Hey guys, been a lurker on here for a few months reading up on the 6.5 engines and upgrades that you can do to them in the timespan they were available from 92-00 in the trucks. This is my buddie's name here on the forum, but he doesn't get online that much and I wanted to finally ask some questions about the 6.5 turbo diesel engine. I've learned about as much as I could about them here from searching and reading a lot of the topics posted here about power upgrades, reliability, etc. I'm most attracted to the 92-93 years because it is still a mechanical injection diesel engine w/ mechanical operated turbo/wastegate control. The 599 block seems to be the strongest and most reliable block that they put out for them even considering the late 6.2's used them. Question, if you were to build a 6.5 engine to make high power/torque (and I know there is a limit to them as they aren't a direct injection design as far as fuel injection is concerned) would you start out with a good condition 599 block that tested to have no cracks or stresses for a strong baseline to build a powerful engine? About a week ago I noticed a year old post over at The********** titled Peninsular diesel offering a forged steel crankshaft for the 6.5 engine. The damn thing wasn't cheap at about $800-900 and does anyone know if it is in existence for sale by them? I know the 6.5 engines used a cast iron crank from the factory and it seems if you want to strengthen the bottom end a forged steel crank is a good idea. A Cummins or Duramax diesel engine has a forged steel crank and in general they never need any crank upgrades given that. 18:1 compression pistons are a good upgrade while you're at it so you can lower the compression ratio and at least immulate a direct injection engine. I know Peninsular also sells the upgrade ported, higher flowing cylinder heads for the engine and would it be a good idea to install these heads with a forged crank in a factory (great condition) 599 block? A hanging ATA intercooler, water/methanol injection, better intake and exhaust, and pump/injector upgrades would make me think you could get to 300 HP measured at the rear wheels and still have the engine be reliable/strong. Is this feasible? If you were to put on a 300 HP output mechanical injection pump or even a 250 HP output from Kennedy could you get to 300 rwhp? I know you're not going to see high output power like any new age Cummins, Powerstroke, or Duramax but it seems as though a lot of trucks I've read about have dynoed in the lower end of the 200 HP range and it makes me think a mechanical engine could get to 300. I know a lot of guys say putting in marine injectors is not needed because the pump is what is going to deliver more fuel, not the injector. But in the case of the 300 HP output injection pump if it delivers an XX cc's amount of fuel more then a stock mechanical pump delivering an XX cc's of fuel and couple it with the marine injectors you're heading in the right direction for pumping for fuel. You just need to make sure you are upgrading the air flow equally with that fuel increase to have temperatures stay safe. 97+ air intake/box, intercooler, and water/methanol injection ought to cover that part of the problem. Heck, you could even try to put in an aftermarket cam if they even help for an upgrade in this case scenario. Doing all this wouldn't be real cheap, but I think getting to the 300 HP mark would happen. What do you guys think? My friend doesn't own a diesel yet, but we are looking into possibly buying a 1993 Chevy 2500 6.5. So the bug is just starting for us now, haha. Thanks for any advice.

Holly long post batman;). Yes you could build a relatively high output motor. Cost is going to be the issue. With the right money you could build anything. If you are going to spend the money to get custom block, heads, crank, balancing, pistons, etc, might be easier and cost effective to just get a P400 and have a pan made to fit a CK truck. The injection pump is still going to be a limiting factor.
To put things into perspective. Ian (formally of Heath Diesel) dynoed a relatively stock 6.5 with all the Heath goodies and NOX and propane at 303 rwhp. As far as a ATA intercooler, I would wait. There is the A Team Turbo that just came out that so far does not require a intercooler. Saves money. Some members who switched to the *** even took off there intercoolers.

Have you priced what all the upgrades and the block-machining-parts would cost? You would be very close to the price of a new gep engine with improved block and cooling.300rwhp is right on the edge. A ticking time bomb. Very hard to have durability with those output numbers. Remember, this engine was originally designed as 160 hp.

A 6.5/ DS4 electronic IP produces more fuel each RPM @ max than the DB2 thus more power potential available.Couple that with the Heath or Kennedy modified PCM's & it is no contest for power or economy .If one remote mounts thePMD ,creating a FSD on a heat sink in the air stream the engine with the DS4 will stay running very well. You're right on the money with the early 599 block with 18 to 1 pistons though.The most powerfull /fastest 6.5 to climb the mountain in Montana @ the Diesel page tow off contest is a Ds4 equipped 6.5 95 Surburban.Either the Mitisubishi Turbo or the Holset Turbo is the final top off for making a powerful 6.5. For you a non running engine project truck would be a logical starting point,if your up to it. IMO.

ARP studs on ALL the main caps is what I would consider one of the most important structural upgrades for the bottom end. I'm pretty sure Heath diesel has them listed on their website now.

As far as a ATA intercooler, I would wait


Intercoolers are a waste of money now we have the ATTurbo

Definatley the route to go......Best of both worlds



2 Cents

Yes, almost forgot about the ARP head studs because while you're in there you might as well get rid of the idea of using head bolts when they are inferior to studs. And also on the main caps is a great idea for the block. What about any info for the supposed forged steel crank? Do you even get a forged steel crank in a P400 engine if you were to happen to buy one? Huh, I didn't think a DS4 would put out more fuel then the highest output DB2 with all the goodies inside?? I bet a DB4 would be better than a DS4 and you could still have good ol' mechanical injection. And I have read about the *** turbo and I did even send a PM to Stateman asking him about it. I agree it's pretty much the first and last turbo you'd ever need to put on a 6.5 period. Well, if one couldn't get to 300 rwhp and also have it be safe then I guess we could settle for the 250-275 range. Thanks for the replies.

Do you know of the 6.5 Power Project on the Page? Basically almost exactly what you want to do, just without some of the newer more expensive mods, and has reliably lived beyond 200K miles at somewhere around 280 RWHP, IIRC. I, however, would not use a GM 6.5. I'd look into an AMG P400 instead. IIRC, they have the forged crank, and are comming from the factory with ratings in the 250-ish range. Wouldn't suprise me if with the P400 and the right combination of turbo and IP, the ole' 6.5 could hang with many modified Duramax's. Going to take a lot of testing though.