Cracked Piston?
04-16-2017, 06:14 PM
#22
04-16-2017, 06:31 PM
#23
I would break it at the bell housing, just keep in mind when you go to reinstall the engine the clutch disk needs to be properly center so the input shaft will line up and go into the crank.
04-16-2017, 06:46 PM
#25
I will check it out. Trying to familiarize myself with the process, next on my bucket list I suppose of work on the car. Up next will surely be a tranny rebuild, depending how this turns out...
I want to record all I can for some insight on the failure and also how the current motor measurements stack up.
I want to record all I can for some insight on the failure and also how the current motor measurements stack up.
04-16-2017, 07:15 PM
#28
Yes I just hope to account for all the pieces...
Once I get this motor out and on a stand I hope to start ordering some of the basics as I do some reading. Maybe I can get it back up by fall. I already have most of my money spoken for this year on house projects and am trying to convince myself to spend slowly to give myself plenty of time.
Normally I am planning projects based on wants, not have to. I am not very prepared with all my options chosen. The more I think about the more I find I meed to address.
Once I get this motor out and on a stand I hope to start ordering some of the basics as I do some reading. Maybe I can get it back up by fall. I already have most of my money spoken for this year on house projects and am trying to convince myself to spend slowly to give myself plenty of time.
Normally I am planning projects based on wants, not have to. I am not very prepared with all my options chosen. The more I think about the more I find I meed to address.
04-17-2017, 11:38 PM
#29
I wouldn't go overboard, I'd get a set of pistons, rings gaskets etc keep it simple. Also find the best machine shop in the country to change those pistons out so its done properly. You can't imagine the BS you can end up with from some IDIOT pressing pistons that doesn't understand what they are doing<most machines shops IMO I'm fussy because I find very few professionals today. Most shops are setup by guys that worked on a this and that and really don't have the experience and knowledge to deliver quality work. Don't be afraid to buy from major machine shop and ship your parts off the be checked resize pressed what ever by a guy that is a complete pro.
I'll tell ya a little story from a guy that posted up here a while back. He had his LS block bored and honed for new pistons from a reputable local to him shop. THEY MISREAD THE WISCO SPEC SHEET AND BORED THE BLOCK TO DOUBLE THE CLEARANCE! Of course no one knew this until the guy started the engine ..............you can imagine the hootin and hollarin that went on when the guy discovered all this.
QUESTION EVERYTHING.
I'll tell ya a little story from a guy that posted up here a while back. He had his LS block bored and honed for new pistons from a reputable local to him shop. THEY MISREAD THE WISCO SPEC SHEET AND BORED THE BLOCK TO DOUBLE THE CLEARANCE! Of course no one knew this until the guy started the engine ..............you can imagine the hootin and hollarin that went on when the guy discovered all this.
QUESTION EVERYTHING.
04-18-2017, 06:54 PM
#30
That is my biggest concern right now is finding a good machine shop. I want to find someone with good experience on LS motors. There are several in my area, I just need to gather the facts and questions to ask them about.
I am going to build a 383. I am not going to go this deep and spend this much to keep a stock cube bottom. Plus I want to build something I don't have to worry much about. I have been wanting to do this for a while.
I am also going to assemble it myself. I am reading all the books, tips and talking all the engine builders I can. I've never built a bottom end before, but I have always wanted to.
I have time to save which also makes time to learn. I am going to mess around with the stock parts to start with to go through the process. This way I also get to document all the details and specs on the motor.
I am going to build a 383. I am not going to go this deep and spend this much to keep a stock cube bottom. Plus I want to build something I don't have to worry much about. I have been wanting to do this for a while.
I am also going to assemble it myself. I am reading all the books, tips and talking all the engine builders I can. I've never built a bottom end before, but I have always wanted to.
I have time to save which also makes time to learn. I am going to mess around with the stock parts to start with to go through the process. This way I also get to document all the details and specs on the motor.
04-19-2017, 04:45 AM
#32
Far enough, but I was going to call Jonathan up to see what machine shop they use. From what I understand it may be one close to my work.
I will bring the transmission to them, have to save up for that first. Was actually looking at doing that before the motor issue came up.
I will bring the transmission to them, have to save up for that first. Was actually looking at doing that before the motor issue came up.
04-29-2017, 09:51 PM
#33
So I pulled the heads off Wednesday waiting on the cherry picker from my neighbor to find #7 did not have a crack on the top or anything close. I am going to clean it better and look under a magnifier, but it really doesn't matter.
Attached is what I found and what was expected. Cracked ringland on #7. When I pulled the top ring out to check ring gap it came loose. The crack is all the way through to the back side of the piston. This is in the same area where the bore scope looked like there was a crack, so I suspect that was not just a coincidence and want to look closer. I called it a night after pulling the motor and dropping #7 out.
I did end up pulling from the top. It was really easy. The worst part was the cherry picker had to hook to the front of three spots due to clearance with the bumper (probably will pull the bumper to reinstall). I ended up having to jack up the back of the bellhousing to level. Then we had to rest the front part of the pan (which worried me a little) on the k-member to rehook. Came out easy after that. I had a scissor jack under the transmission to help. I have time to come up with a better plan to install level and align - assuming I don't pull the transmission, not sure I liked how it sounded spinning by hand. More to investigate...
Checked some numbers out real quick, will go back in more detail when I have time.
Check both rings by squaring in bore the depth of the 1st ring for a quick check.
Top ring - 0.021" gap
2nd ring - 0.032" gap
Need to investigate what factory specs were. My wife tried a quick search that sound like 0.019" top and 0.021" bottom.
I also noted the skirt wear looked suspicious on the top side (need to learn terms here to sound a little more intelligent). It was biased a little towards one side. #7 seemed to rock pretty bad, I am going to reinstall and check that too (forgot before I removed).
Checked the top of the bore (again, quickly and only one spot) at 3.8988" and near the bottom of the contact at 3.9000". Not sure how much to expect variation from factory number of 3.898" at 68,000 miles.
Just to note, the bottom end has seen a couple of bad over-revs due to mis-shifts (probably 4) and I was knowingly taking a risk trying to make it through the traps in the 1/8th topping out 3rd going to 7000-7100 in less than a dozen passes. Not sure how or if any of that may show itself.
Attached is what I found and what was expected. Cracked ringland on #7. When I pulled the top ring out to check ring gap it came loose. The crack is all the way through to the back side of the piston. This is in the same area where the bore scope looked like there was a crack, so I suspect that was not just a coincidence and want to look closer. I called it a night after pulling the motor and dropping #7 out.
I did end up pulling from the top. It was really easy. The worst part was the cherry picker had to hook to the front of three spots due to clearance with the bumper (probably will pull the bumper to reinstall). I ended up having to jack up the back of the bellhousing to level. Then we had to rest the front part of the pan (which worried me a little) on the k-member to rehook. Came out easy after that. I had a scissor jack under the transmission to help. I have time to come up with a better plan to install level and align - assuming I don't pull the transmission, not sure I liked how it sounded spinning by hand. More to investigate...
Checked some numbers out real quick, will go back in more detail when I have time.
Check both rings by squaring in bore the depth of the 1st ring for a quick check.
Top ring - 0.021" gap
2nd ring - 0.032" gap
Need to investigate what factory specs were. My wife tried a quick search that sound like 0.019" top and 0.021" bottom.
I also noted the skirt wear looked suspicious on the top side (need to learn terms here to sound a little more intelligent). It was biased a little towards one side. #7 seemed to rock pretty bad, I am going to reinstall and check that too (forgot before I removed).
Checked the top of the bore (again, quickly and only one spot) at 3.8988" and near the bottom of the contact at 3.9000". Not sure how much to expect variation from factory number of 3.898" at 68,000 miles.
Just to note, the bottom end has seen a couple of bad over-revs due to mis-shifts (probably 4) and I was knowingly taking a risk trying to make it through the traps in the 1/8th topping out 3rd going to 7000-7100 in less than a dozen passes. Not sure how or if any of that may show itself.
