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360 Shenanigans

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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Topic: 360 Shenanigans
    Posted: Jun/03/2018 at 4:29am
This is follow on from my thread in the drag racing section, but probably more relevant here:

http://www.theamcforum.com/forum/stock-360-output_topic91270_page18.html

So I've pulled the engine and trans out:





This is originally a P code 360 from a 71 Javelin and was running a custom converter to go from the flat crank to the 727 on the back of it. One of the main goals here is to modify the crank so that I can run a regular 727 converter or more importantly a decent high stall to improve my 1/4 mile times. It's a drag only car at this stage and not street driven. In the first instance, I've just pulled the crank out the bottom to see what I'm dealing with.



I now this is a bit backwards and I'm still undecided if I should pull the heads and do a proper freshen up or just jam the crank back in since I really don't want to spend a lot of money on it.

Bearings are pretty much shot and will need replacing:



Assuming the numbers at the bottom are date codes 1 71 and 2 71, these have possibly been in there since it left the factory, the numbers don't come up in my parts book, but it looks like std on the rods and -10 on the mains. -10 also stamped on the crank, not sure what the 20 above it is for. Journals generally look ok, but I will measure them properly before proceeding.



Engine was running well, plugs generally look ok:



Compression is a bit subjective, but looked something like this before I started messing with cams:

1: 130
2: 130
3: 130
4: 130
5: 125
6: 120
7: 125
8: 130

Not fantastic, but not a total disaster for an 8.5:1 engine.

Heads are 993, large chamber with stud mounted rockers, I've converted them to adjustable rockers and added some better valve springs, retainers and locks. I don't have a proper leak down tester, but I've pressurized the cylinders and don't appear to have any issues with valve seal, just a little bit of minor blow by on the rings.

Ideally I'd like to bump up compression, but the bore appears to be standard size at 4.08". Now I was thinking of dropping a set of Wiseco flat tops to boost compression up to around 10.5, but these are only available in +30 and +45 sizes and I don't really want to re-bore it if I don't have to. That pretty much leaves me with cast re-pop 343 pistons, so I guess the initial question is if the offerings from Falcon Global, Egge and others are any good?

Just looking for some thoughts and options with this thing for a very low budget build?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jun/03/2018 at 6:10am
While it's out, I'd pull the heads, hone and ring. Not huge dollar but for a drag only car, a little loose is fine.
As for the pistons - that's going to put money into it and others are better at providing potions for your application.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/03/2018 at 9:14am
imho you need good used stock original AMC 343 Pistons to use, 2 barrel or 4 barrel, because the aftermarket replacement 343 pistons are about .030 shorter in compression height than the original AMC factory 343 pistons.  2 Barrel ( ? 14cc ) or 4 Barrel ( ? 4cc ? ), either one will give more compression than the stock soup bowl 27.5cc ( ? is this correct ? ) Dished 360 Pistons. ? Wonder if Wiseco would make you a standard bore size set if you contacted them and asked?

Edited by PHAT69AMX - Jun/03/2018 at 9:19am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401jim Quote  Post ReplyReply Direct Link To This Post Posted: Jun/03/2018 at 9:55am
Why not buy a 304 crank and stuff it in. They share the same stroke. There should be a ton of those around.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/03/2018 at 1:08pm
Agree, a 1972 and up 304 Crank is the same as a 360 Crank.
Here is the Performance American Style drawing about machining early crank for 727 trans...


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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jun/03/2018 at 4:40pm
That's what I'm working with to mod the crank Phat69AMX, main reason for going this way is that I can get it done for free at work, then give the crank a quick polish and I'm good to go. I have a late 360 crank here, but it's a bit weathered and needs a trip to the machine shop.

I gather the weak link in the 360 is probably the rods/rod bolts, so if I change pistons, I will at least get the rods re-sized with some ARP bolts, the budget doesn't stretch to a set of forged rods.

From what I can see, cast pistons are available from Egge, Kanter, Falcon Global, Rebuilders Choice, the AMC vendors and a few others. What I  don't know is if they are all made in the same place, saw an old post that said Falcon used the Kanter pistons. Egge pistons appear to have have 1.57" compression height, which is probably a little short, but I'm guessing all the others are probably the same, most don't list detailed specs.

Any particular choice for bearings, tri-metal or aluminium? Seems like I might be scraping the bottom of the barrel with options and may not have a choice.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/04/2018 at 10:26am
Comp Ratio calcs, Stock AMC 343 Pistons in a stock 360
and old supposed pics of Egge 343 RAMBLER Pistons...
Revision, Note: Uncertain 343 2V Dish Volume? 8.0cc or 13.5cc?
Picture says 8.0cc, Stock '69 2V CR Calc says 13.5cc?






Edited by PHAT69AMX - Jun/05/2018 at 12:11am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jun/04/2018 at 5:24pm
Third down is the plan, although compression height on those aftermarket pistons is more like 1.57", which will make it more like 10.1 compression on those numbers.

PS: just picked up some ARP rod bolts from a parts store 30 minutes away in suburban Australia for US$53.50, cheapest available on the planet, who would have thought?


Edited by WesternRed - Jun/04/2018 at 5:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jun/04/2018 at 6:17pm
Cast or Moly rings for a quick and nasty hone and re-ring/piston swap considering this thing only gets driven on the 1/4 mile? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/04/2018 at 6:30pm
I have a 343 sitting here that I plan on building at some point. It's a 2bbl if I recall correctly. 
I have NOS flat pistons (I think they look up as 343 4bbl types) still in the original AMC/Rambler boxes to use in my 343 so will have the originals - but not for a few weeks. I bet you want before then
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