How about some opinions on these main bearings and their wear. Im stupid when it comes to understanding what im seeing here so im in need of help. mains 2/3/4 look weird as shit to me. application is a blown 355 SBC street car with a 6-71 @ 11% overdriven on pump gas ( 93 octane ). Timing is retarded per amount of boost. Its been sitting on the stand for over 3 years and decided to look at it before putting it back in the car. I only pulled one rod bearing to take a look. Any thoughts on wear patterns or am I being paranoid ? Im not the builder of the bottom end and clearly I dont know what the hell im looking at.
Looking at the pics on my crappy phone. That first bearing looks like it has a lot of miles on it. But I have seen a lot worse. Can you hang a fingernail in any thing in the crank journals. STD means the bearing journals are the OE size. You can check the clearance with plastiguage
those bearings have less than 10K street miles on them. that #1 main plastigaged at 4 thou. the builder said he set it up loose. he promised it was 3+ thou. I cant catch my fingernail on any of the scratches on the journals. I think the forced induction is not so nice on the bearings. 2/3/4, WTF is up with the weird chatter pattern ? Is that normal ? its all forged eagle rotating assembly with speed pro 21cc D cup supercharger pistons with dart 215 / 64 cc heads. I also have vertical scratches on the cylinder walls that match up to the piston skirts. Maybe its time to go to a dart little M and be done with this 1975 truck block. IDK. I wish I knew how to read what im seeing.
Just looking at it, your crank looks great. The main cap surface, seems to have been machined a tad rough to me. But that helps hold the bearing in place. I see some bearing wear, but very little. It does seem to have an odd wear pattern, but I don’t think it’s anything to be alarmed about. If it was just a stock engine, I would put it back together, but since it’s a hot rod engine with a blower, I would install new bearings. Hard to see the rod bearing, but from what I see it’s good. But a new set of bearing are cheap insurance! Just my opinion, based on pics. Bones
Wear but do not appear to be horrible. As stated above if the fingernail test is ok put another set of standards in and measure with plastic gauge.
Crank journals look very good to me . Main bearings are beginning to show some use,,,,,,but remember,,,this is a blown application with 11% overdrive on 93 octane . They Look pretty good considering all that . I would roll some new bearings in ,,,mains and rods,,,and call it good,,,,,if everything else checked out okay. Tommy
For me .004 is a little on the loose side for a street engine. And could possibly be responsible for the odd pattern! I said “ could possibly “ ! Bearings are made that are .001 under or over depending on which way you look at it, but either way they will decrease your clearance a little. Usually loose clearance is for racing engines. At least they used to make these bearings. Might want to explore this option! Bones
I observed that strange pattern on some main bearings in a friend's shop. (looked to be from the crank 'chattering') Old friend and very sharp guy looked and remarked he had seen a similar wear pattern on an Indy Chev. (sharp guy was former Indy winner Joe Leonard...) Joe said they replaced bearings, but didn't check afterwards. I'd like to know what caused that pattern: But, I suspect the excess clearance in bearings was the culprit. One Cad engine in Frank Martinex's '40 was built 'loose'...(.005" at mains, .003" at rods; High RPM it got NOISY, like a loud 'Chirp'. I asked, "WTF?" Frank said the Forgedtrue pistons were also 'loose' (he called it 'sloppy') piston skirt clearance: .008"!!!) Should have heard it...First time I did, it was past 6,000 RPM. I pulled my legs back waiting for the 'rattle' that was bound to follow. Scary. That engine lasted 'forever', it seemed. But that 'chatter pattern' on the mains was quite familiar... I had a SBC 327 and the mains plastigaged excessive. Crank was turned below specs... It was a used engine, and I had to get my car running again, so I inserted some good bond paper behind the Federal Mogul bearings, in between the insert and the cap. Plastigaged, a snug amount... Assembled, after warm up that dude idled with 35 lbs. oil pressure...Ran great for all the time I had it.
that bearing part number is for a +1 thou clearance . the guy who set it up is a racer and a machine shop owner that builds almost strictly racing engines. He prefers to be a little on the loose side as opposed to the tight side. I ordered a sharktooth oil pump and bought the standard volume one. That may have been a mistake with that clearance. I can always send it back to summit and order the high volume one. since im a bottom end idiot, im going to have to replace the rear main seal once I pull that rear main, correct ?
We had the same issue with Clevite 77 bearings in a 12.5:1 compression BB Chevy road racing engine. So we took the bearings up to ACL and got their lab to inspect them.[the experience there was worthwhile] The top coating looked like a dry lake under a microscope. This was caused by extreme pressure causing the oil film to "Hydraulic" [or explode] the top coating from the surface. I am not referring to oil pressure, but the forces applied when there is full flame propagation at TDC. The remedy is simple............Use "H" series bearings [The ugly ones that look like they have been in a fire] "H" series bearing don't have the top coating We went from a Bearing life expectancy of 2 meetings, to still running the same set after 3 seasons when the car was later sold. Edit: to give you an idea of the loads on the bearings! A race engine has about 1600 psi cylinder pressure just after TDC. Multiply this by the bore area [my car had a 4.31" bore or 14.58 sq inches] That equals 23,343 lbs force onto a very small area of the bearing [and oil film]
Actually the Mellings shark tooth Standard comes with a higher pressure spring installed, and a normal pressure spring in the box. If you've tossed it, I may still have the higher pressure spring in my tool box.
That would explain the dark look of the bearings. The bearings with uneven wear(#4 main) maybe from a bend or bending, or out of round journal. On the 'chattered' bearings I recall having s similar issue, the machinist stated it was an artifact of how the bearing was made, and in a lo-po street car it's nothing to worry about. Measure them, if the bearing surface is even(radially) then it is most likely just from the bearing manufacture process.
no the pump will be here tomorrow. it was supposed to be here yesterday but never made it. Im just wondering if I should have ordered the high volume model.
I think im pushing the ragged edge of pump gas with this mouse. the reason its 11% overdriven is because it really started breathing when I put the solid roller in. I was under driven prior to that. BDS said take it to 1 to 1 and I told them they were crazy. when I did, I still only had 3lbs of boost. The BDS tech was ecstatic and said that mouse must be really breathing , now lets overdrive it. So that's where im at. they are dart 215 pro 1 platinum heads with 64cc chambers 2.05 x 1.625. I had the builder rework the heads and put the biggest exhaust valve in I could. the springs are 1.540 BBC springs with a measly 150lb on the seat at 1.900. the cam is 260 / 270 @.050 625 lift 110 lobe centers with crane stainless 1.52 rockers ( sadly it appears they dont make those rockers anymore ). I honestly think I've taken things too far for a street motor. I mean a real street car that can be driven anywhere on the 16gal fuel cell. seriously, with that few of miles, it should look better than that I would think. but as we have already established, im bottom end ignorant and ive proved it here.
You need a high volume pump for loose clearances, and high pressure for tight clearances. I got hold of the Castrol tech sight after my ordeal and they recommended their CRF40 diesel oil [for a race engine] They explained that a diesel engine is normally 18:1 to 22:1 compression with short duration timing. And some are turbo'd above that. "there was no way my race engine would load the bearings the same as a diesel engine" Anything above a 40wt should really have an oil cooler. I tried a Kendall 50wt and the dry sump would cavitate [oil spills were good for catching cockroaches on the concrete floor]
I have always ran castrol 20w50 in it, its had nothing else. a quart of Lucas oil stabilizer also goes in at every change. I think I probably screwed the pooch ordering the standard volume shark tooth instead of the high volume one. I guess ill be paying to ship that back. oh well, better to know now than after the motor is in-between the fenders. someone I know suggested I go to 20w50 synthetic. I dont know about that.
I would replace the rear seal, while you have it out. But that’s just me! Also if you replace the bearings, with the crank in the block, be sure to slip some gas hose over the rod bolts while replacing the rod bearings, so you don’t scratch the crank. Bones
Im scared to death of scratching the journals. those eagle H beam rods have bolts going from the bottom into the top so there's no bolts sticking out. I will order a rear main seal for it too. does anyone know if a tool exists the sits in the crank oil hole and pushes the top half of the main bearings out while the crank is still in the block ? I saw a guy on YT drop something in an oil hole on a main journal and then rotate the crank and it pushed the top half out.
If it was mine, I would keep the standard volume oil pump. I would actually check what you have for bearing clearance. For a street only engine, I am not a fan of getting too loose with the bearing clearance. And maybe take a bit of overdrive out of the blower. I don't mind having to routinely service a race engine, but not my hot rod.
the one main that I checked, number 1 , had 4 thou according to a piece of red plastigauge. the bottom end builder told me it would have 3+ in it and it did. if I take some pulley out of it, I'll most likely loose the blower surge. not really a fan of loosing that .
One thing I know for sure. Synthetic motor oil will take more of a beating than any other. Was hesitant to use it, at first, and will never go back to anything else. Just my two cents.
Sounds like you have a nice set up there. Instead of being afraid of the bottom end, why not consider this an opportunity to do something and learn something. First I would buy a couple decent OD micrometers. You can find used name brand ones on eBay dirt cheap, or get a set of lesser known ones. Probably a $100 will be plenty. Then buy a dial bore guage that reads in .0001 (Not .001). Then you can check the crank and the bearings to see what they really are. I would then polish the crank with Emery paper after removing it and replace the bearings. Just take your time and ask questions as you proceed. Many engine builders set bearings up loose as there is much less chance of a loose clearance causing a problem in the short term. The thing is, they may need servicing in the mid- term.......which is what you are about to do. Not much hurts an engine builders reputation than an engine that seizes soon after it was built......so they tend to err on the loose side because most people won't complain if the engine blows up after 10k miles. Not critizing the builder, he is merely doing what many builders do.
Wonka, I have been wondering why the engine was pulled to start with 3 years ago,,,,any issues ? Also,,,,,,the main bearings 2-3-4 are telling you that you are pushing the limit of a blown application,,,just before a problem maybe ? The chatter marks is probably the crank flexing,,,which will result in an unpleasant sickness in your wallet . 11 % over in a 355 with a 6/71 will result in a lot of boost usually ,,,unless the static compression is unusually low ,,,,and on 93 pump gas,,,I am amazed ! And you are retarding the timing to keep it from detonation,,,,,how much will it take ? That much bearing clearance on a street engine is over my head . And the bearing is marked STD on the back,,,,,I don’t understand how it is +1,,,,unless they were cut down,,,,,in that case that might explain the chatter marks ? I wouldn’t put a piece of Emory to the journals unless you have a very steady hand and some very fine cloth .,,,,those journals look pretty good as is . There is no way I wouldn’t replace the rear seal,,,,it’s only a few bucks,,,,and this is a blown application,,, they put a fair amount of pressure against the seals and the lips wear at an accelerated rate . I don’t really worry about some small scratches in the cylinders,,,,,,and this is a street engine . Good luck man . Tommy
If your worried about the main and rod bearings, get the rods re-sized and the block aligned honed. Looks like shoddy machine work to me. Also, 4 on the mains is real loose for a street engine blown or not. Forget all about high volume pumps. JMO Lippy
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