Mid- Engine Modified Sports

[fordboy628]

Fordboy, I appreciate your (and everyone else's) opinion. It does look like loose soft metal (aluminum?) swarf that was not completely flushed out of the block. That is completely my fault, I should have been more careful.

Regards, Neil  Tucson, AZ

Neil,

x2 about Line-to-Line.

Some other, random thoughts . . . . .

A/    It's your Lucky Day!       Well, because it's a Chevy.   Race bearings are available in .001" under size, so if your crank polishes up slightly under spec, you can use a set of those.   And .001" unders, are available for many engines.   King lists .002" u/s for Chevys, in both mains & rods.

2/    Don't get paranoid about getting all the cylinder "scratches" out by honing the bore.   Tiny, fine scratches, (not DEEP ones), while not ideal, can be ignored.   Anything that is equivalent to service wear is acceptable, UNLESS the cylinder is "out of round".    O/o/r conditions prevent ring seal with "tool steel" rings.   Softer rings can accept more o/o/r.   And, BTW, forget about cylinder scratches in the lower 1/3, or so, of the bore.   Rings don't go there.   Bore should be smooth enough so that the piston skirt is not "compromised".    Chromed, steel aircraft cylinders are purposely "scratched" by specialized honing methods and/or reversing the plating polarity.    Those small to tiny "defects" hold oil essential for piston skirt lubrication.

d/    On most "conventional" engines, the mains are fed oil first, and then oil flows to the rods from a combination of oil pressure and rotating forces.    "Nose fed" crank oiling is an exception to this convention.    Crank oil passage drillings & rpm range used, determine whether a crank requires a "low" or "high" pressure for bearings to receive adequate oil.   Additionally, pressure is somewhat misleading as it is the oil pressure, plus the volume of flow, plus the flow timing, that keeps the surfaces out of contact.   Note that many specialist produced "Chevy" type blocks use "priority main oiling systems".    These systems are designed to prioritize oil feed to the crankshaft.    Mains first, then rods.   Everything else, after that.

JMHO and YMMV

 
Fordboy

[wobblywalrus]

The contamination particles embed themselves in the shell surface and in other respects, the shell looks OK, based on what I have seen in the past.  The scoring and color of the one shown are a concern.  The main idea is to make sure that there are not multiple problems happening.  Gross contamination can score the oil pump so it does not produce the needed pressure.  Also, junk can lodge in the excess oil pressure bleed valve and cause a pressure loss there.  Or, there might be two problems happening independent of each other.

At a minimum, it might be smart to send an oil sample to a lab, cut apart the filter and look at contaminates on the paper, get a second opinion on the bearing shells, take apart and inspect the oil pump and check valve, and recheck all crank and rod bearing clearances and crank end play.  Also, prussian blue is put on the back side of all bearing shells and the motor is assembled.  Then it is taken apart and the shell seating on the block and rods is examined.  The goal is to verify that oil is not escaping out from under a shell. 

Keep in mind that I know very little about this engine.  This is only some things I have learned from experience with bike motors.   

[manta22]

Big decisions Neil.

So you think there was swarf in the oil passages?.

Yes, Mike, from the condition of the rod & main bearings it is clear that there was some debris in the oil passages that did not get completely cleaned out.

I originally used Clevite H-series bearings but this time I think I'll try King XP bearings.

Regards, Neil  Tucson, AZ

[manta22]

Neil, sometimes the coating comes off of a shell and it is pounded back into the shell at a different location.  This appears to be contamination from an external source, but it is not.  Shells contaminated from an outside source often show embedded particles without a lot of pitting elsewhere on the shells.
The dark color of the big end in the photo suggests another problem source, like low oil pressure.  I am not sure how the oil passages go, but if the rod big ends are downstream from the main bearings, and they show more distress, this is another indicator of an oil pressure problem.   

I think the "dark color" in the photo is just the lighting. I just put the bearing on a table and used my cell phone camera. The oil pressure gauge showed 60 psi during the run so it looked OK.

Regards, Neil  Tucson, AZ

[manta22]

Fordboy;

Thank you for your observations. I've tentatively already decided to switch to King XP bearings and they do offer a slightly undersize choice. I'll clean out the block oil passages with a set of brushes that I'll order from Speedway Motors. I'll clean out the Melling oil pump as well.

Re your comment about hard chrome aircraft cylinders: I had a few 4 cyl McCulloch drone engines and they had hard chrome plating on their aluminum cylinders. McCulloch's solution for oil retention was a series of thousands of little indentations about the size of this "_" in the cylinder walls.

L-to-L is sounding better all the time.

Regards, Neil  Tucson, AZ

[manta22]

My Donovan aluminum block is now at Gary's Machine Shop here in Tucson. I'm getting the cylinder liners honed/bored, new cam bearings installed, and the crank polished. I had asked Gary to take a few thou' off the deck to clean it up but he noticed something that I had not- the liners are all o-ringed. I had used a usual Fel-Pro head gasket when I built the engine and it seems like if I could have made a good, strong run I might have blown a head gasket. As it was, the gasket survived intact.

Now that I know that the liners are all o-ringed I've ordered a set of Miladon copper head gaskets. The gasket bores are 4.060" so the o-ring will be well into the copper. The thickness is 0.030" while the Fel-Pro was 0.039" so I'll pick up a little bit of compression. Any advice on installing copper head gaskets?

Regards, Neil  Tucson, AZ

[jacksoni]

I've sprayed mine with copper coat. Cylinders with special o rings and they seal ok. Other stuff, not under pressure, tends to seep a bit. fine wire around water/oil holes or hylomar or yamabond may help that. Nothing big, just sl seep.

[manta22]

It looks like I lucked out. Gary called yesterday and said that my crank polished to much less that 0.001" under standard size so I went ahead and ordered new King XP main & rod bearings in STD size. He had good news on the cylinders, too. Honing them out +0.002" (from 4.030" to 4.032") cleaned up the bad spots. This means that I can still use the Cosworth pistons and the ring gaps will not increase more than one tenth with the slightly larger bore.

The machine shop should have the block & crank cleaned and new cam bearings installed by the end of this week. I also ordered a set of block cleaning brushes so I'll clean the oil passages myself, too.

Regards, Neil  Tucson, AZ

[salt27]

Neil, that's great news.   
You best go buy a Loto ticket. 

  Don

[manta22]

The set of engine cleaning brushes and the bearings arrived so I cleaned the oil passages in my crankshaft this afternoon. The machine shop did a good job of cleaning it; I did not see any evidence of any remaining debris when I ran a brush through all the passages or when I sprayed them with brake cleaner. I used a lintless fiber cloth to wipe everything down before spraying on a light coat of WD-40 to prevent rust. Now to tackle the block...

This is a 51 lb forged 4340 steel Lunati crankshaft, 3.75" stroke, with knife-edged counterweights. USA steel and USA forged, not Chinese.

Regards, Neil  Tucson, AZ

[jl222]

 
 We use red hi=temp RTV silicone on our KB aluminum block just a very thin coating around water and oil holes. 1st on block and then on top of copper gasket. we have be care full around small oil holes that feed rocker shafts, to much and
silicone covers hole, We torque from ends to middle so gasket doesn't squeeze out.

  OUR heads are o-ringed with a small stainless wire that matches up with on ring in sleeves. No RTV used on our o-rings.

                                 JL222

                   

[manta22]

I planned on using either red or Ultra Black RTV around the water passages in the copper head gasket, too. SCE recommends using KW Copper Kote around water holes in their copper head gaskets. That sure is sticky stuff!

Regards, Neil  Tucson, AZ

[Peter Jack]

A lot of years ago we used Copper Kote on the head gaskets of a big block Chev in a pavement sprint car where the engine would run for much longer periods of time without any problems. The cylinders were O-ringed with grooves in both the head and the block. It's a formula that seems to work.

Pete

[manta22]

I hope, so, Pete. That's what I plan to do. Really nasty, sticky stuff, though.

Regards, Neil  Tucson, AZ

[Crackerman]

I have been using copper kote for almost 15 years now on MLS head gaskets. I have never had one leak coolant or oil.

Brake clean takes the stuff right off.

I would be hesitant to use anything silicone related on a head gasket, that stuff squishes out, gets in oil and water passages and hardens up. Prior to copper kote I was using hylomar, and now a permatex brush on non hardening sealant. But never rtv.the only spot it's good for is the oil pan corners, and China walls on the intake manifold.