6L w/noisy lifter
10-18-2007 | 08:02 AM
#1
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From: Marysville, WA
6L w/noisy lifter I have an on-going issue that I would like some suggestions about. 
I bought this motor from a guy on this board to give my Avalanche a little more towing power. It was supposed to be a good running, no issues, plug-n-play hot rod motor. Stock bottom end 6L w/ stage 2 heads & a ported oil pump. But it had a racing type cam, so I installed a Ling GT2-3 in it for better mid range tq.
During the first test drive it developed BAD lifter noise, and the oil pressure wasn't what I expected (15 psi at idle, 30 driving, never above 40). So I dropped the pan to inspect the o-ring. It was fine, but the fit seemed a little loose, so I replaced the pump & added a 2nd o-ring. That brought up the pressure to more normal levels but the noise was still there.
So then I took the heads off & looked at the lifters. At least 3 of them were damaged (partially compressed) with #7 intake being the worst. So I installed some LS7 lifters & GM head gaskets from SDPC & that seemed to clear it up. Then 300 miles later it blew a head gasket (the reason GM pulled it out of a truck & how the guy I bought it from got it).
So I decided it was time to take it to the machine shop. After spending another $2k having the block & heads decked, new rings put in & the cyl's honed, and all the bearings replaced (the mains & rods were scarred up & the cams were into the copper) I stuck it back in - with the same LS7 lifters that "felt good".
After the intial warm-up / cool down / re-torque the head gaskets ritual, I took it for it's maiden voyage. Within 1 mile The damn lifter(s) was making noise again. I only used 1 o-ring this time because the 2nd one was pinched when I took it apart, so I figured that wasn't the right thing to do. But it has 30+ psi at idle, 45 cruising, & 50-60 at WOT.
We looked at the oil passage for the lifters when it was apart and while they aren't perfectly straight they are ~75% connected (evidently GM bores that hole half way from the front & half way from the back so the middle sections don't line up exactly). And the o-ring on the "dumbell" was a tight fit. So I'm preplexed.....WTF is wrong with this engine?
Apologies if this isn't the right forum, but this seems to be where the smartest motor heads hang out.
Mark
I bought this motor from a guy on this board to give my Avalanche a little more towing power. It was supposed to be a good running, no issues, plug-n-play hot rod motor. Stock bottom end 6L w/ stage 2 heads & a ported oil pump. But it had a racing type cam, so I installed a Ling GT2-3 in it for better mid range tq.
During the first test drive it developed BAD lifter noise, and the oil pressure wasn't what I expected (15 psi at idle, 30 driving, never above 40). So I dropped the pan to inspect the o-ring. It was fine, but the fit seemed a little loose, so I replaced the pump & added a 2nd o-ring. That brought up the pressure to more normal levels but the noise was still there.
So then I took the heads off & looked at the lifters. At least 3 of them were damaged (partially compressed) with #7 intake being the worst. So I installed some LS7 lifters & GM head gaskets from SDPC & that seemed to clear it up. Then 300 miles later it blew a head gasket (the reason GM pulled it out of a truck & how the guy I bought it from got it).
So I decided it was time to take it to the machine shop. After spending another $2k having the block & heads decked, new rings put in & the cyl's honed, and all the bearings replaced (the mains & rods were scarred up & the cams were into the copper) I stuck it back in - with the same LS7 lifters that "felt good".
After the intial warm-up / cool down / re-torque the head gaskets ritual, I took it for it's maiden voyage. Within 1 mile The damn lifter(s) was making noise again. I only used 1 o-ring this time because the 2nd one was pinched when I took it apart, so I figured that wasn't the right thing to do. But it has 30+ psi at idle, 45 cruising, & 50-60 at WOT.
We looked at the oil passage for the lifters when it was apart and while they aren't perfectly straight they are ~75% connected (evidently GM bores that hole half way from the front & half way from the back so the middle sections don't line up exactly). And the o-ring on the "dumbell" was a tight fit. So I'm preplexed.....WTF is wrong with this engine?
Apologies if this isn't the right forum, but this seems to be where the smartest motor heads hang out.
Mark
10-18-2007 | 09:43 AM
#2
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From: Marysville, WA
Sorry, I was in a hurry but should have also said....
The block was shaved .010" and the stock 6L heads I put on this time were shaved .005". And I used Cometic .051" gaskets. Also, when I did the lifter zero lash / pre load it took 1/2 to 3/4 turn to go from finger tight to snug, & then about 1 1/2 turns to reach 22lbs. So I think the valve train geometry is setup correctly.
The block was shaved .010" and the stock 6L heads I put on this time were shaved .005". And I used Cometic .051" gaskets. Also, when I did the lifter zero lash / pre load it took 1/2 to 3/4 turn to go from finger tight to snug, & then about 1 1/2 turns to reach 22lbs. So I think the valve train geometry is setup correctly.
10-18-2007 | 12:52 PM
#3
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From: Marysville, WA
One more minor detail (I'll get this all eventually) the ticking / knocking is only present some of the time. It might make noise upon starat up, but then is quiet for the first 15-20 minutes of driving. Then it will usually make noise for about 5 minutes or so & then quiet down. And it sounds like it's from cyl 7 again.