If Rings Don't Seat:

[jhv48]

Here's the deal, I recently had my Roush 427sr rebuilt from heads to pistons to bearings. It was broken in on the chassis dyno with royal purple 20w50 XPR high zinc synthetic oil.

The pistons were replaced using the same weisco pistons and plasma moly rings
that came in the engine originally. Since the rebuild (3000 miles), I have been burning a quart of oil per 250 miles.

There is no smoke on hard acceleration or steady deceleration. The backs of the valves are clean, so it's not valve guides or seals. We ran both a compression and leak down and all cylinders are at less than 5% leak down. Compression is where it should be too. We stuck a bore scope in each of the cylinders and couldn't see anything out of the ordinary. Cylinders were still clean with cross hatch showing.

So my question is this, if the rings didn't seat, then why are the leak down and compression numbers so good? Did the first two rings seat and the oil rings fail?

Is it possible the oil is so thick and slippery that the oil ring can't adequately scrape the heavy oil from the cylinder wall allowing it to remain on the walls and ultimately be burned?

The only other thought is that the block wasn't honed smooth enough for the plasma moly rings (the cross hatch is still visible on the cylinder walls). Plasma moly rings seem to require a finer hone rather than a rougher one.

So, I'm going to change to dino 10w30 oil and try the break in procedures again. If that doesn't work, I don't know what to look at next.

Any thoughts from you engine builders?

[Gaz64]

I would get someone else to drive it while you follow in another car.

It must be smoking to be using that much.

One of my cars didn't appear to smoke until I saw it from behind, it did settle down to next to nothing visible, but still did consume oil between oil changes.

You could have a leaking inlet manifold, the fuel could still keep the valves clean.

[mrmustang]

Have you changed the break in oil yet?

If not, I suggest that first.......


If you have, then my vote is to check the intake manifold gasket installation before digging any deeper.



Bill S.

[madmaxx]

20w50 synthetic on break in? Fnd a mechanic wtf. Should have been 10w30 Dino. Don't give bs about corvettes comming from factory with synthetic. Did GM hone your block with their $1mm machine? You probably glazed the cylinders. You should see cross hatching after 100k miles. The cross hatching is what holds the oil, if you don't see it cylinders are glazed and need rehoned.

[madmaxx]

Put a 160f thermostat in it. That way the pistons will be hot and the cylinders cold and you can wear the engine out in 5k miles. Another idiot boy racer idea.

[RET_COP]

He said the back of the intake valves are clean, that would leave out the intake gasket and anything entering the runner. I had severe oil wicking through my rocker studs which cause the back of my intake valves to look like tar and my plenum had an oil sheen as well as the runners, plugs were a mess also. I had to really do some cleaning and seal the studs. Problem went away.
Something doesn't sound right, any signs of a leak? What do the plugs look like? Pull the pcv and see if it's really puffing and what it looks like.

[jhv48]

Thanks for the replies. Here's some further clarification:

Break in oil was used for the first twenty minutes of warm up prior to changing it out for the RP 20w50 XPR and the subsequent dyno pulls.

Bore scope shows good cross hatching in all cylinders. No glazing.

I followed the car down the street and no smokle was evident on accel or decel. On cold startup, when the car has been sitting for a few days, there is a SMALL puff of smoke on initial firing, oil can be smelled but only for a moment. I also pump the throttle once prior to a cold start. Puff could be excess fuel and oil. Hot starts, without pumping the throttle result in zero smoke or oil smell.

Intake manifold was pulled so we could check the backs and stems of the intake valves. No intake gasket malfunction. The stems and backs of the valves looked like new. No oil in the intake runners. PCV working just fine.

Plugs are light brown. No signs of excessive oil.

No oil leaks on garage floor.

Now what? Need some creative thinking. We're out of ideas! Don't want to swap out the rings until we're sure what the problem is. Has to be the rings though, doesn't it?

[ERA Chas]

Don't know for sure but you may have 'low-tension' rings that Ford is so fond of.
'Low-tension' is another term for 'no oil control'.
Maybe you got to go in there if there's no other apparent cause.

[DAVID GAGNARD]

I would change out the present oil to any name brand 10/30 conventional oil, then get the engine and oil fully warmed up to operating temp...
then get out on a deserted road somewhere,go thru the gears normally and when you get to 3rd gear,don't punch it, but accelerate quickly to say 5500 rpms,when you hit 5500 rpms, let off the gas and coast back down to about 2000 rpms,then accelerate back up to 5500 rpms all the while leaving it in 3rd gear......... do this 6 to 10 times in a row and watch your temp gauges....then cruise for a few miles in high gear to let things cool off and repeat one more time.......

if this doesn't work, then I'm afraid you may need to pull the engine down...

BTW: you shouldn't put any synthetic oil in it until it is fully broken in and have at least 500 miles on it.....

David

[jhv48]

Thanks, David,

Thats what I have planned for the next step! Going to try to break in the rings all over again.

And I questioned the change to RP 20w50 XPR after break in. That oil is super clingy and slippery. Hope this works.

[DAVID GAGNARD]

Originally Posted by jhv48

Thanks, David,

Thats what I have planned for the next step! Going to try to break in the rings all over again.

And I questioned the change to RP 20w50 XPR after break in. That oil is super clingy and slippery. Hope this works.

I'd go down to the nearest wally world and get some 10/30 Valvoline or similar oil.........start your car and get it up to operating temp, then shut it down and change the oil and try to re-break it in again.....leave the 10/30 oil in for a few hundred miles and see how it does.....
you have nothing to lose and everything to gain.....

David

[carmine]

Sounds like your running Teflon valve seals.
They are a stiffer seal and don't have good sealing capabilities for the slight side ways motion that a valve has when moving up and down thus seal can create slight gap during side motion and with the higher vacuum conditions at lower rpms (idle and cruising) when throttle plates hardly open allows oil to be sucked through intake valve and mixed with fuel and burned.
You wouldn't notice any oil burning out the tail pipes during higher rpm tromps because throttle plates more open allowing high vacuum conditions to take there effect through the carb.
Chances are you wouldn't notice at low rpm operation either because oil amount leaking is small but continuous and mixing with fuel and keeping valves clean looking.
Have seen this problem many times and it gets compounded even more when running high volume oil pump because more oil being pumped to the top of head and drain holes in head usually haven't been increased to allow this extra oil to be drained back down fast enough thus creating a higher pooling level in the heads which can come up high enough to completely immerse the valve seals in oil.

Solution to this problem is to change the valve seals to Viton valve seals.
These seals are a special rubber that seal and move with the valve sideways motion.
They were developed especially for this problem.

[jhv48]

Valve seals are viton.

[Jerry Clayton]

You can sprinkle Bon Ami powder into the carb intake while running---it has been used on some difficult to seat rings many times in previous decades------------

[DAVID GAGNARD]

Originally Posted by Jerry Clayton

You can sprinkle Bon Ami powder into the carb intake while running---it has been used on some difficult to seat rings many times in previous decades------------

I have done this myself a time or two,I know of some drag racers that used to do this on all their engines for quick break-in/ring seat as they couldn't very well drive the cars on the street for break-in.....

David

[carmine]

jhv48 "Valve seals are viton."

Are they blue color?

[jhv48]

I considered it as we'll, but the engine builder about popped a vein when I suggested it to him. Got to keep the warranty in place. Right now he's ready to tear it down and hone and ring it again.

I'm going to try to break them in one more time, using David's method. If that doesn't do it, then it's coming apart.

[Turbonut48]

My 418W took almost 1500 miles to break in, and stop using break in oil.
And my builder didnt want me to change to regular oil until 2000 Miles.
Good Luck.
The Nut

[ERA Chas]

Originally Posted by jhv48

Right now he's ready to tear it down and hone and ring it again.

Pay attention to ring selection. No low tension. A finished Ra of 15 - 20 for Moly, 20 - 25 for Chrome.
If run-in on a dyno, 20 minutes at 2500RPM, 3 or 4 pulls to 5K or so under load. !5W-30 or 15W-40, no synth. Try to use a System1 filter.

[Frank Messina]

We used Comet straight in through the spark plug holes with a little shot of air to distribute onto the walls. Not sure about pouring it in the carb though. OTOH a 5%leakdown rate is pretty good and not indicative of an unsealed motor, besides this procedure isn't going to help the oil rings.

On a low mile new motor it's possible for oil to enter through the intake track and not leave any obvious signs on the valves......yet. Not saying that's what the problem is but it should not be discounted. Pull the intake and run your finger into each intake port. If it's oily you found it. If it's not that then that leaves the oil ring package.

Frank