MaxPF
1/2 ton status
OK, let's say a guy has a Blazer that is a DD/weekend wheeler, and it will eventually need a new motor. Current motor is a TBI 350 with a freshly built 4L60 behind it. Said individual (
) has narrowed his choices down to either a SPFI 383 that would end up making around 400hp/450lb/ft tq, or a 6.2 diesel with a hairdryer that will make a similar torque number, but about half the HP. Said truck sports 4.56 gears and 33's, but 35's or 37's are in the plans when the 33's are worn out. So, there are some pros and cons to each setup. Here are some off the top of my head:
383 pros:
It'll make plenty of power and torque
It'll cost less to maintain
It'll be a simple swap, since it is replacing another SB
383 cons:
Worse milage than the diesel (with 35's or 37's - I don't expect the diesel to get very good mileage with 4.56's and 33's)
More expensive to build (plans are for an internally balanced, US made 4340 crank, ETEC heads and an aftermarket sequential port FI setup... mucho $$$)
6.2 pros:
Better fuel economy (but not necessarily cheaper to run with diesel being more $ than gas and the need for ULSD additives, frequent fuel filter changes, etc.)
It'll cost less to build (assuming the hard parts are all servicable - I know how much an IP and pistons will be, and it is still cheaper than the 383)
It sounds kinda cool (not the loud obnoxious clatter of the older Cummins, more of a subdued knock/rumble)
6.2 cons:
Less power, and since it would be a TD it won't have any more torque without boost (where it will run when wheeling) than a NA 6.2
Potentially less reliable (we have all heard stories about broken main webs and broken cranks, especially when boosted)
Tranny needs to be modified to shift properly, and a new TC would be needed
Possible future emissions legislation could render it unregisterable without retrofitting to current emissions standards (i.e. particulate filters, NOx cats)
I like the idea of being able to wheel all day on a few gallons of diesel, but the uncertain future of diesel fuel quality and emissions regulations gives me pause. Plus the fact that the gas motor will flat outperform it, although it will suck the tank dry much faster. The cost of the diesel conversion will be less than the build of the 383 (albeit not by much, and only if I score the hydroboost, filters, etc. from a donor vehicle), but it will be more work.
The question is, which is likely to be more satisfying and less hassle over the long run. I've pretty much come to the conclusion that the 383 is the best choice (short of a 15MPG 454
), but I'd like to hear other people's opinions. Hypothetically, of course 
) has narrowed his choices down to either a SPFI 383 that would end up making around 400hp/450lb/ft tq, or a 6.2 diesel with a hairdryer that will make a similar torque number, but about half the HP. Said truck sports 4.56 gears and 33's, but 35's or 37's are in the plans when the 33's are worn out. So, there are some pros and cons to each setup. Here are some off the top of my head:383 pros:
It'll make plenty of power and torque
It'll cost less to maintain
It'll be a simple swap, since it is replacing another SB
383 cons:
Worse milage than the diesel (with 35's or 37's - I don't expect the diesel to get very good mileage with 4.56's and 33's)
More expensive to build (plans are for an internally balanced, US made 4340 crank, ETEC heads and an aftermarket sequential port FI setup... mucho $$$)
6.2 pros:
Better fuel economy (but not necessarily cheaper to run with diesel being more $ than gas and the need for ULSD additives, frequent fuel filter changes, etc.)
It'll cost less to build (assuming the hard parts are all servicable - I know how much an IP and pistons will be, and it is still cheaper than the 383)
It sounds kinda cool (not the loud obnoxious clatter of the older Cummins, more of a subdued knock/rumble)
6.2 cons:
Less power, and since it would be a TD it won't have any more torque without boost (where it will run when wheeling) than a NA 6.2
Potentially less reliable (we have all heard stories about broken main webs and broken cranks, especially when boosted)
Tranny needs to be modified to shift properly, and a new TC would be needed
Possible future emissions legislation could render it unregisterable without retrofitting to current emissions standards (i.e. particulate filters, NOx cats)
I like the idea of being able to wheel all day on a few gallons of diesel, but the uncertain future of diesel fuel quality and emissions regulations gives me pause. Plus the fact that the gas motor will flat outperform it, although it will suck the tank dry much faster. The cost of the diesel conversion will be less than the build of the 383 (albeit not by much, and only if I score the hydroboost, filters, etc. from a donor vehicle), but it will be more work.
The question is, which is likely to be more satisfying and less hassle over the long run. I've pretty much come to the conclusion that the 383 is the best choice (short of a 15MPG 454
), but I'd like to hear other people's opinions. Hypothetically, of course 
I drive the ones at work whenever I have the chance. they are fast.
