I've got 2 engines to choose from that I have not seen run. One is seized from sitting and the other one the guy said ran fine when it was removed from my project jeep and appears to be fine. My plan is to do a complete rebuild of one of them so I know the condition of the motor when I go to install, it will most likely be the locked up one since it still has the engine #s stamped in the block so I know it hasn't been too molested and I can resurface valve cover/head. I figured it needs an overhaul anyway assuming it is not cracked this is going to be the the block to tear apart. Ive been buying Nos parts as I find them.
My overhaul question I have is I'm going to buy a NOS camshaft to take up all the wear I can in the block since it doesn't have any replaceable bearings other than the front so I can't do much other than replace with a new shaft and hope to get it within spec. I don't know the current condition or tolerance of the engine shaft or bores now but figured it wouldn't hurt to throw in a new cam. I've looked through the tech books military and civy and couldn't find any specs for max out of tolerance bore size or max clearance between the bore and shaft. I've looked at the spec sheets but it only tells of the factory standard size I can't recall exactly but I believe it was .001 clearance but would like to know what the max allowable clearance is after installing a new cam before the block is considered out of serviceable tolerance.
My other overhaul question is while I'm in there should I have hardened seats installed at the machine shop and should I be replacing the valves with the new modern style valves with the updated lockers and keepers or should I stay with the older style NOS valves? _________________ Jason
1953 M38A1
You should be reading TM 9-1804A, Page 125. There's plenty more info there besides new specs - limits. The civvy Willys/Kaiser manual has less info then the TM.
The minimum cam journal diameters (read max wear here)are:
#1 = 2.182
#2 = 2.121
#3 = 2.085
#4 = 1.621
The max clearance between the cam journals and #1 bearing is .004 and the max clearance between the #2, 3 & 4 cam journals and the block bore is .004
Before I bought a new cam I would measure cam lift at each lifter, then check end play within .004-.007 limits. Then remove the cam, inspect lobe profiles and fuel pump cam profile then mike the journal diameters and the #1 bearing ID and #2, 3 & 4 block bore's ID. If not out of tolerance then retain the original cam.
Hardened valve seats are not a necessity with these 60 HP engines. Now if you beef up valve spring loads, make performance changes that increase cruising RPM above 3500, and increase compressions to use higher octane gas then by all means they become more of a necessity.
The bottom line is to give every engine being considered for overhaul a complete teardown, cleaning and proper inspection BEFORE committing to the overhaul.
That #1 cam bearing comes in several undersizes. Don't overlook lifter diameters and lifter bore diameters. The lifters are also available in oversize.
Makes no difference weather you use the late or early type valves so long as you do not try and mix and match.
Thank you wesk that's exactly what I wad looking for and wanted to hear. I looked for that info but guess I was looking in the wrong books. _________________ Jason
1953 M38A1
Last edited by Jason86 on Tue Jul 25, 2017 10:56 pm; edited 1 time in total
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