LQ4 knocking after rebuild.
01-01-2016, 08:04 PM
#1
LQ4 knocking after rebuild. I got an 00 WS6 with an LQ4 in it. Had low oil pressure, drove it 170 miles home without issue. A cam bearing walked and was causing the low oil pressure. I had my local machine shop check the bore and it was fine, they knocked in new bearings and I built the engine.
Reman crankshaft with matched bearings
Melling high volume oil pump
Reused the lifters that were in it
LS1 cam, stock valvetrain
317 heads with fel pro gaskets.
I got it all back together, fired it up, ran for 20 minutes in the garage while checking for leaks and getting the cooling system filled. Drove it 2 miles and it was fine. Went to test drive it and it started knocking.
Limped it home and it's still knocking pretty bad. No metal in the oil, 45PSI hot idle oil pressure with a mechanical gauge. Pulled the valve covers off looking for a bent pushrod and everything looks fine. While running it with the valve covers off, the passenger cat converter started spitting melted material out of the tail pipe.
Took that off and it's still knocking. The cat is worse than anything I have ever seen, it has a hole melted clean out of the middle. The noise sounds like it's coming from the top end, but it is very loud. Moves with the RPM, really doesn't get quiet with a balance test, maybe just a little. Any ideas before I go pulling the motor?
Reman crankshaft with matched bearings
Melling high volume oil pump
Reused the lifters that were in it
LS1 cam, stock valvetrain
317 heads with fel pro gaskets.
I got it all back together, fired it up, ran for 20 minutes in the garage while checking for leaks and getting the cooling system filled. Drove it 2 miles and it was fine. Went to test drive it and it started knocking.
Limped it home and it's still knocking pretty bad. No metal in the oil, 45PSI hot idle oil pressure with a mechanical gauge. Pulled the valve covers off looking for a bent pushrod and everything looks fine. While running it with the valve covers off, the passenger cat converter started spitting melted material out of the tail pipe.
Took that off and it's still knocking. The cat is worse than anything I have ever seen, it has a hole melted clean out of the middle. The noise sounds like it's coming from the top end, but it is very loud. Moves with the RPM, really doesn't get quiet with a balance test, maybe just a little. Any ideas before I go pulling the motor?
01-02-2016, 08:13 AM
#4
EGT is out of site on that bank....You have a serious fueling issue. Is the inj harness installed correctly?
Inj harness shorted and injs are on 100%?
Some pistons are likely toast.
"Any ideas before I go pulling the motor?" Just 1, don't waste your time w/ other ideas. As 96 said, pull it.
Inj harness shorted and injs are on 100%?
Some pistons are likely toast.
"Any ideas before I go pulling the motor?" Just 1, don't waste your time w/ other ideas. As 96 said, pull it.
01-02-2016, 01:14 PM
#5
EGT is out of site on that bank....You have a serious fueling issue. Is the inj harness installed correctly?
Inj harness shorted and injs are on 100%?
Some pistons are likely toast.
"Any ideas before I go pulling the motor?" Just 1, don't waste your time w/ other ideas. As 96 said, pull it.
Inj harness shorted and injs are on 100%?
Some pistons are likely toast.
"Any ideas before I go pulling the motor?" Just 1, don't waste your time w/ other ideas. As 96 said, pull it.
01-02-2016, 04:50 PM
#6
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The only time I've seen loud banging in the top end was from the piston hitting the cylinder head. Cause was a spun rod bearing allowing the rod/piston assembly to reach up out if the bore and kiss the head.