thoughts/questions on swapping from 350 to diesel..

[imiceman44]

Just don't overboost it, good way to destroy your engine. Keep a close eye on your EGTs and keep your boost at reasonable levels.

In my experience a 6.2L is not as quick of an engine as a 350 is by any stretch. What they have going for them is fantastic mileage, and despite being slow all the time, the torque they produce makes sure that you don't go any slower when loaded.

If you are looking for a go fast engine, or are looking to improve acceleration, a 6.2L / 6.5L is not going to impress you regardless of how well geared it is. My 6.2L powered offroading truck has to be decelerated then downshifted to climb up hills all the time. Thats with 4.56 gears and 33.5" overall diameter tires. With the 2.73s and the same tires I was hardly able to maintain 65 mph, literally drove it in 4th gear (1:1) with the pedal on the floor the whole way, shifting it into O/D (I have a 5 speed manual trans) would result in a loss of speed. With the 4.56 gears I am able to cruise at 75 mph in 5th gear on flat ground, but definitely not in hilly areas.

The reason I said to use a turboed 6.5 with a Banks turbo is that the engine already has lower compression to take a turbo, that way it's hard to overboost it, just take advantage of the margin that was available and the stock turbo didn't use.
I agree the GM diesel isn't a screamer it's more of a torque engine, which is why I like it.

 

[tRustyK5]

Just don't overboost it, good way to destroy your engine. Keep a close eye on your EGTs and keep your boost at reasonable levels.

In my experience a 6.2L is not as quick of an engine as a 350 is by any stretch. What they have going for them is fantastic mileage, and despite being slow all the time, the torque they produce makes sure that you don't go any slower when loaded.

If you are looking for a go fast engine, or are looking to improve acceleration, a 6.2L / 6.5L is not going to impress you regardless of how well geared it is. My 6.2L powered offroading truck has to be decelerated then downshifted to climb up hills all the time. Thats with 4.56 gears and 33.5" overall diameter tires. With the 2.73s and the same tires I was hardly able to maintain 65 mph, literally drove it in 4th gear (1:1) with the pedal on the floor the whole way, shifting it into O/D (I have a 5 speed manual trans) would result in a loss of speed. With the 4.56 gears I am able to cruise at 75 mph in 5th gear on flat ground, but definitely not in hilly areas.

That motor must be pretty sacked...my '83 pick-up will cruise 65 mph in OD with the throttle at about 10%. That's 1830 rpm. It'll pull 90 mph no problem.

My Jimmy with 4.56's and 39.5's would break the tires loose under heavy throttle right after the 2-3 shift on wet pavement (NV4500), and could hold 5th gear nicely as low as 50 mph on flat ground (1400 rpm). Neither have a turbo on them...

Rene

 

[Russell]

I did just purchase a new engine for that truck, as it does have low compression in one of the cylinders, but even driving other diesels in good shape I've yet to drive one that truely impressed me unless it was turbocharged. And I'm easy to impress, I thought my 4.3L was pretty quick

 

[tRustyK5]

You'd think if one was low the rest would be marginal at best...

Really, the 2.73's and 33's on the highway should feel on par with my pick-up that has 3.42's, 235's and OD. Freeway rpm is within 100 for the two combo's. On hills my convertor will unlock at 1/3 throttle, and it'll kick down to drive at ~1/2 throttle or so. Never needed that though.

3/4+ throttle to maintain 65 mph is just wrong...

Rene

 

[Russell]

Yeah, hard on the engine too. Lots of black smoke on anything more than a very slight incline! This new engine I just picked up is in way better shape than the original, it only has around 80 000km on it vs 350 000 on the original unit. I'd love to be able to cruise at 115 without having to downshift on every other hill. Biggest problem with downshifting is that I come close to the rev limiter even going back to 4th (like 3000 rpm), so I always have to slow way down to downshift so I don't over-rev the poor engine.

My turbocharged 6.2L feels simply awesome though, gets to speed very quickly and rarely has to be downshifted even on reasonably steep hills