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white halftrack 09-27-2012 22:31:12 69.80.123.107 Report to Moderator	I am now working on a 4000 early and have a strategy question. Here are my clues on the engine. I bought the tractor not running. Engine has no paint on it like it was hot tanked recently. Blue paint on transmission so engine was removed. Clutch good. Got engine running but missing bad. Found wiring from insulator to points block loose. Fixed and runs smooth. Smokes really bad when idling, then no smoke then smoke. More smoke than not smoke. Had a knock in upper end so I took the valve cover off and found the oil tube was loose, and was hitting the lifters, removed and replaced bad tube. Under valve cover no gunk. Looked clean. Still smoke. Oil pressure gauge comes up to 60. Seems high. Maybe bad gauge. Checked compression. 175 165 155 170 Seemed too high to me, might suspect bad gauge, but not sure. Tested with no choke, full throttle other plugs out. 12 volt conversion spins pretty fast. Smoke is blue to white. Seems to be oil. Engine starts good, but smokes bad. I drove tractor around and tranny shifts well, stays in gear and clutch feels good. My strategy right now is to pull the head and see what I see. if no major ridge in top off cylinder, replace rings and possibly replace bearings. My thought is that maybe a couple of cracked oil rings? Perhaps prior owner could not get to run or start right and tried ether as they didn't find the bad wire. Before replacing fire it would run a bit really rough and then eventually die. Any ideas as to what may be causing the smoking with high compression? Head? I am kinda thinking out load, but would appreciate input. I am sure some of you have dealt with this type of engine before. I don't really want to do a full engine rebuild right now, and if it needs it, I will switch an industrial power unit engine into it, but would rather work with what I have. [Reply]   [No Email]
white halftrack 09-30-2012 18:14:44 69.80.123.107 Report to Moderator	Re: 172 Gas engine questions. in reply to white halftrack, 09-27-2012 22:31:12   Thanks again for the responses. I will check the valve seals. Jason [Reply]  [No Email]
soundguy 09-28-2012 18:56:02 173.103.182.143 Report to Moderator	Re: 172 Gas engine questions. in reply to white halftrack, 09-27-2012 22:31:12   i agreee with the others. oil pressure is not too high.. relief cracks mid 50's.. seeing 60 at cold startup with a lil thrittle.. 60 is normal. your comp #'s are great.. I'd also think oiling from the top end is the smoke. run her a bit and see what happens... [Reply]  [No Email]
Operator4100 09-28-2012 13:40:11 71.12.84.77 Report to Moderator	Re: 172 Gas engine questions. in reply to white halftrack, 09-27-2012 22:31:12   If it were mine I would run awhile before going into it, put her thru her paces and watch the temp and oil gauges, [Reply]  [No Email]
Dean 09-28-2012 12:41:40 152.216.3.5 Report to Moderator	Re: 172 Gas engine questions. in reply to white halftrack, 09-27-2012 22:31:12   Could be valve seals but check air filter cup before delving into engine. Ether will not damage oil control rings in your engine. Dean [Reply]  [No Email]
wisbaker 09-28-2012 11:35:56 184.157.215.49 Report to Moderator	Re: 172 Gas engine questions. in reply to white halftrack, 09-27-2012 22:31:12   I'd check the valve stem seals and maybe see how the valves fit into the guides, if I didn't find anything exciting I dose it with an upper cylinder lubricant and work it hard for a while, maybe it got rebuilt and the rings haven't seated or if it sat a while the oil control rings may be a little gummed up (good) OR someone rebuilt it and the cylinders weren't properly honed or it has the wrong sized rings and/or the oil control isn't doing it job (bad). With good compression and oil pressure I'd work it and watch it carefully to see if it'll wear in or I could learn more about what ails it. Worse case you might have to do an in-frame on the cylinders & rings. [Reply]  [No Email]
Bill Rowles 09-27-2012 23:37:13 76.2.232.2 Report to Moderator	Re: 172 Gas engine questions. in reply to white halftrack, 09-27-2012 22:31:12   Check valve stem seals on intake valves. If oil pressure is correct, doesn't need new bearings. Rings may be stuck but high compression makes you wonder.....combustion chambers may be really carbon-fouled if it was run long burning oil. [Reply]  [No Email]
Texasmark1 09-28-2012 07:47:46 67.142.175.25 Report to Moderator	Re: 172 Gas engine questions. in reply to Bill Rowles, 09-27-2012 23:37:13   Agree on valve stem seals possibly leaking. Oil pressure is not high as I have experienced with these engines; it's ok. Confusing thing is intermittent periods of smoke. Seals could be the reason also. With that much compression you certainly don't have worn rings, not even stuck if you ask me. Possibly the engine has had an overhaul and whomever did it didn't replace the stem seals. That would account for worn seals and good compression. No sludge indicates detergent oil and at least getting it to running temp most of the time. I guess if it smokes that bad your oil level in the crankcase drops. You don't have it over filled do you? Correct dip stick? Might run some Marvel Mystery oil through the uppers and lowers and see if that helps. Otherwise, got me. Mark [Reply]  [No Email]