This rear main bearing came out of a 250 Chevy 6 in a 63 Chevy 2. Fun job yanking the oil pan. A young guy rebuilt the engine,drove it about 500 miles before pulling the pan for a suspected rear seal leak.The engine was prelubed with a drill motor on the oil pump.Broke in with Comp Cams break in oil. See the shiny wear areas,doesn't look exactly what I would expect.The crank journal looks polished smooth,no scratches.His dad,a machinist,miked the crank and bearing inside diameters and said .002 on all of them. And the suspected rear main leak? Seal looks like new................
Looks like a home brew rebuild. Some oil contamination, Typical wear pattern, but very usable. Does the crank have any seal wear? Offset seals are available. Also rotate the seal in the housing. End out 1/8" on one side and down a like amount on the other. A dab of RTV on parting surfaces. Then a small amount of RTV across the cap face from seal to outer edge of cap. Oil can weep across this area and look like a seal leak.
The seal was installed offset as the photo shows. No sealer was used on seal ends because he read the Felpro directions that said no sealer.You can see sealer was used on the main bearing cap parting line.The crank seal is the offset stle and where the lips ride looks clean. The seal fits loose on the main cap,I assume it "tightens" when the cap is installed. The oil leak was sudden....dry for 400 miles then all of a sudden a silver dollar sized puddle after driving just for 15 minutes. Zero oil leaks from valve cover,side cover etc. He said galley plugs at the rear of the block are new and installed by the machine shop having a good reputation.
My response was standard operating procedure that I go thru with customers. I was paying more attention to the bearing. The seal should fit tightly on the back side. Try imbeding it in RTV on re-assembly. Make sure the block side seal is correct. You never Know..
Ok thanks,I'll pass on the info to the youth under the car swearing up a storm while scrapping off RTV sealant.
Tell him to slow down. Walk away for a bit. It's just a machine. Then grab a can of Brakeclean and a scraper. Back in the mid sixties I had a hot rod Studie with a nailhead in it. Ate rear ends. Spent a lot of time under it, laying in the hay and straw of a cow barn. Drop a nut/part and never find it. Good luck.
As far as the wear pattern, only checking the housing bore with a dial bore gauge will confirm or not confirm the taper, and out of roundness. Using plasti-gauge or telescoping gauges will approximate the size and clearance. By approximate I mean roughly to the .0010". Most of your production engine rebuilding shops measure to the .0005", and of course race shops never settle for less than .0001". That said, how is the " register "? or how well does the cap locate in the block? If the register is poor it is very easy during assembly to locate the cap off to one side. In fact it's almost impossible to locate it in crank saddle ceterline without correct register. Now silicone was not used correctly at the mating surface. He and his dad did a resonably nice job for do it your selfers, I'm not disputing that. Done correctly, you don't even have to offset the seal halves. So, lets make it better. Radius the 2 main bolt holes slightly, and brake ALL the parting line edges with a small flat file. Do the same thing for the block half of the mating surfaces. This is important and will quarantee the cap sit's flat on the block. Now clean all of the mating surfaces with laquer thinner and air dry. The RTV should only go accross the rear of the cap equal to the inner edge of the seal, no further than that. Another way to look at it is equal to the outside edge of the cap where the pan seal goes. Now very critical is the slightest FILM of RTV, nothing more!!! You do NOT want it to spread anywhere nears the bearing parting line as it has done in the pics on the left side. The right side doesn't seem to have any if at all. So 1 side too much, 1 side not enough. I run the slight film of RTV right up to the edge of the seal completely. be sure to LUBRICATE the seal with engine assembly lube so the seal doesn't suffer from a dry type of start. TR
I see a tiny spec of blue on the left side that looks like a piece of seal. If the little plastic installation tool that comes in the seal bag is not used on the back side of the seal when it is "rolled" in the sharp edge of the cap will tear the backside of the seal and it will leak through at the back side.
2 sounds a little tight. I like mine 2.5 3 or even 3.5. I don't know these motors and what they like though.
Thanks for replies . This was built by a young guy with little engine experience.It's going back together with a new seal and the prep work mentioned by Traditions Racing.
I had some time so I pulled all the mains one at a time. All the arrows are facing forwards and in the proper order 1-7.Bolts seemed torqued properly. The wear pattern on the mains is identical to the photo in the first post. The main caps have the edges cut slightly by the machine shop or by GM.The caps fit in the block "registers" with a easy push in fit. Hecho en Mexico is cast into all the parts I doubt most hobbyists on a reasonably budget would line hone a slightly hot rodded inline 6. The engine has 150,000 miles on it before being overhauled.This engine had good oil pressure and ran well for what it is. I rolled out the top of the rear main seal. it looked fine except I see a line of dark gray material in the cavity between the seal lips.The Kid said he used Redline assembly lube,it's red. Nothing to see here I guess,put it back together with a new seal
Felpro instructions say the larger lip goes towards the inside of the engine (or forward) so it appears the seal is in properly. Some people have said they get better sealing with the Felpro red seal, vs. the blue. It's a slightly stiffer rubber, and might be an option if leakage is an issue.
He needs the offset seal because of wear on the crank seal surface. It appears the offset comes in blue.Yes,very soft seal... This engine does have the stock PCV system and it works as it should.
This isn't a good place to skimp, think of how much money you have in a finished engine, even a mild build. What's a couple hundred bucks to make sure your mains are as straight (or straighter) than when the block left the factory?
It'l run a long long time as long as you don't try to pass the big boys too often . If it just leaks or sweats a little then check it and add accordingly . Oh yea don't waste money on synthetic that drips on the ground.
The seal is installed properly ....big lip towards the oil,just like it shows on the Felpro packaging. After replacing the seal he took a nice ride last week when the roads were dry. Still leaks exactly the same leak as before.The car is jacked up again,he feels it may be leaking from the rear of the block.maybe an oil galley or cam core plug.So the tranny, bellhousing,clutch flywheel is getting pulled to check the block. For sure not a valve cover or head gasket,the rear of the block is bone dry. I'll see if he'll post here....
The seal looks right to me. What does the upper bearing look like? If only the lower bearing shows this kind of wear, could there be foreign material under the bearing shell? You can't mix up the rear main cap, but is it from the original block? I agree that it might need a line hone.
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