Rebuilt Engine Using Oil-AOD

GBS 90 SC

Registered User
After a recent engine rebuild, I need to add a quart of oil about every 800 to 900 miles. I have about 2,800 miles on the engine now and a bit concerned. I hear engine knock at about 1200RPM and after the engine is good and warm. Most recently I have noticed an occasional puff of white smoke coming out of both tail pipes(hard acceleration). I changed the PCV valve to the Motorcraft about 2 weeks ago, just to make sure that wasn't the problem.
Could this be a stem seal problem? Anything else?
I have also ordered a new knock sensor from Ford.
 
If the engine is burning the lost oil, then it will knock.

If the engine was rebuilt, the valve seals should have been replaced when the heads were done.

You could be sucking in oil through the intake, if the gaskets are leaking.

I am assuming you don't have any leaks.

Did you do the rebuild, is so tell us what was done?

Aaron
 
The engine was completely rebuilt by a local shop, top to bottom.
I would assume that intake and exhaust gaskets were replaced.
Are the valve seals different for SC's than standard 3.8L engines?
Thanks for the response, Aron
 
Could be the piston rings havent seated yet. Are you using synthetic oil? Was this engine bored?:)
The valve seals are the same for both engines.
 
Yes Mike, the engine was bored .030" over. I am using regular Valvoline 10w/40 motor oil. It sure is using a heck of a lot of oil...
 
Do you know what kind of rings they used in the motor?
Has the engine always used this much oil since the rebuild?
How have you driven the car to break in the engine?
 
The builder used "moly" rings. The oil usage has been the same since I got the car back from them. It was recommended that I drive the speed limit for the first 1K miles so I didn't waver from that. Since then, I've had my foot in it like I would. I never added oil to this car between changes until I had the engine rebuilt.
 
Oil consumption

Sorry to argue with MIKE38, but I believe the stem seals are different than a N/A 3.8. If you are getting white smoke out the back, thats usually water in the cylinders, correct me if Im wrong guys. Are you sure its white smoke? If you are burning oil it should be blue. Check for external oil leaks first. If you dont find anything there, do a compression check. Something is definitely wrong here, my rebuilt sc stopped using oil after about 1000 miles.
 
Actually James, I think it is more "blue" than white. It is difficult to tell because it will only smoke once in awhile. In stop and go traffic on the highway, when I accelerate, is when I see a pretty good amount of smoke. But just for a second ot two. It does this only when the engine is warm/hot.
I agree, the rings should have seated by now. Do you know what kind of rings were used on your rebuild?
 
James5275:

Sorry to argue with MIKE38, but I believe the stem seals are different than a N/A 3.8.James we're not argueing, you just disagree with me. But then again I did'nt say anything about the valve seals. Anyway I looked the part #'s up for the NA and SC engine and they are the same.

my rebuilt sc stopped using oil after about 1000 miles.1000-1500 miles is normal but there are exceptions to that rule. Thats why I asked what type of rings were used.

GBS 90 SC:

The builder used "moly" rings. The oil usage has been the same since I got the car back from them.Those rings with the proper finish on the cylinder walls should have been seated by 1500 miles at the most. Since your oil usage has not waivered since the rebuild it sure sounds like they are not seated yet.

It was recommended that I drive the speed limit for the first 1K miles so I didn't waver from that.Thats good advice but more importantly they should have told you not to keep the engine running at a constant RPM such as highway driving. It is much better to vary the engine RPM accelerating and decelerating as much as is possable and safe to do on the roads your driving on. A better way to break in the engine is stop and go traffic, now I'm not talking about the kind of stop and go traffic you would experiance in a big city where you may end up idleing for very long periods of time. Do you understand what I mean?

Since then, I've had my foot in it like I would. I never added oil to this car between changes until I had the engine rebuilt.I DO NOT recomend that you drive the car in that manner yet, if you continue to do so the rings will never seat. Try driving it for awhile as I described earlier and when driving around in town or at speeds of 55 or less take the tranny out of OD so that you can use the engine for alittle braking, this will help to seat the rings. I recomend that you accelerate(NOT hot rodding) at a good medium pace and let off and coast using engine braking as much as is practical. That is the best way to seat rings not highway driving where you stay at a pretty constant RPM.

If after a couple hundred miles or so you see no improvement let me know and I'll tell you about something else to try.
I dont want to get into what it is right now because I beleive in doing it the right way first and I save this trick for those engines that are really stuborn.:)
 
Mike-
Thanks for the great advice. I will try and use the engine to "brake" as much as possible for now. To be honest, much of the milage I have put on this engine has been stop and go. The traffic on I-80 dictates that style of driving. I will, in addition, try and use the engine's compression for stopping as much as possible in the near future.
Will the engine stop knocking after the rings have seated?
Do you think a new knock sensor would help?
 
Will the engine stop knocking after the rings have seated?
Cant say for sure, but I dont like the fact that its knocking. Have you talked to your engine builder about these problems? I think maybe you should. He may want to check some things before it blows. I hope your running a stock blower pulley for now until you get the engine good and broken in. How bad is this knocking?


To be honest, much of the milage I have put on this engine has been stop and go. The traffic on I-80 dictates that style of driving. I will, in addition, try and use the engine's compression for stopping as much as possible in the near future.
Hmmmmm........What kind of vac are you showing on your boost gauge at idle? Are you using a stock cam? When letting the engine brake the car please dont foreget to just hit the brakes hard enough to light the brake lights when traffic is behind you. Dont want to cause any accidents because some numb person failed to notice you were slowing down. Fact is it doesnt hurt to use the brakes along with engine braking so I advise using brakes as well. I just did'nt want you to get the wrong idea as to what I meant. Have that talk with your engine builder and let me know what he thinks about whats going on with your engine.
 
I just advised the builder of these issues and he thinks that the rings just haven't seated yet. He mentioned something about checking the spark plugs to see how they look. He does though, want to take a look at it next week. The concern being the knock.
I can only hear the knock(fairly loud, about 1-2 seconds)when the engine is hot or going up hills. I can't hear a thing when it's cool.
I have kept everything stock so I wouldn't have these problems.
But guess what?

Am I potentially causing damage by driving it this way?

No worries, I won't let anyone plow into me.

I'll look at the vac at idle and let you know tomorrow-
Thanks Again,
Greg
 
why is it that everyone thinks that a motor will not break in with synthetic oil.

Corvettes, all porsches, Mercedes AMG, Viper, Mustang Cobra R, Aston Martin, all use synthetic straight from the factory, never hear of any problems with rings seating correctly. Just curious on why this myth is all over the place? There seems to be a lot of myths about synthetic, like you can't mix it with normal oil, or that it will make the engine leak, or that once you switch you can't switch back. Any info would be great.
 
why is it that everyone thinks that a motor will not break in with synthetic oil.
I think youre reading far more into my qeustion about what oil he was using than was there. I at no point said that synthetic could nt or should not be used during break in. Infact I broke in the wifes new SVT 2 years ago on the stuff so I dont have a problem with it. I will say this though breaking in an engine with synthetic will take longer to do. That was all I was getting at, so dont be so sensitive. ;)
 
oh no don't take me wrong mike, I know that you weren't saying that. We are in a middle of a hurricane and i was not typing to clearly. :) I just always see people saying things like that and I just always wondered why a bunch of people think synthetic is tricky to use. lol :)


I don't know how many times i hear people coming up with all of these different things you can and cannot do with synthetic.
 
Ahh were cool!! So whats that Hurricane like?
I got to watch a tornado jump over my place this spring.
I dont ever want to do that again! We were very lucky.

I know what you mean about the synthetic oil thing. I've been using it for over 20 years and if there was anything bad about it my first time to use it would have been my last.
Some of the things that get said about synthetic oil just keeps me on the floor laughing.:D

Batten down the hatch's and stay safe. ;)
 
Well pulling that kind of vac at least the compression rings are seated. The problem may just be the chrome oil rings havent seated yet.
I know you had Moly rings installed but only the compression rings are Moly, oil rings are chromed and chrome takes alittle while longer.
Get the car to your engine builder and let him take a look. Ask him about using 5W30 oil in the engine, that may help them seat alittle quicker.
Before you get it to him why dont you pull a couple of the easy spark plugs and see what they look like. Its just something good to know.:)
 
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