minimum if at all possible.

Will the exhaust manifolds fit? If not, should I use 6.2 manifolds with a banks turbo piping kit? Will any 6.2 manifolds work, or should I get a particular year? Can I use the the GM3 turbo with the banks piping? Would it be easier to just make a custom piping set for the GM3?

I'm pretty sure the transmission will be fairly easy to mount in, but I'm less sure about the NV241, I'll need it for the passenger drop. Will it bolt up? Will it need a new input shaft? The output shaft has already been changed to a fixed yoke.

It looks like the drive shafts will probably have to be custom length, no big deal.

Where can I find a factory 4000 rpm diesel tach for the Blazer? Did they use them on the military 6.2 trucks/blazers?

Thanks guys, any info would be appreciated!

Sean Harbour
West Linn, Oregon
 
I have that exact combo in my K5, except mine is a 6.2L disguised as a 6.5L. I am running a GM-3 turbocharger on mine, using the entire 6.5L turbo setup, serpentine accessories etc.

It is true that you'll run into clearance issues with the 6.5L exhaust manifold on the driver's side of the truck. I used a stock 6.2L driver's side manual, and the 6.5L turbo manifold on the passenger's side with a custom made crossover pipe. The turbo manifold does clear the pass side frame rail, by fractions of an inch. I opted to grind my frame down a bit to pick up some clearance room. The turbocharger will most definitely run into your AC housing on the firewall. It is possible to do some major surgury to install an S-10 air box, but I found it easier to simply swap my truck to non-AC. The exhaust down pipe presents something of a challenge as well. First of off, it dumps directly into the passenger's side frame rail, and secondly, without installing a 3" body lift, you will not have enough room to route it to remain within the frame rails. I had my exhaust shop run my exhaust on the outside of my frame rail, and it dumps right before my rear wheel. I am running a 3" straight pipe on mine, without any kind of muffler.

Having an electric fuel pump is to your advantage. Your existing TBI fuel pump is well suited to act as a lift pump for your diesel engine. You will able to simply un-bolt the braided steel lines on the 6.5L engine that pass down to the driver's side frame rail and connect them directly to your existing TBI fuel lines. You will want to replace both the gasoline filter on the frame rail (the extra filtration is a good thing, leave it there) and the filter on the engine just to be sure it is fresh. You will need to wire the fuel pump relay up in such a way that the fuel pump is activated when you turn the ignition on.

Since your K5 already has an SM465, you'll already have the hydraulic clutch assembly in it. Buy a quality industrial grade compression fitting (such as offered by Swagelok) to splice your existing clutch master cylinder and line to the new external slave cylinder that will be on the NV4500. Since you have a 6" lift, driveshaft to external slave cylinder clearance issues should not be a problem. You will need to cut your floor pan to move the shifter hole back several inches, which will also require you to cut your floor pan to move the NP241 shifter back by a few inches as well. You can simply remove the t-case linkage rod and add more threads to it and shorten it as required. This is done so you will have room to fit the NV4500's shifter boot on in a centered position without it running into the transfercase shifter. The NV4500 uses the same reverse light wiring as your current SM465, simply plug it in.

Your existing 32 spline NP241 will bolt directly up to the NV4500 without any spacers or adapters. Since the NV4500 is within 1/4" of the length of the old SM465, you will not be required to move or modify your transfercase crossmember, or modify your driveshafts. Everything bolts right together just like it is meant to be in there. You will not be required to make any modifications to your electric speedometer assembly, as you will still have the factory transfercase.

No Chevy light duty diesel truck ever came with a factory tachometer. That said, you can purchase an engine vacuum pump that is equipped with an engine speed sensor. It produces a sawtooth waveform that is not directly compatible with a factory tachometer as the amplitude of the wave form can generate way too much potential at higher RPMs. However, the frequency is right. You can build a simple universal bias transistor circuit to convert the signal to a proper 12V square wave signal that a factory tachometer utilizes. Since the factory tachs only range out to 5000rpm anyways, they work well with the diesel engine. This is what I did with my truck, and it works very nicely, accurate across the scale as compared against my diesel timing meter.

Wiring the engine up is easy. Simply find yourself an 87+ 6.2L equipped truck (78-86 use a different bulkhead connector on both their gasoline and diesel engines) and grab the engine wiring harness (including the wiring for the low coolant sender in the rad), the connector on the firewall, and small diesel specific wiring harness within the cab of the truck (including the idiot light pod in the bezel, and diesel specific idiot light lenses in the instrument cluster). Plug everything in, and you'll be good to go. If you are unable to find yourself a compatible wiring harness for your TBI bulkhead connector you may need to do some wire splicing, or modify your existing TBI engine harness to operate the diesel engine. Being a 93 and therefor mechanically injected, wiring is very basic. You will also need to make some modifications to the fuel heater and water in fuel indicator in the factory 6.5L fuel filter to be compatible with the older 6.2L wiring and indicator system.

Another two considerations you may want to make is in the braking system and the cooling system. Diesel engines produce no vacuum, and your engine mounted vacuum pump is unable to support a vacuum power brake booster. You'll need to swap over to a hydraulic booster system. They bolt straight onto your firewall in place of the vacuum booster, but will require you to re-locate the stud on your brake pedal due to a difference in pedal throw length. The cooling system required by a 6.2 or 6.5L diesel engine is massive. You absolutely need to install a 6.2L radiator in your truck. Your core support has all the holes, captured nuts etc required to install a factory diesel radiator. You simply need to get the two upper rad support brackets, fan shroud and upper plastic rad cover from any 82-91 6.2L diesel powered old body style truck to bolt them directly into your existing front clip. Integrating the 93's radiator, shroud etc would be considerably more work, and would require some custom fabrication on your part.

Good luck with your swap, and if you run into any more trouble, don't hesitate to post up, or send me a PM, I should be able to help you out with just about any issues you might run into.
 
Wow Russ, that's an awesome writeup! Should make that a sticky, just about covers all the bases :bow:

only thing, factory tach's were pretty common on the 90's diesels. They use a feed off the alternator, I'm no electronics wizard like you but I bet you could easily build a circuit that would convert the tach signal from the alternator to feed a standard tach. I'd even give you one of the diesel tach gauge clusters that's on my shelf so you could figure it out :wink1: 'Course, that's assuming a guy was using the CS series alternator . . .
 
Wouldn't be a whole lot of figuring to do there :D The nice thing about using an ESS vs the alternator is that the circuit doesn't require nearly the amount of electrical protection. The Alternator can make all sorts of spikes in voltage, which most basic electronics don't like so much. Also, changes in pulley sizes anywhere will throw the tach right out, and requires some degree of calibration right off the start. That said, if a guy were to grab a tach from a 90s diesel, and trace the wiring around a bit, I bet you could find a GM-built module somewhere in the mess of wiring which could be adapted to an older tachometer ;)
 
Thanks Russ, that's way more information than I hoped for! I'll start gathering parts right away. My donor truck has an alternator driven tach already, so I might try to salvage some of it. Also, I did find some information about diesel tachs in the 73-87 body style. Apparently tachs were very rarely offered as an option over the years, but they did show up in special orders occasionally, even in diesels, and were usually found in trucks that were ordered as chassis cabs for conversion to light duty dump trucks, etc. I found a few pictures of factory 4000 RPM tachs in the factory cluster. However, it sounds like they are practically non-existent.

My main concern this summer will be making sure the engine is running correctly. I used it to tow my 4000 lb trailer last weekend over the coastal mountains in NW Oregon, and it had approximately the same power as my 350TBI, and averaged 15 mpg vs less than 10 mpg. I was hoping for a little better performance, as 35 mph was the best it could do on the steepest grades, about the same as the 350. I'm sure that transplanting it to the Blazer will help a little as it should cut about 1000 lbs off the weight, but I'd like to add a little boost and fuel as well. Not much, maybe 10 psi max, and I'd be happy if it would hold 50 mph on the hills. The overall gearing will change a little as well, I'm tending to think that 4.11 gears with 35" tires would give me about the best overall highway/mileage gearing with the nv4500 at about 1800 rpm in the 60-65 mph.

How do you like your combination? Pretty happy with it? One more thing. Is the water temp supposed to stay around 180 degrees or so? Mine stays much lower, maybe 140, and only gets up to 180-190 during really steep hills. I'm thinking I need to check and see if the thermostat is stuck open or missing. The water pump and radiator are new.

Sean
 
I got around 22 mpg with mine on the highway back when I still had it installed in my 1980 3/4 ton 4x4 reg cab longbox. That was with 35" tires and 4.56 gears at the time. Getting 15 - 18 mpg is quite decent for a 6.5L that is towing something, but you'll get significantly better mileage running empty.

I am actually really happy with the whole combo. I am running it in my fullsize K5 blazer now as an offroad only rig. I have 34" tires with 3.73 gears at the moment, and do have some complaints with the gear spacing on the NV4500. Goes from revving too high to bogging and loosing all it's boost when you upshift. The engine runs really well, and as you mentioned, has similar acceleration to a TBI 350. Significantly more torque however.

My 6.2L runs 190 at all times, never hotter, never colder. These engines throw a lot of heat, particularly turbocharged, when they are working hard up the side of a hill, and can easily be overheated. Since my rig is offroad only, it never has to do more than short high RPM passes every now and then, and spends most of it's day idling around running less than 1800 rpm.
 
Great Write up!

A couple of quick questions to add to it. I am in the process of the exact same powertrain into a 70 blazer, It has 4inches of lift but there still looks like I will have driveshaft/slave cylinder clearance issues. Any suggestions?
 
I'd just run it! I ran the same combo with a 4" front lift and never made driveshaft to slave cylinder contact. If you have a really flexible front suspension, you may want to install bump stops that'll prevent the axle from traveling up so far that it can hit anything
 
Great! I think that's what I try. It didnt look like there were any major differences between the first and second Gen blazers. The only think I had to do was to use a clocking ring to get front drive shaft clearance with the first gen trans cross over. otherwise th 6.2/nv4500/208 sounds just like the combo you're running.

Thanks again, I just needed to know that someone had done something similar with out too many issues.
 
subscribed!

someday, before i die, i want to turbo my 6.2, put an NV4500 behind it, and be one of the cool kids :)
 
Subscribed.......

I have a donor 94 K2500 with a 6.5TD/NV4500/BW4401 that I plan on swapping in to my K5. I really don't want to use an old wiring harness as I was looking to have all the wiring replaced with new. However my search for a new harness is not turning up anything. Also I am up in the air as to what to do about the front driveline issue. Swap in a 205 or 241 and keep my 3/4 ton D44. Or keep the BW4401 and swap in a Ford D60, which would also avoid slave cylinder issues at the same time. Also need to swap out the injector pump and lines to a non electronic style.
 
Update: More Power!

So, I bumped the fuel up a quarter turn and raised the boost pressure to 10 PSI. Much better, I can now pull my trailer up the hills at 50 mph in 4th instead of 35 mph in 3rd. Still on track to swap it into the K5 this winter.

However, I'm puzzled. I cleaned all the leaves out from behind the A/C condenser, and then I threw the condenser away, and it still runs about 160 F at cruise and 230 F pulling up the hills hard. What else should I check? The radiator is fairly new, and I put in a new thermostat as well.

Sean
 
you should be verifying that the guage is accurate.


get a laser temp gun. and hit the stat housing.
 
Cruise control

I noticed that the '93 factory cruise control still works with the NV4500. :woot: How hard would it be to wire it in to an older style cruise control stalk on the '91 K5 steering column? This is going to be a dual purpose rig, and cruise control for those 12 hour freeway jaunts would be really nice.
 
Parts list:

Okay, I found a couple of 6.2 'Burbs in the local wrecking yard for parts. Here's my shopping list so far:

6.2 radiator and shroud.
6.2 wiring harness
6.2 driver side exhaust manifold
6.2 power brake system
Late 80's tilt/cruise steering column
S10 A/C firewall box

It's the last that has me concerned. Does anybody have any suggestions on how to relocate the A/C box to make room for the turbo? I'd rather not delete the A/C, the significant other gets really cranky when the inside temps go over 100F. :thinking:

I looked at some S10s. The A/C box is a little smaller than the one on a full size. It still looks like I would have to move the box toward the passenger fender, and possibly turn it sideways, deal with bending the lines, etc, which also means making a new box out of fiberglass. Sounds messy. Is there a better way?
 
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