pistons
Thread Starter
Advanced
Joined: Jun 2009
Posts: 74
Likes: 0
From: ord nebraska
pistons
I am just about to rebuild the bottom half of my L82. I am still trying to get my Sh$t together.
If the cylinders check ok and only need honed. Would you keep the pistons, and just re-ring them?
Thank, marty
If the cylinders check ok and only need honed. Would you keep the pistons, and just re-ring them?
Thank, marty
Advanced
Joined: Sep 2008
Posts: 72
Likes: 0
From: Essex
I have reused pistons many times over, usually OE are very good quality.
You need to check for wear though, check the outside dimension is to spec with a micrometer, round not oval, any damage will be obvious, they will be OK normally.
BUT, and very important this one, you need to check the area where the rings sit, this is called the ring lands, clean them up so they are spotless, soak them in diesel fuel for a couple of days to get rid of any blow residue, don't bead blast them!
It's not the springyness of the ring that seals piston to the bore, its the action of the gases getting behind the ring, forcing the ring out to the bore, there are tolerances you need to check with a set of feeler gauges, this is the gap between the ring and piston, tooo much float and they flutter and don't seal....they are normally OK but this is more important and often overlooked.
When you fit the new rings check the ring gaps by slipping them down the bore they are to be fitted to, too small is even worse than too big and file down with an india stone to suit for best fit.
You need to check for wear though, check the outside dimension is to spec with a micrometer, round not oval, any damage will be obvious, they will be OK normally.
BUT, and very important this one, you need to check the area where the rings sit, this is called the ring lands, clean them up so they are spotless, soak them in diesel fuel for a couple of days to get rid of any blow residue, don't bead blast them!
It's not the springyness of the ring that seals piston to the bore, its the action of the gases getting behind the ring, forcing the ring out to the bore, there are tolerances you need to check with a set of feeler gauges, this is the gap between the ring and piston, tooo much float and they flutter and don't seal....they are normally OK but this is more important and often overlooked.
When you fit the new rings check the ring gaps by slipping them down the bore they are to be fitted to, too small is even worse than too big and file down with an india stone to suit for best fit.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Why are you rebuilding just the bottom end of your engine? Is it smoking? ...knocking? If neither of those and your compression checks OK, leave it alone. If you just want to freshen up the engine, do the job right: check bores for roundness, taper, wear...remachine bores if necessary; check bearing bores for wear/damage; replace any worn/cracked parts; upgrade part sets if you want more power; thoroughly clean-out the oil passages in the block and repaint it. If the engine has had a recent rebuild and is smoking, that might justify just the ring change. If the engine has lots of miles on it, just do a decent rebuild on it...to stock specs with stock parts, or with upgraded parts to get more power.
Thread Starter
Advanced
Joined: Jun 2009
Posts: 74
Likes: 0
From: ord nebraska
Thanks guys I will make sure it is checked out very well. I was thinking the pistons were forged and wanted to reuse them if at all possible but was not sure about doing so.
The engine has 58,000 on it. Does not smoke or knock that I know of. I am going to rebuild the top end for more performance and my only reason for rebuilding the bottom is, that while I have the motor out, just seems as good as a time as any.
Thanks again, marty
The engine has 58,000 on it. Does not smoke or knock that I know of. I am going to rebuild the top end for more performance and my only reason for rebuilding the bottom is, that while I have the motor out, just seems as good as a time as any.
Thanks again, marty
