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Found light cylinder scuff during upgrade
https://cimg0.ibsrv.net/gimg/www.off...cd5fc1124.jpeg Guys I found this light scuff taking one of my heads of last night. You cannot feel it with your finger but if you drag a finger nail on it you can just barely feel some light rumbles. These are GM ZZ572 crate motor bottom ends that have never been apart. They probably have 125-130 hours on them. Engine never burned any oil or smoked. I was hoping not to have to get into the bottom ends. What do you guys think?? |
I would run that. Do you cut your oil filters open? I agree the visual is not pleasant but if there are no ridges you should be fine. I had a weird stain in one of the cylinders of my drag race motor that drove me and my machinist crazy but never caused an issue. Looked bad though.
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I initially thought skirt scuff, but with it coming all the way to the top of the bore, it maybe something else causing it ?
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If they are out of the boat I would pull that piston and look at it. What are you upgrading? |
Going from NA to a 12-71 blower setup. |
My old boss had 425ho in his boat loaded up on choke and washed the rings out of it that was the only time I ever saw that and than came Black Death. |
Ok 12-71 I would re ring both motors probably need more end gap anyway or you might be sitting on the side lines this summer. How much power you looking for? |
Probably around 950 on 8 pounds. |
Can you do the bottom ends yoursel if you can won't cost to much if nothing else is wrong. Definitely would rering it set the gaps rite for that power. |
any other markings in the other bores ?
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is the compression ratio still 9.7 it wont go to 8lbs boost on pump gas.
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It definitely needs to come apart. Whatever is causing the problem is not going to get better, only worse. Might be a stuck ring or may have been fuel washed. Like the others have said you need to open up the ring gaps some anyway so be glad you caught it early.
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No compression is going to 8.5 with chamber porting and a little thicker head gasket. So you guys would recommend a hone and new rings? What is the hot ring setup and gap these days? |
I would run a plasma Molly ring and I would do .030 top and .032 second. Last motors I did set top .031 and second .033 run a Napier second. There will be lots of different options on this. To little and you will have problems. |
old true saying............a little too much gap only you know......a little too little gap everyone knows.
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Originally Posted by SS496
(Post 4669416)
old true saying............a little too much gap only you know......a little too little gap everyone knows.
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I took my engines apart at 250hrs and they do not have anything close to that.
But i`ve had scrapes like that before and it was due to wrong timing, (dizzy got loose) the piston got too hot and expanded scraped the sides. Piston didnt look so good either. Piston that got too hot , you can see the oil burned : https://cimg8.ibsrv.net/gimg/www.off...3651570b2d.jpg https://cimg9.ibsrv.net/gimg/www.off...63b9296df8.jpg https://cimg0.ibsrv.net/gimg/www.off...f79e1753bf.jpg https://cimg1.ibsrv.net/gimg/www.off...da0c95d1cc.jpg |
One other thing you should do put good wrist pins in it. Probably need to be balanced again. |
Stupid question guy’s but I am learning. Will a hone take care of my issues with the new rings or will a hone remove enough material that a different size pistons will be required. I can buy these pistons in a 4.565 overbore stock is 4.560. SRP tells me they will be just fine with 10lb’s of boost. My temptation now is to go to a JE dish piston but my heads are having 10cc removed from the chamber as we type. |
Need to bring it to a machine shop have them do a clean up home with a plate. Let them measure it after. If it's good run it. To bad you opend heads up already. |
Heat. To lean, Higher compression need to run cooler. Air pockets. Not enough water pressure
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If these were automotive bottom ends and You plan on putting a blower on it the bottom end should be taken apart and clearanced for marine high HP.
I bet you are going to find that the pistons are tight. Spend the $ now OR spend the $$$ after it blows up. Doing it right and bullet proof the first time is CHEAP. BTDT |
Originally Posted by rob vanharten
(Post 4669337)
https://cimg0.ibsrv.net/gimg/www.off...cd5fc1124.jpeg Guys I found this light scuff taking one of my heads of last night. You cannot feel it with your finger but if you drag a finger nail on it you can just barely feel some light rumbles. These are GM ZZ572 crate motor bottom ends that have never been apart. They probably have 125-130 hours on them. Engine never burned any oil or smoked. I was hoping not to have to get into the bottom ends. What do you guys think?? |
Originally Posted by F-2 Speedy
(Post 4669378)
any other markings in the other bores ?
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Originally Posted by rob vanharten
(Post 4669475)
Ya, actually I have been looking closer at the other cylinders and most of them have some very light scuffing at the north and south edges of the cylinders and some have light marks at all four corners. When I first bought this boat the timing was set to all in at 50 degrees. I caught it and fixed the timing issue, but with what Dan posted earlier wonder if to much timing caused these scuffs....? |
https://cimg2.ibsrv.net/gimg/www.off...97fe9c4b5c.jpg Running closed loop bad tuneup. Expensive day. |
16 Apache whoa buddy , that don`t look so good. lol
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Lol one day I wanted to cry lol. Only had about five hours on motors. Start of a poker run motors where cold had no corrections from close loop yet and was a cold day. Finished a cooler of beer on the way home on the other engine. |
Talked with my local machinest this morning and I am bring him both short blocks. He will be doing final disassembly and inspection. Check the cranks, upgrade rod bolts and reman rods, hone cylinders with torque plate, new rings, new rod bearings, new crank bearings, and new cam bearings. They will wash block and reassemble short block with the appropriate clearances for a supercharged marine application. Little more money than I had expected to spend on this upgrade but I think it’s money very well spent for peace of mind!!! |
That sounds like a proper plan, and much much cheaper in the long run. I believe that youd want a little more clearance on the piston to wall anyways, right? |
Originally Posted by Baja Rooster
(Post 4669653)
That sounds like a proper plan, and much much cheaper in the long run. I believe that youd want a little more clearance on the piston to wall anyways, right? |
Originally Posted by Baja Rooster
(Post 4669653)
That sounds like a proper plan, and much much cheaper in the long run. I believe that youd want a little more clearance on the piston to wall anyways, right? |
Just to commiserate, I pulled my 502 for a cam change and now the only thing original is the block, crank, and rods. A $500 fix went to $5000 in a heart beat - damn boats! Lol. |
ROB - Just don't let More Power chose the cam.
Nothing against them as a builder " BUT" they tend to be a little on the conservative side. I use Dave Wesseldyke or Performance Eng. both in Jenison. More power does Good work though. Just do some research on the cam design. |
Originally Posted by Tinkerer
(Post 4669802)
ROB - Just don't let More Power chose the cam.
Nothing against them as a builder " BUT" they tend to be a little on the conservative side. I use Dave Wesseldyke or Performance Eng. both in Jenison. More power does Good work though. Just do some research on the cam design. |
I think you are leaving some HP on the table with those cams. They seam a little small for a 572.
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