rebuilt 350, smoking blue
#1
rebuilt 350, smoking blue
Ok, upfront, sorry for all the posts, but this forum is amazing... I've learned more in a couple months about engines and cars on here than I knew my entire previous existence..... So here's what we've got, maybe you can help... it's a rebuilt 350... holley 1850 carb... it burns blue smoke on startup and sometimes when idling, not a drastic amount but more than it should. When I replaced the plugs, every single plug had oil on it, both sides of the block. Also, oil seems to wick up the bolts on the intake manifold and puddles on them underneath the carb. When I accelerate hard and drive around it doesn't seem to smoke as much and after a while it does seem to go away. Is it possible the intake manifold gasket needs to be replaced or could it be valve seals? I'm hoping to avoid anything costly here, but it is what it is.
#2
im trying to understand, does the motor never stop smoking? it sounds like valve seals and/or valve guides are bad. usually its just one or two cylinders are bad, but every single plug is oily? have you driven the car and then pulled a random plug?
#3
I've been driving the car a good bit here recently. It doesn't always smoke, it smokes when I start it up for the first time of the day and will smoke for a bit and usually goes away after the car has been warm for a little bit. I haven't pulled any of the plugs since I changed them and i'm not sure how long they were on the car before but every plug had oil on it at that time.
edit: I adjusted the timing last night and during adjustments it started smoking a decent amount, not sure if it was related.
edit: I adjusted the timing last night and during adjustments it started smoking a decent amount, not sure if it was related.
Last edited by kuhlman187; 12-03-2014 at 11:14 PM.
#4
I agree with 68SS, valve stem seals.
Pull a cover and check valve spring assembly.
OE design has a square ring seal between the retainer and stem AND a cover over the top of the spring.
Sometimes in an cylinder head overhaul, the spring cover will be removed and a stem seal cup will be pushed over the guide, aka, older - mid-60's-'70's Cadillac, or a spring-loaded Teflon® seal will be installed on the guide and the seal pops out of the holder on the guide.
The OE spring cover and stem seal prevented oil from getting into the guide and seeping into the intake port later to be sucked into the combustion chamber and burned.
Or just too much side-to-side clearance of stem to guide.
The inside manifold bolts, excluding the two on the very ends, are through holes to the crankcase. Oil wicks up the threads if the threads are not sealed - normal.
You can remove a bolt, clean the threads, both bolt and head with BraKleen® removing the oil, coat the threads with Permatex gasket sealer, or RTV, and retorque bolt. BraKleen will evaporate. Do one bolt at a time.
Pull a cover and check valve spring assembly.
OE design has a square ring seal between the retainer and stem AND a cover over the top of the spring.
Sometimes in an cylinder head overhaul, the spring cover will be removed and a stem seal cup will be pushed over the guide, aka, older - mid-60's-'70's Cadillac, or a spring-loaded Teflon® seal will be installed on the guide and the seal pops out of the holder on the guide.
The OE spring cover and stem seal prevented oil from getting into the guide and seeping into the intake port later to be sucked into the combustion chamber and burned.
Or just too much side-to-side clearance of stem to guide.
The inside manifold bolts, excluding the two on the very ends, are through holes to the crankcase. Oil wicks up the threads if the threads are not sealed - normal.
You can remove a bolt, clean the threads, both bolt and head with BraKleen® removing the oil, coat the threads with Permatex gasket sealer, or RTV, and retorque bolt. BraKleen will evaporate. Do one bolt at a time.
#5
Who did the rebuild? Ran into the same thing with a corvette a guy did and it smoked way to much for his liking. Sold it for the right price and I tore it down and found out he or some one had put the second ring on the piston upside down and was pushing oil up in the cylinder instead of pulling it down. In the rebuild was the motor honed with the proper cross hatch and if not the rings may not be sealing. Just two things that might help explain your problem.
#6
no clue who rebuilt the engine.
Everett... i actually bought the RTV because i had read about using it for those bolts but wasn't sure if that was related to the burning oil that's going on. I will be working on those hopefully this weekend.
Everett... i actually bought the RTV because i had read about using it for those bolts but wasn't sure if that was related to the burning oil that's going on. I will be working on those hopefully this weekend.
#7
This can also be attributed to a bad PCV valve, it allows oil to be sucked up and in to the intake and you get blue smoke out the back. This is the easy to fix if it is the culprit. Also bad seals valve seals, wrong valves, piston blow by or rings, the blue smoke represents oil is getting in to the combustion chamber and out the exhaust. Start at the PCV it maybe sticking partially open... Just get a new one..
#8
Easy way to see if valve seals are leaking. Get the car up to highway speed and then let it coast down while in gear, don't apply brakes unless necessary. If the car blows blue smoke while coasting down, then a very good chance the valve seals are bad. The high vacuum created while coasting in gear will try to suck oil through the seals. Otherwise, if the engine smokes heavily under load, the rings aren't holding. May want to follow up with a compression or leak down test before tearing the engine apart.
#10
If the rings are bad it won't be an easy fix. The engine will need to be dismantled, the cylinder bores inspected to determine if they just need a hone job or a re-bore. Re-boring can get expensive as in addition of a new set of rings, oversize pistons will have to be installed.