Have a friend that had a 350 chevy rebuilt for him by a reputable machine shop 1 yr ago..since then he has had nothing but trouble..everything from rough idle to major engine smoking..he has replaced as much as he can including carb (EB 650cfm)..he got most of the other problems fixed but has since developed a smoking problem and oil fouled plugs on all cylinders...heads were pulled and checked (one was cracked, replaced it), intake checked and found no problems (EB alum Mid rise), put engine back together and started engine..within just a few min oil smoked out the exhaust just as before and all plugs were oil fouled, i talked him into tearing the engine down and going thru it again with my help this time.
I looked thru all parts and found no unusual wear except on the rod bearings...found evidence of lack of oil wear on 6 bearings...checked cylinders and found no excessive wear( could still see hone marks in all cylinders), both comp rings and oil rings show no sign of wear or failure...pulled first comp ring off piston and reseated in its cylinder to check ring end gap and found no more the .027in gap.
I asked him about cranking compression on the cylinders before he tore it down and he found compression from 164-182 psi..2 cylinders hit 170psi and 2 hit 180psi..only 1 hit 182psi...engine is running .060 over bore piston and rings.
any ideas as to what could cause the problems he has been experiencing?
A couple of things come to mind. Did the shop use a torque plate when honing the cylinders to final size? The thinner the walls, the more easily they can distort. Did they use the right hone for the rings used? Different rings require different hone textures. Do the pistons fit the bores correctly? Make sure there isn't excessive clearance. It sounds like the rings may have not seated properly. Did you do a dry and a wet compression test? What was the difference if the readings? Adding a little oil to the cylinder after the initial compression test, then retesting will show the condition of the ring seal. If adding a little oil, the pressure goes up, then the ring seal isn't correct. Did you check the valve guides for excessive wear? Make absolutely sure that the heads have the correct valve seals.Was there oil in the PCV hose? The PCV may have been pulling oil into the intake if not properly baffeled. Just some ideas of the top of my head.
Many years ago I was approached by a guy with a Nova that just had the 307 rebuilt by a good shop and it was smoking really bad. He asked me if I could help him out. I don't know if the shop wouldn't fix it or if he just didn't ask. I had a 327 in a '69 wagon I knew ran good so I offered to put it in his Nova, for a fee of course. I put the 327 in and used the intake, carb and fuel pump from the 307 to make things easier. When I fired it up it smoked just like the 307. I was more than a little rattled. After much head scratching I took a fuel sample from the carb fuel line. It looked like two-stroke mix. A sample taken from the tank was clean. It turned out the fuel pump was the culprit. It was drawing oil from the engine and mixing it quite efficiently with the fuel. I swapped the pump and it cleared right up. I probably should have told the owner, but after the deal on the 327 and engine swap I gave him, I just kept my mouth shut. I really didn't feel like putting the 307 back in the Nova and the 327 back in the wagon anyway.
Good points, if the engine was getting excessive oil in the combustion chamber due to a bad diaphram in the fuel pump, excessive valve stem clearance, or improperly installed oil seals on the valves the rings will never seat. The cylinder will also still show a pretty good cross hatch. I've rebuilt plenty of engines by just using a glaze breaker on the cylinder walls and installing new cast iron rings and new bearings. Many will run 100,000 miles after this type rebuild, but you must inspect everything very thoroughly. I really wouldn't call it a rebuild though most oldtimers called it an overhaul.
Guys..thanks for all the ideas..some i should have thought about but since i wasnt the one working on it the entire time i guess i had a brain fart..the first things im going to check is the PCV and the fuel pump then get the cylinders MIC checked...as for the correct MIC,hone stone and torque plate...all unknown..but I will be the one putting his engine back together..will let ya'll know how it goes...so far every engine i have rebuilt/overhauled is still on the road so i guess i have done something right!
I am going to take a stab at this and say it is one of two thing's
#1 if this car has an auto tranny the valve that makes it shift could be bad they will draw trans fluid up thru the vaccum line and cause horrible smoke but it is hard to dettect because once the engine is stopped the fluid drains back down and you would not notice it ,
#2 it could be the ring's if they put the MOLY ring's in it they will cause this they cost ten times more but this is one of those times where you don't get what you pay for , the cheapest set of ring's an auto part's has will seat in to the cylinders and last for many moon's where as the moly rings that cost a hundred buck's will smoke and cause you trouble till they finally (IF EVER) seat ,