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Dug up the GM Service Bulletin for "Lifter tick when cold", 57-61-09. '91 to '95 LQ1 (VIN X)
The parts kit has been discontinued by GM long ago. My quest was to find sources for those parts; and complete the procedure on my '93 Lumina Euro 3.4 which was torn apart to replace the rear head gasket.
There are three critical part numbers in the GM service kit (aside from gaskets and O-rings) required to perform this operation. Two of the three are readily available in the aftermarket--the 10-32 set screws, and the cup plugs. I hadda buy a box of cup plugs and a batch of set screws; if you can't find 'em locally, send me a PM. All gaskets 'n' seals are readily available, and are included in the gasket set I needed to replace the head gaskets (Fel-Pro HS9113PT1 Head Set.) This leaves one item that is expensive to source--the replacement thrust plates.
Reading the bulletin, and seeing the cam carrier gave me a clear understanding of how to proceed. Note that in some of my photos, the thrust plate is UPSIDE DOWN. I intended to leave the camshaft positioning tool in place while servicing the camshafts, and the thrust plate was in the way to drill the front camshaft. I re-positioned the thrust plate--but the drill bit wasn't long enough, and I had to remove the positioning tool so I could rotate the camshaft and drill straight down instead of at an angle.
The thrust plate should be left in position, otherwise as soon as you start to install the cup plugs, you'll knock the camshaft out of the cam carrier.
Assure that all the metal chips have been removed from the camshafts. I used a nylon brush and aerosol carb spray, finishing with compressed air. The brush I used has four or five inches of bristles, the hole in the cam is not deep enough to get all the bristles inside.
This is REALLY EASY when the cam carrier is "on the bench". It would be much more time-consuming with the cam carrier on the engine.
Cup plugs with no holes, original thrust plate (looks like a headless eagle)
Original huge oiling hole for thrust plate lubrication
Drill hole in cup plug small enough that a sturdy sheet-metal or wood screw threads in. Pry out cup plug. Mine came out surprisingly easy. They did not appear to have any sealer. Once the end of the camshaft is opened up, install brush (not shown, yet), and drill the 4mm hole with a #21 drill bit.
Tap hole for 10-32. Do not tap all the way through. Tap only deep enough so the set screw will go just below flush with the camshaft surface. Set screw therefore CANNOT POSSIBLY vibrate deeper into the hole and come out the other side.
File the burr at the top of the hole. Clean the hole, remove brush (not shown) to pull chips out of camshaft. Aerosol solvent and compressed air assure no chips remain.
Set screw is driven into place using thread locker to assure it won't vibrate out-of-position. Original 4mm hole is now plugged.
First cup plug driven into place in right side camshaft, using thread locker as sealant. A #22 bit will fit into the 4mm oil hole, shown in left camshaft, provides visual confirmation of exact drilling angle. As said earlier, I had to rotate the left camshaft so the oil hole was "straight up"; but I don't have a photo of that. Drill that hole with a #21 bit, tap, file, clean up the chips just as was done with first camshaft.
Cup plugs are drilled with #47 bit--very close to 2mm specified in bulletin. Remove burrs from inside and outside of hole you've drilled in the cup plug. I smacked the cup plugs into place using a socket that exactly fit the raised edge of the plugs. If you don't have a perfect-sized driver tool--socket or otherwise--you can pound on the inside of the plug. Be careful. These plugs distort easily. A BIG hammer with controlled swing works better than beating the hell out of them with a small hammer and lots of velocity. LEAVE THE THRUST PLATE IN PLACE or you'll knock the cam out of the carrier. There is a small ridge in the camshaft hole that the plugs will seat against. (Be careful to not drive them in too far.)
Two set screws locked into place, two ventilated cup plugs installed after thorough cleaning of the metal chips. All that's left is the new thrust plate. (and to do it all again with the second cam carrier!)
The oil holes in the camshaft cup plugs fill the cover plate with two pools of oil. The end of the cams are bathed in this oil, and that's what lubes the thrust plate instead of having the plate sprayed directly by the original oil hole as the cam rotates.
The new camshaft thrust plates (I bought ONE; $30 at the dealership) are exactly like the originals--except they are .0025 thinner by my measurement. No problem, you say. Take the originals, put a piece of solvent-wetted sandpaper on a glass plate (for flatness) and sand off two-and-a-half thousandths. Use a 0-to-1 micrometer in several places on the thrust plate to gauge how much material you're taking off, and to assure it's coming off evenly across the whole plate.
Pack a lunch. You'll be there all day. The thrust plates are hard as hell. My arm wore out and I've only rubbed half-a-thousandth off. A local machine shop wants $21 apiece to surface-grind these things down. The thrust plates are discontinued from GM, so milling originals will soon be the only way to go.
Surface grinding the thrust plates makes the oil grooves shallower, after the photo was taken I used a Dremel with a cutoff wheel to grind the grooves a bit deeper. I don't expect any problems here.
The Service Bulletin says the lifter tick is the result of oil pressure fluctuations "unseating the internal lifter check ball". This is the lifter check ball and seat--the "nipple" looking piece lower left of this photo:
My thread on disassembling the LQ1 lifters:
The thread where the head gasket popped and started this mess:
LQ1 Block Heater Warning
The parts kit has been discontinued by GM long ago. My quest was to find sources for those parts; and complete the procedure on my '93 Lumina Euro 3.4 which was torn apart to replace the rear head gasket.
There are three critical part numbers in the GM service kit (aside from gaskets and O-rings) required to perform this operation. Two of the three are readily available in the aftermarket--the 10-32 set screws, and the cup plugs. I hadda buy a box of cup plugs and a batch of set screws; if you can't find 'em locally, send me a PM. All gaskets 'n' seals are readily available, and are included in the gasket set I needed to replace the head gaskets (Fel-Pro HS9113PT1 Head Set.) This leaves one item that is expensive to source--the replacement thrust plates.
Reading the bulletin, and seeing the cam carrier gave me a clear understanding of how to proceed. Note that in some of my photos, the thrust plate is UPSIDE DOWN. I intended to leave the camshaft positioning tool in place while servicing the camshafts, and the thrust plate was in the way to drill the front camshaft. I re-positioned the thrust plate--but the drill bit wasn't long enough, and I had to remove the positioning tool so I could rotate the camshaft and drill straight down instead of at an angle.
The thrust plate should be left in position, otherwise as soon as you start to install the cup plugs, you'll knock the camshaft out of the cam carrier.
Assure that all the metal chips have been removed from the camshafts. I used a nylon brush and aerosol carb spray, finishing with compressed air. The brush I used has four or five inches of bristles, the hole in the cam is not deep enough to get all the bristles inside.
This is REALLY EASY when the cam carrier is "on the bench". It would be much more time-consuming with the cam carrier on the engine.
Cup plugs with no holes, original thrust plate (looks like a headless eagle)
Original huge oiling hole for thrust plate lubrication
Drill hole in cup plug small enough that a sturdy sheet-metal or wood screw threads in. Pry out cup plug. Mine came out surprisingly easy. They did not appear to have any sealer. Once the end of the camshaft is opened up, install brush (not shown, yet), and drill the 4mm hole with a #21 drill bit.
Tap hole for 10-32. Do not tap all the way through. Tap only deep enough so the set screw will go just below flush with the camshaft surface. Set screw therefore CANNOT POSSIBLY vibrate deeper into the hole and come out the other side.
File the burr at the top of the hole. Clean the hole, remove brush (not shown) to pull chips out of camshaft. Aerosol solvent and compressed air assure no chips remain.
Set screw is driven into place using thread locker to assure it won't vibrate out-of-position. Original 4mm hole is now plugged.
First cup plug driven into place in right side camshaft, using thread locker as sealant. A #22 bit will fit into the 4mm oil hole, shown in left camshaft, provides visual confirmation of exact drilling angle. As said earlier, I had to rotate the left camshaft so the oil hole was "straight up"; but I don't have a photo of that. Drill that hole with a #21 bit, tap, file, clean up the chips just as was done with first camshaft.
Cup plugs are drilled with #47 bit--very close to 2mm specified in bulletin. Remove burrs from inside and outside of hole you've drilled in the cup plug. I smacked the cup plugs into place using a socket that exactly fit the raised edge of the plugs. If you don't have a perfect-sized driver tool--socket or otherwise--you can pound on the inside of the plug. Be careful. These plugs distort easily. A BIG hammer with controlled swing works better than beating the hell out of them with a small hammer and lots of velocity. LEAVE THE THRUST PLATE IN PLACE or you'll knock the cam out of the carrier. There is a small ridge in the camshaft hole that the plugs will seat against. (Be careful to not drive them in too far.)
Two set screws locked into place, two ventilated cup plugs installed after thorough cleaning of the metal chips. All that's left is the new thrust plate. (and to do it all again with the second cam carrier!)
The oil holes in the camshaft cup plugs fill the cover plate with two pools of oil. The end of the cams are bathed in this oil, and that's what lubes the thrust plate instead of having the plate sprayed directly by the original oil hole as the cam rotates.
The new camshaft thrust plates (I bought ONE; $30 at the dealership) are exactly like the originals--except they are .0025 thinner by my measurement. No problem, you say. Take the originals, put a piece of solvent-wetted sandpaper on a glass plate (for flatness) and sand off two-and-a-half thousandths. Use a 0-to-1 micrometer in several places on the thrust plate to gauge how much material you're taking off, and to assure it's coming off evenly across the whole plate.
Pack a lunch. You'll be there all day. The thrust plates are hard as hell. My arm wore out and I've only rubbed half-a-thousandth off. A local machine shop wants $21 apiece to surface-grind these things down. The thrust plates are discontinued from GM, so milling originals will soon be the only way to go.
Surface grinding the thrust plates makes the oil grooves shallower, after the photo was taken I used a Dremel with a cutoff wheel to grind the grooves a bit deeper. I don't expect any problems here.
The Service Bulletin says the lifter tick is the result of oil pressure fluctuations "unseating the internal lifter check ball". This is the lifter check ball and seat--the "nipple" looking piece lower left of this photo:
My thread on disassembling the LQ1 lifters:
The thread where the head gasket popped and started this mess:
LQ1 Block Heater Warning
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