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AMC 360 - Bad sound after overheating (VIDEO) |
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BrotherBamc 
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Joined: Jan/22/2009 Location: Lewiston Status: Offline Points: 2248 |
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 Posted: Oct/27/2022 at 10:06pm |
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Do you guys happen to have a part number for those sealed power pistons.?
I just had a 360 rebuilt for my Jeep and I used a set of sealed power pistons. I'll have to do some digging to find my part numbers, but I also used .60 over pistons in my Jeep build as that was all that I had on hand. I do know that I had them for quite a few years before I got around to using them. You know how a "budget" build is supposed to go. It's never seems to be in the "budget" range. LOL Thanks..!! EDIT: Found my list of parts.. Sealed Power Pistons 362NP is what I have written down.
Edited by BrotherBamc - Oct/27/2022 at 11:03pm |
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Trader
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Joined: May/15/2018 Location: Ontario Status: Offline Points: 6912 |
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Posted: Oct/28/2022 at 6:25am |
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With this piston scuffing issue, you can do one thing to provide some protection if your build is already in progress.
PO, would be to use a thinner engine oil. A xW30 engine oil with a ILSAC rating of C3 or CE or an ACEA A3/B4 will provide High Temperature High Shear (HTHS). Thinner oil cools the engine better also. If the piston to cylinder clearance is closing up, you want to remove heat and also have lubrication film that will accommodate a tighter tolerance. None of the common xW20 motor oils have good HTHS ratings, there may be some out there! The pore points of an xW20 vs an xW30 at 100 degrees C are almost identical. |
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J10_Shorty
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Joined: Oct/16/2009 Location: Boston, MA Status: Offline Points: 71 |
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Posted: Oct/31/2022 at 5:24pm |
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A quick update -- regardless of how sideways this goes, you guys have been great with questions and advice so I'll be sure to bring you along.
Plan was to wait until this shop could get to my motor and see about doing a .060 piston. Which one, I don't know. Then I found a rebuilt shortblock from well known machine shop. All work done, .030 over, assembled and ready to go for a very reasonable price. I'm likely going to have to swap out the pistons but for the price and fact it was ready to go, I decided to grab it. I have 58cc chamber heads which I'm pretty sure means that a 343 flat top piston will put to too high a CR for my use case. The plan would be to have new dished pistons pressed on and go from there. I guess that brings me back to which pistons. I can get a set of the Sealed Power units for a very reasonable price but after everything I'm reading I'm leaning towards a set of Wiseco forged units. The shorblock came with a Crane Cam 272-H in it which the person who ordered the build wanted. I think I'll stick my me Comp XE256 but cam selection is certainly a lower priority at his point.    Edited by J10_Shorty - Nov/01/2022 at 7:42am |
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Mopar_guy
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Joined: Jun/07/2009 Location: Ohio Status: Offline Points: 4837 |
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Posted: Oct/31/2022 at 6:28pm |
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IMO you would be crazy to Sealed power cast pistons in it. You're much better off with a forged piston. Here's another example of more bad pistons. https://theamcforum.com/forum/forged-pistons-in-a-daily-driver-amc-360_topic117444.html
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DMack
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Joined: Mar/27/2019 Location: California Status: Offline Points: 226 |
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Posted: Nov/01/2022 at 11:07am |
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[QUOTE=Mopar_guy]IMO you would be crazy to Sealed power cast pistons in it. You're much better off with a forged piston. Here's another example of more bad pistons. https://theamcforum.com/forum/forged-pistons-in-a-daily-driver-amc-360_topic117444.html
I've got to agree with Mopar_guy 100%! Go with a forged piston. When I was asking the Forum for some recommendations on pistons, the "Wiseco" pistons got referred over & over.
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DMack
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Posted: Nov/01/2022 at 11:14am |
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Sealed Power 362NP were the pistons I had in mine. I'd also be curious to hear what everybody thinks is a proper bore to piston clearance. I've heard as low as 1/1000th to as large as 2.5/1000th. Has anyone gone higher than 2.5? I would think you'd get piston "slap" on cold start up with any more clearance than 2.5.
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PHAT69AMX
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Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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Posted: Nov/01/2022 at 11:16am |
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J10_Shorty Those 343 pistons are most likely .020" or more shorter than stock compression height so your compression with the 343 slugs already in the new short block are probably just fine for pump gas because those 343 slugs are a MILE down in the hole in the block are they not ?
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J10_Shorty
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Joined: Oct/16/2009 Location: Boston, MA Status: Offline Points: 71 |
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Posted: Nov/01/2022 at 1:19pm |
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PHAT69AMX - thanks for the reply and I was honestly hoping that would be a possibility. The piston in the pic above wasn't at true TDC but I've taken another one. Best I can tell with a straight edge and my digital caliper is around .035 in the hole.
I started reading about 343 pistons in a 360 online and honestly got so confused I practically give up on the idea. I know I've got stock rods, crank, and the block isn't decked but I'm not 100% on everything else. All the treads I found pointed to getting down to close to 10:1 with some special tricks. Some mentioned clearance with counterweights as well. If I knew for sure with my 58cc heads I could get under 10:1 then I'd certainly be open to it as they seem to be a decent piston. I'm not running a big cam so I don't suspect valve clearance is an issue either. Outside of that I think I'll have to just do the safe thing and order the Wiseco dished forged pistons.   Edited by J10_Shorty - Nov/01/2022 at 1:45pm |
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Joseph Lamb
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Joined: Nov/15/2018 Location: tampa florida Status: Offline Points: 112 |
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Posted: Nov/01/2022 at 4:51pm |
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dear member !!!
that sound is what I would call pre-TERMINAL do not drive that old beauty . Pull her out and tear her down untill you find the cause , please . That does not really sound like regular valve train noise to me and my friends . Sorry for your poor luck , I tow a 13 foot whaler with my Javelin and know how you feel . Joe in Tampa Florida Home of the Free .
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1971 Javelin 360 SST
1973 RS Z28 350 L82 4SPD 38 YEARS 1958 Chevy Biscayne 235 powerglide 1997 Jeep TJ 151 5 speed 1960 Lark Convertible |
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Joseph Lamb
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Joined: Nov/15/2018 Location: tampa florida Status: Offline Points: 112 |
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Posted: Nov/01/2022 at 4:53pm |
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ooops, you already did !!!
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1971 Javelin 360 SST
1973 RS Z28 350 L82 4SPD 38 YEARS 1958 Chevy Biscayne 235 powerglide 1997 Jeep TJ 151 5 speed 1960 Lark Convertible |
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