that's rough.

anyways, your question whether bad cam bearings can cook your crank bearings?

absolutely.

SBC oil flow is top-down.

oil pump will pump it right to the top, to the cam bearings first, then it splits off and goes to the main bearings, and the lifters.

if you lose a bunch of pressure from a roasted cam bearing then not much oil is going to get to the crank at all.

i'd be chasing the shop that did your cam bearing install?

 

Here is the other problem the cam bearings are barely scared. They dont look all that bad. Sorry didnt put that in last message. But yea im really disappointed with them they have done about 5 or 6 sets of cam bearings for me over the years first on a lt1 though but other sbc and bbc. Not sure what happened maybe a new hired hand or something. But I cant understand what happened.

 

could be something else. you said the cam bearings were 'clocked wrong' though..?

 

unlike old SBC where you lined up oil hole of bearing to journal, the LT1 has a full groove in the oil journal. Ideally the oil hole of cam bearing (with block facing up) wants to be at the 2-3 o'clock position so when you have cam rotation you get a good "oil wedge" to lubricate between bearing & cam

There is also specific order cam bearings come in with # 5 bearing having 2 holes in it that want to be about the 2 & 10 o'clock position (block facing up

typically the block is upside down when installing so the "o'clock" positions I mentioned are with the block right side up. I just put a sharpie pen mark on the cam bearing so I can confirm I am putting it in right

Sadly many machine shops don't know the difference.

Also there is a steel check ball located in the rear main gallery hole, adjacent to oil filter boss. Drive this out from the top but remember to replace it after block cleaning. Without removing it you can't completely clean out oil gallys

maybe your shop that did it thought gen 1 SBC where they line up bearing hole because the journals are not slotted like LT1.

so yes cam bearings installed wrong will FU oil pressure and flow and kill bearings

 

...

Also there is a steel check ball located in the rear main gallery hole, adjacent to oil filter boss. Drive this out from the top but remember to replace it after block cleaning. Without removing it you can't completely clean out oil gallys

maybe your shop that did it thought gen 1 SBC where they line up bearing hole because the journals are not slotted like LT1.

BALL mentioned a good possibility. If that ball is left out the oil filter gets bypassed but still goes directly to the brgs. But only u can look at bearing and see the type of damage. Particles leave long scratches. Is that what u see. Or are the brgs have deep wear exposing lower metal layers? Maing and rod brgs same type damage? Like the crank is hammering in in localized spots? Got any pix??

 

Yeah the holes in most of the cam bearings are not to be installed with the holes lined up with the holes running down to the main bearings and the ones at #2,3,4 were and those main bearings were damaged the worst.

 

Yeah the holes in most of the cam bearings are not to be installed with the holes lined up with the holes running down to the main bearings and the ones at #2,3,4 were and those main bearings were damaged the worst.

cam bearings 2,3,4 had oil holes lined up....not right

if oil holes are aligned up exactly (oil hole in the bore saddle and oil hole on the cam bearing) oil pressure can potentially feed back, momentarily preventing oil from traveling around the journal.

I would think this would also cause interruption or minimize oil on crank & rods. If those bearing clearances were on the "tight" side...they would be more vulnerable to any interruption in oil flow through engine passages potentially affected by having the cam bearing holes lined up with the journal hole

Dynamic brings up a point on running slightly wider bearing clearances as many builders do this and spec a HV pump so a thicker oil wedge can get between bearings for crank & rods

 

it takes a while to wipe a cam bearing out. with only 200 miles, im not suprised that you aren't seeing evidence of a damaged cam bearing, but something definitely starved your bottom end of oil... what else would it be?

 

Well thats were im stuck. I think the cam bearings are the culprit but im not sure. I know what the clearances were and it had decent oil pressure for a little while. But something isnt right.

 

Just to add, I ran my motor at WOT and then a minute or so with no oil pressure what so ever, and my cam bearings look great. May wanna look elsewhere as well.

 

One thing to remember is the cam is turning at half the speed of the crank so crank bearings usually get toasted first. Had a bad oil pump melt my crank bearings to the crank one time. Cam bearings looked brand new.

 

While it IS possible for a cam bearing to cause an oil pressure loss, it should be pretty obvious on a visual inspection.

Those rod and main clearances are extremely tight. And how were they checked? Plastigage or bore dial and micrometer?

I'd add .001" to both rods and mains and run a HV oil pump.

 

I checked with plasti gauge and dail caliper. Not ideal but I know how to use them. I have worked in a machine shop in the past. Did not have a bore gauge available If the tolerances were the case I would think the rods would be damaged the most and they are not that bad compared to the middle mains. I am not thinking the .002 mains are that bad. I could easily spin the crank with a finger and it spun freely with no dragging. The rotating assembly and bearings were a balanced and matching kit I did see any real variation between any of the bearing surfaces I measured all the mains and rods even wrote them down. The rear main has the most clearance at almost .0025 but all the others were .002 and the rods were .0015 all measure the exact same no variation. Ive assembled other sbc's tighter and have had good luck I just dont rag on them right off the bat. But this one im pretty confident the mains and rods arent the issue. But after about 15 other motors ive built this is the first. "Play with fire enough your bound to eventually get burned lol"

 

I will post some pics soon! Ive been busy! Sorry

 

Anything past .0025 is throwing oil away and creating more heat, according to the callies study.

Still, .002 is potentially .00198 area depending on mic tolerance and what not. I am shooting for .0025-.003 on my rebuild.

 

with wider bearing clearances you run a thicker oil. 10-40 or 20-50 depending on how much wider

 

I wouldn't use Plastigage on my lawnmower... You need a dial bore gauge and micrometer that are capable of reading down to .0001" to accurately set up bearing clearances. Otherwise you're just hoping to "get it close"...and "close" can be a pretty subjective term. And .002" on the mains, and .0015" on the rods is too tight for a performance engine with journal diameters of that size. I wouldn't even run a truck engine that tight.

It's all about cooling the bearings. You have to allow more clearance on a performance engine so that more oil flows through and keeps localized bearing surface temperatures down. In order to flow the extra oil through there, you have to run a pump capable of pumping more oil - a HV oil pump. But, there seems to be so much misinformation out there in cyber-land about HV pumps that everybody is scared of them. Not every engine needs one, but a properly set up performance engine that's going to see any kind of rpm should have bearing clearances that necessitate one.

I set up my 396 bottom end at .0028" on the mains and .0023" on the rods, and I'm running a Melling M155HV oil pump. On my race car engine (late model stock car), bearing clearances are .0033" on the mains and .003" on the rods, with a 4-stage dry sump oil system. As mentioned, thicker oil should be run with wider clearances. The 396 will get 20W-50 Mobil 1, and the race engine runs 15W-50 Schaeffer's.

 

here is a pic of the mains

 

What I dont understand is why didn't the rods burn like the middle mains did there is little damage to the rods vs the mains. I have had a bad encounter with a high volume oil pump on a bbc in the past thats why i shy away from them. I was toying around with a guy in town and was keeping the rpms up around 4500-5500 for about 10-15secs and noticed they oil pressure started to pulse. 60psi then 25psi then back. scared the crap out of me.. And this car is more for show not really a race build. I am not all that serious. I may jump on it for a little bit but it probably will never go to the track.. I have a 2011 hayabusa for my speed fix. I built the bottom end more closer to stock that is why my cam isnt really all that big. it won't see a bottle or anything like that.. I just wanted more torque and hp than stock with a good sound to it. Plus a long lasting build.. I have a sbc that I have over 100000 miles on and it was even closer in tolerance than this build. im not arguing with you guys on a race motor should be more loose on the tolerances.. I get that... There is a place for it.. I was basically going by the service manual.. "please note I have a dial bore gauge on the way' I have learned my lesson.. I still think there is something else that is the cause of the problem.. But guys thanks for all the help and advise!!! it is not falling on deaf ears..

 

Well it looks like low oil press. I dont see any real scratches like from metal particles. And i dont see any "hammered" local areas.

U could take a long thin drift/punch and try and see if that steel ball is missing. I believe u have to knock it out from the top of block on rear "china wall". The ball comes out on the rear main saddle in a hole next to the bolt hole on drivers side (i think) when block is right side up or other side when upside down looking at the saddles. But i does look more like low oil press or lack of oil.

Now no oil at all would have seized things up and melted/welded some brg material.

Dont know what to say of the better condition rod brgs other than just a matter of time for them also. Rods maybe a little less loaded. Who knows - but im sure someone here will claim they do. U did say the rods ran a tigher 0.0015" clearance. But that wont explain the 0.0025" gap on the rear main - it looks the best.

Have to ask did u use "fresh" plasti-gauge"?? It tends to dry out in the tool box over time - sorry dont know the self life myself.

 

Hope you didn't cheap out on the dial bore gage.The cheap ones only measure to 0.0005" which is worthless when checking engine parts.

You need a bore gage that truly measure down to 0.ooo1" They cost more.

 

Did you check the crank for TIR?

 

this is why guys just building an engine or two should let a machine shop do the measuring.

the proper tools to do this stuff dont pay for themselves until you've built quite a few engines.

then after you've used them, you need tools to calibrate your tools

I have used plastigauge quite a few times, though, but to use it properly is a real bitch.

 

Im getting a better quality bore gauge. Thanks for the insight.
What is TIR? Sorry dont know what it means
yeah the plastgauge was fresh. I tried getting measurements with my calipers and mics but wasnt really the best tool for the job but I do know how to use them well. I worked In a machine shop and did QC work so I know how to use them. Im pretty confident in my measurements. Thats why im asking about other possibilities other than to loose or to tight of bearing tolerances.
I did notice the very rear cam bearing was not pressed all the way in. The oil hole was barely open to the galley. Like ony about 1/3 of the oil hole was open. But the cam and bearing looked okay. But it kinda looks like the oil was possibly passing between the bearing and block towards the back of the block. But cant really confirm that I will drive out the cam bearings to check. And from what I have read says the rear main is feed right off the pump right after the filter and all others are feed after the cam. May explain why the rear main isnt really bad. But dont really explain the front main. But guys im just asking for ideas. I know it may very well be my measurements were off. But is there something else wrong with either the block or something else.im already gonna have the block line honed and checked by another shop.

 

Ok dude i did some research for as i see your trying hard to find this answer. And i read theres really no bad way to install cam bearings other than having the holes lined up with the oil galley holes. What im saying is u dont want the cam brg holes to line up with the galley feed holes - can create a backpress - but this would only affect the cam brgs and not the mains or rod brgs. U want the cam brg holes at 'bout 2 o'clock from the feed holes to ensure the oil flows in the block grooves around the back of the brg and do that oil wedge thing once on the cam journal. But i dont think the hole alignment can affect the main press - only a large cam to brg clearance would drop press.

The more i read on this ball plug the more it could be the problem. The Chevy Power manual says without that plug (on a bowtie block its a regular metal plug rather than a ball) the engine will loss oil lube to the mains and not live/survive. TPIS says that also. Im think'n w/o the ball (plug) u would still read good press but oil would no longer be forced into the main gallery.

U really need to check the ball/plugs is there. U need a long small dia drift to knock it out from the top of block.

Now a bad/large TIR (total indicator reading) could cause that damage but the second check for that TIR is the turn by hand method which u said it passed. U could retest TIR now but maybe in a set of V-blocks.

Bore gauges are cumbersome to me because i rarely use them and have to relearn how to take and how many readings to take. Theres some handling methods to get the right orientation needed to taking a correct reading. Good luck to u.

 

Now a bad/large TIR (total indicator reading) could cause that damage but the second check for that TIR is the turn by hand method which u said it passed. U could retest TIR now but maybe in a set of V-blocks.

Total Indicated Runout...not total indicator reading. With something as big as a crankshaft this is typically done in a lathe between centers with a dial indicator. Putting something this heavy on v blocks will scratch surfaces that shouldn't be scratched.

The idea is to check if your crank is straight.

 

If you are only out a few thousandths with runout, it could most likely still spin, and a bent crank will beat the crap out of the middle mains. At the very least its something I would check before reassembly to make sure everything will be checked off the list to worry later about.

 

Okay thanks for all the responses. I didnt check for run out. I didnt think it would be an issue cause it was new. But after thinking about it maybe it should have been checked. I will have the machine shop check it cause the crank needs to be turned. I will definitely check the check ball/plug to see what is going on. This is the help I need. I doubt the crank was warped but hey ya never know. But I wanna explore all of the possibilities. THANKS GUYS!