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Refreshing my ZZ502 short block.

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Refreshing my ZZ502 short block.

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Old 02-12-2018, 02:26 PM
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Default Refreshing my ZZ502 short block.

I yanked my motor mostly to retrieve the sockets at the bottom of the bilge and decided to give it a check up. I did a leakdown test, and granted it was cold, but was losing over 50% on three holes. At one point I sucked up some sand to get it hot enough to pop the head gasket at the water passage to fill the intake galley with water but the rings between the cylinders were fine, so I had the heads freshened up at that time. But over the few days while it was apart it did get a little surface rust on #4&6 so I took a scotchbrite and wd40 and scrubbed it out in a cross hatch pattern, but oddly enough those are holding ok.

Im hoping to just run a ball hone and new rings this baby but it doesn’t seem that straight forward on a ZZ502 block. I emailed Speedpro, but do you guys have any suggestions on where to go with this? I didn’t measure the depth of the rings but I read these pistons have unusually shallow grooves, otherwise the usuall 1/16,1/16,3/16 set.

The engine has less than 100 hours total and new pistons/machine work would be a season killer.

Last edited by Baja Rooster; 02-12-2018 at 02:33 PM.
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Old 02-12-2018, 05:51 PM
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I have the zz502 but bought block only the stock Merc pistons use total seal rings part number CR5750
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Old 02-12-2018, 07:45 PM
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I don't know where you are located, but I could get any machine work done in a matter of a couple weeks. No reason to lose a boating season waiting for something like that.
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Old 02-12-2018, 07:56 PM
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I' thinking he means financially, btw snap your imco plate is going out in the morning.
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Old 02-12-2018, 07:59 PM
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Originally Posted by snapmorgan View Post
I don't know where you are located, but I could get any machine work done in a matter of a couple weeks. No reason to lose a boating season waiting for something like that.
Its more of a matter between $400 or $4000. I donít mind yanking it for a full rebuild a few seasons down the road but itís not in the cards this year. I live in the SF Bay Area where a machine shop can pay $7500mo in rent, so everything here is near double than most places. I spoke with one shop that has a great reputation for its work and fair (relatively) prices and figured about $2500 for just rings and bearings.
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Old 02-12-2018, 08:04 PM
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Thanks jd

JE makes a set of 502 pistons that are a couple thousands bigger that are reasonable. I have used a couple sets on stock rebuilds. They work well if you have a little cylinder wear. Light hone and drop them in. There is a very good chance with only 100hrs that you won't need pistons though.

http://www.jepistons.com/Products/281916.aspx
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Old 02-12-2018, 08:14 PM
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That is about the only good thing about living here in the Midwest. Labor is relatively cheap.
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Old 02-12-2018, 08:20 PM
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Originally Posted by snapmorgan View Post
Thanks jd

JE makes a set of 502 pistons that are a couple thousands bigger that are reasonable. I have used a couple sets on stock rebuilds. They work well if you have a little cylinder wear. Light hone and drop them in. There is a very good chance with only 100hrs that you won't need pistons though.

281916 Product Detail Information - JE Pistons

Good to know. Most of the info Iíve found is on the Chevelle sites, and it seems unanimous that these are not honed with a torque plate, and honing with a torque plate to make them perfect hogs them out too wide, so those pistons may be a good last resort.
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Old 02-12-2018, 08:32 PM
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I bet the ring pack is metric, mine were. I bored and honed with Torque Plates because you have more options with standard ring packs. The metric ring packs are to expensive and bad from the start. Used way to much oil also! My 2 cents
Your link above was exactly what I used. You have to have the correct honing or the rings will never seat. Pay a good machine shop to do the job correctly!
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Old 02-12-2018, 09:16 PM
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I finally got home to double check things, and it already has JE700 pistons.


Edit in
It May also be worth mentioning that one reason I yanked the motor was to change out the 110lsa cam for a Crane 731. Even with headers there was moisture in the cylinders that may have washed the rings out from reversion.

Last edited by Baja Rooster; 02-12-2018 at 09:35 PM.
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