AMC 360 PISTONS

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   I use premium in all my AMC engines, even the ones with 8.5:1 compression ratio.  You might be able to run less than premium with 9.5:1 compression ratio but you will probably have to back the timing down.  You could also use the 1975 and later heads that would lower the compression some more.

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SC397 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5476	Post Options Post Reply Quote SC397 Report Post Thanks(1) Quote Reply Posted: Feb/21/2019 at 1:47pm
	I use premium in all my AMC engines, even the ones with 8.5:1 compression ratio. You might be able to run less than premium with 9.5:1 compression ratio but you will probably have to back the timing down. You could also use the 1975 and later heads that would lower the compression some more.

LMM1996 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Nov/03/2015 Location: Ohio Status: Offline Points: 31	Post Options Post Reply Quote LMM1996 Report Post Thanks(1) Quote Reply Posted: Feb/21/2019 at 2:17pm
	When I bought my pistons we had some problems getting to the compression ratio that was advertised. We ended up going with the flat top version and the compression ratio ended up at 9.8:1. I think at the time Wiseco was advertising 10.5:1 for those with a 58cc chamber. One reason we were having problems was the combustion chambers actually measured 64cc instead of the 58cc they were supposed to be. Milling the heads down to 58cc brought it up to 9.8:1 which I was fine with. But I think the reason we didn't get over 10.0:1 like advertised is, and I could be wrong here, I think Wiseco calculated their compression with the piston at zero deck height. We just installed in the hole at the original spec so I think that is where the difference was. Another good thing about the Wiseco pistons is they have very generous valve reliefs. I think when PTV clearance was measured there was enough clearance for over .650" lift. I apologize for being a bit long winded, but I just wanted to share a couple things I found when building my engine. Hopefully somebody can use the info to help them choose when building their engine. Edited by LMM1996 - Feb/21/2019 at 2:19pm

SC397 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5476	Post Options Post Reply Quote SC397 Report Post Thanks(0) Quote Reply Posted: Feb/21/2019 at 4:21pm
	Yep, it looks like they are a little off in their calculations. Wiseco21cc+58cc by Rick Jones, on Flickr Wiseco21cc+60cc by Rick Jones, on Flickr Wiseco21cc+64cc by Rick Jones, on Flickr I just called them and the flat top pistons have a 8.6 cc valve relief which is not listed on their sheet. WisecoFlatTop by Rick Jones, on Flickr Edited by SC397 - Feb/21/2019 at 4:38pm

PHAT69AMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919	Post Options Post Reply Quote PHAT69AMX Report Post Thanks(0) Quote Reply Posted: Feb/21/2019 at 6:30pm
	There are some AMC 360 with Wiseco Pistons Compression Calcs also in the thread linked below. Might it be that Wiseco "assumes" an "industry standard" .010" Block Deck Mill and .010" Cylinder Head Mill ? ( edited: changed .020 to .010 on both ) http://www.theamcforum.com/FORUM/wiseco-choice-help_topic98247_page1.html Edited by PHAT69AMX - Feb/21/2019 at 9:29pm
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SC397 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5476	Post Options Post Reply Quote SC397 Report Post Thanks(1) Quote Reply Posted: Feb/21/2019 at 7:19pm
	.020" mill is not a standard. It should be .010" at the most unless you tell the machinist otherwise. I think that the Diamond Piston compression calculator is just more accurate than the Wiseco one. Maybe they don't calculate the area of the head gasket. Edited by SC397 - Feb/21/2019 at 7:21pm

WesternRed Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5799	Post Options Post Reply Quote WesternRed Report Post Thanks(2) Quote Reply Posted: Feb/21/2019 at 7:43pm
	Not sure why they chose 1.59" compression height as opposed to factory 1.60". Stock 360 pistons are nominally 0.012 down the bore anyway, so plenty of scope to deck the block. Giving up compression on an already low compression engine in this way is a bit counter productive. Putting a slightly smaller dish on the piston on the other hand was a great idea, but they have given with one hand and taken away with the other.
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PHAT69AMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919	Post Options Post Reply Quote PHAT69AMX Report Post Thanks(0) Quote Reply Posted: Feb/21/2019 at 9:28pm
	Ok, yes, thanks SC397, using .010 milled from stock nominal 360 Block and 58cc heads with Wiseco +.030 8.6cc 1.590 CH slugs & 4.27 x .043 Gasket comes up ~10.5 CR in my calculator which does not include the small area above the Top Ring like the Diamond Calculator does. Will edit previous post to .010 Red: ? might it be the 1.590 CH is -.010 from stock to "match" also milling the block .010 ? Edited by PHAT69AMX - Feb/21/2019 at 9:58pm
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Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6882	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Feb/22/2019 at 12:20am
	OK, I do street builds only. I have never seen a 360 or 401 that has needed the block milled. Stone or float glass with paper and full contact (0.001" to 0.002") which any gasket and very tin coat of Hylomar takes care of. No leaks, ever! Unless the engine has seen extreme use, who is milling and why??? ... Beyond custom performance modifications. Never seen a cast head warped over 0.002", this does not need machining if you take off high spots (very little elbow grease, 10 to 15 minutes work). A manufacturer of custom parts should be assuming stock. If not then they should be stating required modification. My opinion.

69 ambassador 390 Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539	Post Options Post Reply Quote 69 ambassador 390 Report Post Thanks(1) Quote Reply Posted: Feb/22/2019 at 12:56am
	You should always mill to get the correct RMS surface for the specific gasket you are using. Stoning can lead to too smooth of a surface and gasket issues. MLS gasket require a different RMS than composite or steel shim gaskets. You should always mill the decks even it is just to get the right surface. .001-.003 is all that is needed if the surface is really still that good.
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oldguy Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Nov/07/2011 Status: Offline Points: 94	Post Options Post Reply Quote oldguy Report Post Thanks(0) Quote Reply Posted: Feb/22/2019 at 1:47am
	I have a set of wiseco .030 over pistons I bought but never used