New project - 6.5 NA

[scottm]

For no good reason, I bought a 6.5l builder motor at a wrecking yard for $350. It is a goodwrench replacement engine in a 1990 c2500, so it is NA with mechanical pump. The block is a 12555506, date H269 (8-26-99, right?) heads are 1932567, and pump is DB2823-4153.

I am going to build it up for max NA top end, so it is going to get gas engine types of hop ups. I want it to run strong up to 4000 rpm, with a few hundred extra rpm for a safety cushion in case of a momentary over-rev. The Heath Bonneville racer ran to 5000 with a Scat crank and prepped rods, but no other bottom end tricks.

So I plan to prep my rods the same way, with beam polishing, shot peening, and arp bolts. Then for more volumetric efficiency, it will get ported and flow tested heads, custom cam with more lift, duration and overlap, real headers for proper scavenging effect, and if necessary, a custom sheet-metal intake. If it is still making 300 ft-lbs torque at 4,000 rpm, that is about 230 hp, and I think a worthy goal.

My questions have to do with the IP. What is different in the various part numbers, like the 4974 marine pump, etc? I want good fueling to 4000+, with the governor set to maybe 4200. Can any DB2 be built up specifically to do what I want, or do I have to start with a military or marine or whatever first?

[crashz]

I'm pretty sure the DB2 can be built up to your specs, but a local Standyne re-builder would need to build it to suit. You probably should have the injectors rebuilt and blanced to match.

From reading here, I'm guessing that a stock block is not going to like that much revving. I'd go over Robyn's block prep guide with a finetooth comb, and combine that with the best girdle you can find. That along with a Fluid Damper, and balanced injectors ought to keep it as smooth as possible.

I really have no idea on the cam choice, but it seems to me that more overlap may not work out right on these engines. Just thinking of the air flow here, as a NA diesel does not have a throttle. IE no appreciable vacuum. I'd like to know more.

[scottm]

Thanks for the reply! Since it will be NA, there will be less pressure and torque on the bottom end to cause block cracks. After a year of reading on the 6.5, I figure about half of all cracks are due to overheating, and the other half are due to excess injection advance. And a lot of crank failures, IMO, are due to the heavy external balance. I spent the last couple weeks trying to figure out how to get it to balance internally. Ati can make a neutral balanced damper, and Wiseco can make lighter pistons, so I should be able to do it. Then it should rev to 4500 or more with no crank and rod worries.

For a better pump (and block in better shape), I bought a 93 engine with a 4911 pump. I will post more as things progress.