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AMC 360 PISTONS

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Category: The Garage
Forum Name: AMC V8 Engine Repair and Modifications
Forum Description: AMC-made V8 engine mechanical, ignition and fuel from basic repair to high-perf modifications
URL: https://theamcforum.com/forum/forum_posts.asp?TID=98652
Printed Date: Mar/28/2024 at 5:39am
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Topic: AMC 360 PISTONS
Posted By: bdavis100200
Subject: AMC 360 PISTONS
Date Posted: Feb/19/2019 at 9:44am
I took my late 71 model AMC 360 appart to find that I need new pistons. What are some good pistons that are just as good or better than what came in it? The engine won’t see anything past 6000RPM.



Replies:
Posted By: Javelin_GT
Date Posted: Feb/19/2019 at 9:57am
I have a new set of Sealed Power cast .030 pistons if interested.  Somewhere in the for sale section if you dig around.


Posted By: Trader
Date Posted: Feb/19/2019 at 10:01am
Well that 6000 RPM is the edge number. Have a read and decide for yourself (the article has pop up adds but can be closed):
https://www.musclecardiy.com/performance/understanding-piston-speed-in-high-performance-engines/" rel="nofollow - https://www.musclecardiy.com/performance/understanding-piston-speed-in-high-performance-engines/


Posted By: 1982AMCConcord
Date Posted: Feb/21/2019 at 8:06am
Plenty of options for a 360. 

OEM pistons
Wiseco
Egge 343 pistons
Falcon Global 343 pistons
Custom forged from Bulltear


Posted By: SC397
Date Posted: Feb/21/2019 at 8:16am
If you don't buy these, I probably will. http://theamcforum.com/forum/pistons-headers-rods_topic98562_post866146.html?KW=360+pistons#866146
If you want forged. https://www.wiseco.com/PDFs/Wiseco-AMC-360-401-Piston-Rod-Kits.pdf" rel="nofollow - https://www.wiseco.com/PDFs/Wiseco-AMC-360-401-Piston-Rod-Kits.pdf


Posted By: 1982AMCConcord
Date Posted: Feb/21/2019 at 8:49am
Originally posted by SC397 SC397 wrote:

If you want forged. https://www.wiseco.com/PDFs/Wiseco-AMC-360-401-Piston-Rod-Kits.pdf" rel="nofollow - https://www.wiseco.com/PDFs/Wiseco-AMC-360-401-Piston-Rod-Kits.pdf

Wow... I didn't know they made a kit like that! That is a good price for forged pistons and rods for an AMC!
 


Posted By: LMM1996
Date Posted: Feb/21/2019 at 9:46am
I used Wiseco pistons in my 360 with reconditioned factory rods. I think my pistons were a little over 400.00 with pins and rings included. In my opinion there was no sense in going with a cast piston when there was a decent forged set available for a few bucks more. Especially when you factor in the increased compression you can get from them. My engine guy was definitely impressed with the quality of them and they were substantially lighter than the cast pistons that were in it.


Posted By: PHAT69AMX
Date Posted: Feb/21/2019 at 10:47am
Not that you or anyone else should do it, but just so the info is there, don't know about now, but in the past on the Egge web page and catalog, some AMC Pistons are listed under RAMBLER not AMC and they do not show up under AMC only under RAMBLER like the 343 pistons they offer for sale.

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Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video



Posted By: SC397
Date Posted: Feb/21/2019 at 10:52am
I have used a few sets of these.  9.5:1 compression ratio with a 58cc head makes it nice.
https://www.ebay.com/itm/282933284108" rel="nofollow - https://www.ebay.com/itm/282933284108


Posted By: 1982AMCConcord
Date Posted: Feb/21/2019 at 12:18pm
Originally posted by SC397 SC397 wrote:

I have used a few sets of these.  9.5:1 compression ratio with a 58cc head makes it nice.
https://www.ebay.com/itm/282933284108" rel="nofollow - https://www.ebay.com/itm/282933284108

Hey Rick... Would this CR require regular, mid grade or premium?


Posted By: SC397
Date 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.


Posted By: LMM1996
Date 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. 


Posted By: SC397
Date Posted: Feb/21/2019 at 4:21pm
Yep, it looks like they are a little off in their calculations.
https://flic.kr/p/2dtw95v" rel="nofollow"> https://flic.kr/p/2dtw95v" rel="nofollow - Wiseco21cc+58cc by https://www.flickr.com/photos/149168736@N07/" rel="nofollow - Rick Jones , on Flickr
https://flic.kr/p/2dtw95R" rel="nofollow"> https://flic.kr/p/2dtw95R" rel="nofollow - Wiseco21cc+60cc by https://www.flickr.com/photos/149168736@N07/" rel="nofollow - Rick Jones , on Flickr
https://flic.kr/p/SJbYYA" rel="nofollow"> https://flic.kr/p/SJbYYA" rel="nofollow - Wiseco21cc+64cc by https://www.flickr.com/photos/149168736@N07/" rel="nofollow - 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.
https://flic.kr/p/2dtwzLa" rel="nofollow"> https://flic.kr/p/2dtwzLa" rel="nofollow - WisecoFlatTop by https://www.flickr.com/photos/149168736@N07/" rel="nofollow - Rick Jones , on Flickr



Posted By: PHAT69AMX
Date 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" rel="nofollow - http://www.theamcforum.com/FORUM/wiseco-choice-help_topic98247_page1.html


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Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video



Posted By: SC397
Date 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.


Posted By: WesternRed
Date 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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I've finally given up drinking for good...........now I only drink for evil.


Posted By: PHAT69AMX
Date 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 ?


-------------


Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video



Posted By: Trader
Date 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.
  



Posted By: 69 ambassador 390
Date 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. 

-------------
Steve Brown

Algonac, Mi.

69 Ambassador sst 390

84 Grand Wagoneer

69 Cougar XR7

65 Fairlaine 500XL

79 F-350 Super Camper Special





Posted By: oldguy
Date Posted: Feb/22/2019 at 1:47am
I have a set of wiseco .030 over pistons I bought but never used



Posted By: LMM1996
Date Posted: Feb/22/2019 at 8:57am
My block didn't need decked so we didn't do it. I always try to do as little of that as possible that way it leaves me something to work with later on. The heads were milled .015 I believe to get the chambers to 58cc. This is just a street engine going in a jeep so I wasn't going for max compression. Just wanted to get it around 10:1. All in all I don't think you can go wrong with the Wiseco pistons as they are a great value. You just have to do a little homework which isn't a bad thing.



Posted By: Trader
Date Posted: Feb/22/2019 at 9:49am
So sorry to offend anyone, but machining is not always required. You can scrape/stone a flat surface finish a block or head by hand.
We did steel to steel surfaces on turbines, pumps, compressors ... by hand with scrapers and stones. All to correct manufacturer specified finish and tolerance. No gaskets or compounds for sealing.
You need a couple of good quality machinists straight edges, machinist carbide scrapers, feeler gauges, flashlight, and dedicated stones of several grits. And cleaning supplies!

If you have ever scraped a lathe bed/ways or milling machine, you will be fine. 

Do not use a power tool. Fastest way to ensure you need a machine shop.


Posted By: wheelz
Date Posted: Feb/22/2019 at 10:12am
I dont see the point in running nice Wiseco forged pistons on stock cast 360 rods in any performance build. Spend another 400 bucks and get Molnars and eliminate the weak link. I have one 360 I bought used and refreshed recently with .060 Badger pistons and has stock rods with polished beams and ARP bolts. If Wiseco made a .060 piston I would have thrown out the pistons and rods but went with a cam with a 6000 rpm limit which is pretty much the limit for a cast piston 360 


Posted By: SC397
Date Posted: Feb/22/2019 at 10:29am
Originally posted by Trader Trader wrote:

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.
  


90% of my builds are for street as well but most of the blocks I get look like they came out of Lake Erie.  Most cores have been torn down and sit for years as a bare block.  Regardless, I have them all decked to at least made square with the mains and to have a good gasket surface.  usually it is no more than .008" on the block and heads.


Posted By: Trader
Date Posted: Feb/22/2019 at 11:06am
Have to agree, if the surfaces are bad, machine.
On the pistons question, calculations are 5500 RPM (rounding off) for top end of the factory components due to rod length. I know many, including myself have gotten away with more, and sometimes not.
From my experience it's the top cast piston ring lands that fail first. This would be a case for forged pistons as extra insurance for a spirited street driver.
Would like others to chime in on what they have seem as the most common failure point of hard driven 360's.



Posted By: LMM1996
Date Posted: Feb/22/2019 at 11:19am
Originally posted by wheelz wheelz wrote:

I dont see the point in running nice Wiseco forged pistons on stock cast 360 rods in any performance build. Spend another 400 bucks and get Molnars and eliminate the weak link. I have one 360 I bought used and refreshed recently with .060 Badger pistons and has stock rods with polished beams and ARP bolts. If Wiseco made a .060 piston I would have thrown out the pistons and rods but went with a cam with a 6000 rpm limit which is pretty much the limit for a cast piston 360 

  Its all a matter of opinion, but you don't really need aftermarket rods unless you are using a power adder or plan on turning some RPMs. I can't speak for everybody, but in my case I didn't need to spend 600.00 on aftermarket rods. The motor will most likely never be over 6000 rpm, and will never have a power adder on it. I doubt my engine will make 400hp so I didn't see any reason to upgrade those parts. The stock crank and rods should be good up to around 500hp so I just had ARP bolts put in and had the original rods resized and the rotating assembly balanced.  Again I can't speak for everybody, but in my case, I had to buy new pistons so an extra 50-100.00 for the Wisecos was a no brainer. Especially since they made it much easier to get the compression bumped up to a more ideal number. Getting the compression above 9.0:1 is one of the best things you can do to these, or any low comp motor for that matter.


Posted By: 1982AMCConcord
Date Posted: Feb/22/2019 at 11:43am
Originally posted by LMM1996 LMM1996 wrote:

Originally posted by wheelz wheelz wrote:

I dont see the point in running nice Wiseco forged pistons on stock cast 360 rods in any performance build. Spend another 400 bucks and get Molnars and eliminate the weak link. I have one 360 I bought used and refreshed recently with .060 Badger pistons and has stock rods with polished beams and ARP bolts. If Wiseco made a .060 piston I would have thrown out the pistons and rods but went with a cam with a 6000 rpm limit which is pretty much the limit for a cast piston 360 

  Its all a matter of opinion, but you don't really need aftermarket rods unless you are using a power adder or plan on turning some RPMs. I can't speak for everybody, but in my case I didn't need to spend 600.00 on aftermarket rods. The motor will most likely never be over 6000 rpm, and will never have a power adder on it. I doubt my engine will make 400hp so I didn't see any reason to upgrade those parts. The stock crank and rods should be good up to around 500hp so I just had ARP bolts put in and had the original rods resized.  Again I can't speak for everybody, but in my case, I had to buy new pistons so an extra 50-100.00 for the Wisecos was a no brainer. Especially since they made it much easier to get the compression bumped up to a more ideal number. Getting the compression above 9.0:1 is one of the best things you can do to these, or any low comp motor for that matter.


I completely agree... I was going to say something similar but you already beat me to it.  I have spent a lot of time talking with the guys on here and Facebook about my future 360 engine build. The 360 rods are the same at the 290, 304 and 343. And none of those engines are known for breaking the stock rods. While there are some guys that have abused their 360 to the point of killing it... I don't remember a single one of them blaming broken rods. I have several local friends who have said the same thing.. that they have routinely abused a 360 to within an inch of it's life and the rods haven't been what caused it to fail... its always the stock cast pistons or spun bearings. Honestly.. from my readings.. these engines are actually very hard to totally kill. I personally would not hesitate to use the stock rod with the Wiseco's for a standard street or hot street/strip build. If someone is running the drag strip every weekend... then yes.... swap rods... K1, Molnar... even the Scat rods are pretty nice for the money.. but beware.. there are two versions of the Scat rods. One uses 8740 chromoly steel and the other uses ARP2000 alloy... and that means a $125 price difference.


Posted By: 69 ambassador 390
Date Posted: Feb/22/2019 at 6:58pm
Originally posted by Trader Trader wrote:

So sorry to offend anyone, but machining is not always required. You can scrape/stone a flat surface finish a block or head by hand.
We did steel to steel surfaces on turbines, pumps, compressors ... by hand with scrapers and stones. All to correct manufacturer specified finish and tolerance. No gaskets or compounds for sealing.
You need a couple of good quality machinists straight edges, machinist carbide scrapers, feeler gauges, flashlight, and dedicated stones of several grits. And cleaning supplies!

If you have ever scraped a lathe bed/ways or milling machine, you will be fine. 

Do not use a power tool. Fastest way to ensure you need a machine shop.
 
You are right, If you have the correct tools.  Most people will just use a harbor Freight stone to do it.  I will stone and scrape a block myself if it's in good shape.  Most people will make it too smooth.


-------------
Steve Brown

Algonac, Mi.

69 Ambassador sst 390

84 Grand Wagoneer

69 Cougar XR7

65 Fairlaine 500XL

79 F-350 Super Camper Special





Posted By: BassBoat
Date Posted: Feb/22/2019 at 7:26pm
I recently tore down a 360 that had been run hard for a long time.  Bracket raced for maybe 25 years.  I knew the 5 other owners of the car over the years.  The car got a performance valve job about about half way through its life, and a replacement crank and fresh valve springs just before I bought it.  I ran it to 6000-6300 for the three years I had it.  I got the engine from the guy I sold the car to when he had issues and put his 401 in.  I was always skeptical about those skinny bolts and cast rods in a 360.  But this car had 1973 amc cast pistons and rods and had the snot run out of it.  So I don't have concerns with stock rods and bolts any more.  Honestly, there was no obvious visible issue with the pistons or rods.  I suspect the rods are at the end of their life and will not re-use them.  But pistons?  only takes one bad tank of gas or one time with the timing off and you can bust the ring lands.  So I can see putting forged pistons on stock rods....
  


Posted By: 1982AMCConcord
Date Posted: Feb/23/2019 at 9:50am
I have seen a few guys use these too...

http://racetecpistons.com/pages/autotec.php" rel="nofollow - http://racetecpistons.com/pages/autotec.php

Facebook picture...

https://d.facebook.com/129459243784841/photos/a.347164795347617.82346.129459243784841/1514569355273816/?type=3&__tn__=EH-R


Posted By: SC397
Date Posted: Feb/23/2019 at 11:10am
Originally posted by 1982AMCConcord 1982AMCConcord wrote:

I have seen a few guys use these too...

http://racetecpistons.com/pages/autotec.php" rel="nofollow - http://racetecpistons.com/pages/autotec.php

Facebook picture...

https://d.facebook.com/129459243784841/photos/a.347164795347617.82346.129459243784841/1514569355273816/?type=3&__tn__=EH-R


I am on a first name basis with these guys.  I use them for the more custom jobs.  Good guys to work with but sometimes a little slow.


Posted By: 1982AMCConcord
Date Posted: Feb/23/2019 at 11:17am
Originally posted by SC397 SC397 wrote:

Originally posted by 1982AMCConcord 1982AMCConcord wrote:

I have seen a few guys use these too...

http://racetecpistons.com/pages/autotec.php" rel="nofollow - http://racetecpistons.com/pages/autotec.php

Facebook picture...

https://d.facebook.com/129459243784841/photos/a.347164795347617.82346.129459243784841/1514569355273816/?type=3&__tn__=EH-R


I am on a first name basis with these guys.  I use them for the more custom jobs.  Good guys to work with but sometimes a little slow.

Cool. Good to know. Do you know if they have more sizes available and are the prices close to the Wiseso? Something tells me they are probably a bit more.


Posted By: SC397
Date Posted: Feb/23/2019 at 2:53pm
They will make whatever you want and no the prices are not even close to Wiseco. 


Posted By: 67 Marlin
Date Posted: Feb/23/2019 at 11:26pm
Originally posted by SC397 SC397 wrote:

They will make whatever you want and no the prices are not even close to Wiseco. 

About $750 shipped to your door, including rings.


Posted By: 1982AMCConcord
Date Posted: Feb/26/2019 at 12:50pm
Thanks guys! 



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