I have a SBC 327 that has recently started to smoke. Here is the catch, no smoke on start up, engine has vac*** at oil fill tube while at idle. Once engine warms up still little to no smoke. Cruising thru the neighborhood no noticable smoke. Give it some gas and get RPM's up and put a load on engine and we get smoke in engine compartment, that makes it way past firewall and into cabin of car. Get car good and warmed up and run it on the freeway for a while and then it gets weirder. Smoke when you give it gas (smoke in engine compartment that comes into cabin of car) and then when running 50 to 70 MPH constant and load on engine drops once spee acheived, very little smoke, but still some. When you let off gas at high speed after motor is very warm you will then get heavy white smoke out of driver side exhaust only, not p***engers. Plugs on both sides seem to be clean, nut gummed up with blowby oil. Car has plenty of power. Does not seem to be missing or weak. Have not run compression or leakdown on it. Car has very lumpy cam, and may be cause of pcv vac*** issue. Vac*** is ok when cool, looses alot of vaccuum when gets good and warm. Used to run valve covers with no breather, has early SBC oil fill in front of manifold. PCV was run behind manifold and connected to carb. Engine has some miles on it, but not sure how many. Was purchased as a "clean running motor" . For 1.5 years no problems, then recently added different valve covers with pcv in each, and stock (total of 3), and still getting smoke out of oil fill, and under hight RPM get oil spitting out of oil fill. Oil fill has copper pot scrubber pushed down into tube, still get oily mess. Heavy wieght motor oil used, oil changed several time recently, and nothing else new since problem started. Just looking for advice, could it be the heads???? 305 heads..... th350******. New manifold, new carb, any help appreciated.
I'd look at the vacuum modulator on your ******, if it's white smoke as you described. Are your Pcv's working? and are the facing correct direction?
pointing right way, and seem to be working, all three (yes three) are new. push in variety, not inline style.
Of course oil isn't the only thing that might be causing the smoke. Oil smoke tends to be blue-ish while coolant, brake fluid or a/t fluid tend to be white. It doesn't take much ****** or brake fluid to make a fair amount of smoke. Check the trans fluid level as well as the hose to the vacuum modulator and the modulator itself to make sure there isn't fluid where it doesn't belong. If you have power brakes check the brake fluid level. A bad master cylinder can leak fluid back into the booster and a bad booster diaphragm can allow fluid to be ****ed into the intake manifold. If the problem started after you changed the valve covers you may have too many pcv valves and not enough venting. This can be especially true if the covers are not sufficiently baffled under the holes where you've located the valves. Oil splash from the rocker arms can get picked up by the pcv valves under the right conditions. Try running things for a while with just one pcv valve and one crankcase vent and see if that makes any difference. The fact that it's getting into the cabin makes me wonder if you might have a leaky heater core, but coolant has a pretty distinctive smell and you'd likely also have a slimy film on the inside of the windshield. Unless, of course, you're just running with straight water for coolant.
I would suggest checking the rear seal of your intake manifold. A friends Camaro had this same issue. Also check rocker covers/gaskets. Are you running a PCV without a baffle, or an improper one? This may cause the same type of issue. I burned two quarts of oil in 400 miles and never smelled smoke running a pcv on MT rocker covers with no baffles....... Valve guides?
Front mounts or side mounts? P***enger side front mount bolt (the one that holds up the fuel pump push rod on installation) will push out oil while driving but usually nothing idling w/ your head under the hood. 3 PCV's & no breather? Why?
Wouldn't blowby show on my plugs? Problem started before any changes were made. No heater core. You can lift the hood, and rev engine manually and get smoke out of oil fill. Thanks for the help so far. Engine has breather thru oil fill tube on front of manifold. The early SBC style oil fill. Tried 2 pcv after replacing number one, then tried three... just giving stats on what has been tried so far.
Not a pro, but wondering why vacuum at dipstick tube? Intake gasket leaking? It is mainly smoking at high vacuum producing times.
Vacuum at the dip stick due to the PCV valve (s) I would suspect the PCV valves in the valve covers. The ONE at the back of the valley should be all that is needed or for that metter all that is wanted. The valve cover units are no doubt getting oil splashed up against them due to no or incorrect baffling. As the oil gets hot is gets thinner and there is more misting oil for them to **** up.
Your valve covers are likely not baffled but they can still do whaat yo're describing with the baffles. You sound like you have too much pcv and combine the number of places for vacuum to pull hot/thin oil you have a recipe for smoke clouds. First you need to do a leakdown. Wont always wipe out plugs so do the test to arm yourself with the data. If you're getting smoke and oil out of the fill then you're pressurizing the crankcase pretty well. If leakdown checks out then compression check for headgasket or possible head crack pressurizing the cranck case when hot(and opening up). Let us know what you find.
Regardless what the plugs say...when gases come out the breather, it's coming from somewhere. That's blowby. good luck
I thought SBC's are supposed to smoke? I had a very similar problem on a 350 and it ended up being a hairline crack through a coolant p***age on the driver side head. I swapped heads in off a destroyed GM crate motor and that fixed the problem. It could also be as simple as a head gasket. Good luck brother.
Just to maybe clear up a little confusion in terminology. Blowby isn't oil that's found its way up into the combustion chamber. It's unburned fuel vapors that have made their way down past the rings during the compression stroke before ignition. When the pcv system is working properly it pulls these vapors out of the crankcase and reburns them. That's why there should be a slight vacuum at the oil fill tube with the engine running.
That's your problem right there. You should only have a PCV in ONE V/C going to the manifold and an OPEN VENT HOSE in the other V/C going to the air cleaner above the carb intake. Trust this!
Well, started having all the probs....then changed to valve covers that had access for pcv/vent. Previous are cal-customs with zero holes. Used one breather per valve cover, one breather on oil fill, and original pcv location with new pcv. No help, then moved to one VC with pcv and one VC with vent. No luck....... see the pattern......thats how we have made it to three. I have vac*** thru breather, but as engine warms and load is put on, thats when I get faint white smoke..... thanks for all positve input. this gives me more directions to look into.
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