Riddle me this batman -

[Duke Mk1a]

Riddle me this Batman -

Just completed a 1100 mile round trip to Fort Campbell in the Tiger.

Here is a pic of my plugs I just pulled. Let me know what you think.

While on this 1100 mile road trip I noticed blueish smoke from the exhaust on powered deceleration. I just figured that my new carb is running rich and I will have to jet it down. I also used two quarts of oil during the trip. I figured it was due to the rear main leak getting worse.

Plugs do not indicate a rich or oil burn condition......what is causing the smoke? Also included are two pics of the tail pipes. The right pipe shows where I wiped all the crud off of the bumper from the smoke. Any ideas would be great.

 

[Moondoggie]

Bummer Duke........

2 quarts of oil in 1100 miles is not very good. First thing to do is a compression check to rule out rings. If that checks out then the cause is most likely valve seals or a bad manifold seal. Looks like you will be pulling that motor soon, did you NOT machine the rear main for a one piece rear main seal ? If you blew that much oil out the rear main the under side would be soaked in oil. Speaking of rear main leaks, did you use teflon tape on the
flywheel bolts ???

Moondoggie

 

[Bryan]

oil

duke- blue means oil- usually thru the valve seals/guides-

 

[Duke Mk1a]

1991 5.0 HO block. Has one piece rear main.

The guy who worked on the heads install Teflon valve guide seals. My simple rear main seal replacement just got a lot more expensive....the stinking head gaskets are over $100 alone. What are good compression numbers for a 10.8:1 engine?

Update, compression numbers (dry) -

#1 85
#2 110
#3 115
#4 100
#5 105
#6 105
#7 110
#8 105

WTF #1, new engine one year ago with just a few thousands miles? No smoke on acceleration and #1 plug is not oil fouled. How about this -"The engine be ingesting oil via the PCV system during decel. The intake manifold is at max vacuum during decel" I had to remove the baffle for the VC to fit over roller rockers.

 

[Duke Mk1a]

Speaking of rear main leaks, did you use teflon tape on the flywheel bolts ???

Moondoggie

No. Would be so nice to know these things. I used locktite blue.

 

[Moondoggie]

Duke,

The compression should not vary by more than 10 lbs per cylinder so they all
look good except #1. Now it could be that the rings have not set yet in #1 if you can do a leak down test on say #1 &#2 that should tell the story on #1.
Now if you removed the oil baffle in the valve cover for rocker clearance
you could be pulling oil from there thru the pvc valve. You might try disconnecting the pcv and see if the blue smoke goes away. You can plumb in an oil catch can in the pcv valve line as a long term solution. I am going to have to do the samething on my new 306 as I know the rockers will not clear the baffle so I won't run the baffle either. The baffle came off in my old engine
and was eaten by the rockers going down to the pan and then back thru the bearings...it was ugly !!!

Moondoggie

 

[66TigerMK1A]

I thought most roller rocker-ized SBF's have oil restrictors installed which would lessen the oil available for the PCV to suck out of there??

I have a 306...roller rockers...restrictors, PCV and no baffles but can't say that I've had any oil consumption problems...


Jim
B382000446

 

[Moondoggie]

No. Would be so nice to know these things. I used locktite blue.

The rear main seal mates to the OD of the rear crank flange so there
is oil pressure applied to the back side of the flywheel bolts. I don't know if
locktite blue is a good sealant which is what you need on those threads. When I took my tranny off the motor I found that my rear main seal leak
was really the oil getting past the flywheel threads,whomever put it together
used nothing !!! Oil was everywhere in the bell housing but the clutch still
worked......

Moondoggie

 

[Moondoggie]

I thought most roller rocker-ized SBF's have oil restrictors installed which would lessen the oil available for the PCV to suck out of there??

I have a 306...roller rockers...restrictors, PCV and no baffles but can't say that I've had any oil consumption problems...


Jim
B382000446

I would think that the oil requirements would be the same since they are just
rockers. But as you said, you aren't having a problem and I know of several others not using a baffle and it works fine for them as well. That said, it is something easy for Duke to look at before biting the bullet and pulling the motor....I will be at my engine builder on Wednesday next week so I will make a point of asking him about restrictors.

Moondoggie

 

[Duke Mk1a]

I would think that the oil requirements would be the same since they are just
rockers. But as you said, you aren't having a problem and I know of several others not using a baffle and it works fine for them as well. That said, it is something easy for Duke to look at before biting the bullet and pulling the motor....I will be at my engine builder on Wednesday next week so I will make a point of asking him about restrictors.

Moondoggie

There is enough oil to be weeping around the PCV value gasket on the valve cover. Bottom of PCV valve has oil on it and in it. I had/have a problem of oil filling the cruise control vacuum line that is tapped into the PCV line to the carb.

Great idea on the catch tank. You guys rock.

 

[Bryan]

bryan

duke- all compress look on the low side with#1 the worst. try putting cyc on TDC and putting a rubber tipped air nozzle in the spark plug hole, if you hear air leaking thru carb that would give you a lot to go on. leak down test is as good as it gets.Bryan

 

[0neoffive]

Read them plugs

Plugs #4 & #8 show a diluted oil burn consistant with coming in from the pcv valve and mixing with fuel air below the carb. Plug #1 shows more oil saturation and I would be apt to hook the air hose to the plug hole and look for either valve guide leak or oil ring failure. In any event, the rate of oil use is not a fun issue. Post road draft tube SBF's had a natural crankcase overpressure condition from the get-go and a common rule of thumb was 1200 miles to the quart was acceptable.

 

[cobrakidz]

If you rub the exhaust tip is it black? Feel oily?

 

[TigerBlue]

Is it broken in yet??

Back in the day new engines got break in oil. Something single weight and low viscosity. 10 or 20 I think and advice was to limit throttle and rpm while varying cruise speeds. Break in oil was changed out at 500 miles?

"Breaking in" the piston rings was helped by marginal lubrication. Break in requires wear of piston rings and bearing high spots. This initial wear is important to compression and bearing life in the long term.

Manufacturing tolerances are much better today so the importance of proper break in is diminished but not eliminated. New parts (engines) need to break in.

What oil have you been using? The best synthetic? Do you have chrome rings?

The previous owner and engine builder of Tigerblue used Mobil One from the start. Oil consumption has improved over time. That's the good news. No really bad news.

I also have roller rockers and no baffle in the LAT valve covers. When I had Rhodes Lifters (variable lift) I had smoke on high speed downshifts. (open track events 2 - 3 times a year) The Rhodes lifters passed a higher volume of oil than conventional hydraulic lifters. That extra oil in the space under valve covers must have resulted in more oil sucked into manifold through PCV.

Oil consumption has reduced over time (break in?)and changing to standard hydraulic lifters has stopped the puffs of smoke on downshifts.

Rick

 

[Duke Mk1a]

Great points guys.

I am using Clevite Perfect Circle Moly Rings and have run 10W30 dyno oil from day one.

Compression numbers....will do some of the checks a look for a different gauge as mine is old and cheap. I am going to do a leak down test of #1 and check valve clearance of rockers.

 

[chirodoc]

OIL CONSUMPTION

If your engine is sucking oil through the PCV valve, JEGS has an air /oil separator for $ 47.00 (555-52205) which is a whole lot cheaper than an engine teardown for the oil consumption Problem.

 

[Duke Mk1a]

Leakdown test of #1 shows a 6% loss. I can hear a leak of course but 6% is healthy.

Rockers are completely loose.

Compressor regulator is set to 100 PSI, test rig regulator open completely and showing 100 PSI, leak gauge indicates 94 PSI. I made the tester from plans on the internet. Called around to see if anyone had a professionally made loaner with no luck. Did a comparison check of #2 and got a 4% loss of pressure.


Just did a wet compression test and got 100 PSI.

Thoughts?

 

[cadreamn67]

Where do you hear the leaking air coming from? Intake manifold/carb? Exhaust pipe? dipstick or oil breather? That tells you where the bad seal is.

If by wet test you mean you squirted oil in the cylinder and got no pressure drop, it must be the rings are leaking. Does that match with where you heard air leaking? Did the leak noise stop?

It could be that the gaps in your rings are not staggered on that cylinder. If they are lined up, that might affect your compression seal and cause that cylinder to read low overall. But as you say the amount of leakage itself seems with reasonable limits. But the absolute compression is low. Two different things of course.

I, for one, would vote for the PCV valve circuit being the culprit of your oil consumption problem. Some discussion on the "List" not long ago about that similar to comments already made here. The list posts include one by Jerry Christopherson on how he make a baffle compatible with his roller rockers to fix the problem.

I am intrigued by Chirodoc's suggestion. Do you have such a device already on your air compressor? If so maybe you could remove it, temporarily plumb it into your PCV circuit and test for blue smoke. Out of the exhaust on deceleration of course! It would also collect any oil going through which you could see in the filter. Or more simply, just block off the PCV to manifold connection as Moondoggie previously suggested and do a test drive.

Gene

 

[Duke Mk1a]

HEY, just thought of something! Do you need to have the carb fully opened or removed to do a compression check? I did the checks with the carb on and throttle closed. Seems to me it would be hard to get proper air in the cylinders and thus the low numbers.

Update - Compression test procedure.

Yep...I shanked it. Just read that the engine should be warm, mine was overnight cold and the throttle plates should be wide open, mine were closed. The artical I read had a guy with 120 psi that went to 160-180 psi with the engine warm and carb plates wide open.

 

[chirodoc]

OIL CONSUMPTION

Food for thought:
In the latest issue of MUSTANGS AND FAST FORDS magazine, in one of their featured cars, it took the owner four tries with various engine builders to solve his engine's smoking problem. The cure: replacing the Teflon valve stem seals with Vinton seals. ($20.00 from Jegs or Summit)