393 oil consumption problem

M

MadMikeyL

New Member
Apr 3, 2004
16
0
1
#1
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Hello all. I don't post here too much cause I drive a cougar, not a mustang, but I have a problem that I can't figure out, so I am trying everywhere I can think of to see if anyone knows what is going on. The situation is I just finished swapping a 393 into my 91 cougar. The engine runs good (has a few tuning issues that still need to be sorted out, but overall runs good for a fresh build) and pulls like crazy. The problem is it is burning oil at an alarming rate. When I first started the car, it was blowing enough smoke that you couldn't see through it, even at idle. The smoke calmed down a little bit, and now it doesn't smoke at idle, but every time I get on it, it still lays down a ton of smoke. So far I've driven the car a total of about 30 miles, and in that time (plus the time idling, maybe an hour total in 3 20 minute segments) it burned 2.5 quarts of oil! I was driving it today, and it lost oil pressure so I pulled over and checked the level and there was nothing on the dipstick, so I topped it off with 2.5 quarts and the oil pressure was fine, so I drove it to the shop (only about 5 miles) watching the oil pressure gauge the whole time.

Now, I built the motor myself, and I checked every ring end gap, staggered the rings properly, checked all the bearing clearances, etc. so I know all of those things are correct. I used low tension moly rings, so at first I was kind of hoping that the rings just needed more time to seat, but now having burned so much oil, I know there has to be something else wrong. Hopefully someone will know what is going on. Thanks in advance.

Mike

PS. Pics of the car are located at http://www.putfile.com/blenderhead/images/150240
 

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#4
I don't know what could cause it to use this much oil. I parked the car at the shop and had my grandmother give me a ride home cause she lives just down the street from the shop. Tomorrow I'll do a compression and leakdown test and see what I find. One guy on tccoa.com said that the holley systemax heads have a problem with valve guides, but I had the heads apart and the guides and seals seemed ok. Also I have the systemax 2 heads, and I thought they fixed the problem with the newer heads, but I haven't ruled that out yet. I guess I'll do a compression and leakdown test, and if those are good then it has to be the valve seals, and if they aren't it has to be the rings right? I mean, those are the only 2 ways that oil could get into the combustion chamber at all.
 
#8
I did a compression and leakdown test today. All the cylinders showed between 165 and 175psi, and 2-3% leakdown, so at least I don't have to tear apart my bottom end. All 8 spark plugs were black with oil, and when I removed the upper intake so I could get the valve covers off to check the valve seals, I noticed oil in the upper intake manifold. At this point I suspected the PCV valve, so I replaced it, put everything back together, and took it for a ride around the block. The smoke didn't clear up at all, so I guess that wasn't the problem. I guess tomorrow I will disable the PCV system and take it for a ride again, and if it still doesn't clear up, I'll check all the valve seals though. I find it highly unlikely though that the machine shop that put my heads together would screw up all 8 intake seals though. I'm wondering if there could be some problem from having the breather that came in the valve cover and still running the factory PCV valve in the intake manifold?
 
#9
Ok,first off either set-up the PCV system properly or remove and block it and use 2 breathers going into a tank.Way you got it now,it would pull un-metered air into the engine.Oh,and look into valve cover baffles using either set-up.

The low tension rings weren't a good call if this is a street car,many are made to be used ONLY with a vacuum pump. If you can't afford a aftermarket vacuum pump system,get a Isuzu Trooper II (maybe on there trucks too?) smog-pump from mid 80's.They have actual inlet/outlet fittings that you can put a rubber or maybe stainless braided rubber hose over with some hose clamps.

The last thing is...does it leak oil? Simple I know,but you might have a seal that leaks only when the car is runing.
 
#10
Hey madmikeyl, if you have teflon seals they are the problem, i had the same exact problem with my 393. i changed to the viton seals and no problems. i was burning oil the same way you are. check your valve seals. good luck, let us know how you made out....
 
#11
If you are getting oil through your PCV system, which is sounds like you are with oil in your upper intake, the PCV valve is not the problem!!! Do your valve covers have baffles? If they do not, that is likely your problem. There is no way your rings are causing you to burn that much oil. I would also look for leaks somewhere as was already recommended, maybe on the exhaust pipes especially.
 
#12
There are no external leaks at all. I used whatever valve seals came in the fel-pro head kit, so I don't know what they are made of. Today I'll try disabling the PCV system first, since that is cheap and easy, and if it still burns the oil I will pull the valve seals and swap them.
 
#13
Ok, a little update here. I pulled the valve springs off, and found that the valve seals that the machine shop put on there were too big, and the inside spring on the holley heads ripped every valve seal to shreds. With the help of a friend of mine who has been helping me with the car, we replaced all the valve seals, and I let the car idle for a couple hours to clear any residual oil out of the intake, and as soon as I got on the gas, it has the exact same problem- a cloud of blue smoke so thick I can't see throug it every time I accelerate! Does anyone know of any issues with these heads chewing up valve seals? Maybe they need some special ones or something? Probably tomorrow I'm going to pull a couple valve springs off and take a look at the seals and see if they got chewed up again. If they did, I don't know how to go about fixing this. Maybe holley makes special valve seals for those heads or something. Anyway, if anyone has any ideas or experience, let me hear them. Thanks.

Mike
 
#14
Well, your valve seal problem is not your whole issue, there is definitely something else because you have oil in your intake manifold. There should be zero oil in there. The valve seals going bad and getting ripped up will not put any oil in your intake. I really think you need to concentrate on setting up your PCV system properly first, because that is the easiest, cheapest, and most likely problem. The only other way to get oil in the intake is if your intake gaskets are bad, or some other source of vacuum that is hooked up to anything that could possible leak oil.
 
#15
i might be wrong but.... in picture 28, isn't the hole at the back of the lifter valley supposed to have a freeze plug in it? i think we had that come loose in my brother's old 302 and it caused us to loose oil pressure, didn't burn it though.
 
#16
You will problably hae to have the guide machined and a spring cup with a center guide put on to keep your springs from walking are you sure your retainer is not hitting it. That will clear that problem up now if you get yourself a vacuum pump or a new set of rings you can loose the cloud of smoke that follows you. What heads are you runnin? Stud mount?
 
#17
It wouldn't be unusual to find oil in the upper intake from bad valve seals.

Get a hold of Holley and see what they have to say...
Did the springs come from Holley? Or another shop/vendor?

There could be other things contributing to the problem you're having, but the seals should be fixed before getting too worried about other possibilities...

jason
 
#18
Fast63, I had the PCV system disconnected, leaving just a breather in the valve cover, and I still had oil in the intake. I have since hooked it up with the PCV valve in the valve cover instead of the intake, since I thought that might be the problem. There was no change. The amount of oil in the intake isn't a lot, it's just a residue on everything. This car is very basic, and the only things that have vacuum hooked up to them are power brakes, FPR, and a vac. gauge, so there isn't any other place that oil could be getting sucked into the intake, unless its either a normal amount from the PCV, or its coming from the valve seals.

talladam, there is a plug in that hole.

punisher, the rockers are stud-mount. What makes you think the springs are walking? I suppose it could be the retainer hitting, I guess I'll find out for sure tomorrow. Also, I'm sure this problem is not the rings. I've seen enough motors with bad rings, and the amount of smoke they make. Also if it were the rings, it would make more smoke on decel, but as it is, it just lays down a wall of smoke on accel. It is seriously so thick that I can't see through it. There's no way rings could be letting me burn that much oil.

vristang, I bought these heads used, so I don't know for sure where the springs came from. I just assumed that they were the ones that came on the heads from holley. At this point, I don't know for sure that the seals are messed up again. I'll find out tomorrow, and if they are, I will definitely be on the phone with holley to find out what is going on here. I already have their tech line number programmed into my cell phone.
 
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