Alright guys I have lt1 355 balanced bottom end and all clearances were checked the mains were .002 and rods were .0015 and i used a new gm stock flow oil pump. the only bearings I didn't check were the new cam bearings. "Paid local shop to install them" May have been a mistake. it has a llloyd Elliot cam 226/230. .575 lift with patriot springs 155lb seat pressure well after I built it and ran about 200miles I thought I had a lifter problem then it turns out I had something else. I tore the engine down and found the bearings are all chewed up in the bottom end. I did have oil to the top end and at first had about 60psi cold and about 25 hot idle. but that soon chanced to about 60 cold and about 10-15psi hot. I did notice that the cam bearing were all clocked wrong most are with the oil holes lined up at 6oclock could this cause loss of oil pressure to the mains and rods? What is really odd the mains #'s 2,3,4 were damaged the most. 1&5 had damage but not as bad. Rods varied through out no real pattern any ideas on what might have went wrong will be a big help. The oil pump acted as if it would suck the pan dry at times like it had an internal leak.. I watched the pressure drop while cruising down the highway @ 2300rpm and come back. Any ideas would be a big help guys?
could cam bearings installed wrong cause this?
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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?
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.
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
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
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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.
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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??
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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.
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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.
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"
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
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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.
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Still, .002 is potentially .00198 area depending on mic tolerance and what not. I am shooting for .0025-.003 on my rebuild.
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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.
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.
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..
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