WTF: Excessive crankcase pressure on rebuilt engine

[tcgn]

Fresh rebuilt with 370 miles. The motor sounds and runs great, then I started noticing the bad oil leaks. The intake manifold and valve covers are dry. I found oil coming out of the oil dipstick tube and oil spray all over by the steering column area and the rear main seal area. I have 2 breathers and a new AC delco PCV valve working properly. I pulled out the breather and it was alot of blowby gases so I then use a smoke machine and introduce smoke into the dipstick tube and the smoke came out strong from the rear main seal. M rebuilder came down and seen it. He says maybe the knurl markings on the steel crank cut up the Felpro 2 piece seals and it appears to be for the rope type seal. The knurl marking for front is the same as the rear and I am using a neoprene seal with no leaks. He claims that he uses Sealer Power rings for my TRW pistons, gap them correct and install them 180 deg apart. He suggest that I should perform a leakdown test and check the spark plug running conditions. Can excessive blowby damage the seal? Or did the crank tear up the rubber rear main seals? I bought a steel crank from TR customer. Have anyone encountered this kind of problem? May need to pull motor apart again. Any help will be appreciated.

 

[TurboBuRick]

Are you getting vapors out the breathers at idle?

If crank case gases can not escape when under boost, it will push other things out. Are you sure you breathers are breathing? What kind of grommet are you using? Baffled?

 

[Chuck Leeper]

Some ideas....

Rings on upside down.
Rings in wrong position.
Ring broken on install.
Oil control ring ends over lapped.
Lower side of intake gasket leaking under boost.
Block the stick tube, and do the smoke test on the t/b.?? [Pull the rockers off, to close all the valves]
Delco pcv stuck in open position?
Crank seal in backwards?
What's a vac gauge reading look like at idle?

In the "FWIW dept": If it were my engine, and I paid someone to assemble it, I would do his "tests", then take it back to him, in FULLY assembled condition. He would take it down, while I watched.

 

[tcgn]

Thanks Chuck for the reply. Vacuum appears low, 15 inHg @idle in neutral.
Just enough for power brake operation. Cam was degree-in with crank gear set @ -2 deg. I am using stock breather on right VC and aftermarmarket breather on DS. I made a PCV hose connecting both breathers to air cleaner assembly. My intake pipe is oily from all the mist. When I pull the PCV pipe out of the air cleaner assembly, you can see alot of blowby gases at idle and above idle. I have not driving it hard, just driving it easy to break in the motor. I gave it a short blast of 15-17 psi and let off a few times. I wonder
should I set the cam back straight up to improve inchs of vacuum on the engine? He only put the short block together and valve job on both heads.
I put the motor together. He wants me to call him after I pull the motor apart
so he can pick it up and check it out.

 

[Slow91z]

Thanks Chuck for the reply. Vacuum appears low, 15 inHg @idle in neutral.
Just enough for power brake operation. Cam was degree-in with crank gear set @ -2 deg. I am using stock breather on right VC and aftermarmarket breather on DS. I made a PCV hose connecting both breathers to air cleaner assembly. My intake pipe is oily from all the mist. When I pull the PCV pipe out of the air cleaner assembly, you can see alot of blowby gases at idle and above idle. I have not driving it hard, just driving it easy to break in the motor. I gave it a short blast of 15-17 psi and let off a few times. I wonder
should I set the cam back straight up to improve inchs of vacuum on the engine? He only put the short block together and valve job on both heads.
I put the motor together. He wants me to call him after I pull the motor apart
so he can pick it up and check it out.

Do a leak down see if it's going by the rings, or going out of his valve job...Something is leaking in the cylinders, the other things are just symptoms he needs to fix the cause.

 

[tcgn]

Today I pulled the plugs, they all look clean, like new. Next I did a compression test, results as follows:
#1 cyl. 130 psi
#2 cyl. 123 psi
#3 cyl. 115 psi
#4 cyl. 115 psi
#5 cyl. 130 psi
#6 cyl. 115 psi
Test results are very low in compression. The problem appears to be the rings, either wrong ring size/ install incorrectly or ring gap problem. That explains why my engine vacuum readings are so low and excessive blowby. I will tear the engine apart and one pull piston out to check the rings and go from there. What a big disappointment.

 

[turbofabricator]

Have you put a hard hit of boost to the engine yet? If not, do that FIRST. The rings just may not be seated yet. It take boost to seat the rings properly. Put it in gear after warm up, slowly increase boost against the converter, (with foot planted on brake pedal) and then when the boost reached 4-5 psi., SLAM the throttle hard and let the boost slam the rings against the cylinder wall hard and seat them. Then do a compression test all over. It would be best to do a leak down test, though. There is no such thing a s taking it easy on an engine that is rebuilt. just a quick break in. If your machinist is telling you to "take 'er easy for 500-1500 miles before you drive it hard". FIND ANOTHER MACHINST!!!! The only thing that needs breaking in on an engine is the cam lobe to lifter face if using a flat tappet cam, and the rings. THAT is the ONLY thing that needs breaking in. The bearings should NEVER touch the crank. (there will always be a film of oil between them IF machined and assembled correctly) The rings NEED boost to "break in". Run a new engine on a dyno and watch it smoke until you load the engine against the water brake. The smoke THEN goes away.

 

[Alky V6]

Have you put a hard hit of boost to the engine yet? If not, do that FIRST. The rings just may not be seated yet. It take boost to seat the rings properly. Put it in gear after warm up, slowly increase boost against the converter, (with foot planted on brake pedal) and then when the boost reached 4-5 psi., SLAM the throttle hard and let the boost slam the rings against the cylinder wall hard and seat them. Then do a compression test all over. It would be best to do a leak down test, though. There is no such thing a s taking it easy on an engine that is rebuilt. just a quick break in. If your machinist is telling you to "take 'er easy for 500-1500 miles before you drive it hard". FIND ANOTHER MACHINST!!!! The only thing that needs breaking in on an engine is the cam lobe to lifter face if using a flat tappet cam, and the rings. THAT is the ONLY thing that needs breaking in. The bearings should NEVER touch the crank. (there will always be a film of oil between them IF machined and assembled correctly) The rings NEED boost to "break in". Run a new engine on a dyno and watch it smoke until you load the engine against the water brake. The smoke THEN goes away.

I was thinking the exact same thing. Were the rings seated properly? With the miles he has on it now, it may already be too late to do a proper seating of the rings. The engine will need to be disassembled, new rings installed, a new finish put on the bores and then break in the engine properly. Don't baby the engine. Put a load on those rings!

The rear seal problem could be a too aggressive knurling pattern on the crank. I've run accross that before with a customers engine. I had to polish the knurled area a bit to keep it from tearing up new seals. I went through two seals before I got the finish right. Forged steel crank from a well known manufacturer. All they had to say was, "Ooops. Sorry."
I didn't have to pull the engine completely out. The polishing was done with the engine in the car. Not fun at all.

 

[Chuck Leeper]

So, it takes boost to "set" the rings?? I wonder how rings would ever "set" on an NA application??

"He only put the short block together"... That gives him "ownership". Like I said, let him take it apart.

 

[L8TRH8R]

I was thinking the exact same thing. Were the rings seated properly? With the miles he has on it now, it may already be too late to do a proper seating of the rings. The engine will need to be disassembled, new rings installed, a new finish put on the bores and then break in the engine properly. Don't baby the engine. Put a load on those rings!

The rear seal problem could be a too aggressive knurling pattern on the crank. I've run accross that before with a customers engine. I had to polish the knurled area a bit to keep it from tearing up new seals. I went through two seals before I got the finish right. Forged steel crank from a well known manufacturer. All they had to say was, "Ooops. Sorry."
I didn't have to pull the engine completely out. The polishing was done with the engine in the car. Not fun at all.

The rear main on my motor was an issue as well. Took the seals to get the finish right, actually took it down to smooth, then imitated the pattern and depth of stock and used a rope seal. Still no leaks.

 

[tcgn]

Just pulled the motor out tonight. Tomorrow morning I'll pull out one piston and one ring to check the ring end gap in the cyl. bore. Thanks for the tip on the smoothing of the crank knurl on the steel crank. I'll get it smoothen out alittle and hopefullly no leaks. Till tomorrow. Thanks guys

 

[TurboBuRick]

By tearing it apart you are assuming all responsibility. Don't do it. Take it back to the builder and let him take it down in front of you.

 

[pajo]

x

"By tearing it apart you are assuming all responsibility. Don't do it. Take it back to the builder and let him take it down in front of you"


x2

 

[supercrackerbox]

So, it takes boost to "set" the rings?? I wonder how rings would ever "set" on an NA application??

Pretty much the same way. It won't see as much cylinder pressure as a boosted engine, but a good WOT pounding or two will ramp up the pressure quite effectively.

 

[Alky V6]

It's not manifold air pressure (n/a or boosted) that works to seal the rings. It's combustion pressure.
A little bit of boost with a turbo engine can easily equal combustion pressures at WOT with a n/a engine.

 

[Alky V6]

The rings need to be seated as soon as possible after the cam is broken in. If you're running a roller cam, even sooner. Check for leaks, top off fluid levels, finalize adjustments, and then get that sucker out there on the road, or load it on the torque converter, and load those rings.
If you use the torque converter, be careful not to overheat the TC. I prefer to do a little loading on the TC as soon as possible, then take it to the road. If this is a non-highway use car, do it on a dyno, or at the track.

NOTE: An a/f mixture that is excessively rich will hurt your attempt to seat the rings.

 

[Ed Valvo]

You might want to check everything else too if you're having problems this early. See if you have any irregular wear patterns on the bearings IF you decide to pull it aparts before sending the engine back. Who did the work?

 

[tcgn]

Pulled one piston out, top ring. The installation is correct, the dot is facing upwards.
Here's the results:
Top Ring end gap @ .023" (specs: .010- .020)
Ring side gap on piston:
Top .004"
2nd .0025" (specs. .003-.005)
Piston clearance (bottom skirt to bore) .004" (specs. .001-.003)

The top ring gap is more than the specs. With more end gap, can that contribute low compression and excessive crankcase pressure? Could the problem be cylinder honing not rough enough for the rings to seat? Should l just have him install Total Seal gapless rings? What is the best rings to use for these TRW pistons? I will ask him to smooth/polish the knurl alittle on the steel crank to prevent chewing up the rear main seal.

 

[Alky V6]

Pulled one piston out, top ring. The installation is correct, the dot is facing upwards.
Here's the results:
Top Ring end gap @ .023" (specs: .010- .020)
Ring side gap on piston:
Top .004"
2nd .0025" (specs. .003-.005)
Piston clearance (bottom skirt to bore) .004" (specs. .001-.003)

The top ring gap is more than the specs. With more end gap, can that contribute low compression and excessive crankcase pressure? Could the problem be cylinder honing not rough enough for the rings to seat? Should l just have him install Total Seal gapless rings? What is the best rings to use for these TRW pistons? I will ask him to smooth/polish the knurl alittle on the steel crank to prevent chewing up the rear main seal.

I would not consider .023" gap to be horribly out of spec for a gasoline turbo engine, depending on the power level.
A little hard to judge the cylinder hone via internet.
Ring style is a personal preference thing. I've had good luck with Total Seal gapless rings, myself. I'll be trying Dykes next time around.

 

[tcgn]

break-in motor reusing same cam with new rings

I found a 25526109 block for my new rebuilt. I will be reusing the TRW pistons, stock rods, steel crank, 2 center main caps, ARP main studs/rod bolts, Erson 208 cam and timing chain set. I kept the lifters in order to reinstall in the motor.
The new parts are the bearings(cam,rod and main bearings), Plasma moly rings and freeze plugs. Since the cam is already break in with 370 miles with no wear on the cam, what are the break in procedure to break-in for the rings? Do I have to hold the rpm @2,200 after engine starts for 20-30minutes again?