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I'm tearing down an LQ4 of unknown mileage. The truck just rolled 300k miles, but that's all I know. The engine does not look like it has been taken apart before. It uses a bit of oil and has about 20 psi of oil pressure at idle. It also has a single lifter that taps really loud most of the time, but not always.
I know the cam bearings in these always look bad in comparison to other engines, but these look really worn out, no? Pics are of the top and bottom. Every cam bearing is just like this.
The rods and mains look fantastic in comparison. The bore is a little polished in the center, but the crosshatch is still visible. I'm taking it to the machine shop to get the bore and crank sizes check before I move forward.
The cam and lifters all look just fine. With that lifter tap I was not expecting that.
My plan for the truck is to use it strictly as a towing rig. I plan to go flat top pistons (making it an LQ9), stock cam, replacement lifters and replacing all the bearings. Anything else I should be looking for or should new bearings and a new oil pump cure my low oil pressure? I don't believe the 20 psi of oil pressure is the cause of the lifter tick. I suspect a failed lifter is the cause. Agree?
Measure the cam bearing inner dia. If top-to-bottom (the direction that wears) is within acoupla .001"s of side-to-side then they're still OK. You can also compare their ID to a cam journal's OD; if there's reasonable oil clearance there, say no more than .003" or something along those lines, they're fine. I'll let you be your own judge of what's "reasonable" in both of these measurement methods. They don't look unusual at all for one of these motors, no sign of destruction and catastrophe anyway. And of course the front one will always wear like that to some extent, due to the timing chain pulling down on it all the time.
It is said by some, of which I have NO knowledge or confirmation whatsoever, that the factory nowadays pays less attention to the cam tunnel machining than they formerly did, and instead, installs undersized bearings and reams them out to the correct diameter and collinearity. Again, I have no idea whether or not this is true, butt if so, then those bearings may have looked about like that before there was ever even a cam in them. Just a thought.
I agree about the rod bearing; looks fine to me.
If your oil pressure is 20 psi at hot idle, it's fine. Remember, old SBCs, which used essentially the same lifters, had about 10 - 12, and the pump bypass valve was set to around 35. Also don't forget, there are ALOT LOT LOT of things that can cause valve train ticking noises besides just lifters, so don't just automatically blame them for that. Inspect all your valve train parts carefully, to make sure you aren't putting the ACTUAL source of the tick, back into your rebuild, even if you change out the lifters.
Measure the cam bearing inner dia. If top-to-bottom (the direction that wears) is within acoupla .001"s of side-to-side then they're still OK. You can also compare their ID to a cam journal's OD; if there's reasonable oil clearance there, say no more than .003" or something along those lines, they're fine. I'll let you be your own judge of what's "reasonable" in both of these measurement methods. They don't look unusual at all for one of these motors, no sign of destruction and catastrophe anyway. And of course the front one will always wear like that to some extent, due to the timing chain pulling down on it all the time.
It is said by some, of which I have NO knowledge or confirmation whatsoever, that the factory nowadays pays less attention to the cam tunnel machining than they formerly did, and instead, installs undersized bearings and reams them out to the correct diameter and collinearity. Again, I have no idea whether or not this is true, butt if so, then those bearings may have looked about like that before there was ever even a cam in them. Just a thought.
I agree about the rod bearing; looks fine to me.
If your oil pressure is 20 psi at hot idle, it's fine. Remember, old SBCs, which used essentially the same lifters, had about 10 - 12, and the pump bypass valve was set to around 35. Also don't forget, there are ALOT LOT LOT of things that can cause valve train ticking noises besides just lifters, so don't just automatically blame them for that. Inspect all your valve train parts carefully, to make sure you aren't putting the ACTUAL source of the tick, back into your rebuild, even if you change out the lifters.
GM 100% uses the FIP method for their v8 cam bearings…and possibly other variants, of which I can’t confirm…Finished In Place. They are indeed final honed to size and collinearity (your term) at final machining before assembly. The cam bearings here look better than a lot of others I’ve seen, especially with 300k on them. Inside of engine is super clean also…this thing was maintained very well with frequent oil changes.
I don't have an inside bore gauge to measure this, but I know who does. I dropped it off at the machine shop to have the bores measured and maybe punched out if needed. I'll ping him in the morning and have him measure those cam bearings.
Thanks for the help!
Joe
Last edited by JoeRJr; Dec 16, 2025 at 09:57 PM.
Reason: spelling
If the bores still have crosshatch, they don't need to be bored again. In fact it's likely that the factory bore is better than what you'd get out here in the RW, unless it's done with a deck plate.
If I was the betting kind (I'm not), I'd bet he'll tell you it needs boring anyway though. Why would he tell you otherwise, and thereby not make any money? Not that machinists are dishonest, or anything like that; only, that's how they make their money, therefore they're biased that way. Just like, if you go to the dentist, they're gonna tell you your teeth need cleaned, even if you just had that done last week somewhere else, and they're spotless. They (a) don't want to take any chances and get blamed for poor service, and (b) it's your money that enables them to take that approach. He's not gonna (a) risk you building a new motor and being unhappy with it and blame his machine work or lack of it for that, and (b) he gets to charge you to keep his a$$ covered. It's just The Way It Is.
It's kinda too bad that it's already torn down... for your stated purpose, leaving the pistons in place and just replacing the main & rod bearings, oil pump, timing chain, cam & lifters including new GM trays, and valve springs, and changing to a pair of 4.8 / 5.3 heads other than Castech 706 castings, would be all you'd need. With modern EFI, blocks hardly ever wear like they did back in the old 2G carburetor days when we all blamed the Powerglide for eating the bores so bad; turns out in hindsight, the reason for that actually was, poor fueling especially at cold startup, washing down the rings. These motors simply don't wear like that.
Factory, OEM cylinder wall crosshatch depth is on the order of one MICRON.
IF crosshatch is intact for the full stroke of each bore.... THEN you can use stock pistons.
Your "local machine shop" is NOT going to improve on a factory bore in good condition.
Looking at those bearings:
I'd put a decent torque cam, ( 212in/218ex .550" lift) new lifters, VALVE SPRINGS and keep the LQ4 pistons: run a .040" head gasket to give 9.9 compression, with a bit of "quench around the edges" put it together, and "there's your TOW Motor"
If the bores still have crosshatch, they don't need to be bored again. In fact it's likely that the factory bore is better than what you'd get out here in the RW, unless it's done with a deck plate.
If I was the betting kind (I'm not), I'd bet he'll tell you it needs boring anyway though. Why would he tell you otherwise, and thereby not make any money? Not that machinists are dishonest, or anything like that; only, that's how they make their money, therefore they're biased that way. Just like, if you go to the dentist, they're gonna tell you your teeth need cleaned, even if you just had that done last week somewhere else, and they're spotless. They (a) don't want to take any chances and get blamed for poor service, and (b) it's your money that enables them to take that approach. He's not gonna (a) risk you building a new motor and being unhappy with it and blame his machine work or lack of it for that, and (b) he gets to charge you to keep his a$$ covered. It's just The Way It Is.
It's kinda too bad that it's already torn down... for your stated purpose, leaving the pistons in place and just replacing the main & rod bearings, oil pump, timing chain, cam & lifters including new GM trays, and valve springs, and changing to a pair of 4.8 / 5.3 heads other than Castech 706 castings, would be all you'd need. With modern EFI, blocks hardly ever wear like they did back in the old 2G carburetor days when we all blamed the Powerglide for eating the bores so bad; turns out in hindsight, the reason for that actually was, poor fueling especially at cold startup, washing down the rings. These motors simply don't wear like that.
Kinda funny you say that. About 4 years ago I brought him my first 6.0. It also had about 300k on it and I was certain it needed bore work. I delivered it there and he returned it, telling me the bore was fine. He said "hit it with a ball hone if you want and put new rings in it." I ended up putting flat top pistons in it, and he had to hone the rods I had because they were made for pressed in pins. This engine came with a K&N air filter, and those things usually do a good job at increasing bore size, LOL, but it wasn't terrible.
Factory, OEM cylinder wall crosshatch depth is on the order of one MICRON.
IF crosshatch is intact for the full stroke of each bore.... THEN you can use stock pistons.
Your "local machine shop" is NOT going to improve on a factory bore in good condition.
Looking at those bearings:
I'd put a decent torque cam, ( 212in/218ex .550" lift) new lifters, VALVE SPRINGS and keep the LQ4 pistons: run a .040" head gasket to give 9.9 compression, with a bit of "quench around the edges" put it together, and "there's your TOW Motor"
The crosshatch is still visible from top to bottom of the bore, but it definitely thins out in the middle. We will see if the wear is in spec.
Thanks for the build recommendation. That definitely sounds like a great setup!
Joe
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Bearing wear 
