California Diesel Conversion Tale of Woe

Cant Write

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@XOLATEM #1 I agree with you whole heartedly!! But hear me out...

The ‘79 C10 currently resides in South Dakota. Has a mild rebuilt 355 sbc with a small RV cam. Originally equipped with TH-350 and 3.42 geared 10-bolt but we got it with no engine tranny. Just a roller.

My ‘84 C10 (first vehicle) bought for $500 with a blown engine. Had a TH-350C and 2.56 geared 10-bolt. For Christmas dad built me a nicely warmed over 355 (camel-backs, pink rods, flat tops, 10:1, 215/220-ish cam) TH-400 and same 2.56 gear. I could boil my 1 and sometimes 2 tires almost at will. I had to buy my tires, so I was a good kid. Required 93 octane fuel (it loved Texaco’s additive). Crisp shifts, and it’d happily run 80.

I use to run between dealerships getting and delivering parts. I was offered new pickups all the time and turned them down cause my pickup drove so much better. More power, better shifting trans. It would smoke the offerings from Ford or Chevy (maybe not the lightning or 454ss) of the late 80’s early 90’s.

Rust took my pickup and it became a red neck trailer. Dads 79 got the TH-350C. It started slipping and dads friend owned a trans shop. He rebuilt the TH350 with a TH400 TC, and whatever else all for $700 in 2010. That’s dropping the pickup off and picking it up. We swapped 10-bolts to be more interstate friendly. (3.42-2.56)

the TH-350 shifts with authority. We have grossed 12,800 with the pickup and trailer hauling lathe and plaster with 2.56 gears and the pickup did NOT feel labored (I was driving).

Point is, we already have a solid TH-350. I don’t have a 700r or 200r, and I don’t own a 3.73 gearset.

My free options are...TH-350 or 400. And (2) 10-bolts in 2.56 or 3.42 gearing.

My dads driving days are numbered (he’s 80) and I wanna keep his ‘79.

I have (2) 6.2’s just sitting. I was thinking the low end, coupled with a turbo would be just fine for light duty and commuter use with the TH350/2.56’s vs a carb’d 355 up here at 7500’. Plus it’d keep me mechanical.

At 60mph with 350/2.56/29”tire it equals 1780rpms not counting slip. At 70 mph, 2076 revs.

I have been driving the 355/TH350/2.56 combo since 2008 on a semi regular basis and it’s peppy.

Any and all advice welcomed!!! Sorry for the thread derailment....again!!
 

u2slow

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@u2slow thank you for your input!! I appreciate it.

Would a 6.2 with a turbo not suffice for a C10 with a turbo 350 and 2.56 gears?

Or would I be better off with the carb’d gasser and just adjust it?

I was hoping to be around 18-20 mpg. At 60 mph.

I dont reckon it will accerlate fast, but top speed should be ok and thrifty!

I ran 3.21 and a 4spd with mine, NA though. Suburban. 17mpg as i recall. The old TH400 and 4.10 got 12mpg.
 

XOLATEM

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Good story....I'll bet you had a lot of fun running that truck...

My old '74 C10 had a stock built 350 and I put a 700 in and it had a 3.42 rear gear...I liked to drive it but Lord it was rusty...

On your 6.2 ....you are going to need a reliable vacuum regulator valve to run your 350...just keep that in mind...and...it works best if you can fab up a good lever for the kickdown cable...

You know that U-shaped link for the manual linkage at the transmission...? I have seen them wore out from manually shifting...

The vacuum modulator has to have adjustment to compensate for your higher elevation...

Gotta get to work...chat later...
 

Cant Write

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@XOLATEM I also agree in that a 700r or 200r with my 3.42 geared 10-bolt would be a descent driver!!

I have the u-shaped bracket for the kick-down cable, but for gassers only, and since so few TH-350’s came behind diesels, I’d bet that piece is more rare than the 700r4 TV cable bracket for diesels....

Things to ponder. I’m sure I’d just run the TH-350 unless a hydro-mechanical OD fell in my lap.
 
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bob_442

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I'm doing a followup post to my original post which started this thread. I started the story. Now it is time to finish it. I spent ~5.5 months pulling the gen1 6bt out of my Dodge donor, pulling the gen2 6bt out of my Chevy, performing misc fixes to the gen1 motor, including the kdp fix (the dowel pin was still where it was supposed to be), and stabbing the gen1 motor back into the Chevy. Yesterday, it passed the Smog Referee inspection. I'm told this is what needed to happen in order for DMV to once again accept this truck as a Diesel. And, being pre-'98, a *smog check exempt* Diesel.

Along the way, I learned a lot about gen1 & gen2 6bt Cummins. I made some small changes to the gen1 motor to throw in some gen2 characteristics. I put a new gen2 thermostat housing on, and added the bubbler valve and the (new to gen2) custom hose to let air bubbles bypass the thermostat. I also switched the fan hub to gen2-style, to avoid moving the fan over towards the passenger side, which would have probably cause all kinds of problems with the shroud. I splurged and put a feramic clutch behind it. BTW, the original clutch on the gen2 motor that came out had less than half a millimeter before the rivets made contact with metal. I replaced the integrated oil cooler and oil filter standoff. I replaced the damper with an aftermarket fluid damper. It was much larger than the OEM one. It barely gives me room to clear the serpentine belt between the damper and the front cross member. The truck used, and still uses the stock in-tank fuel pumps. The gen2 motor which came out was supplied fuel via a pressure regulator that was set to about 30 PSI. That needed to change for the VE pump. I bought a lower-pressure adjustable regulator. But then I read from the paperwork the referee sent me...that any aftermarket adjustable fuel pressure regulators have to have CARB exemption numbers. Oops. I thought about what to do. What I ended up doing was removing the regulator, and installing a 4-way tee. The fuel from the tanks is pumped into the 4-way junction, and returned right back to the tank. The return line is above the feed line to coerce any bubbles to go back to the tank. On the other side of the 4-way junction, the lower connection is the input to the OEM mechanical lift pump. The return line from the engine goes back to the 4 way junction right above it. This way the pumps in the tanks feed the input of the mechanical pump with essentially zero psi, and the mechanical lift pump feeds the VE-pump with exactly what it is used to getting (it ends up being about 4-5 PSI after the filter). I could rethink this now that the inspection is done. But it is working so well, I'm not sure I'm interested in doing that. I kinda wish I had replaced the mechanical lift pump while the motor was on the stand.

One of the interesting things that happened when removing and replacing the engine in the Chevy was that the engine was trapped by the nv5600 behind it, the cross member below and in front of it, and the firewall above and behind it. There was no way the engine was coming out, or a new one going in, without at least one of those things being relocated. I opted for the cross member. The cross member was already aftermarket, and so the rivets had already been replaced with bolts. Once the cross member bolts were out, it could be slid forward, the motor could move further forward, and then the motor was free to be lifted out.

One odd thing that I found about the original fuel pressure regulator. It was installed on the return line. The OEM regulator -- the banjo bolt -- had been replaced with one that simply let the fuel pass. The fuel returned back towards the tank, and it was there that the regulator slowed it down. The back-pressure going back into the pump (and the injectors ???) was how pressure was maintained. It seemed to work well.

The original engine had been heavily modified by past owners. Changes were made to the p-pump, and the injectors, all for the purpose of adding more torque and HP. It should come as no surprise that the bone-stock gen1 motor is a little down on power. It is also (way) down on EGTs. The smoke puff limiter combined with the gen1 turbo means that power builds slowly. In the coming days, I need to tweak the engine mount -- the motor and the exhaust manifold are touching the firewall. I also want to put the waste-gated gen2 turbo back in there. I think that, combined with a little twist on the fuel screw, should get me back where I need to be with a 12K lb combined weight with the camper on back.

I gotta say -- I think the powers that be took a step backwards moving forward from the VE-pump to the P-pump. Along with this transition -- the smoke puff limiter was eliminated and it was replaced with crap in the exhaust system to deal with particulates. I understand why they did this. Getting rid of the smoke puff limiter gives a much more satisfying seat of the pants kick in the ass when you mash the right pedal down to the floorboard. But at what cost? It is inherently inneficient if any smoke is ever being produced. That smoke is unburned fuel. Why replace something that prevents the waste, fixing the problem at the source, and replace it with an inefficient band-aid? Me thinking this way probably shows my age. :)
 

Clb

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I made para #2
I feel y'alls pain.
F u kk carb
 

Eli

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TL;DR
Diesels were completely exempt from CARB regulations until the late 1990s, when the Tran Report came out and CARB (and the EPA) decided that elemental carbon was somehow harmful to carbon-based life. If your timeline is correct, and these were swapped prior to CARB regulating Diesels, they should continue to retain their exempt staus.
Additionally, when did CARB start requiring catalysts on swaps? That was the only exemption for years, because catalytic converters are a known fire hazard, so you could swap a 1998 motor and transmission into a 1958 vehicle and remain cat-free.
I would request the title history, to find out when they were noted as having been repowered by a Diesel; if they date from before CARB regulating Diesels you should be golden.
Also, if I understand correctly, it's a 1-time Diesel compliance inspection? Just swap the 'compliant' motor twice!

Eli
 

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