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401 pistons in an early 390 |
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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5458 |
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Posted: Jul/31/2021 at 2:48pm |
If you have to buy new pistons anyway, and your machinist says that he can fit 0.040 oversize for the same cost as 0.030 oversize, I can see why you are leaning towards going 0.040 over. It's cost neutral and the concern over rust will be gone, or at least minimized to the point where it isn't a factor. Tickled that you kept your SC/. That's a decision you won't regret.
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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brownspirit
AMC Addicted Joined: Mar/07/2009 Location: Georgetown, MA Status: Offline Points: 1021 |
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I went over and saw it in his honing machine, there was still visible rust in 2 of the four bores he had done, and the 2 are at the outer limits of having acceptable wall clearance for .030 pistons. He said if I had the pistons he’d recommend I run it, where I still have to buy them he said just go .040 or .045. He also said the bores are so straight the he can just hone to fit the new pistons, he said it wasn’t gonna cost me any more on his end. He is in a holding pattern until I bring him some pistons. It made sense to me, but I don’t know. Andy
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69' BBB AMX 390/4-speed
69' s/crambler project 69’ International F210d Cummins/5+4 |
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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5458 |
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Andy, before you break out the boring bar, how bad is the surface rust? If you run a ball hone through it will it disappear? I put a 2.2 Mopar together with a bit of rust in the bores (against the recommendation of my machinist who wanted to overbore) and five years and another 100,000 miles it was still going strong when I sold it.
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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brownspirit
AMC Addicted Joined: Mar/07/2009 Location: Georgetown, MA Status: Offline Points: 1021 |
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Okay, 8 months later I got a block to the machine shop, it needs to go larger than .030 over. The bores are true at .030 but there is a small amount of rust. The block had previously had .020 taken off the deck. Anyway, I was going to order the Wiesco PTS540A45 and a set of Molnar 5.858” 401 rods. According to my calculations this should come out to the pistons being .010 in the hole using the 68/9 390 block decked to 9.155, 390 crank 3.574 stroke, Wiseco pistons at 1.500 compression height. Also it should get me about 10.2 compression with the -27 cc reverse dome pistons, felpro head gaskets, and my 291c heads. I actually bet those chambers are bigger as Adkins ported them for me. I will get them cc’d to find out for sure, but I would imagine the compression ratio will be a little lower, which I perfer. Does this all make sense, just asking before I order. Thanks, Andy
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69' BBB AMX 390/4-speed
69' s/crambler project 69’ International F210d Cummins/5+4 |
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AMXFSTBK390
AMC Addicted Joined: Oct/22/2013 Location: SF Bay Area Status: Offline Points: 3489 |
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Was I ever astonished when I tore down the 390 in my 68 AMX. It had 401 rods and pistons at .040. I was told to make that work, customs pistons are required with a different wrist pin location. At that juncture, I acquired a std bore 68-69 390 bare block from Galvin's and went a different route.
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Questions are powerful tools...what's in your toolbox?
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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Have ya called Wiseco direct in Ohio to see if they have any in stock?
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klvn8r
AMC Apprentice Joined: Feb/26/2012 Location: Texas Status: Offline Points: 160 |
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I'm currently helping my son build his first 401.....probably settling on the Wiseco + .045 Is anyone a dealer with IN STOCK? I'm unfamiliar with DSS and Racetech.....but will gladly listen! Thanks! Also, SC397....I posted a reply to you on the topic in the very top, regarding balancers. Thx. klvn8r
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klvn8r
AMC Apprentice Joined: Feb/26/2012 Location: Texas Status: Offline Points: 160 |
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I'm currently helping my son build his first 401.....probably settling on the Wiseco + .045 Is anyone a dealer with IN STOCK? I'm unfamiliar with DSS and Racetech.....but will gladly listen! Thanks! klvn8r
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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On the Wiseco website the last time I looked recently the catalog has a typo error for the AMC 390 Piston Compression Height that is incorrect, even called them and they confirmed. Maybe some day the online information will get updated.
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garland performce
AMC Apprentice Joined: Nov/19/2013 Location: sibley mo Status: Offline Points: 172 |
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Yes .020 rings are .060 400 sbc can get several ring packs
I`m a race tech dealer if I can help you give me a call at the shop Monday -Friday 7 to 4 816-547-5695 John Garland
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