Cylinder Scoring...help

[VETDRMS]

I have a problem that I need to discuss with my machinist tommarow, but I need to have a rough idea of what caused my cylinder scoring. The motor only has 2500 miles on it, but the heads I purchased from the builder have bad seals. Oil has leaked past the seals and into the cylinders. The result is a ton of an oily carbon buildup that has the consitency of rough sludge. My question is could this carbon buildup have gotten into the top ring and somehow caused it to lightly score the cylinder?
The scoring is still above the cross-hatch, but after 2500 miles the thing should still look brand new. I'm hoping the guy will be stand-up about it, and find someway to correct the problem.

Thanks, your opinions would be helpful.

New member here, seems like a nice place

 

[GerryLP]

Vetdrms,

Sounds like you have taken off the heads???

The carbon could have built up into the piston grooves and forced the compression rings with uneven alignment to make the ring ends "stick out". The oil rings slots could have clogged and prevented the "scraped" oil from the cylinder wall to flow into the piston skirt slots. However, this would most likely be from the crack case end.

I have heard of condensation formed between frequent cold starts/ short drives causing grooves on the cylinder walls, but I do not understand fully how it happens.

Cylinder distorsion, although never 100% preventable, can be made worse by uneven torquing sequence and/or uneven torque on the head's bolts.

Depending on the amount of leakage from the valve stems, the oil coking (in sludge stage right now) may have forced its way into the compression ring grooves.

I know that Mike (Stingray6974) can tell you more. He's a pro builder and repair man. Maybe he'll chime in.

 

[VETDRMS]

Thank you, Yes I have taken off the heads. The intake valves are covered with sludge, this is only after 2500 miles and the scoring on the cylinderwalls and the carbon is worse than when i tore it down at 35000 miles to do all this. THe pistons are a set of sealed power hypereutectic flat tops, and i'm using a moly top ring with standard tension oil ring. I took great care in accurately torqueing the head bolts, and from a compression test I'm pretty sure the problem isn't the rings letting oil in from the crank case.

I will talk to the builder tommarow and hopfully he will fix the problem.

Thanks for the info

 

[AKRAY4PLAY]

it sounds as if there are a couple of things that maybe amiss. you mentioned that the sludge is only on the intake vavles. with bad seals, they are the most likely to leak because of the vacuum applied to them. but you also need to look in other places. if you have a bad intake gasket(s) then oil will be sucked into the intake ports from the lifter valley. decking the cylinder and/or heads change the way the intake ports line up, and can lead to gaskets that do not fit. to correct this problem you need to go with a thicker intake gasket like a Felpro 1266 (i think that is the number). another thing the possibility of pulling a lot of oil in from the PCV system. new motors are known to have blow-by until the rings seat. the problem is compounded dramatically if you do not have baffles in the valve covers. on to the scoring. yes carbon can score the cylinders. it is a possibilty, but i think your problem is clearence. hyp-tic piston use a closer tollerence than natural aluminum. some builders go to the way close side of the specs, and scoring is going to happen. hyp-tic pistons have a high silicon content, that is why they are great for not expanding and also use tight clearances. also the silicon is sand, and will score the cylinder walls. pulling a piston will tell you if the piston skirts were dragging, and also if the clearance is in the manufacturer's specs. and double checking the machinist's build sheet is nice, provided he gave you one. sorry for the lengh, but wanted to throw out a few possibilities for you to muttle over in preperation for your negotiations. best of luck to you, Brian

 

[cruzer99]

Cracked rings are a common problem and will score cylinder walls in new motors if who ever put it together wasn't careful.

 

[Jack]

I do not disagree with the others' suggestions. If the scoring is from too much oil that's become coked ... let me add this. It is very easy to install top or second rings upside down ... when/if this happens they usually will not seat ... and will push oil past them into chamber.
JACK:gap

 

[Stingray6974]

Very good replies from everyone. I would also have to question the heads. 2500 miles and the seals are bad? Are they new heads or rebuilt ones? Were the valve guides replaced or just knurled? Scoring can also be caused by a very rich fuel mixture.

Mike

 

[cntrhub]

Were the cylinders bored and honed? Even if you just "Bottle Brushed" the walls with one of those cutting type honing balls with a drill, will leave enough grit to score the cylinders. Pro builders, and also those in the know, always take hot soapy water, and a cotton cloth to wash the walls clean after honing. Who cleaned the cylinder walls before the pistons were reinstalled? A leak in the air cleaner housing (before or after the filter) will cause enough dirt to score the walls.

 

[VETDRMS]

Thanks for all the great info!

AKRAY4PLAY
I have been using a Mr. Gasket Ultra Seal 2 gasket. One thing I did notice was some oil around one of the intake bolts at the heat-riser??. When i took the bolts out that one was oily. The heads had their first rebuild, and were surfaced, but I was told it was not enough to need the intake angle milled to match.
One thing I did notice was there is a little piston movement in the bore. You can rock it up and down, but very little. The scoring is at the top and bottom of each cylinder.
I am using a set of chevrolet tall cast valve covers with breathers.


cruzer82 I installed the rings, and was very careful in the whole process. Everything was checked twice, so I don't think it is specific to that.

Jack The rings were all installed meticulously to the directions they came with.

Stingray6974 The heads are a GM 041. They have been ported and are rebuilt. The guides are cast and have been cut and re knurled. I do not think the fule mixture was too rich. I am running an EPS 1406 carburator leaned out 6%.


I will talk with the machinist tommarow, but while its a part, here is what I may be doing with it:

Scrap block and rotating assembly.
I have a high nickle high tin 4 bolt block std bore.
Scat 9000 383 Crank
Scat ICR I beam rods
TRW Forged Flat Tops
Dart 200cc Iron Eagles with Manely Pro Flo valves (2.05/1.625)
Comp Cams Spring Retainers to match:
Comp Cams Solid XS268 Cam.
weiland stealth intake
TCI 2600rpm stall

I was planning on keeping my current shortblock and just doing all the above minus the 383. So I may just now take the plunge and go all out. Should be quite the runner when finished.

Thanks again!

 

[VETDRMS]

cntrhub The block was honed using a torque plate with the finer stones for moly rings (280 grit). They were washed and cleaned prior to installation.

 

[cntrhub]

My question now is: Are all the cylinders scored or just one or two? If all are scored, then I would have to suspect each cylinder receive the same contaminants to each cylinder. And this would either be: faulty air cleaner, no air cleaner used, air cleaner housing leak, or grit from the ported heads? Just trying to eliminate the variables.

 

[VETDRMS]

cntrhub I cannot recall, I believe at least half of them were lightly scored. They aircleaner and seal were always in place and working. The car was never driven in any high-dust situations.

 

[AKRAY4PLAY]

Travis,
the biggest thing that is forgotten during a build is the matching of the intake gasket and ports. if one of your bolts has oil on it and it did not come from the valve covers, then it came from the lifter valley. any surfacing of the block or heads will cause the ports to misalign. this is the reason they make different thickness gaskets. it can take some time to properly line things up, and you usually get rushed because the build is almost over. use some Gaskasinch (bad spelling) when putting on new gaskets. i put a small amount, drop on each end of the head, and place the gaskets so they won't fall. then put more on your intake manifold, and when you remove the manifold, the gasket should stay with it and show you just how everything lines up. trial and error with result in happiness if you take time. best of luck with the 383, hope you are going for 6 inch rods, Brian

 

[vette-dude]

You said that the pistons were hypertechnic type. The boring and the honing is a different process than with standard forged pistons. The reason is the hyper's expand differently when hot. I suspect that the block was bored and honed for a standard piston. The scoring you have is common for a block incorrectly bored and honed for hypertechnic pistons. The tolerances should be a little looser than the normal fit on standard pistons.

Randy

 

[cntrhub]

I am going to assume you are using something like a K&N air cleaner that has a higher air flow rate. Simple enough. These air cleaners have less material used for higher air flow. This means more chance for tiny particles to go past the air filter pleats and work their way on top of the compression ring. When the piston travels back up, you have this little piece of grit being "rolled" as the piston travels up. This is how you get those fine little long lines in the cylinder walls. If you are going to pull the pistons, check the face of the rings for line scores there also. Just remember that if one surface is damaged, most likely the other is also. Rub your hands together. Which one stayed cold? This simple analogy explains that if one side is damaged, so will the other sided that rubbed up against it.

 

[VETDRMS]

AKRAY4PLAY I did notice an oily film on the surface of the intake, but the intake runners were dry as a bone. Thanks for the heads up on installing the gasket. I was looking at using a 6" rod, but need to find the right piston for the job. Possibly KB?

vette-dude The cylinders were honed (not bored) for the hypereutectic pistons. I am going to talk to the machinist in 30 minutes, so hopefully i'll have some answers. I will bring that up, thanks.

cntrhub Yes, a 14x2 K&N filter. I do not think that is the cause because I have used it on the previous motor for 20000 miles, and after the tear down at 35000 there was little to no scoring. I believe the grit that caused the scoring was from the oily carbon, there is a LOT of it after only 2500 miles. Hopefully I will have some answers this morning.

Thanks again for all the valuable input.

 

[JohnZ]

Hyper pistons (KB's, at least, which I've always used) require a little larger gap on the top ring than cast pistons (and larger than the ring manufacturer recommends); if the top ring gap wasn't set specifically larger, it can "bind" and will definitely score the bore surface.

If the valve guides were indeed "knurled", that may explain the "coking" on the intake valves; knurling is a band-aid which temporarily closes up the valve-to-guide clearance, but the little points on the knurls wear very rapidly and the clearance becomes excessive again in short order and they start sucking oil again. The only long-term fix is new valve guides.

 

[AKRAY4PLAY]

Travis,
KB makes the right pistons for the 6 inch rods as well as Speedpro, Weisco and my favorite JE/SRP's. there are more i am sure, but those will get you in the right direction. the 6 inchers are more spendy, but well worth it when it comes to volumectric effecency. as far as not seeing any oil in the runners, your fuel/air charge most likely washed it clean. gas is such a great solvent. one last point, the 6 inch rods will place the wrist pin in the oil ring land. it is MANDATORY that you run support rings for the oil rings. it looks a little poor-boyish, but works good. i have not had any problems with mine in the 406. if there is anything else we can help you with, please ask, Brian

 

[VETDRMS]

JohnZ I will take the gaping into consideration when I build the 383, thank you for pointing that out. I took the heads into my machinist today, and it seams that the bulk of the deposits were fuel deposits from it running extrmely rich!? He pulled all the valves and cleaned them up and also installed a new set of positive pressed in seals He has been very stand-up about everything, and he will definitely get more business from me!

AKRAY4PLAY Thank you very much for the valuable information. I will most likely seek your advice as the project progresses. Here is a general idea of what kind of combination I plan on using:

Dart Pro 1 200cc Heads 2.05I 1.60E
Bowls Blended, Possibly Pocket Ported (professionaly)
Manley Race Flo Valves
Comp Springs/Locks/Retains to Match:
Comp XS268 Solid Flat Tappet Cam 230/236@.050 .501/.510
High Tin High Nickle 4 bolt block
SCAT 9000 Series Crank, 350mains 6" Rod, Internally Balanced
Keith Black Flat Top Piston 1/16 1/16 ?? rings, 6" rod 383.
-I may use SRP*
~10.5:1 compression
SCAT ICR 6" Rods Cam Clearanced - Bushed
Rotating Assembly fully balanced and blueprinted
Crane 1.5:1 Full Roller Rockers
Weiland Stealth or Edelbrock RPM intake
Holley 750 carb, mech secondaries
TCI 2600rpm stall converter
3.70 Rear Gear
26.45" Tire

How do you think it will run? I think it will get the beast moving

Thanks again for the help, and please excuse the spelling errors, I am fighting sleep so I can this reply written. Goodnight.

 

[AKRAY4PLAY]

Travis,
that is a nice set up. it should run good on the street. the only things that i can reccomend up front are not running a solid lifter cam and maybe looking at some AFR heads. http://www.airflowresearch.com/
they are about the same price as Dart, but flow better. i love mine, and the only bad thing i have heard is poor Fred's missized rocker stud. he got one 7/16 stud in with all the 3/8's that were susposed to be in te heads, AFR made it right though. solid lifters are for turning big rpms, not really what you need for street racing especially if you stay with an automatic tranny. besides, i hate setting valve lash every weekend. you can build a potent 383 that will run almost forever with a nice hydrolic roller cam. your cam profiles are right in the performance area that most everybody likes and 10.5 comp ratio with aluminum is great. i really like the Weiand dualplane intakes, they flow better than Edelbrock. check in with Fred (FC3), he is almost finshed with a 383 that is almost a mirror of what you want to build. in a week or so he should have it done. he has a bunch of posts in the C3 tech and mod sections of this forum. don't worry about spelling, i suck at it as well!! get some sleep and check out the 383 Retro posts, Brian