Diesel to gas reversion

[GMJakers13]

Hey guys. just got a 62 3/4 ton 4wd with the D351 Toroflow. the only problem seems to be the injector pump but was wondering for future reference if you could convert this engine back to a gasser. Any and all info is much appreciated. Thanks.

[bigblockv6]

First of all the ToroFlow 351 Diesel isn't a converted gas to Diesel type engine, yes the ToroFlow shares similar architecture to the gas V6 engines there are too many differences that would not make it practical to convert to gas. The balancing is completely different between the two engines. The Toroflow uses a balance shaft with weights, the head bolts are a larger diameter. It would be far more cost effective to just swap in a gas 351 or any other larger gas V6 like a 401 or 478. The only Toroflow that was the same with it's gas counterparts was the 637 V8, it was designed as a Diesel and a gas version only differed with a different set of heads and possibly balancing.

[GMJakers13]

awsome. Thank you.

[GMJakers13]

3649

[alanorion]

Hi I owned aboat with a turbo diesel toroflow it worked well and gave no trouble. I was able to get all the usual parts ie filters hoses and parts from later models. However in Australia no other parts where available. I had a stainless conector for the engine to turbo made. And a new exaust manufactured. One disadvantage was that even at reasonable low revs it drank fuel at about 40 litres (10galls) an hour however I love the truck it looks awsome
Best wishes with the restoration post a picture when its done Alan

[quest]

Hey guys. just got a 62 3/4 ton 4wd with the D351 Toroflow. the only problem seems to be the injector pump but was wondering for future reference if you could convert this engine back to a gasser. Any and all info is much appreciated. Thanks.

Is that a rare original truck or modified by someone? If it is a rare factory truck then all I can say is with such a unique vehicle it would be a shame not to do an original restoration, it should be pretty valuable.
I heard that these diesel options were available but rarely ever ordered so you might have a very desirable unit there.

Would love to see pictures or video on here?

Good luck with it!

[bigblockv6]

There was no Diesel option in pickup trucks, though many GMC truck dealers could do such a conversion if the customer requested such.

[BobS]

Does anyone have pictures of a dealer-installed Toro Flow into a 6066 pickup? I'm mostly interested in motor/transmission mounts but would love detailed pics of everything. GMJakers13, does your conversion look like a dealer may have done it? I'm assuming a dealer installation would look professionally done. I have a DH-478 in a 72 5500 that I'd like to put in the 65 2500 NAPCO and want to do it the way a dealership or upfitter would have done it.

[6066gmcguy]

I think what he really ment about converting it back to a gas engine is more like Swaping it back. I would say it would not bee too hard a job to remove the D351 and in stall either a 351 or 401 back in its place.

The Toro-Flow diesel did not come out tell 1964, a lot of the later trucks got dieselized, and many of the factory trucks that came with those diesels, got gas engines installed. the rating on the diesel were not really that good, a D478 had about the same power as a 401, and the D351 was not much better then a 305.

I think GMC missed the boat with the Toro-Flow, it should have been a light truck diesel, they work good in 14000 lbs or less trucks, and they also got good fuel milage when compeared to a GMC V6 gas engine.

the D351 was more rare of the two Toro-Flow sizes, a lot more of the D478 or DH478 got built, so don't scrap that engine, if you don't want it I'll bring my trailer to Wyo and pick it up. I got a 351C here at the house if you wanted to trade, I was told it ran when pulled but it been here for about 15 years now.

[turbobill]

the rating on the diesel were not really that good, a D478 had about the same power as a 401, and the D351 was not much better then a 305.


Nothing a turbocharger won't fix!

[bigblockv6]

Actually GMC did have a twin turbocharged DT478 Diesel used for military ambulances and fishbowl buses, they never gave out any horsepower ratings though. The D351 was rated at a 130 horsepower, so that was actually less than the 305 and the DH478 was last rated in 1974 at 150 horsepower only two more than the 74 305C V6.:lolsmack2:

[BobBray]

DT478 in a Fishbowl??? I did see DH478's in the 'baby' TDH 3301's, but not the turbocharged version. Interesting.

[turbobill]

I do remember the turbocharged Army buses. Had two of them at the local military base in the late 60's.

By the time I was in the service, the Toro-Flows were being changed out for triple nickel Cummins V8's. The triple nickel was one gutless engine!

[GMJakers13]

hey thanks for the input! BobS, As far as dealer installed originality goes, I have my doubts but anything is possible. Everything looks well-done, but I have definately done both sides of work, rigged and proper, with a heavy lean to rigged, so maybe my eyes are off. If you want it done professionally, then think how they would have done it. cleanly and with new or nicely refurbished parts, and maybe an extra support or two properly bolted in the right places. Barring internal damage itwill be keeping the D351, and im already on the hunt for stainless steel tubing to make turbo manifolds. my next question is about the injector pump assemblies. how different was the timing on them from the D478 to the D351? Im new to the diesel ordeal but if its feasible and remotely close would it not add a touch more power putting the 478's pump on the 351? And thanks for the offer Jolly I will keep it in mind. I did actually mean about parts changing and making it a gasser but after looking through the factory service manual and listening...haha. And Alan, did that happen to be the DH478 in your boat? as far as fuel consumption goes, a winter truck is all she will be for a while, so guzzle away, so long as dependability is there. after a shutdown or two, a spicer with overdrive is on the list, if I can find one in decent order or worth going through.

[GMJakers13]

and dual tanks, factory set as well. the switches are driver side, on the floorboard by the seat.

[bigblockv6]

GMJakers13, I'm curious how is the power of the D351 in a pickup truck for a rating of 130hp, is it responsive or sluggish?

[GMJakers13]

bigblockv6, I would love to say but cant seem to get it to pop off. I havent ran a full set of procedure but pushed fuel to the pump and still wont run.

[bigblockv6]

I have to admit when it comes to Diesels I'm no expert, my interests are primarily with the gas GMC V6, ask me a question on one of them and it's never a problem.

[GMJakers13]

im pretty sure that it's just the pump. Id like to find a good 2wd that I can put a gasser in. ive got a 305 and spicer 4spd out of a 66 school bus with 48k on the set coming from California. have been thinking about some port work and a little intake modification for it. one day id like to see a billet crank and rods for one of the little 305s with a small dual turbo setup. dreams. Bigblockv6, can you swap the crank from the larger displacements, the 3.86in, in to tho 305 without much issue?

[bigblockv6]

Myself, I would not waste time and money on the 305, just go with a bigger V6. I pulled the 305 out of my 68 K2500 and replaced it with a 478M V6. Putting a 3.86 stroke in a 305 will require custom pistons, the longer stroke will make the pistons travel slightly above the bore, some say you can have the stock pistons machined down. You want a stroker V6 GMC made a 379 from 1973-74, basically a 351 with a 478 crankshaft. Same thing with the 432, a 401 with a 478 crankshaft.

[bigblockv6]

Myself, I would not waste time and money on the 305, just go with a bigger V6. I pulled the 305 out of my 68 K2500 and replaced it with a 478M V6. Putting a 3.86 stroke in a 305 will require custom pistons, the longer stroke will make the pistons travel slightly above the bore, some say you can have the stock pistons machined down. You want a stroker V6 GMC made a 379 from 1973-74, basically a 351 with a 478 crankshaft. Same thing with the 432, a 401 with a 478 crankshaft.

The 3.86 crankshaft has eight mounting bolts to the flywheel along with external balancing on the flywheel and front balancer, the 305 has six flywheel mounting bolts and is internally balanced. You would be putting way to much money into a 305 just to accomplish and extra 25-30 more cubic inches, just not worth it:lolsmack2::noway:

[GMJakers13]

I appreciate the input. As far as cubic inches go it really doesnt matter. I understand its a different application but I built a few SBC stroker 305s and really liked the outcome. I like to play and build things just to see what happens, and was just curious. Now I need to find someone that knows about these PSJ injector pumps.

[LEWISMATKIN]

Hi gang! It's been a long time since I have posted on this group. As for the T/F, my deceased dad (Lewis Sr.) said he saw one dh478 converted back to gasoline, but their is a great deal of conversion to do to make it a gasser. And with such a weak crankshaft, why would anyone want to do a conversion?? T/F cranks cannot be cut to an undersize bearing unless the shaft were either chrome plated or rehardned. Anyway, it is good to see the group still up and running. Take care & God bless,

Lewis Ellis Matkin, Jr.
Ridge Manor, Fla
1965 1002 305e

[FetchMeAPepsi]

Hi gang! It's been a long time since I have posted on this group. As for the T/F, my deceased dad (Lewis Sr.) said he saw one dh478 converted back to gasoline, but their is a great deal of conversion to do to make it a gasser. And with such a weak crankshaft, why would anyone want to do a conversion?? T/F cranks cannot be cut to an undersize bearing unless the shaft were either chrome plated or rehardned. Anyway, it is good to see the group still up and running. Take care & God bless,

Lewis Ellis Matkin, Jr.
Ridge Manor, Fla
1965 1002 305e


LEWISSSSSSS!

We were just wonderin about you a few months ago. Good to see you back!:upyes:

[Ed Snyder]

Hi gang! It's been a long time since I have posted on this group. As for the T/F, my deceased dad (Lewis Sr.) said he saw one dh478 converted back to gasoline, but their is a great deal of conversion to do to make it a gasser. And with such a weak crankshaft, why would anyone want to do a conversion?? T/F cranks cannot be cut to an undersize bearing unless the shaft were either chrome plated or rehardned. Anyway, it is good to see the group still up and running. Take care & God bless,

Lewis Ellis Matkin, Jr.
Ridge Manor, Fla
1965 1002 305e

Welcome back to the forum, Lewis! We've missed you and your expertise!

[LEWISMATKIN]

the problem with turbocharging a diesel engine is that the compression ratio must be lowered in order for the engine to operate without melting the pistons or bending the connecting rods. In the other GM diesel (series 71) the compression ratio went down from 21.5 to 1 to 17.5 to 1 and the connecting rods had to be changed because they were of a different material.

Cordially,
Lewis Ellis Matkin, Jr.
Ridge Manor, Florida
1965 1002 305E V6

[turbobill]

My DH478 has an advertised compression ratio of 17.5:1. Makes it plenty suitable for turbocharging.