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I’ve been following along and I read in your posts that you want to save time and money, so you’ve got the engine pulled apart and you’re slapping a band aid on it for a couple of months.
It will cost you twice the time to do all the work a second time and you’ll be spending more money in the long run because you’ll be replacing some parts a second time.
I would never rebuild an engine and reuse the same bearings, and I doubt you could reuse the rings on new pistons.
If it’s really the time having the car down that’s the issue, then order a new GM replacement long block, drop it in, bolt up the accessories and get your son back on the road.
Unless you go into something hi performance it would probably cost you less in the long run and you might even end up with some type of a warranty.
I think you miss the point on the rings and bearings. I would only put new bearings if the tolerances are out of spec. Now, I could put file to fit rings as a band aid for now. Later on, rebuild with .020 or .030 pistons, bearings and rings. Inspect the crank when the machine work is getting done on the block. Our local machine shop can not grind down the crank or polish the crank. Nobody in our area does that.
Second time around it would be the cost of rings replacing once more rings and some gaskets. You can install bearings and reuse them. Thats not a problem as long as no metal goes into the bottom. Heck, I have replaced rod bearings before on my 62 thinking that there was a oil pressure problem. Come to find out it was a bad oil pump. That was over 10 years ago and still to this day the corvette runs great.
Otherwise, I can leave it as is that are installed and put everything back together with new timing chain, lifters, push rods, cam and gaskets.
Either way, I know the block is a standard bore so no need to buy a crate motor. I have another engine out of a 70s truck thats supposed to be good. I can go get out of my my father-in-law's shop.
If its just $200 bucks do it once, your pulling it to rering it, whats another week or 2 while its at the shop getting bored.....If you put a dollar price on your time your going to be unhappy when you are doing this a second time when you could be out driving your car and your son could be pout chasing girls...If the clutch plate looks good you can just have it resurfaced and maybe get a new disc....what kind of clutch is it?
Its more than 200.00 because the cost of pistons. Not sure about the clutch since its a new corvette to us and never torn it apart.
If you have a dial indicator I would check the piston rock. On my fresh blueprinted 454 forged piston (2618 alloy) build we had .005" piston to wall clearance, and the piston rocked .010" up and another .011" down. .005" is the spec for those pistons. Most others are tighter.
You could use that as an indication as to how worn your bores are. My LT-1 always rattled a little bit. It was blue-printed too. Cold anyway. It was just part of it's character.
Last edited by leigh1322; Feb 7, 2023 at 12:41 PM.
I think you miss the point on the rings and bearings. I would only put new bearings if the tolerances are out of spec. Now, I could put file to fit rings as a band aid for now. Later on, rebuild with .020 or .030 pistons, bearings and rings. Inspect the crank when the machine work is getting done on the block. Our local machine shop can not grind down the crank or polish the crank. Nobody in our area does that.
Second time around it would be the cost of rings replacing once more rings and some gaskets. You can install bearings and reuse them. Thats not a problem as long as no metal goes into the bottom. Heck, I have replaced rod bearings before on my 62 thinking that there was a oil pressure problem. Come to find out it was a bad oil pump. That was over 10 years ago and still to this day the corvette runs great.
Otherwise, I can leave it as is that are installed and put everything back together with new timing chain, lifters, push rods, cam and gaskets.
Either way, I know the block is a standard bore so no need to buy a crate motor. I have another engine out of a 70s truck thats supposed to be good. I can go get out of my my father-in-law's shop.
Personally if you don't want to put alot of money into it and have a known good bullet that will bolt into the car so it can be driven that's what I'd be doing.
Something smells alittle off to me. The fact its standard bore but has different pistons and such tells me something is weird. Many times these old motors are badly egged at the top of the bore and have to be bored to get everything cleaned up. To me this looks like a shade tree rebuild where a guy bought some pistons and rings, had a ball hone, ran the hone in it to take off the ridges, get a crosshatch, but never bothered to actually check the bore.
250HP must be an L82. I assume this is the 74 you have been writing about. So yes it came with forged pistons. The piston to wall clearance was always a little loose on those. Just like my LT-1. 84K miles is about all the life it has in it. Piston bores are probably a little egg-shaped. Ring edges are a little rounded off due to the piston rocking. Valve guides are probably leaking too. If all the pistons rock about the same it is bore wear. If one piston rocks much worse than the others it could have broken a skirt off. Based on the scuff pattern the bores look egg-shaped. 135 psi is too low, it comes from a low CR and too big of a cam duration mis-match.
If the rings are have rounded edges a fresh new set will help, but only for a little while. If the pistons are rocking badly they will just wear the new rings shortly. And it sounds like that may have already happened once. If the cylinders are a little egg shaped, as they appear to be, new rings may not help a lot. Only a fresh bore/piston job. These days there are 2 forged piston materials to choose from, and one needs a lot of bore clearance but the other one can be run much tighter. 46182618 forged pistons are the stronger but looser fitting ones. The 4032 formula pistons are almost as strong, and way better than hyper ones, and can be run with much tighter wall clearance. Fo a non-race car I would stick with those.
So I am not sure why you pulled it apart in the first place. Was it just for the noise? If that is the case just put it back together and run it, it will be fine for a long time. New rings if you want but it won't make much difference.
When it comes time to really rebuild it and fix it for years, it needs bored, with new pistons, and new guides put in the heads. Then you quickly go down the "performance" rabbit hole on how many other things to fix "while you are in there". LOL! Better heads, bump the CR, put a newer style cam in it, etc etc.
Have fun! Only 1 of my boys got into cars, and I am grateful for that, but he is into his little Purple S-10 Pickup truck with Pokeman decals on it, and mini-coopers. Oh well we still had fun building that.
Last edited by leigh1322; Feb 7, 2023 at 12:41 PM.
What about the edge of the pistons? It looks like a lot of blow by. What's your thought on that? Do you think I can just get away with .005 oversized file to fit rings?
If the maximum clearance right now is on the order of .005 to .007, yes you can hone it, and file fit new rings. It may sound like a diesel bus when it's cold, but it will certainly get you by until you can rebuild it thoroughly. Better yet, get one or another brand of gapless rings. They'll cut blow by and leak down quite a bit.
If the maximum clearance right now is on the order of .005 to .007, yes you can hone it, and file fit new rings. It may sound like a diesel bus when it's cold, but it will certainly get you by until you can rebuild it thoroughly. Better yet, get one or another brand of gapless rings. They'll cut blow by and leak down quite a bit.
.009 on just one side. There were some broken rings on 4 and 6. So, we are gonna pull the engine. We are going to leave the crank alone if its within tolerance. Nobody in our area works on cranks anymore.
The wrist pins were not seized nor any of the skirts broken.
250HP must be an L82. I assume this is the 74 you have been writing about. So yes it came with forged pistons. The piston to wall clearance was always a little loose on those. Just like my LT-1. 84K miles is about all the life it has in it. Piston bores are probably a little egg-shaped. Ring edges are a little rounded off due to the piston rocking. Valve guides are probably leaking too. If all the pistons rock about the same it is bore wear. If one piston rocks much worse than the others it could have broken a skirt off. Based on the scuff pattern the bores look egg-shaped. 135 psi is too low, it comes from a low CR and too big of a cam duration mis-match.
If the rings are have rounded edges a fresh new set will help, but only for a little while. If the pistons are rocking badly they will just wear the new rings shortly. And it sounds like that may have already happened once. If the cylinders are a little egg shaped, as they appear to be, new rings may not help a lot. Only a fresh bore/piston job. These days there are 2 forged piston materials to choose from, and one needs a lot of bore clearance but the other one can be run much tighter. 4618 forged pistons are the stronger but looser fitting ones. The 4032 formula pistons are almost as strong, and way better than hyper ones, and can be run with much tighter wall clearance. Fo a non-race car I would stick with those.
So I am not sure why you pulled it apart in the first place. Was it just for the noise? If that is the case just put it back together and run it, it will be fine for a long time. New rings if you want but it won't make much difference.
When it comes time to really rebuild it and fix it for years, it needs bored, with new pistons, and new guides put in the heads. Then you quickly go down the "performance" rabbit hole on how many other things to fix "while you are in there". LOL! Better heads, bump the CR, put a newer style cam in it, etc etc.
Have fun! Only 1 of my boys got into cars, and I am grateful for that, but he is into his little Purple S-10 Pickup truck with Pokeman decals on it, and mini-coopers. Oh well we still had fun building that.
The heads were recently rebuilt. There were felpro gaskets installed under the heads. Actually the head look good. None of the valves are leaking. We are not looking to make it a screamer. Just something that is reliable. The noise... It would not let off after lashing down all of the valves twice even after it was warmed up. I would not have worried so much about it during startup while it was cold.
1. We though lashing. Went through the lash once more.
2. Then went to thinking collapsed lifter or wiped cam. - Nope.
3. Thought it might be a bent valve since it sounded on the top end. - Nope all of the valves were fine.
Then we saw movement in the piston plus you can see the wear from the skirts on the walls and on the piston skirts.
The broken rings make sense if there was too much space between the cylinder walls and the pistons. I know we can install file to fit rings. My friend has everything we need to do that job. The broken rings made me change my mind. It had the factory cam in it. The timing chain was really loose. Not sure why someone would rebuild the heads and not go through the effort of replacing the rest of the parts. Who knows... We bought a melling 22200 cam, new lifters and cowles timing chain and gear. It costs about 200.00 to have the bore done plus pistons pressed onto the rods. We can get pistons for about 200.00. So probably under 1k to get it back onto the road. We will install new bearings and see if someone can polish the crank. All of the rod bearings looked fine. I could not see much excessive wear. Lets hope the mains look the same.
My white 80 L82 has some piston slap cold too , almost completely goes away warm (almost but not totally) , we are getting ready to do a valve job on it with the heads from my black 80 L82 (it received aluminum heads) that just got cut for positive style valve seals and fresh valve job so I'm going to be looking at the bore real close and bore out .030 if it's questionable at all , I'm using the buy once cry once theory so when I'm done it will be ready for many future miles , sounds like yours needs an over bore too
My white 80 L82 has some piston slap cold too , almost completely goes away warm (almost but not totally) , we are getting ready to do a valve job on it with the heads from my black 80 L82 (it received aluminum heads) that just got cut for positive style valve seals and fresh valve job so I'm going to be looking at the bore real close and bore out .030 if it's questionable at all , I'm using the buy once cry once theory so when I'm done it will be ready for many future miles , sounds like yours needs an over bore too
I am with you on that one. Its my son's corvette and I want it reliable for him. We made it safer for him so now its time to make it reliable. We will still be money ahead when its all done. My son wants to drive it right now. I told him its best we get it done while we have it torn down. Plus, he will get to learn how to rebuild his engine even though the crank will not get turned. Nobody in our area does that anymore. It will run better plus not use as much gas. I did not get to check his oil but I could tell he was washing the cylinders with gas based on what I saw on the top of the pistons.
Interesting thing too. The starter was never taken off. It still as all of the original wrapping.
Sounds like you're going backwards to cast or hypereutectic pistons vs forged ones you have? They will be quiet and Ok for just running around....but not for more serious performance. As mentioned, some nice 4032 material pistons vs the 2618 versions will allow you to have plenty of strength and quiet operation.
A good torque plate bore/hone and good pistons will make a nice shortblock. No need to turn the crank if it's in good shape.
And as mentioned above....rocking the piston will give a good indication of true wall clearances. It's entirely possible the skirts have collapsed some over the years. But 2618 material grows a good bit as it warms up and the clearance dissipates.
Sounds like you're going backwards to cast or hypereutectic pistons vs forged ones you have? They will be quiet and Ok for just running around....but not for more serious performance. As mentioned, some nice 4032 material pistons vs the 2618 versions will allow you to have plenty of strength and quiet operation.
A good torque plate bore/hone and good pistons will make a nice shortblock. No need to turn the crank if it's in good shape.
And as mentioned above....rocking the piston will give a good indication of true wall clearances. It's entirely possible the skirts have collapsed some over the years. But 2618 material grows a good bit as it warms up and the clearance dissipates.
JIM
None of the skirts are broken other than worn and some of the groves are now gone. We did not measure the skirts to see how those look. Its for a 16 year who is driving to and from school. He does not need more performance. I am running speed pro hypereutectic in my 62 and it has plenty of power for that ride.
Sounds like you made a wise decision concerning what you found inside.
If you have not bought pistons yet, I would reconsider some 4032 forged ones. The Hypers are just cast and brittle. When they break they break badly. And they do not tolerate pinging from bad gas, or a carb out of adjustment, etc like forged would. Think of them as a durability "insurance policy". A few $ well spent.
The crank may not need to be turned. Feel it with your fingernail, if your nail can feel ridges it needs attention. If you can barely feel them, you can just have it polished. But if the nail catches on them, then it needs to be reground & turned undersized.
The polishing you can do at home with a cloth rope and the correct paper. IIRC it is fine emory paper, but if you like I will check with my machinist buddy to find the grit. Just wrap the rope around the paper and give it 6-8 spins back n forth. Don't go overboard. Then check it for feel again. Check it with a mic before & after. If it's smooth you are good to go. Ihave done them in his shop with the motorized polishing machine and it is just a few seconds on each journal.
If only you weren't 3000 miles away, I could help you check it, regrind it, or polish it, for you.
All right it's a $500 difference. Easy for us to spend money for you LOL!
Last edited by leigh1322; Feb 7, 2023 at 12:54 PM.
None of the skirts are broken other than worn and some of the groves are now gone. We did not measure the skirts to see how those look. Its for a 16 year who is driving to and from school. He does not need more performance. I am running speed pro hypereutectic in my 62 and it has plenty of power for that ride.
OK..you know him...but I know how my 16 year old self drove and I KNOW how I would have driven if I had a Corvette!
As mentioned...cast/hyper's (especially the cheap rebuilder styles) don't do well with detonation or tuning issues..or high RPM etc. They are not the same quality as Porsche and new Vette Hypers and we don't have instant tuning ability that can retard timing before the next cylinder fires. But it's your call of course. I'm talking about longevity...not HP or performance with piston choice.
Not sure if you're saying some of the ring lands are broken on the pistons along with the broken rings? If so...that engine has seen some detonation or hydraulic'ing sometime in the past. Probably why head gaskets are different. It's a good thing you're going through it...it wasn't going to grow back for sure.
At least ck to get the actual deck height of the pistons as many are made "short" to allow for block decking and you'll end up with a dismal compression ratio.
And if you run the Hypers...make sure to pay close attention to ring gaps...they typically take a LOT looser so they don't rip the top ring land out of the piston.
And on the crank...make sure to actually ck the clearances, A pretty one can still be worn too loose.
Whereabout in No Cal are you? There's a fantastic machine shop in Laytonville if that's anywhere in the area. Lewis Racing Engines. I've been there and know him well.
The crank can look perfect but journals can be worn into an "egg" shape. Check it in several rotations/places around each throw. If you get some throws with worn journals, you can just buy a crank kit ready to install. Pretty cost effective.
If you are anywhere near Napa, CA. Contact John at LJ’s Speed and Machine in Napa.
They have been in business for close to 60 years and they build any and all types of engines.
One day they might be building a blown alcohol monster, and have an MG racing engine on the dyno.
John and his crew build them all, even the occasional John Deere and vintage Ferrari.
