Seating the rings (part 2)

[texasturbo]

I just had my engine freshened up with new bore job, pistons, rings, cam, bearings, valve springs, all that good stuff. I still have one cylinder that gets the threads wet with oil up to the seat of the spark plug. The engine now has about 600 miles on it. When I first started the motor I broken in the cam and lifters and then as I drove it, I would not beat on it, but drive around in third gear at a decent speed, and put a 190 thermostat in it to make sure the engine was good and hot for the new rings( it never overheated). I have not put more than 15 lbs of boost in it ( very very short burst when I did). The pistons were speedpro cast turbo pistons/ with moly rings(part # e-434k). Anyone else had this problem? Any thoughts on a solution?? Thanks in advance...

P.S. for the break in I put everything back stock on the engine,(turbo, fresh injectors, chip, intercooler etc. etc.).

 

[Intercooler]

Well more heat in the engine will cause the block to expand more. Running cooler will make the cylinders tighter for ring seating. Are these cast pistons or hyperutectic? Cast pistons will get hot and grab the pin causing your pistons to be two piece Sounds like you have something going on there. Maybe it is time for a compression/leak down test.

 

[lazaris]

"Running cooler will make the cylinders tighter for ring seating"

I disagree there. The block and its mass will not expand more than the piston and its ring set. The hotter the piston the tighter the seal of the ring.

 

[Steve Wood]

Were the pistons really cast or Hypers?

What clearance was used? Is the electrode oily or does it look like the others?

A hotter engine will be a tighter engine...the pistons will expand more than the block.

 

[Intercooler]

Originally posted by lazaris
"Running cooler will make the cylinders tighter for ring seating"

I disagree there. The block and its mass will not expand more than the piston and its ring set. The hotter the piston the tighter the seal of the ring.

Ok to disagree but here is a bit of info that may cast doubt on your theory from years of Speed-Pro testing. This is from their site that I put in another post:

There is some controversy as to the effect of water temperature on ring end gaps. Some racers feel that if their water temperature is low, compared to another engine of identical size, they could narrow up on ring gaps This is not true! Basically, piston and ring temperatures remain the same whether the water temperature is high or low. Theoretically, if you consider thermal growth or expansion, be it ever so slight, the engine with hotter temperature would have bigger bores. The engine with the lower temperature would have smaller bores. The above chart was developed for “normal” engine temperatures. If your engine water temperature tends to be low, you should run a larger end gap than recommended to compensate for the smaller bores.

Maybe I am taking it out of context but just common knowledge of metals shows the more you heat a piece of metal the more it expands. I guess this is the reason people heat pipes and such to get them apart. JMO on it but seems an engine where the cylinder bores are running 200º will swell more than one running at 170º making your effective ring gap, etc.. looser. Guess this is also kind of the reason most machine shops like to measure cylinder bores at temps near ambient room temp. We checked the bore on my last motor after pulling it off the back of the truck in the hot sun and measured it hours later and it varied 1/2 of thou. I guess my point is running it on the cooler water temp side of the coin would help in keeping the metal temps down also.

 

[Intercooler]

Originally posted by Steve Wood


A hotter engine will be a tighter engine...the pistons will expand more than the block.

Correct, aluminum does have a higher expansion rate than iron:http://www.handyharmancanada.com/TheBrazingBook/comparis.htm

It is a balancing act of running the right piston to wall clearance so it isn't too tight or too loose at the desired operating temp and use intended. More heat (piston) , more piston to wall needed. Less heat (piston), less piston to wall needed. A hotter engine (cylinder walls) with a colder piston will be a much looser engine as evidenced by piston slap on start-up with forged units.

 

[Steve Wood]

HUH?

the forged piston has more clearance in a cold block. As the engine warms up, the piston grows faster than the block and the clearance decreases-thereby eliminating the slap. The hotter the engine runs the more the the piston expands and the tighter the fit.

Colder equals looser, hotter equals tighter.

 

[texasturbo]

seating the rings!!!

Thanks to all who replied. I have never used these rings before. I did do some research and found that they like to seat well with with engine heat being careful not to shock the rings with alot of unecessary heat ( too much boost ). I understand cylinder pressure is what seats the rings and followed the recommendation of several fellow buick members, engine builders and of course my machinist. They all basically said the same thing, "after initial breakin, good engine heat, random boost and sustained rpm varied at times. To answer Steve Woods questions "Does the electrode look like the others?" Yes, only the threads up to the seat of the plug gets wet with oil. Initial leak down with a hot engine shows all the cylinders holding 90% of what is going in. I will run it for now and see what happens. If it still has a problem I have to assume possibly the tension spring on the oil control rings has collapsed or the oil control rings themselves never seated before the cylinder wall hone was cleaned....

Thanks again guys!!! Any more suggestions from anyone are appreciated!!!!!!!

 

[Intercooler]

Yes and no. Depends on which is being heated more.

 

[Intercooler]

Re: seating the rings!!!

Originally posted by texasturbo
Thanks to all who replied. I have never used these rings before. I did do some research and found that they like to seat well with with engine heat being careful not to shock the rings with alot of unecessary heat ( too much boost ). I understand cylinder pressure is what seats the rings and followed the recommendation of several fellow buick members, engine builders and of course my machinist. They all basically said the same thing, "after initial breakin, good engine heat, random boost and sustained rpm varied at times. To answer Steve Woods questions "Does the electrode look like the others?" Yes, only the threads up to the seat of the plug gets wet with oil. Initial leak down with a hot engine shows all the cylinders holding 90% of what is going in. I will run it for now and see what happens. If it still has a problem I have to assume possibly the tension spring on the oil control rings has collapsed or the oil control rings themselves never seated before the cylinder wall hone was cleaned....

Thanks again guys!!! Any more suggestions from anyone are appreciated!!!!!!!

Were they cast or hyper pistons? If they are cast you better get them out of your motor before you start putting boost to them.

 

[texasturbo]

pistons!!

The pistons are stock 3.8 turbo replacements. Cast pistons with the oil relief slots in the pin area, not oil drain back holes through the ring land area. Expansion limiter metal insert around the pin area inside the piston on both sides of the pin boss area and full base skirt

 

[FJM568]

If your leakdown #s are all pretty even, I would think that means your rings are all seated pretty evenly...I would look into maybe you have a torn valve seal letting oil run down the valve...That would be an easier fix than to tear down the motor again to do the rings again...Change the seal on that one valve and see if it fixs it...If it doesn't, then dig into it deeper...

 

[Steve Wood]

Then I assume they were all fit tightly. Is oil showing on the electrode or only on the threads...which cylinder is it?

 

[FJM568]

hmmm...where'd you get those pistons at??? I've got a set of unknown's in my motor on the stand that look identical to the factory stock ones on the gnttype website, but I can't see the "steel insert under the crown which forms the top ring land" as stated on the photo guide...Other than that, they "look" identical...Mine have a 30 stamped on top with a cast in arrow to show direction toward the front...

I haven't got any idea where the shop that built my motor got these pistons at...But one thing I do know, the motor always did have some blowby(oil dripping from DS valve breather...My current motor has the TRW forged and the same rings you have and I have very little blowby(if any) with them...Maybe the pistons don't have enough support on the top ring land to handle the cylinder pressures that we build up with the turbo's...I don't know...

 

[FJM568]

Forgot to mention it earlier, but a good way to seat new rings in is to find a stretch of road with steep hills and keeping the car in first or second, accelerate and decelerate w/o using the brakes(let engine decelerate the car) up and down these hills...This will put a load on the motor and will load the rings differently than if you just drove the car normally...

The automotive shop at work has a stand that hooks a pump up to the flywheel and pumps water against the rotation of the motor at varying levels and motor rpms for a certain amount of time to break the motor in on the test stand...Then they would check the motor out, crate it up and send it to the facility that needs it for their vehicles...They would install the motor and wouldn't need any break-in time on their end...Put it in and go...Basically, driving up and down steep roads, accelerating and decelerating in first or second gear is the same principle, you're just doing it after the motor is installed in the car...

 

[texasturbo]

FLM568

I did the whole load the car down, don't go into overdrive, get the engine warm, vary the rpm with ocassional boost here and there thing. It is the #6 cylinder, the valve seals are the full teflon, I pulled a valve cover just to see, but they are all still intact and seated on the guides. Plus I cannot see that much oil coming down the guide as evident by what is getting on the plug threads. I would be having other problems.....

 

[Steve Wood]

still have not found out if the electrode has oil on it or not. It is pretty common for coil to get into the threads from a valve cover gasket leak in the rear but the electrode will not be oily....If there is oil on the electrode, you have a problem..if not...you may not have one.

 

[texasturbo]

electrode

Steve, the electrode is not wet from the oil but instead has a brown tint to it from the oil being burned in the mixture. The oil is collecting on the threads and what was is not burned is being forced or hydraulic'd up to the seat of the plug in the head. There are no oil leaks externally on the engine.

 

[Steve Wood]

If the plug look different than the others....I would guess it is leak down test time, then...rings should be well seated by now...most modern rings break in instantly...it's kinda hard to believe it could be the rings tho' if the clearances are right.