7.4 Vortec Head Gasket job in vehicle?

So newbie here but have lurked for a decade…. And I feel Ive done due diligence and just can’t find a good thread for this question here, Youtube, etc. I can find TBI threads, I can find out of vehicle 7.4 Vortec threads or videos, but I am wondering of any “gotcha” caveats to doing the 7.4 Vortec head gaskets in vehicle (99 Burb in my case.)

History , this is 130k mile rig, I am second owner, but a series of calamitous events has me questioning. 2 years ago I replaced the crank sensor, tried using my new Chinese scanner (great for wife’s Mbz) to do the reset, oversped the engine (hey I hadn’t done this repair in 15+ years, used my old Genesis and did fine) which took out the likely already failing original water pump. Bought a “premium” set pump/fan clutch from Autozone as needed it now, then was riding a week later stop/go with my 15yo getting in hours for her license. Smelled warm from passenger seat, I look over at the temp gage is right at the bottom of the red, likely for the last 20 minutes. Go home cool off, take apart that junk pump, ends up it isn’t reverse rotation and even if it were the 1/4” gap from impeller to housing wouldn’t pump crap. In goes Amazon Delco pump and original fan clutch and all is well, or is it? Temps stay fine all the time but loosing 1/2” coolant a month/5-700 miles, some coolant on oil analysis. Also mild misfires, stumble at cold idle, which were admittedly there even before. I do intake manifold gaskets (were probably original and clearly had been leaking), fuel regulator, Bosch injectors, new ISV, new aluminum dizzy, still the mild stumble, mild misfires which improve warmed up. Coolant better for a couple oil analysis, then over last 2 creeping back up. Head gasket tester is just indeterminate for me. Test fluid stays “mostly” blue, sure doesn’t go yellow or green, but perhaps the blue gets ever so faintly “less blue” after many minutes. Compression excellent (175-180) all round, like I said runs cool, did have some leaking this winter over at heater valve plumbing but seemed to be botched past owner flush fitting install, since replacing all the hoses (excellent thread on here) no hose leaks. Coolant does go down slowly in tank, perhaps 1/4” down a month.

So here I am, ready to pull the heads. I am a more than advanced amateur here, for instance I will likely skim them myself on the Bridgeport over in the corner before reinstalling, but I am looking for issues trying to do this in the vehicle. Big for instance is there clearance with the exhaust manifolds, getting nuts off or studs out? Is there room with steering to pull drivers manifold off the studs if the studs don’t come out? Is there room to lift the heads out? Can a fat 55yo guy heft a what 70lb? Big block head out of the car? Would pulling the core support, radiator, A/C help said fat 55yo guy do this, I don’t care if I have to break open the A/C as actually I’m going to anyway as folding up and hanging the compressor was a pain doing the intake last time. That job took me 2 solid days but I did do a lot of extra stuff, re crinkle coated the valve covers, Alodined the intake manifold, etc. Which brings me to time…. Is this 2 solid days, 3 solid days, 4? Despite having owned 6-7 of these over the last 20 years, wife was not enamored when I sold the (err, sorry guys ‘18 Expedition) for a nice profit at the height of the pandemic nonsense and bought this rig. If this is going to take me more than 3 days, I’m going to be in trouble and I have to wait until the now 17yo goes off to school this fall, or do it right now as they are both on a Greece trip and I got 3 solid days…

Thoughts, opinions, TIA

I did a head gasket job on a BBC many years ago when I was young and dumb...swore I'd never do it again and I haven't I often wondered would it be plausible to use a cherry picker to lift them heavy ******** up and out of the engine bay.
Is there a possibility of getting help?

grampadirt said:

I did a head gasket job on a BBC many years ago when I was young and dumb...swore I'd never do it again and I haven't I often wondered would it be plausible to use a cherry picker to lift them heavy ******** up and out of the engine bay.
Is there a possibility of getting help?

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No help unfortunately, but the cherry picker occurs to me as well. Time pressure for decision of when to do work is off as on a whim I started surfing parts thinking about the added time to skim the heads, pull em apart to do a quick lap and replace the valve guide seals and voila in the time since I posted I somehow bought a rebuilt set off ebay. I sure hope there is no true difference between the 12560241, 10141279 heads, quick search seems to say no and I presume my ‘99 originals are 12560241 and I bought the 10141279. Anyway again to anyone with in car tips, TIA, but this will become a late August job now as I need the vehicle this summer now.

The heads are about 72lbs without the rockers. I can't remember which castings I had. I've since sold the heads to another member.

If you're not losing a lot of coolant, I wouldn't bother. I'd guess it's the intake manifold gasket, rather than the head gaskets.

Have you tried putting a cooling system pressure tester on it?

454cid said:

The heads are about 72lbs without the rockers. I can't remember which castings I had. I've since sold the heads to another member.

If you're not losing a lot of coolant, I wouldn't bother. I'd guess it's the intake manifold gasket, rather than the head gaskets.

Have you tried putting a cooling system pressure tester on it?

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I did a pretty careful job on the intake manifold gaskets, Felpro set, and again the concern either way is that coolant is climbing again on oil analysis, so I’d need to redo intake manifold if I screwed them up somehow. Yes and no on pressure testing, yes I had one on last winter when I found the leaks around the heater valve/flush filler the PO had in there, after yes it held pressure well for 5-10 minutes I didn’t go longer than that and I haven’t since. Because I’m getting coolant in the oil (and I do mean not even visible here, like oil not milky, no residue on cap) I feel I do need to figure it out. Plus the stumble and misfires although minor have actually been there from day 1, the cold exhaust is a bit white until warm, subtly more than normal condensation? I don’t know. I might scope #2 which gets the most misfire counts vs a few others to see if it is “too clean “ but I’m going to bite the bullet though wait till August. Perhaps I will photo document well and put in a thread, if there indeed isn’t one for Vortec’s.

wvukidsdoc said:

I did a pretty careful job on the intake manifold gaskets, Felpro set, and again the concern either way is that coolant is climbing again on oil analysis, so I’d need to redo intake manifold if I screwed them up somehow. Yes and no on pressure testing, yes I had one on last winter when I found the leaks around the heater valve/flush filler the PO had in there, after yes it held pressure well for 5-10 minutes I didn’t go longer than that and I haven’t since. Because I’m getting coolant in the oil (and I do mean not even visible here, like oil not milky, no residue on cap) I feel I do need to figure it out. Plus the stumble and misfires although minor have actually been there from day 1, the cold exhaust is a bit white until warm, subtly more than normal condensation? I don’t know. I might scope #2 which gets the most misfire counts vs a few others to see if it is “too clean “ but I’m going to bite the bullet though wait till August. Perhaps I will photo document well and put in a thread, if there indeed isn’t one for Vortec’s.

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This doesn't seem like a bad head gasket at all. Every one of your comments points to a problem with the intake manifold again. Not only would I pull the motor to do that work, there are exactly zero instances where I would put a rebuilt ebay head on a motor. For your misfire, I would start by looking at the distributor, possible vacuum leaks, or injector issues. The stock injectors are well known to be terrible and with the low miles for the year, all of the ignition and fuel system would be suspect to me.

wvukidsdoc said:

I did a pretty careful job on the intake manifold gaskets, Felpro set, and again the concern either way is that coolant is climbing again on oil analysis, so I’d need to redo intake manifold if I screwed them up somehow. Yes and no on pressure testing, yes I had one on last winter when I found the leaks around the heater valve/flush filler the PO had in there, after yes it held pressure well for 5-10 minutes I didn’t go longer than that and I haven’t since. Because I’m getting coolant in the oil (and I do mean not even visible here, like oil not milky, no residue on cap) I feel I do need to figure it out. Plus the stumble and misfires although minor have actually been there from day 1, the cold exhaust is a bit white until warm, subtly more than normal condensation? I don’t know. I might scope #2 which gets the most misfire counts vs a few others to see if it is “too clean “ but I’m going to bite the bullet though wait till August. Perhaps I will photo document well and put in a thread, if there indeed isn’t one for Vortec’s.

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I'd leave the pressure tester on for longer than 5-10 minutes. I'd probably leave it over night.

What did you use on the bolt threads on the lower intake manifold. GM spec is thread locker.

454cid said:

I'd leave the pressure tester on for longer than 5-10 minutes. I'd probably leave it over night.

What did you use on the bolt threads on the lower intake manifold. GM spec is thread locker.

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Used the good Permatex thread locker. I will put the pressure test on this weekend.

BeXtreme said:

This doesn't seem like a bad head gasket at all. Every one of your comments points to a problem with the intake manifold again. Not only would I pull the motor to do that work, there are exactly zero instances where I would put a rebuilt ebay head on a motor. For your misfire, I would start by looking at the distributor, possible vacuum leaks, or injector issues. The stock injectors are well known to be terrible and with the low miles for the year, all of the ignition and fuel system would be suspect to me.

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So dizzy, new, injectors, new, coil, wires, plugs, all ignition new, ISV new, well all of this 2 years ago. I could smoke the intake I guess but don’t have any reason to suspect a vacuum leak and doubt that would affect only a few cylinders consistently. Generally #2 counts 8-12, #1 and #3 count 3-5, the rest 0, occasionally 1 here or there, so consistent and on both sides of the motor (though I admit considering this now all at the front.) I have changed plug on #2 since all the work, haven’t changed wires but it did the same before all the work and didn’t change with new dizzy, wires, plugs. None of that helped or hurt the misfires/stumble or changed anything obviously in any way. The eBay heads were not from a rebuilder, they were a set being sold off a project where the guy stated he had a good local shop do them, then he went aluminum on the application. I believe him, the pics look very good, all surfaces (exhaust, intake) not just the head face skimmed, quality new valves, no spray paint rebuild here, so I figured very reasonable to take a chance.

wvukidsdoc said:

Used the good Permatex thread locker. I will put the pressure test on this weekend.

So dizzy, new, injectors, new, coil, wires, plugs, all ignition new, ISV new, well all of this 2 years ago. I could smoke the intake I guess but don’t have any reason to suspect a vacuum leak and doubt that would affect only a few cylinders consistently. Generally #2 counts 8-12, #1 and #3 count 3-5, the rest 0, occasionally 1 here or there, so consistent and on both sides of the motor (though I admit considering this now all at the front.) I have changed plug on #2 since all the work, haven’t changed wires but it did the same before all the work and didn’t change with new dizzy, wires, plugs. None of that helped or hurt the misfires/stumble or changed anything obviously in any way. The eBay heads were not from a rebuilder, they were a set being sold off a project where the guy stated he had a good local shop do them, then he went aluminum on the application. I believe him, the pics look very good, all surfaces (exhaust, intake) not just the head face skimmed, quality new valves, no spray paint rebuild here, so I figured very reasonable to take a chance.

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New doesn't mean good.

What do your fuel trims look like? What does the spark plugs in those cylinder and the #1 O2 sensors look like. If enough coolant is getting into the cylinders to cause a misfire, you will see the coolant contamination on the plugs and O2 sensor. Coolant residue in the oil sample without any signs of it on the plug or O2 sensor says that it would have to be a VERY small leak between a coolant passage and oil passage. If it was leaking into the combustion chamber you would have combustion gasses in the coolant and evidence of it on the plugs and O2 sensor. None of that would cause misfires. If you had a headgasket failure to the combustion chamber your compression tests would show way more than a 5% difference between cylinders.

I just can't imagine a scenario where it makes sense to roll the dice on someone shipping you a set of iron BBC heads. Unless you got them for ~$100 for the set, the shipping on that 150lbs of iron must be crazy.. .assuming the shipping company doesn't destroy them along the way. I would consider it if they were local and I could go see them and pick them up in person.

I paid ~$500 to have my L29 heads fully rebuilt by my trusted local cylinder head guy. That was new 454 HO springs, retainers and rotator eliminators. Cleaned, surfaced, inspected, all new guides, valve job and set the installed height and spring pressures. He had them for about 2 weeks.

BeXtreme said:

New doesn't mean good.

What do your fuel trims look like? What does the spark plugs in those cylinder and the #1 O2 sensors look like. If enough coolant is getting into the cylinders to cause a misfire, you will see the coolant contamination on the plugs and O2 sensor. Coolant residue in the oil sample without any signs of it on the plug or O2 sensor says that it would have to be a VERY small leak between a coolant passage and oil passage. If it was leaking into the combustion chamber you would have combustion gasses in the coolant and evidence of it on the plugs and O2 sensor. None of that would cause misfires. If you had a headgasket failure to the combustion chamber your compression tests would show way more than a 5% difference between cylinders.

I just can't imagine a scenario where it makes sense to roll the dice on someone shipping you a set of iron BBC heads. Unless you got them for ~$100 for the set, the shipping on that 150lbs of iron must be crazy.. .assuming the shipping company doesn't destroy them along the way. I would consider it if they were local and I could go see them and pick them up in person.

I paid ~$500 to have my L29 heads fully rebuilt by my trusted local cylinder head guy. That was new 454 HO springs, retainers and rotator eliminators. Cleaned, surfaced, inspected, all new guides, valve job and set the installed height and spring pressures. He had them for about 2 weeks.

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I do agree that I’m sort of conjecturing two things, sure would seem that I’m mostly worried about small coolant to oil leak, which may/may not also associate with a small combustion to/from coolant leak which would cause misfiring, but would seem to have to be real small not to show on the test fluid, smaller than one would think would cause misfires. The compression test was after the overheat but was last checked over a year ago, perhaps this weekend I will check again and scope the easy front cylinders. Fuel trims are great, I replaced pre O2 sensors at time of all the work but have not pulled them since, a good idea to at least look at the #2 side. Did not do downstreams but they look like they do what they should based on waveforms (as do the cats.) #2 plug did not seem overly scrubbed nor fluffy, but I haven’t pulled it in 4-5000 miles. Shop prices up here are ridiculous, in WV where I grew up I could get your price, here it is $225 a head just to disassemble and surface, $35 a hole to regrind valve and touch up seat. So $500 a head just to put your existing crap back together after surfacing. I actually have a flycutter that takes a 10” pass and have skimmed a lot of small block heads, but figured I’d take my chances with this set.