I am working on a frame off restoration of a 1985 Chevy K30 Crew Cab. The frame has been modified to take a short bed. Before I move on with the project I am trying to decide how to power this project. GM 6.5 of Cummins 12v. I am NOT looking for horsepower and smoke. I am looking for reliability and fuel mileage first then enough HP to make it up a hill with an older cabover camper on occasion (long trip). Most of the time it will be around the mountains of Idaho, camping, hunting and wood cutting.

I have an opportunity to get a crack free "599" block. So your thoughts and ideas on the following. I do want to stick with the mechanical injection.

1) 18:1 pistons? Cold weather starting issues?
2) Mains studs? Girdle?
3) Stock cam?
4) A Team Turbo? 15 psi boost absolute max?
5) CAI?
6) Free flow exhaust?

Any others I may have missed?

 

Personally, I would never touch another GM cast 6.x block again. I had a 599 block in my truck after the original 506 block, it crapped out just the same as the original 506.

Navistar cast GEP engine or you're wasting your money. Just my .02.......

If you want mechanical injection stick with a DB2 pump. Turbo engines came with the DB2 in 92-93.

1. Meh, not too impressed by 'em. You want the 20:1 jobbies if you want fuel mileage over power. Most guys seem to report no problems starting a 6.x with 18:1's

2. Studs - sure, why not? Girdle - the only ones that you can buy or make are waste of time on a 6.x IMHO

3. Sure, long accepted as the best cam for a turbo 6.x. definitely best for MPG. There are a few "hot grinds" just coming out on the market.

4. ATT would be fine. So would a GM8, for your stated uses. I wouldn't go over 15. An ATT is non wastegated so you get what you get with your right foot. I've got my Optimizer limited to 13 on a new GM8, even though the engine is rated to handle 25.

5. Well, ya gotta have an intake of some sort, why not make it as cold as possible....

6. Always important on a turbocharged engine. Shoot for 3-4" system on a 6.x. A 3.5" system will flow more exhaust than a mild 6.x can make.

Figure on 20-ish mpg as an absolute best on a turbocharged 6.x with any kind of decent gears and hp. My 98 is new everything (see sig line) with 4:10's and gets right around 14-15 mpg. Dyno's right around 200 hp at the rear wheels. Towing the trailer in my sig line is right around 12-13 mpg.

Slightly wicked up 4BT sounds like it might fit the bill for you better if you want MPG and durability. 250-300hp is relatively easily attainable and more than a 6.x will ever make (without mega bucks invested), 20-25-30 mpg is within reach. Durability will be miles better than a 6.x.

Bit heavier than a 6.x though.....bit more vibration and noise also, if you don't do the swap right.

6BT will do anything you could ever want it to, but it's somewhere around 1200lbs! I seem to recall the 80 style frames need a bit of reinforcement to handle a 6BT, but don't quote me on that.

Have you put any thought into what transmission you want to use yet? Gasser torque convertors don't work well on diesels. Stall speeds are a bit "off".

Don't forget; diesels don't make vacuum. If you have power assist brakes you're going to have to install a Cummins with the vacuum pump or swap to hydroboost brakes. There is a vacuum pump on the 6.x engines, but it's only meant to run a tiny vacuum wastegate on the GMx series turbos. I don't think I'd trust it to put out enough vacuum to effectively run something as critical as brakes.....they're also prone to failure.

Good luck.

 

Welcome to my quandry!

There is no doubt that you can do some amazing things with the Cummins. But with no disrespect to the real bombers out there, how much horsepower is enough. There is a point where all of those modification take a toll on engine reliability. GM, Cummins it doesn't matter.

The pro's to a Cummins is that you can make easy horsepower without a lot of mods. It is reliable. Gets good fuel mileage.

The con's are they are heavy and they are noisy. The weight could be an issue with my frame although it is a 1-ton.

 

We all know that you can make more power with a cummins but for an everyday driver andmpg its hard to beat a 6.5. That would be my choice: #1 because you don't have to Fab motor mounts. #2 it will mate to your tranny. #3 there cheaper and easier to find. I would keep the comp ratio at 20:1 for MPg, studs, and totalseal rings with a-team and you should be pleased. On a side note have you considered a supercharger, they work very well on these engines?

 

Thanks for the input. There are several companies that make crossmembers and engine mounts that bolt right in. That said, I am trying to determine how to fit an intercooler in without cutting up the radiator core support or by screwing up the grille. With the Cummins the a/c box or the slave cylinder does not present a problem. With the 6.5, the turbo location presents a problem with the a/c box and the drivers side exhaust manifold also presents a problem with the slave cylinder. As far as engine cost, I can get a complete Cummins cheaper than a 6.5. Just more stuff to sort through. So in the mean time I am having the axles rebuilt, putting together the suspension, and trying to locate some H2 wheels. I am hoping to have a complete rolling assembly by the end of September. Then on to the engine and drivetrain.

 

reguardless of wich way you go if you could plese post some pics. Im a susker for the older cc trucks ford or gm.

 

I will get some pictures up tomorrow.

 

As promised here are some pics.

 

Looking good. I want to follow this one

 

Not to be a buzzkill dieselboy but superchargers are hard on engines I have heard of guys having front main bearing failure in as little as 40k due to all the stress the pulley belt puts on the front of the engine,not to mention for 5 grand you could put a wicked turbo on the rig and still have a poket full of cash????