Help with new engine decision

jdmcleod wrote:
Dave, that is an impressive rig you have there! How much did those engine upgrades/additions set you back? That 502 looks like it would be a beast. How has your mileage been? How close to the physical dimensions of your 454 was it? What octane do you run now? Will my current ECM do to run new chips? Do you run ODB-II now? Sorry to throw so much at you. You have me intrigued that I could resurrect this old gasser to be a diesel warrior.

As far as dollars, I went a little crazy - about $8200 into the engine and Edelbrock package including all the other little details when you do an engine swap. The block is a BBC GEN VI block, which means roller lifters and better oil flow. It is a direct drop in swap. Even the old 454 headers bolt on. Old engine mounts bolted on, but had to be notched with a grinder to fit around some tabs on the casting. The only other difference was that all the accessories used larger bolts, so I had to drill out a couple of the mounts. Other than that, I can't think of much else that would apply to a standard swap. (My coach is front wheel drive, so I had to deform the oil pan to clear the differential)
Mileage is a little over 9 at 70 mph. I'm looking at changing my gear ratio, as I have plenty of roll on torque at cruise, and way more than I can use off the bottom end. Yeah, it will smoke the front tires from a 20 mph roll on. Sure was a surprise to everyone the first time it happened. We were data logging for tweaking the mixture. Thought it was safe to floor it at 20 mph, but she squealed the front wheels.
The ECM is stock GM from a '95 truck OBDI - see sig below for numbers. Uses the stock harness, but adapts to MPFI. The ECM bank fires, which means it thinks it still has 2 injectors, instead of 8. I know this ECM was used '93-'95, but I do not know what they used in '92. It may be the same, because I can't think of any other ECM that ran the 4L80E. No matter what ECM you have, it can be programed. The process is pretty well documented, and those documents are free. There is a couple of forums that support the tuning software, which is shareware - pay if you like, but is also included with the chip burning hardware. You can set yourself up with everything you need for about 200 bucks including adapters to plug into your ECM. I chose an adapter that allows me 8 different tunes on the fly, as I figured that would be the easiest way to experiment with small tweaks. For a little more money, you can buy an emulator, which allows you to make programing changes on the fly, while the engine is running - or while DW is driving. Programing is not like writing software. Basically there are tables of memory locations. Changing the value in each of these locations means something to the ECM. The software is set up to translate meaningful values into raw binary code. ie if you want the timing to be at 36 degrees, you type in 36, and it will translate that into the value the ECM reads.
As far as octane, I set it up to run 91, but I can safely run 89 if I need to. The knock sensor will detune the timing, it has a learn function that figures out you are running cheap gas, and retards the timing. It will unlearn on the next tank full.
Performance wise, there is nothing like listening to a 502 running wide open at 5200 RPM. The sound tells you it is something bigger than a 454. The HP is double the stock 454. It will pull a 6% grade at 80 mph, towing a 4600 lbs Jeep Grand Cherokee. ( I actually don't know if the peak grade was 6%, or just most of the grade, as there was a steeper section right near the end. Before that it had accelerated to over 90 mph)

Of course the other option would be to find a boneyard 8.1L. Pull the harness and the engine and drop it in. These blocks are all basically the same on the outside, even though the inside is much different. It will bolt in as well - I have a friend who did this swap in his '82 Revcon. The engine was pretty much a bolt in. Yes, even his old headers fit. While the 8.1 doesn't have the top end, it will get better mileage because of the fast burn heads.

havasu wrote:
It will be fun learning and you will get a great sense of accomplishment afterwards.

No it will be a vain sense of accomplishment - I still have to hang my head out the window every time I step on the gas. I'd probably get better mileage if I could get over it.