txstang84
15 Year Member
Oil getting into new Cobra Upper I/T
- Thread starter 50canuck
- Start date
txstang84
15 Year Member
vristang, from what i understand with that one, if you don't have positive crankcase ventilation (PCV) then you could reduce the life of your rings due to overpressurization of the crankcase...if you look at some of the early 50's engines they have no provision for it-tales told from my Dad and all the other folks that were around for the hay day of the first small blocks say that those older engines used to sh** out rings fairly quickly, so the mfr's got wise and installed breathers and a little one way ck valve (pcv) to promote clean air and equalization of the pressures produced by blowby and oil vaporization-it also helps keep down all that nasty varnish inside the block and heads which can lead to disgusting deposits...hope that helps
GREG91GT said:
txstang84 said:
My response to both of you guys is the same. The intake most likely has nothing to do with the oil control problems you are experiencing. From my personal experience and what I have seen on this site, it is usually related to blowby. If putting a fuel filter on the PCV line keeps some of the oil out of the intake, that's great! But it doesn't fix the problem. The PCV and oil filler line should have no problem venting crank case pressure in a normal way (You may have issues if you are running boost however).
I recommend a leakdown test and a compression check on all cylinders. I think this will find your problem. Everything else is just a temporary fix, which may or may not be necessary.
Good luck to you both
txstang84
15 Year Member
we did do a lk-down and compression ck with excellent results-the worst cylinder was only 10psi less than the highest-the highest being 160psi...that and the huge puddles of fresh viscous oil in the pcv valve, pcv hose, and intake plenum are why i personally don't think it's a blowby problem...in addition, it's a fresh rebuild with standard tension rings (i noticed you made reference to that earlier), good bores, and everything was professionally cleaned and clearanced.
it's got us both kinda confused, but like i said there have been some changes to try and slow it down, which have worked with marginal success...it still burns a little bit, but only when it's hot started-now we both think that might have something to do with valve stem seals...
it's got us both kinda confused, but like i said there have been some changes to try and slow it down, which have worked with marginal success...it still burns a little bit, but only when it's hot started-now we both think that might have something to do with valve stem seals...
txstang84 said:
Yes, low tension rings suck @$$.
After reading this I am dumbfounded. With good compression readings within 93% if I know my math (and I usually don't), you should be fine. What were your leak down numbers like? Sometimes this can give an indicator that the compression check misses due to bore wear not being consistent along the length of the bore.
Valve seals are definitely worth looking into. However I am having a hard time seeing how this will cause oil to blow out of the crankcase, or be sucked into the intake, depending on how you look at it.
I can't think of a reason why oil would only be burned on hot start either.
Can you list the changes you have tried and what the current setup is? It may help.
Agreed! It would be like having a leaking roof and putting a bucket under the drip. Sure the floor stays dry, but to fix it one has to fix the roof. The oil in the intake, TB, etc is just a symptom in the middle of the closed-loop path. Get it at the source and it should go away.vristang said:
Other than ensuring all baffling (and then some, sometimes) is present, I cant think of much else to suggest to the latest posters' issues. A guy on the Corral had put the PCV in the end of his valve cover, with a 90* fitting. he reported decent results (after having tried many other things). No personal experience with that method though.
Good luck.
txstang84
15 Year Member
vristang said:
i can't remember exact numbers from the lk down test, but I do remember there was no reason to believe that blowby was a problem. See, this is where I'll stand by my original belief that the cobra intake just sucks the oil right out of the lifter valley (which makes absolutely no sense whatsoever). Before that swap was made, this freshly rebuilt engine (which normally will burn a small amount of oil until the rings seat) burned virtually nothing at all, never a minutes trouble...then we installed the cobra intake and lo and behold, there's oil being pulled from the crankcase with no loss of power...aside from the fouled plugs. On a trip to the dyno (about two+ hours away, it burned over a qt of oil) So, we discovered that we'd routed the line in the wrong way...ok, fixed that to the way it's supposed to look...mostly worked
Well, it finally stopped burning oil...or so we thought, then the damn thing starts burning it again-but this time only on hot starts...like an old worn out chevy 305 with bad valve stem seals (once again, makes no sense-BRAND NEW heads, not reconditioned)....ya know, that small cloud that billows from the pipes until the engine feels like stopping. When it's running and warmed up, you could beat the dog out of it, nary a puff of oil smoke-but when you shut it down, and come back in a couple minutes, there she is...poooof, and then it clears up after a few moments....and the plugs don't show any fouling...yet another reason for me to believe that it's not blowby, but stem seals instead...maybe all the oil being pulled from the intake messed up the stem seals-IDK...
txstang84 said:
Do you still get oil in the intake? I think if it were just bad valve seals there would not be puddles up near the throttle plate or along the upper manifold at all. How much is the oil level dropping? Is it back to where it should be? The reason I ask is that if the plugs are not fouled and the oil level is not dropping then it could be that you are burning something else, like coolant. Is the cloud of smoke there at cold start. Here's my thought, if you have a small leak in the head gasket there would be very little smoke coming out of the exhaust when it is warm and running steady. When the motor stops there is less pressure in the cylinder than there is in the cooling system, so water trickles into the chambers and pools up. You start the car and out comes a big cloud of smoke. This is only a theory though as I cannot tell what the smoke looks like from here. Oil smoke should be blue, coolant smoke should be white? You could also have someone stick their hand under the exhaust pipe when you warm start the motor. If they feel moisture on their hand then there is a coolant issue. This is the best I can come up with, even if it is a long shot. However, you would not be the first person to fix one problem just to have something else get screwed up.
Could be other sources of fluid leaks as well, such as oil past the valve seals, coolant past the lower intake manifold, coolant from the EGR (if you have it hooked up). I am just thinking out loud right now hoping that something will ring a bell for you.
I'll keep trying to help as long as you keep coming back.
txstang84
15 Year Member
vristang said:
ok, that's what i was trying to say in the last reply was there was no more oil problems up in the intake...i suppose i should've said no more in the intake runners. but it still burns oil-not coolant-i know what that sh** smells like in the exhaust. and yes the oil qty still goes down, but verrrrrry slowly...but since the plugs are not fouled, that's the reason i believe it to be stem seals, since most of the oil that gets burned that way is going over the valve first, and since the engine is nice and warm when it happens, the combustion temps just cause the oil to "flash" off the valves and the resulting smoke gets poured down the exhaust...I'm sure we'll find out for sure. he's had a couple other people diagnose the problem as that (stem seals)...and Edelbrock has already sent him new ones free of charge-since the heads have less than 5k on them...but like i mentioned before, we believe that possibly all the oil that got burned from the intake may have-in part, at least-caused this new oil burning problem
but trust me, it's not coolant-it's most definitely oil smoke, i know that stench anywhere. and yes, coolant smoke (steam) is most definitely white, and it smells kinda sweet and sticky...just like the liquid form. on top of that, the car fires right up with no problems-now to me, if you try to put water in an engine...it doesn't fire off very well, it'll probably stutter, and if you leak too much of it, you will probably bend a rod (seen that one happen more than once) and since antifreeze and distilled water are most certainly not flammable, that kinda pinches that theory
Seems like alot of 302's have this problem. I installed a Cobra intake a while back and had the same issues. Tried all the easy fixes, reroute vacuum, install filter in valve cover to release excess pressure, etc. None helped. Figured it was the engine. Put in a new engine with an Edelbrock Performer. Burning oil issue is gone, but the upper intake is still full of oil. BUT, do to the design, the oil pools and runs down the pcv hose back to the motor when sitting and can't get up to the runners unless air pulls some thru. The only other things is to get a oil seperator in the pcv line, or install a lower intake gasket out of a 1982 cougar with a 255 v-8. It is a solid intake gasket. Drill some holes in it for pcv flow. This reduces the amount of oil to the pcv. The low tension rings and valve guides are the biggest culprits.
oil in upper I/T
I didn't expect this big a response to this issue, just a added note, with my stock intake set up i was not getting the oil pooling in intake, that was without oil seperator. The plugs were clean also after 3000 miles, maybe the design of stocker allows oil to flow back to crankcase after motor is off.The cobra also has a deeper bowl in back side of intake where oil can pool. I'm out of ideas, Its a pain in ass to have to clean out intake all the time, I may just go back to stock intake. thanks for the feed back
I didn't expect this big a response to this issue, just a added note, with my stock intake set up i was not getting the oil pooling in intake, that was without oil seperator. The plugs were clean also after 3000 miles, maybe the design of stocker allows oil to flow back to crankcase after motor is off.The cobra also has a deeper bowl in back side of intake where oil can pool. I'm out of ideas, Its a pain in ass to have to clean out intake all the time, I may just go back to stock intake. thanks for the feed back
