I know alot of people are trying to steer you towards a crate engine. There is nothing wrong with rebuilding an engine yourself as long as you work with a reputable machine shop and check everything as you assemble. Don't skimp on the quality of components either.
My 1996 Vortec had a dead cylinder when I bought it. It ran fine except when idling in gear. It would shake your teeth out. Once you started moving it ran just fine. When I bought it, I was certain that it was a bad fuel injector or something minor, but somebody traded it in for a reason and I knew with the price I paid for it that even if I had to rebuild, I was still into it for the right amount of money. I drove the truck for a month or two until it irritated me too much.
Once I did a compression test and found one cylinder @ 60psi I knew it had to come out. I then pulled it out and dissassembled it. It had a bent connecting rod (rod actually hit the crank) and both heads were cracked. All eight combustion chambers were a blueish color (excessive overheat). The engine had a ton of new parts (outside) because somebody was trying to fix the issue - water pump, radiator, wires, cap, rotor, and it even looked like new intake gaskets. The engine was even clean, like it wasn't original to the truck (truck had 122k on it when I bought it), and may have been replaced at one time. Once I pulled the engine I saw a GM GoodWrench sticker on the top of the 4L80e, so I'm certain that was replaced at one time.
I sent all the components to my machine shop for inspection. The crank was ok, all the rods (except one) were in good shape and properly sized for standard bearings. The block was fine and the alignment of the main bearings was fine (line hone check). I had the crank polished, bought all new rings/pistons/bearings/gaskets/oil pump/timing chain set and they were all good components - clevite 77 bearings, hastings rings, melling pump/pickup, fel pro gaskets, sealed power pistons, and one used good rod from another 5.7L vortec. I bought a used set of vortec heads for $100 and took them completely apart, had them checked for cracks and my father did the valve job/reassembly. I reassembled the entire engine and also had the vortec intake boiled out and then I glass beaded it to get it really clean as well as cleaned out the EGR passage to make certain I wouldn't have any other idle issues.
I installed it with all new hoses, belt/tensioner, new AC Delco oem replacement spark plugs (probably the thing that aggravated me the most is how expensive these are), and new GM oil cooler fittings/Intake coolant fitting. At one time I added all of my receipts up and had less than $1000 in the whole deal. Of course I have built many engines so I have the tools/knowledge/experience to do it and wasn't concerned if it would run right or not. My father helped with the cylinder head reconditioning and I have a great guy at the machine shop that takes care of me. I always check their work, and it is always right on the money.
The truck has run great since. I wanted to do the injector upgrade at the time, but knew it wasn't a big deal to do afterwards, so I just put the old one back in. I reused the original cam/lifters as hydraulic rollers - especially oem - rarely wear out. I checked the lift/duration when assembling and it was spot on. If I would have had the extra $$ at the time I would have done the machine work to the heads and put in an aftermarket camshaft, but decided against it. I basically built it to 100% stock spec. It now has 9500 miles since rebuild (two years later). I don't drive mine everyday.
I just did the injector upgrade two weeks ago. I did a dynomax ultra flo dual 3" in/out muffler with 3" tailpipes about 6 months ago. The injector made a bigger improvement over the exhaust, hands down. I too am running 285 series tires (285/70-17 on Hummer H2 wheels), and this took a little power away during towing from the 245s that were on it when I got it.
This past Sunday I towed several camper trailers for my buddy's business from the local rv show. He had 21 trailers of all makes/sizes and I towed a 7000lb trailer, a 4000lb trailer and something in between (didn't ask him the last one's weight). He advertises the actual mfgr curb weight when these are on display, so the weights are pretty accurate. I personally have a 24' enclosed trailer that I tow my GTO in that weighs about 8200-8500 lbs loaded. I have not weighed it but basically added the car's weight with the trailer unloaded weight.
I have been pretty vocal about how poorly these vortec 5.7L's tow - even on here - because my old 1990 TBI 5.7L 200k ECLB seemed to tow better than this truck. Things are definitely getting better and like I stated above the upgraded fuel injector made the biggest improvement. Right away I didn't notice any improvement in seat of the pants driving. But the more I drove it the more I noticed the difference. Especially in the mid range (2k-3200rpm) where with the old poppet valve setup the truck just didn't seem to gain any speed/rpm, whether towing or empty. With the new setup, it gradually keeps gaining speed and the rpms keep going up. I no longer have to get it to downshift and rev to the moon. Sure with the 7000lb trailer I knew it was back there and the truck was working harder than without, but the temperature never went over 210.
I want more and I plan to replace the camshaft next. I'm not sure the LT4 hot cam is for me as I am more interested in mid range torque than all out horsepower. The LT4 hot cam raises the rpm where power is made. I want to lower the rpm where power is made. If I do decide to change the cam, I will definitely do a tune first and then again after the upgrade. I have a friend with EFI live or whatever the other one is and he has been doing a bunch of tuning on GM trucks. I may let him give it a try first. I have access to a chassis dyno too. I would love to turbocharge/intercool this thing, and may just do it down the road. I think it would be perfect then. My truck weighs 5600lbs empty and this little small block is working already when the truck is empty. the 4000lb trailer - it really did not struggle at all.
Sorry for the long post, but I am a firm believer in building my own engine, not buying an auto parts store crate (especially) and no desire to spend the extra $$ to get a GM crate motor.
