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Some really good info here. Thank you and the other posters as well. When I measured all the pistons, I placed the dial gauge towards the center of the piston to find the tdc. I then measured deck clearance on both sides of the piston and averaged them when trying to choose a head gasket to set quench distance. I guess by doing it this way, I didn't capture the max distance a piston can clear the deck due to piston rock. The compression height on my forged pistons is 1.335" and I was aiming for a quench of 0.035" based on reading posts on this site, figured the stock gasket at 0.052" would get me close taking into account the deck and head surfaces haven't been milled.
I am going to pull the heads off hopefully by next weekend. Might just pull the engine back out to check the pistons and clearances while I am at it. To answer some of the other questions, engine was originally pulled because it was consuming a lot of oil and oil pressure was very low. Machine shop recommended against re-ringing it due to low spots on the cylinder walls and so down the rabbit hole I went.
I scoped the 4 cylinders on the driver side, labeled pics attached . I think the #7 cylinder is also definitely touching based on the markings. Car only has roughly 200 miles on it since all the rework. I noticed the #1 and #5 cylinders were almost spotless on the top while #3 and #7 had a lot of carbon deposits. Any reasons why this could be? Thanks.
Based on the pictures, we think you got lucky. It looks like you're definitely hitting the head with one side, but not both. There's a good chance the skirts haven't collapsed but you'll know more when you pop the heads and look for witness marks. As for oiling Those PTS523A3903 +.005 pistons come with 1/16 1/16 3mm ring pack and they aren't fully broken in yet in our estimation. We're hopeful that a .060 head gasket such as the Cometic CGT-C5475-060 will be enough to get you across the goal line. Let us know what you find.
Bringing back my old thread with an update to close it off. Finally got some time and space to pull the heads off to try and dig into this knocking sound I had after my fresh rebuild. Thoughts based on input from this thread suggested possible piston/heads interference. I ended up finding what looks like a crack in the #5 cylinder wall and similar issue in the #8 cylinder. I have a 1998 LS1 block and safe max overbore is considered 0.004". My machine shop felt we could try for 0.005". Everything looked fine to my eye when I got it back, but I am new to this so not sure if I could have caught it before I put everything back together. I wonder if this was causing the knocking sound I was hearing but that's irrelevant now lol.
Long story short, a poster on this site told me at the start to throw my aluminum block in the garbage and get a 5.3L iron block and not look back. I should have taken that advice but everything's a learning process at the end of the day!
Almost looks too straight to be a crack.
Did you find for sure whether the pistons were hitting the heads?
What I've read is that the max safe bore on 97-98 blocks is 0, since the sleeves can be out of alignment in the block.
I didn't see any obvious signs of the pistons hitting the heads, but it looks like in some spots they could have been very close to hitting based on the patterns in the deposits?
Just got my rebuilt 1998 LS1 back in my car and on the road and it's making some noise mostly when it's cold (link below). Local machine shop put together the short block for me. Nothing major done to the car: had some cylinder wear so they did a hone and installed forged Wiseco +4cc 3.903 pistons, stock rods, new bearings all around. Running stock 241 heads and stock cam LS7 lifters which I installed and put back together myself. Added LS6 intake and ARH 1.75" headers plus other basic bolt on's.
When car is cold and in gear (A4), I'm hearing a lot of knock or piston slap noise. I've had this car for 20 years and I am used to the piston slap sound these engines make but it usually went away after 5-10 seconds of driving. Now it takes 10 minutes of driving and it doesn't entirely go away. I'm a little concerned the machine shop or myself messed something up. Noise is noticeably louder when in gear but can still hear it faintly when in park or neutral. I've read that forged pistons and piston slap go hand in hand but this things sounds like a diesel when I first fire it up. Any thoughts on what it could be? Towards the end of the video below, the car is dropped into neutral and you can see the noise reduces drastically.
You are running the Wiseco Pro Tru pistons with 4cc dome? They are 4032 alloy and only require .003 piston to wall max clearance, more than that create noise issues. You should ask your machine shop what the finished bore size is.
You are running the Wiseco Pro Tru pistons with 4cc dome? They are 4032 alloy and only require .003 piston to wall max clearance, more than that create noise issues. You should ask your machine shop what the finished bore size is.
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I borrowed a telescoping guage and micrometer to take some measurements. Measured all 8 cylinders numerous times at different depths and angles. All measurements came out between 3.9030" - 3.9036". The pistons are Wiseco 5523A903 for a 3.903 bore size so maybe a half thou over on some measurements but overall it was pretty good. I think the messed up cylinders are probably from taking 5.5 thou off a 1998 LS! block.
Looking for options now to replace block. Car was a daily driver before and ideally would be again one day. Guy near me is selling a complete LS2 so might end up going that direction.
Sorry to see this happened. I have a 98' and bored it to 3.903 and have always thought in the back of my mind that it might go. Knock on wood, it's holding together. The LS2 would be a nice little bump but if it were me, I'd consider a fresh short block from any of the reputable builders in the LS community.
I’m using those same pistons in my 347, no noise when cold, .003 PTW finished honed on a Rottler. They’re kinda heavy IMO at 486 grams but give 11.65:1 static with 64cc heads, their 1.335 CD has them hanging way Hell out, used a .051 gasket
01-22-2019, 08:50 AM
