[70oldgoat]

I need some suggestions on where to start looking.

During March/April, 2009, a local garage rebuilt my 1970 400 engine. Restoration of the car was completed the following year. I only drove the car locally just a few miles at a time to shows. I did not pay much attention to the oil consumption as I changed the oil every four or five months whether it needed it or not. Until the first of last month, I had only put a little over 2000 miles on the engine rebuild.

Then, the first of June the wife and I put about 2600 miles on the car on a ten day road trip.

Driving a consistant 55 to 65 mph, the motor used an average of a quart of oil every 300-400 miles.

No noticable blue colored smoke except just a little every now and then when I first start the engine.

Driving at a steady speed, I get no noticable smoke.

At times I get quite a bit of black smoke when I accelerate WOT. It doesn't happen all the time. The black smoke at WOT doesn't happen all the time. When it does occur, it comes from both sides.

At the end of the day on the road trip, I would have a little black on both sides of the rear bumper from the exhaust, but it wasn't bad.

Sometimes when I start the engine, I initially get black water spitting from both tailpipes, but the substance does not look "oily" and cleans up easily.

Before the 2600 mile trip, I changed the points and plugs. I changed the plugs again when I returned from the trip. The four plugs I changed out on the right side appeared "blacker" than the plugs from the left side and a couple of them were slightly "wet".

No leaks.

Other than using the oil, the engine starts and runs great.

I am using Valvoline VR1, 20-50 weight.

I use 93 octane pump gas. I do not add anthing to the gas. The engine does not "ping".

Anyone want to hazard a guess as to why my engine is using so much oil?



The 2009 rebuild was as follows:

Engine Was Balanced
Value Job + New Seal and Resurface

Cam MC 1778 In. 204 L. 420 L.S. 105
EX-214 L. 443 L.S. 115
Cam Bearing P-4 Dura Bond
Double Roller Timing Set
Freeze Plugs
Gasket Set, Fel Pro – 260 – 1025
Intake Valve Guides
Main Bearing MS 496P STD
Oil Pump, M 54 DS Melling
Pistons, Speed Pro L2262F 030
Rear Main Lip Seal, B.O.P.
Rings – 40784
Rod Bearing CB 758P STD
Torque Cam & Lifter Set


Thanks.

[getmygoat]

Having plugs on one side with an issue might indicate something with the valves on that side. I recently had an exhaust restriction on one side that burned up the value guides on that side.

Another possibility - the black smoke likely indicates you are running too rich - you could have a stuck float or just improper tune/calibration. - if you have too much gas in the mix - you can potentially wash the rings out... i.e. the gas runs down the cylinder walls and washes away the oil, resulting in ring wear.

Other than that, perhaps a compression test is in order - as experience has shown at least with this enthusiast, having an engine rebuilt doesn't really provide an indicator of engine condition- as more often than not, the rebuild is not done properly resulting in an engine with a short life.

[70oldgoat]

Darn, my bad - I did not mention the compression check.

I did one when I changed out the plugs after the road trip. Compression readings were almost all same with a couple +/- not more that 15 difference.

I understand your comment RE the carb running too rich. Will check that. Thanks.

[BB70]

If its not leaking it, its burning it. I would have someone follow you on a test drive and get a real view of what's coming out the tail pipes. Try to get a hand signal set up to when you are under decell at a fast road speed. If you have smoke under decell its a valve guide-seal issue. If its under steady road speed-throtlle setting, I would lean towards a ring seal issue.

If you leave the spark plugs in for about a 1000 miles or so you can examine them to see what cylinders are the culprit. They will have a white crusty buildup on them indicating oil consumption.

Hope this long winded reply is of some help.

John

[ID67goat]

What are you running for a PCV setup?

[70oldgoat]

Factory PCV installation. Has been checked and is functioning correctly.

Thanks for suggestions.

[Goatoligst]

I know this seems dumb but I had the same problem. I was using valvoline 10w 30 and 10w40. I starting using Pensoil 10w30 and problem solved.

[67drake]

I see this was an old post,but you never mentioned if you broke those rings in when the engine was fresh. "I only drove the car locally just a few miles at a time to shows" - I assume that was around town too,is not the best way to break in a new engine.

[70oldgoat]

Thanks for the input, guys.

Quote: "...the black smoke likely indicates you are running too rich...if you have too much gas in the mix - you can potentially wash the rings out..."

Quote: "...If you leave the spark plugs in for about a 1000 miles or so you can examine them to see what cylinders are the culprit."

Quote: "...I was using valvoline 10w 30 and 10w40. I starting using Pensoil 10w30 and problem solved..."

Quote: "...drove the car locally...I assume that was around town too,is not the best way to break in a new engine."

After my first post, the car was put on the back burner for a while. Early on, after changing the oil, I was looking at my reproduction tires and noticed one of them was damaged. It took about four weeks to get the tire exchanged, mounted and back on the car.

Then, the car started having an electrical problem. Turned out the wire that goes thru the bottom of the distributor had come loose and was shorting out. It's fixed now. What the heck, it's a 40+ year old car...

Anyways, concerning the oil consumption issue, I am going to start with the "simple" things first. We spoke with the engine rebuilder. Eventho it had been quite a while since he did the rebuild, he was more than willing to stand behind his work. He offered some of the same suggestions this forum did.

Per above suggestion RE the carb running too rich. This apparently is not all that uncommon. On occasion, I had noticed the smell of gas after stopping the engine. Minor adjustments were made, I don't smell the gas now. Wait and see.

I changed the oil and added Lucas oil additive. Wait and see.

The car has been driven a couple of hundred miles locally and so far, has not used much, if any oil. No smoke noticed except for small puff of blue smoke sometimes when the car is started. It continues to run strong and smooth.

The real test will be next month when the wife and I take the car to the Gulf Coast for the Mississippi cruise thing. Wait and see.

It may very well be I did not break in the rebuilt engine correctly as mentioned, but I wanted to start with the easy stuff first. I intend to check the plugs at 1,000 miles as was suggested.

If it uses oil on this Mississippi trip, I will go back and start over.

I'm retired and enjoying my cars (this "restored" car plus two other 70 GTO project cars). I learn something every day from this forum.

Thanks to all.

[70oldgoat]

UPDATE

I'm at a loss. Oil consumption still continues.

I have three cars. Two 400s and one 455. All three rebuilt.. One of the 400s and the 455 by one shop. Another shop did one of the other 400s.

All three use oil at a quart every 300 - 400 miles on the road at steady highway speed of 60 - 65 mph. All three cars have been on trips of 2000 - 3000 miles.

All three have about 5000 miles each on the the rebuilds.

The cars are not leaking the oil. Smoke is not noticeable at highway speed. All show black smoke at WOT.

I have changed brands of oil to no effect.

All spark plugs look same. All look "clean". The cars all start and run great except for the oil consumption.

Any thoughts?

[68WarDog]

You might consider putting some fluorescent dye in the oil, get your black light out and search everywhere, including the tailpipes for leaks. Years ago I own another 68 and was losing oil past the valve seals and it showed up in the tailpipes with dye

[pggto]

Wow, that's pretty crazy that there all do the same thing. Whats the common denominator with all three engines? Did you use a synthetic oil when breaking them in? I hope not. Did you assemble the engine or did the two engine shops? Might want to post this in the Pontiac Street section, there's a lot more engine people that frequent that section. Hope you find a solution.

[70oldgoat]

Originally Posted by pggto

Wow, that's pretty crazy that there all do the same thing. Whats the common denominator with all three engines? Did you use a synthetic oil when breaking them in? I hope not. Did you assemble the engine or did the two engine shops? Might want to post this in the Pontiac Street section, there's a lot more engine people that frequent that section. Hope you find a solution.

Two of the engines are original to the cars and the shops were asked to rebuild them as close to factory specs as they could. Stock Q-Jet carbs, original intake manifolds, original heads, original exhaust manifolds. Using factory spec spark plugs. Stock exhaust systems. Only difference from stock with these two cars is I am not running points in the distributor.

All plugs in all three look to be burning the same. No indication any particular cylinder(s) is the issue..

Also, both sides of the rear bumpers show the same amount of "some" discoloration after 200 - 300 miles. Two of the cars do not have "cross over pipes" so each side of the bumper(s) shows results from it's corresponding exhaust manifolds. No one side of the bumpers show more discoloration than the other side.

Therefore, as the plugs look to be burning the same and the bumpers' discoloration appears even on both sides, I figure maybe whatever is going on is happening evenly in all the cylinders.

One of the local guys suggested oil mist may be moving into the combustion chambers thru the PVC valves. I personally have my doubts that could be happening in all three cars. At any rate, I have changed the oil this morning in one of the cars and disconnected/plugged the vacuum line from the PVC valve. I will drive it a couple of hundred miles to see if there is any difference in the oil consumption.

I used Valvoline VR1 20-50 in all three of the engines from the get go. I did change the oil on one occasion in two of the cars to regular Pennzoil 10-30 on the off chance that would make a difference. It did not and I have since gone back to the VR1.

[pggto]

If you block off the PCV valve you might need to put breathers in the valve covers to let out some of the internal pressure. (I think)

[70oldgoat]

Originally Posted by pggto

If you block off the PCV valve you might need to put breathers in the valve covers to let out some of the internal pressure. (I think)

Yep. Thanks for the tip.

The valve covers are stock so the passenger side has a vent tube running from the top of the valve cover to the air cleaner. Under normal operating conditions, I understand that tube is for input of fresh air into the system. Without the vacuum hookup to the PCV valve, I'm thinking the breather tube should temporarily function as a "relief" for any internal pressures.

The valve cover on the driver's side has the oil filler cap.

I plan to run up and down the highway for just a couple of hundred miles to see if there is any change in oil consumption. Then it will all go back together. I put 50 miles on it today. I will finish up the test by FRI.

[Carmine]

My very limited experience with this issue. I had the 409 engine in my '62 Impala SS rebuilt about 2 years ago. Top to bottom. Professional rebuild. Even dynode it before installing. Short story, it used a quart every 400 miles. Break in they said. 2000 miles later, still using the same amount. Spark plugs were clean and never fouled. Engine ran well except for the oil consumption. I determined that the oil was being used from the top down and not the bottom up, as if bad rings were the source. Asked the machinist about the heads, namely the valve guides. He said they appeared fine and weren't replaced. Wrong. This is the only thing it could be. Reluctantly and unfortunately, took the heads off and back to the machine shop. New valve guides installed. Heads put back on. Have run the engine about 1000 miles with no oil consumption at all. Right on the mark. Hope this is helpful to you, Carmine.