Diesel Conversion

[Firearmfiend]

OK guys and gals, here's one for you. I'm converting my '70 C-10 to diesel. I'm seriously thinking of using a Cummins 6AT 3.4L (about the same size as a 292) but would consider using a Cummins 4BT or GM 6.2L.

My main question is this: Any thoughts or concerns with these motors? Also, what should I watch out for technically when it comes to the nuts and bolts of the conversion (glow plugs, fuel delivery, dual batteries, etc.).

Any of the motors I'm looking at come with the Chevy bellhousing and step van motor mounts. On the Cummins motors the clutch fork is on the wrong side of the motor so I already know I will be using my old bellhousing and replacing the clutch (who knows WHAT those delivery drivers were up to! )

If you've done this conversion a response would be greatly appreciated!

[Beefcake]

6.2/6.5 would be a lot easier because of the footprint. But its a pile of junk. If starting from scratch, cumming, dont forget the 7.3 powerstroke

[70rs/ss]

If you decide cummins, I have a 12 valve in a running driving dually that I want to sell, I bought it for this conversion but will never get to it. LMK

[JAKES 68GMC]

You should PM member TP in Cntl PA. He put a Cummins 3.4AT in a C-30, I'm sure he'd be more than happy to answer your questions.

[Spray-Bomb]

I vote NO to the 6.2 / 6.5td !!!

[67_C-30]

Originally Posted by Beefcake

6.2/6.5 would be a lot easier because of the footprint. But its a pile of junk. If starting from scratch, cumming, dont forget the 7.3 powerstroke

I have had 3 piles of junk (6.2/6.5) in 3 different trucks. My '91 C3500 had over 260K on when it the new owner drove it off. My '83 Suburban had 230,000 when the new owner drove it off 5 years ago, and he's still driving it today. My '84 K1500 has 330K on it, and I drove it Sunday.

With that being said, I'm currently swapping in another pile of junk in my '67 C-30 dually. I've already logged around 500,000 on these piles of junks myself already. I guess another couple o' hundred thousand won't hurt anything.

[Firearmfiend]

Keep the replies coming, PLEASE!!! By the way, I'm not doing this swap because I finally saved up enough money or something, I'm doing it because my current PIECE OF CRAP!!! Kragen 350 (yeah, I know, but I was really poor then) finally took a real s__t on me and for just a little more money I can go diesel, eventually to go to a straight veggie oil conversion.

Beefcake-- Can't afford a Powerstroke... besides, can't afford adapter bellhousings, can't afford different tranny (I have a tranny, divorced t-case, and front axle out of a '66 K-10, but most of that's a different thread entirely!)

Also, can't afford adapting a 12-valve 5.9 into my C-10, sorry, not to mention, I really despise electronic controls and doesn't that Dodge have a few?

67_C-30--I've heard good and bad things about the 6.2... I'm glad to hear you've had good luck with them. Were your's turbo'ed or naturally aspirated?

Again, thanks guys, keep 'em comin'!!

[Bob B.]

My opinion is the 6.2/6.5 makes the most sense for a '67-'72. They can be built into a reliable, economical engine with plenty of power. They fit will few modifications, and have the regular Chevy bell housing bolt pattern. They are about as heavy as a Chevy big block, and will turn fast enough that you usually don't have to change the rear axle gearing. 6.5L's are available brand new cheaper than you will ever find a rebuilt Cummins, and the new 6.5L's have a stronger block and a lot of internal improvements. Now, the others:
Cummins 4B3.9: These are small enough not to require cutting the firewall, but they are tall and the front crossmember might be an issue. GM used these engines in Step-Vans a few years, and there is an adapter to mate a 4B3.9 to a Turbo 400. Good luck finding one. The engine is very reliable, but doesn't make a lot of power, is very noisy and vibrates A LOT. Stock gearing could be a problem, these redline at about 2,300 r.p.m. in many applications.
Cummins 6B5.9: The engine Dodge used. Great diesel, lots of power, pleanty of parts, and a ton of work to get one in a '67-'72. Gearing could be an issue too.
International 6.9L/7.3L/Powerstroke: Probably more trouble then they are worth. Has anyone ever tried this swap?
Cummins 6AT3.4: Not really a Cummins, it was an Onan engine before Cummins bought Onan. Low power, not reliable, getting hard to find parts for. With a long piece of chain, the 6AT3.4 was good in marine applications- AS AN ANCHOR!
That's what I think, feel free to disagree, but I am an ASE certified Master heavy truck tech. with better than 20 years experience.

[JAKES 68GMC]

Originally Posted by Bob B.

Cummins 4B3.9: These are small enough not to require cutting the firewall, but they are tall and the front crossmember might be an issue. GM used these engines in Step-Vans a few years, and there is an adapter to mate a 4B3.9 to a Turbo 400. Good luck finding one. The engine is very reliable, but doesn't make a lot of power, is very noisy and vibrates A LOT. Stock gearing could be a problem, these redline at about 2,300 r.p.m. in many applications.
.

Doesn't make alot of power??? You don't think 300 ft. lbs of torque for a 239 cu. in 4 cylinder is alot of oomph?

[AuggieStyle]

firearmfiend i thought the 5.9 12V WAS NOT computered, but the 24V is computered? please advise as i was going to do the cummings 4bt out of a frito lay truck mated to a 400TH. but was starting to lean to the 5.9 12V because of the fact that it is not electronically controlled.

[Sir Fisher]

my brother drives a 96 diesel suburban; it has the 6.5 turbo and he has to change out the fuel injection pumps (2 of them) every 40k-50k miles or so... the truck has 130k miles right now and it's been done twice, by the dealer (about $3000 each time). a lot of other people have this problem on the diesel forum as well.

[67_C-30]

Originally Posted by JAKES 68GMC

Doesn't make alot of power??? You don't think 300 ft. lbs of torque for a 239 cu. in 4 cylinder is alot of oomph?

300 ft lbs is not bad, but it still only makes 80-120 HP. Its the same principle as to why you took the V6 out of your truck. The V6 makes much more torque below 2500 than your 350, but your 350 is much faster and is better suited for a daily driver. The 4BT peaks at 2500.

Let me say that the best diesel engine on the market is the 5.9L Cummins.
If given the unlimited resources, that would be my choice. However, the 6.2's/6.5's are by far the easiest to swap, and are very reliable, economical engines IMO. I have always got 20+ mpg out them of the except in a Military CUCV that had a TH400 and 4.56 gears. It got about 16 buzzing along at almost 4000 rpm on the highway. My K1500 has got as good as 27 on the highway with the 700R4.

Another aspect is noise. The Cummins are noisy and as others have said the 3BT rattles like a tractor engine. I drove a bread truck once that had one it rattled everything in it. The 6.2/6.5's are fairly quiet and real smooth going down the road. The V design is much better balanced that the L blocks.

[soulman67]

Its not the injection pump going out its the pmd/fsd. The little black box on the side of the injection pump that burns up due to the high under hood temps. I moved mine into the cab and haven't had to change it out since. It's just a 300 dollar part, thats held on buy 4 screws and one plug.

I have had 2 6.2s and currently a 96 6.5 and love them. Both 6.2's hand over 500k on them when I sold them, and are still running. I pulled the 6.5 out at 220k for a broken starter bolt and haven't finished putting it back in. Its been half finished for 2 years. I work in the oild feild and haven't had time to finish it.

[Firearmfiend]

Auggie--dunno, I thought the 12v had some computer stuff on it but I know next to nothing about that motor other than vague recollections at this point

Bob-- knew the 6at was an onan motor... I've heard of some 6at swaps into 4x4 rigs and people seem to like 'em, what kind of problems do you know of on this motor? I respect you ASE guys.

2 reasons why I was leaning away from the 4bt: 1. I heard they were noisy and shaky, 2. I've got a 373's in the back and with a 2300rpm (+ or -) top end I would go SLOOOOOOOOW on the freeway

also, dunno if I was clear, no automatic tranny for me! I like to choose what gear I'm in, not some part that operates on the principles of magic!

hey, been a while since I was on the board, how do I do the quote thingy again?

[67_C-30]

Originally Posted by Firearmfiend

Auggie--dunno, I thought the 12v had some computer stuff on it but I know next to nothing about that motor other than vague recollections at this point

Bob-- knew the 6at was an onan motor... I've heard of some 6at swaps into 4x4 rigs and people seem to like 'em, what kind of problems do you know of on this motor? I respect you ASE guys.

2 reasons why I was leaning away from the 4bt: 1. I heard they were noisy and shaky, 2. I've got a 373's in the back and with a 2300rpm (+ or -) top end I would go SLOOOOOOOOW on the freeway

also, dunno if I was clear, no automatic tranny for me! I like to choose what gear I'm in, not some part that operates on the principles of magic!

hey, been a while since I was on the board, how do I do the quote thingy again?

Just hit the quote button at the bottom of reply window.


I'm a manual shift guy myself. I'm putting my 6.5T in front of a NP-435-GA 4 speed. I'm going with 3.73's also. My buddy has a '97 3500HD with a 6.5TD and 5 speed manual and that truck is pretty impressive. I have been with him when he has pulled his old Michigan 77 loader on a flatbed and it does good considering what it weighs. A 6.2/6.5 with a turbo makes around 400 ft lb and while that is not 5.9 Cummins or Duramax power they are very adequate.

BTW, the 12V up until '98 has a mechanical IP.

[Firearmfiend]

Originally Posted by 67_C-30

Just hit the quote button at the bottom of reply window.

look at that! thanks!

[5150.4.67]

Just my 2 cents,
I think I'd stick with the gm 6.2/6.5 if you are not going to tow frequently. They get great mpg but down on power by todays standards.
If frequent towing is needed, you can stuff a 5.9 12 valve out of early Dodge with mechanical pump (rotary pumps seem to be better)and it makes great power, but may be on the pricey side for a decent condition find. You will need a SAE #3 bell housing to mount to th400 if memory serves me correct. Keeping an eye on the injectors is key, as when they get dirty, i.e. poor spray pattern, pistons get hot and drop off ring lands. No good and lots of noise. My father loves 5.9s who also transplants them into tractors!
By the way, he runs veg oil (peanut to be precise) in all of his. If you live in a fairly cold environment, pre heating fuel with be mandatory. Stuff gels under 48 degrees.
He also likes the 3.9 which is basically the 5.9 minus two holes. But as noted by other members, they might rattle your arse to sleep. I hear running an auto tranny really helps. These engines not only were in step vans, but also many came in tractors also. These are not light duty engines.
Damn that was a long post.
Good luck!
Jay

[70rs/ss]

Also, can't afford adapting a 12-valve 5.9 into my C-10, sorry, not to mention, I really despise electronic controls and doesn't that Dodge have a few?

Supposedly the 12 valve drops right in and 93 is electronic free. so it is a manual pump etc, that is why I chose it, but I won't get it done.

Mike

[Firearmfiend]

btw 67_C-30, sounds like cool setups. I've got an old 3 on the tree tranny now (converted to floor shift when the column shifter broke on me) but I'm going to the sm420 behind the diesel... of course, I need to get the diesel still, hence this thread. Wish I could afford a new truck (newer than 90), then I could semi-retire the C-10 and REALLY fix it up!

[Bob B.]

Originally Posted by 67_C-30

300 ft lbs is not bad, but it still only makes 80-120 HP.

Bingo! 300 ft. lbs. is not going to feel like very much with 120 h.p. and 2000 r.p.m.'s. Torque by itself doesn't get the job done.

[Bob B.]

Bob-- knew the 6at was an onan motor... I've heard of some 6at swaps into 4x4 rigs and people seem to like 'em, what kind of problems do you know of on this motor? I respect you ASE guys.

Thanks for that! As for the A series Cummins, UPS ran a bunch of them in the late 80's-early 90's time frame. Too many failed, and the Brown Guys replaced a lot of them with CNG 4.3L Chevy V-6's. In all fairness, it might be O.K. for what you want to do with it. The engine was just built a bit light for commercial service.

[72 CustomCamper]

I had a 6.2 in my 72 when I got it from by uncle. He did the conversion so I don't know too much about it. It did run strong, and with the 700R and 4:11 rear I got 22 MPG on the highway. The only reason I removed the diesel is I had to drive it 15 miles through downtown traffic with no belts to find a parts house. i was in a bad part of town and 65 miles from home so I wasn't about to leave it there. I know he used the glow plug timer and had to make a wiring harness that plugs into the factory harness to use the engine. He also had to modify the small block stands to look like big block stands to clear the exhaust manifolds...

Chuck

[Bob B.]

Originally Posted by 5150.4.67

These engines not only were in step vans, but also many came in tractors also. These are not light duty engines.
Jay

That's right, the most common place to find a B3.9 is Case construction tractors and equipment.

[TP from Cntl PA]

ROTFLMAO...........Most people who bash the AT's never had a oil pan off of them. They aren't a BT for sure, but they are stout little engines. Parts are harder to find. They were designed by Onan, built by Cummins, later Cummins changes some spec's so they aren't all the same. The AT's will take RPM's unlike the B's, since they were made for gen-set useage, they actually like the rpm's to work well. Drop the pan on a 6AT and then tell me they are weak. For only 210 cubes the bottom end is built like a brick sh*t house. And if you compare weights to other similar sized diesels they actually are very heavy for their displacement.

I put one in my C-20 not knowing what to expect. Now that its done, the little critter impresses the crap out of me. We farm and put that truck through every abuse imaginable and tore the crap out of everything behind the flywheel atleast twice...........And those components were behind big blocks.........Now, I do have the pump on mine tweaked and its still no 6 BT but goll darn will it run..........Having farmed and been around OTR trucks for years, I seen/ran alot of diesels and although I wouldn't call the 6AT the best by far, I can say with certainty, it definitely isn't anywhere close to the worst.

I sent you a pm on the subject.

[earl87gta]

I rilly like the 6.2 and 6.5 I admit its nothing link my d-max but it does what I needed it to do. Im putting a 6.2 in m 68 burb and I will put a turbo on it but im not looking for a lot of power it doesnt tow any thing and but its own waight and i will be geting twice the milage as the 283 thats in it now.