Engine replacement/rebuild recommendations

Ive been trying to chase down the source of a misfire on my 94' Yukon for a year, and its driving me crazy. Im probably going to take the drive of shame to a shop to figure it out, but at 250,000 miles, its probably time for a new motor. Ive basically ruled out anything simple as the cause of the miss, its very likely mechanical issue, probably bad rings on cylinder #8. Still cant find my compression tester, but im 99% sure im have low compression in that cylinder, based on the testing ive done. I may be wrong, but it seems to me that rebuilding heads, or re ringing a 250k motor is a waste of money. Its probably time to do a proper restore on the whole truck. Its been a solid daily driver and road tripper for years now, so i'd like to return it to its former glory.

Been looking at local engine builders and longblocks online, there is a broad range of prices for longblocks. Im quite happy with the OEM motor, so not looking for power adders, also need to pass emissions here. Buying a motor online is a pretty attractive, but I heard a lot of horror stories of people getting screwed on these. There are a couple well recommended engine builders here in Tucson, and a slew of unknown builders.

Looking at ATK engines, that'll be $2600 through jegs, which is a reman 2 bolt. A Blueprint runs $5000, which seems very pricey for a TBI motor, but its a 4bolt, steel crank, roller, new block. Being that I have mostly GMs, I havent had to replace a motor yet. I have a shop crane and all the tools, I also work at a freight company, so I can save on the residential delivery fees.

What kind of luck is everyone having with longblocks? What would be a fair price for a solid OEM type rebuild at a shop? Thanks all.

I have 300,000 miles on my motor and zero desire to rebuild. Hell, I think it was at 230k when the blower went on. Quit thinking motor replacement, have you ditched the factory spider yet? That's notorious for causing misfires.

No spider, its a TBI. Just the two injectors in the throttle body, I believe the spider is for the later vortec 5.7

edit; Seriously, Ive tried all the usual misfire stuff, gave it the good ole parts cannon. Its an issue with that one cylinder, dirty valve or bad rings im thinking.

rob249 said:

No spider, its a TBI. Just the two injectors in the throttle body, I believe the spider is for the later vortec 5.7

edit; Seriously, Ive tried all the usual misfire stuff, gave it the good ole parts cannon. Its an issue with that one cylinder, dirty valve or bad rings im thinking.

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Yup Vortecs have the spider injectors, 1996- up.

Either save some money and get Jegs own 350 tbi rebuild over the ATK or open the wallet and get new GM which surprisingly says it is machined/assembled in the USA .https://www.gmperformancemotor.com/parts/19432778.html

I've been at this for over 50 years, and mine got me a couple seasons ago; chased a slight miss at idle that eventually turned into a nearly-dead cylinder for months, only 12,000 miles into a brand new motor. Turned out my 'brand new' GM Delco spark plug wires had a bad core, parted ways and by the time I found it had nearly an inch of gap inside the insulation. Lesson learned; Ohm your plug wires.

I sold a few ATK engines when I was at Oriellys, the bad online reviews matched what I saw in the crate. One customer had a straight six jeep drop a valve right after startup. It seems like they’re batch built with unskilled labor but I don’t know for sure.

Orpedcrow said:

I sold a few ATK engines when I was at Oriellys, the bad online reviews matched what I saw in the crate. One customer had a straight six jeep drop a valve right after startup. It seems like they’re batch built with unskilled labor but I don’t know for sure.

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And 5 different main bearing sizes

1. Given feedback fuel injection, overdrive transmissions that cut down on RPM/mile traveled, and modern oil, a 250K mile engine may still have so little cylinder taper that re-ringing is entirely feasible. The Vortec short-block I ringed/bearinged/gasketed for my '88 had unknown miles. It came out because of a "rod knock" that turned out to be a broken flexplate. I even re-used the timing set, cam, lifters, and seven out of eight pistons and rods. (One cylinder bored .030 due to rainwater rusting the cylinder wall while the short-block was sitting.) All eight cylinders had only .0015 taper.

2. Before you buy a rebuilt engine--ESPECIALLY "mail-order" with no local representation--VERIFY the warranty terms.
Who is allowed to install the engine? You? A "certified" shop? Any professional shop?
What else has to be changed to validate the warranty? Radiator? Water pump? Injectors? Something more?
Who pays to remove a defective rebuilt engine? You? Them? Do they pay REAL shop rates, or do they pay 1970s shop rates? Do they cover fluids and filters?
Who pays to ship a defective rebuilt engine back to the rebuilder? You? Them? Do they pay realistic tranport fees?
If their engine is defective, who pays for your rental vehicle while yours is apart waiting for them to supply a replacement engine?
Who pays to diagnose problems with the rebuilt?
Who pays to do minor repairs to the rebuilt--resetting lifter preload, re-sealing a rear main, something that doesn't require returning the engine to the rebuilder? Do they pay realistic shop rates including "hazardous material" surcharges, and "shop supplies" that unethical shops tack-onto the bill to screw the customer?

GM sells a heap of new and rebuilt engines because every GM dealership in the country can handle warranty claims, and the warranty terms aren't horrible.

rob249 said:

I may be wrong, but it seems to me that rebuilding heads, or re ringing a 250k motor is a waste of money.

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In my opinion you're wrong. Modern (and modernish) engines have better metal and machining and don't get the bore taper that was common on '60s blocks. Your only worry is if the block was seriously overheated. Have it magnafluxed before you build it.