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Old 01-25-2019, 08:04 AM
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AMC360 build with 343 Rebuild Kit

This is more or less a repeat of this build thread but this time, we are using a complete off the shelf 343 rebuild kit from Ebay. This one is for ELRonDeCuba going to France.
Again, the idea is to use off the shelf 343 flat top pistons to boost the compression ratio just below the magical number of 10.0:1 to be able to run on regular old pump gas.

http://www.ifsja.org/forums/vb/showthread.php?t=177234

This is the kit that I bought off of Ebay.
https://www.ebay.com/itm/AMC-343-MASTER-Engine-Kit-w-Torque-Cam-1967-68-69-pistons-bearings-gaskets/170622487424?ssPageName=STRK%3AMEBIDX%3AIT&_trksid =p2060353.m1438.l2649


This the actual kit.
IMG_0813 by Rick Jones, on Flickr
The cam card.
IMG_0814 by Rick Jones, on Flickr


The first key things that I had to do before ordering the kit was:
1. Select a pair of cylinder heads with the largest combustion chamber (63cc) so that I can keep the compression ratio below 10.0:1. Cylinder heads casted from 1978 and later have the 63cc combustion chamber.
2. Determine what over size pistons were needed.
3. Determine what under size Rod and Main Bearings were needed.

Last edited by SC/397 : 01-25-2019 at 08:56 AM.
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Old 01-25-2019, 08:18 AM
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Here is a picture of the casting number on the cylinder head.
IMG_1201 by Rick Jones, on Flickr


Here is the date code 79.
IMG_1200 by Rick Jones, on Flickr


Just to confirm, I measured the combustion chamber which came out to 63cc.
IMG_1202 by Rick Jones, on Flickr
For reference, here are combustion chamber sizes for the various years.
51cc - 1970 & early 1971 #3196291C
58cc - 1971 through 1974 #3212993, #3213948, #3220502
60cc - 1975 through 1977 #3220503
63cc - 1978 and up.


I measured the head gasket as well so that I could calculate what the compression will be.
IMG_1199 by Rick Jones, on Flickr


The valve reliefs in the piston measured about 6cc.
IMG_1198 by Rick Jones, on Flickr


For calculation purposes, I assumed that the head gasket would crush to about .050"
Here is the calculations for the compression ratio.
360-343CompRatio by Rick Jones, on Flickr

Last edited by SC/397 : 01-25-2019 at 08:38 AM.
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Old 01-25-2019, 08:51 AM
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I had learned that one of the critical measurements that I needed to take is from the piston pin center line to the bottom of the piston to make sure that there will be clearance to the crank throws. The left piston is a normal cast 360 piston. The center piston is the new 343 piston. The piston on the right is a forged 360 piston. From the measurements, the 343 piston will be fine.
IMG_1205 by Rick Jones, on Flickr


Big difference between the 360 dished pistons and the 343 flat top.
IMG_1206 by Rick Jones, on Flickr
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Old 01-25-2019, 09:44 AM
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The timing set that came in the kit is a Cloyes C-3008K which is actually SA Gear timing set. It is also the same as the Summit G6508 among others.
IMG_1189 by Rick Jones, on Flickr


I checked the oil feed cavity on the back side of the timing gear to see if it lines up with the oil feed hole in the cam. It doesn't. This will have to be reworked to assure oil flow to the distributor gear. This is typical. It is rare that I don't have to correct these.
IMG_1190 by Rick Jones, on Flickr


I moved the slot over with my die grinder. I always clean out the transfer slot as well.
IMG_1212 by Rick Jones, on Flickr
Looks like it will work now.
IMG_1209 by Rick Jones, on Flickr


I braze all the slots on the front shut except for the one at the key way slot. The factory didn't put these in and they rob oil from the distributor gear. I learned the hard way that with cast iron like this I need to heat the whole thing up before brazing.
IMG_1213 by Rick Jones, on Flickr


There were no instructions or cam lube provided with the cam so, I use CRC SL3331 to lubricate the cam lobes.
IMG_1188 by Rick Jones, on Flickr
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Old 01-25-2019, 10:02 AM
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The gasket set that came in the kit is a MAHLE AMC 95-3339. There are only rubber valve seals in the kit and there is no nylon type which is the ones I would rather use. We will be using positive seals in the build so not a issue. The distributor gasket is over size and I won't be able to use that either. The rest of the gaskets seem to be ok.

The FelPro 260-1151 is a better gasket set.
IMG_1203 by Rick Jones, on Flickr
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Old 01-25-2019, 10:20 AM
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Short block is together. Not it has to rest for a few days before I can get back to it.


IMG_1214 by Rick Jones, on Flickr
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