Guest Anonymous Posted August 15, 2001 Share Posted August 15, 2001 Hey guys, I know this is not Z related, but i've got a big problem with an LT-1 that a friend and I are putting into his 93 Jeep Wrangler. So here is the problem. We just now got the exhaust done and were able to crank the motor up and listen to it idle for the first time(open headers are LOUD!!). Well, right off the bat there is a loud knocking sound coming from in between the number 2 and 4 cylinders. It sounds like someone is tapping on the oil pan with a small ball ping hammer. The motor is a 96 LT-1 out of an Impala SS. The car had been into a rear end collision and a friend bought the motor. As far as I know, the motor has been sitting for the last 5 months or so without being ran. Now, we do have plenty of oil in it. We are running good Mobil 1 oil. And, it might just be my ears playing tricks, but i would swear that the "knock" is getting a little quieter everytime we start it up. Anyone have any idea on what is cuasing this knock? Quote Link to comment Share on other sites More sharing options...
MYRON Posted August 16, 2001 Share Posted August 16, 2001 does the knock sound like it is coming from the bottom end or top end of the motor? It would be hard to tell any thing until you get exhaust on it. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted August 16, 2001 Share Posted August 16, 2001 Also.. half engine speed or woudl you say full engine speed? Did you have th epan off at all? Is it a different pan? Possible the pan got banged and is touching the rotating assembly? (been there, done that!) Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 16, 2001 Share Posted August 16, 2001 I almost bought a 4th gen f body w/ LT1... but it had a rod knock at start up. It was for sale at the chevy dealership so I asked them about it. The dealership shared with me that the early LT1 s were prone to rod knock and piston slap at start up. The reason stated was that until the production of the LT1, all SBC pistons had the pin offset. This is why you have left and right bank pistons and replacement pistons have an arrow on them, because the in is not located in the center of the piston. On the early LT1s the piston pin is centered which causes more piston rock. This is apperantly only a problem at start up and afer the oil get flowing the problem is lessened due to the oil wedge between the piston and bore. Your engine after sitting up may have had all of the oil drain off the cylinder walls which promotes the piston slap. The rod knock at start up was due to poor oil flow at start up. I was told that GM replaced a number of these engines under warrany but only if the owner was savey enough to notice it. This may be the problem. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 16, 2001 Share Posted August 16, 2001 Well, we found out tonight that it was the oil pan!! Come to find out, when the motor was out of the Jeep, we let it rest on a plywood box. Well, one side of the box was pushing right in the front/center of the oil pan!! it pushed it in just enough for the crank assembly to come around and "tap" it on every stroke!! Luckily, it was not too bad and we were able to tap it back out with a small hammer. Tommorrow everything goes back together and we crank it up, again! thanx guys....... Quote Link to comment Share on other sites More sharing options...
pparaska Posted August 16, 2001 Share Posted August 16, 2001 That's GREAT news. With the rass (cough) of bottom end bad luck the SBC guys have been having (through no fault of GM), it's great to hear you really don't have a problem with the motor! Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted August 16, 2001 Share Posted August 16, 2001 LOL, I KNEW it! I've had this happen myself (V8 Vega) and the noise it made was trly scary Glad it was somehting simple! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 16, 2001 Share Posted August 16, 2001 Excellent! Its good to hear a happy ending like that when it comes to noises from the bottom end. Those noises are usually soooo expensive. Great to hear it was a cheap fix! Regards, Lone Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 16, 2001 Share Posted August 16, 2001 Had exactly the same thing happen. My heart and my son's heart were in our shoes the first time we cranked up the ZX with mufflers on, up until then we thought everything was fine because you couldn't hear yourself think with open hedders. I found the problem with the old "screw-driver to the ear trick". Cleaned off the paint on the oilpan used a stud gun and poped it right out. Then we fired it up again and not a sound other than normal engine noise. What a relief that we didn't have to pull and go back through the motor. Quote Link to comment Share on other sites More sharing options...
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