Project 67 GMC custom 6.5 turbo diesel

[mal68ibu]

Current under hood pics.

[67_C-30]

Originally Posted by mal68ibu

I could kick myself square in the.........well. I personally chopped up that harness in the 93 3500 I pulled my motor from not having any idea what it was. I've now clocked 4000 miles on my "new" truck and have tweaked the fuel mileage up to 14.5 on the highway. I made a bed extender for it out of one of the factory stainless ford units. Huge difference on the HWY. I also stumbled across a Doug Nash (US Gear) under over drive unit for a TH400 at my local pick N pull so that is how I'm getting my overdrive. Tho a 4L80E would be AWSOME.

No doubt about it, an OD would be nice. I did a little number crunching, and found that my set-up is going to be really close to a 4.10 geared truck with a 4L80 in the higher gears, and a little lower in the first 2 gears, so it should work out great. It's amazing that my 3.21's with the NP435 is going nearly identical to a 4L80E truck with 4.10's on the interstate. I'll be able to run 70 at around 2400RPM, and have plenty of gear getting a load moving in the 1st and 2nd gears. I had a '91 C3500 with a service body that had the 4L80E and 4.10's and it worked out well. Here's the comparison between the 2. The top chart is the NP435 with 3.21's and the bottom is the 4L80E with 4.10's.

[Schwinn68]

very cool build! I would love to do this to my truck too. I'd have a manual trans in mine for sure. The fuel mileage would have to be pretty awesome too. I had a 94 half ton longbed chevy with a 6.5/auto and it got around 18 mpg but I drove it hard. It would move pretty well too, I could keep up with my buddy in his Z71 especially when the turbo came on. This would be a screamer in a truck as light as ours are. Can't wait to see the update

[67_C-30]

Originally Posted by Schwinn68

very cool build! I would love to do this to my truck too. I'd have a manual trans in mine for sure. The fuel mileage would have to be pretty awesome too. I had a 94 half ton longbed chevy with a 6.5/auto and it got around 18 mpg but I drove it hard. It would move pretty well too, I could keep up with my buddy in his Z71 especially when the turbo came on. This would be a screamer in a truck as light as ours are. Can't wait to see the update

I used to have a 6.2 truck with a Banks turbo and 4 speed and it really ran well. That's the biggest reason I decided to put a 4 speed in my '67 C-30. I went with a close ratio NP435, so that 1st gear would useable. I'm running a relatively high 3.21 rearend gear, but I broke down the gear ratios on a calculator, and shows that at a 2500 shift the diesel will be in sweet spot the whole time. I would love to have NV4500, but the NP435 was the next best thing I could come up with. Here's how the ratios broke down.

[67_C-30]

When compared to the SM420 that was in truck, you get huge drops in gear ratio causes lugging going into the next gear unless shift a higher shift point than a diesel likes, or unless you run like 4.10 gears.

[mal68ibu]

The other issue that I had was alternator related. I found to run one of these alternators the excite wire needs to be run through an idiot light or some other kind of resistor. I blew up the first brand new alt. on the truck but it was under warranty so I just got a new one. The PVC set up is quite important to these motors I found. It sorta keeps the seals in good health, thats why the big red hose. I threw all the original stuff away before I realized I needed it, and thats the best I could come up with on short notice. Its not broken so I'm not fixing it.

[wildwilly4x4]

I had to build the same kinda air cleaner/ crankcase vent on my rig. I ended up blowing all kinds of oil out of the crankcase through that vent canister while doing burnouts..lol Come to find out that lil canister has to have a slight vacuum on it to work properly.

[mal68ibu]

Originally Posted by wildwilly4x4

I had to build the same kinda air cleaner/ crankcase vent on my rig. I ended up blowing all kinds of oil out of the crankcase through that vent canister while doing burnouts..lol Come to find out that lil canister has to have a slight vacuum on it to work properly.

I've been trying to lay off the burnouts. The load range E tires aren't cheep. Once I get my boost gauge and pyro gauge and get everything tuned up I'll post some vids with some pick-n-pull tires on the truck for fun.

[67_C-30]

Originally Posted by mal68ibu

The other issue that I had was alternator related. I found to run one of these alternators the excite wire needs to be run through an idiot light or some other kind of resistor. I blew up the first brand new alt. on the truck but it was under warranty so I just got a new one. The PVC set up is quite important to these motors I found. It sorta keeps the seals in good health, thats why the big red hose. I threw all the original stuff away before I realized I needed it, and thats the best I could come up with on short notice. Its not broken so I'm not fixing it.

Originally Posted by wildwilly4x4

I had to build the same kinda air cleaner/ crankcase vent on my rig. I ended up blowing all kinds of oil out of the crankcase through that vent canister while doing burnouts..lol Come to find out that lil canister has to have a slight vacuum on it to work properly.

I found this out the hard way on the first 6.2 I turbo'd. On this one, I ran the factory 6.5 CDR tube into my custom/homemade/junkyard scavenged cold air tube!

[67_C-30]

BTW, what did you use for the driver's side battery box?

[mal68ibu]

Originally Posted by 67_C-30

BTW, what did you use for the driver's side battery box?

A factory unit that I pulled out of my 71 burb. I figured there was no good reason for it to be there.

[wildwilly4x4]

Originally Posted by 67_C-30

BTW, what did you use for the driver's side battery box?

I used a really sweet box that you can buy at circle track/ race fab shops. They cost about $20 and have a really nice battery hold down...the only thing bad is you have to fab your own mount tabs for it if you dont want put a couple of small welds to your core support. I was reluctant to weld mine, but I ended up doing that just to save some time. I will prolly also replace the factory passenger side one the same way. These boxes I am talking about are a much better/ clean looking setup.

[67_C-30]

Originally Posted by wildwilly4x4

I used a really sweet box that you can buy at circle track/ race fab shops. They cost about $20 and have a really nice battery hold down...the only thing bad is you have to fab your own mount tabs for it if you dont want put a couple of small welds to your core support. I was reluctant to weld mine, but I ended up doing that just to save some time. I will prolly also replace the factory passenger side one the same way. These boxes I am talking about are a much better/ clean looking setup.

Thanks for the advice! I just saw your build for the first time last night, and I'm very impressed. That is a tough looking truck, and will look great in IH red.

[mal68ibu]

I have not yet seen water temp past 215 towing 7000 lb
s. However the truck has not seen ambient temps over 80 yet. We should be in the 90's in a month or so. With my set up if this radiator does not work out I'm going to look at aftermarket aluminum ones and an electric fan.

[thirdstreettito]

Whats your mileage?

[mal68ibu]

Originally Posted by thirdstreettito

Whats your mileage?

No where near what I was told it would be. Best I've pulled is 14.5. I have one injector thats missing on me inconsistantly. I'm running 5 psi on the highway at 60mph, and it peaks at 11psi when i beat the hell out of it. I've still not installed the overdrive unit. I've just been busy as hell with ebay.

[skoffice]

What?? That's stupid. Sacramento sure is weird sometimes. Well I'll have to stop by sometime and check out your burb since school starts back up next week sometime.

My buddy also has a 6.2 in his 71 K10 with just a stock 4 speed and he's getting around 20-22 mpg with that, so you should see a big difference with that O/D.

[thirdstreettito]

What size tires do you have? Also, how much did you turn up your IP?

[mal68ibu]

Originally Posted by thirdstreettito

What size tires do you have? Also, how much did you turn up your IP?

I'm running 245/75/16 and the IP is ALL the way up. I'm sure its turned up more than it needs to be, but I had a shop do it and they leaned on the side of overfueling versus potential damage from overboosting.

[mal68ibu]

On the fun side of life, I'm putting rear discs on the dana, since the drums no longer work.............so I hope to have a sweet burnout vid coming.

[mal68ibu]

Sorry but no burn out vids. The rear discs were a total pain in the ass to install. One side lined up really nice and the other side was a total battle. But they are on the truck and fully functional now. After 12K miles I've got a new laundry list of stuff to do to the truck.
1. rebuild the turbo. I'm going through oil at a horrifying pace. Rebuild kit is on the way.
1.a. Install heater. It has only been media blasted and refinished since January.
2. Install pyrometer and have injection pump properly tuned.
3. New Injectors if needed. Fuel economy sucks.
4. Brand new aluminum radiator, and electric fans in the summer. The stocker is not in as good of condition as I had hoped.

[thirdstreettito]

Originally Posted by mal68ibu

Sorry but no burn out vids. The rear discs were a total pain in the ass to install. One side lined up really nice and the other side was a total battle. But they are on the truck and fully functional now. After 12K miles I've got a new laundry list of stuff to do to the truck.
1. rebuild the turbo. I'm going through oil at a horrifying pace. Rebuild kit is on the way.
1.a. Install heater. It has only been media blasted and refinished since January.
2. Install pyrometer and have injection pump properly tuned.
3. New Injectors if needed. Fuel economy sucks.
4. Brand new aluminum radiator, and electric fans in the summer. The stocker is not in as good of condition as I had hoped.

1. Sounds like the turbo oil restrictor isnt working, hopefully the rebuild kit has one in it.

2. Good idea!

3. Have your current injectors tested by an injection shop.

4. Make sure you get a rad with an oil cooler and trans cooler built in, it's worth it in the long run. Also, go back to the mechanical fan. As Bill Williamson from Ron Davis Radiators said to me "New trucks still have mech fans. There is a reason for it. If your truck isnt staying cool then switch to an aluminum radiator. The stock fan is more than enough."

[mal68ibu]

I rebuilt a GM8 turbo I had on the shelf. Now I have to make a turbo master for it as the GM3 bracket will not fit the GM8 turbo. I also don't want to shell out another $120 for a new one. So I've found a few links to show how to use the vacuum unit to make a home made turbo master. Other reason I want to ditch the mechanical fan is I have no shroud for it, and honestly I have no desire to make one. The fan is 21" so a stocker is out of the question.

[mal68ibu]

Well I blew the motor up today. I'm drowning my sorrows at the bar now. Going back east for vaca and gonna ponder my options. Thinking of **** canning the gmc for a new truck right now.
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[67chevy1series]

i say put a nice 327 in it or parting it out it does have nice parts and if you do i would like to have first dibs on the passenger side fender and the port windows and some of the dash knobs not to be like a vulture