Main Bearing Clearance

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Rodzilla said:
Its a street car, very little track time. 340 Stroked to 416. Shooting for 550-600HP 550 TQ. Will be Dyno'd. Eagle forged crank, recently balanced, polished and chamfered and apparently no one checked my clearances worth a crap. Glad I did my own plastigauge. This car will see 2000miles a year at most. Show quality resto, but still a driver for local cruising. I want to see .002" for clearance, I think that will be a good number to shoot for and for sure the .001" I have right now aint going to cut it. Redline will be 6800-7000. Oil will be a good quality 10-30 to start and later going to royal purple synthetic 10-30 as well. Oiling is via HV oilpump, oiling mods on sticky in this section done but I went with the bushed lifter bores.
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Yow! Street car at 7k! Ok, I Gotcha... I really think you should be able to hit your stated goals at 6k but anyways, yeah, .0025 should be about right for your intended use. Did you plastigauge that crank at 90 degree intervals? If you did and all was the same, a good polish by a REPUTABLE crank guy will get you where you need to be. If you did not, and do and find an appreciable difference, that crank needs to reground .010 under to straighten out.

BTW, Kudos to you for asking and measuring! You did the right thing.

Break in with dino oil and then switch to synthetic after about 2k. :)
 
I went to one of the most reputable machine shops in the area, thats what pisses me off. I guess it goes back again for more polishing. I measured the plastigauge at 90 degrees from the parting line on the caps. But I didn't do it several times with crank turned 90 degrees for each. I kinda figured if it clearances only a .001" on a couple attempts at same spot then not much point in trying it more. I will give it a go since I have time to kill before Monday when I can get crank back to machine shop.
 
If you do check the clearances at 90 intervals, you'll see if the crank is offset. Your measuring point is correct, the crank just needs to cleaned of plastigauge and rotated 90 for every measurement. Cheap insurance....

Your shop may not be to blame, depends on what you asked of them. You caught it though, and now you know what to ask. ;)
 
sr71mopar said:
Mics are cheap.
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Mine were not.... nor is the time/tutalage taken to know how use one, lol.

A mic will not let you know if the crank was incorrectly ground in a horizontal plane either, plasticrap does work in that respect without a granite table, dial indicator and V blocks..... on the mains anyway.

:happy1:
 
Bearing clearance is the result of the bearing bore, the bearing shells, and the crank surface. Without a mic and measuring you can't tell which might be causing it. this is one of the issues with plastigage and why if you're serious (and it sounds like you are) then buying the right tools can only help. You're beyond the "street engine" power levels and thigns have to be right, not "ok". In any event, you should be able to get the bearing shells to get the clearance you want. But if it was me, the shop should mic the bearing bores and the crank while you watch (pay them for the labor) and then you can see how it should be done.
 
i'm just glad that you plastigauged the mains. you saved yourself tons of money and time. good luck on getting it right bro
 
moper said:
Bearing clearance is the result of the bearing bore, the bearing shells, and the crank surface. Without a mic and measuring you can't tell which might be causing it. this is one of the issues with plastigage and why if you're serious (and it sounds like you are) then buying the right tools can only help. You're beyond the "street engine" power levels and thigns have to be right, not "ok". In any event, you should be able to get the bearing shells to get the clearance you want. But if it was me, the shop should mic the bearing bores and the crank while you watch (pay them for the labor) and then you can see how it should be done.
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Yep, gotta have main saddle bore diameter right 1st, it's a measurement of the main bores torqued without bearings, then torqued with with bearings, then mic the crank....it all adds up to a more accurate measurement and clearance reading.
 
moper said:
Bearing clearance is the result of the bearing bore, the bearing shells, and the crank surface. Without a mic and measuring you can't tell which might be causing it. this is one of the issues with plastigage and why if you're serious (and it sounds like you are) then buying the right tools can only help. You're beyond the "street engine" power levels and thigns have to be right, not "ok". In any event, you should be able to get the bearing shells to get the clearance you want. But if it was me, the shop should mic the bearing bores and the crank while you watch (pay them for the labor) and then you can see how it should be done.
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I just paid $4500 at the best machine shop in a 500 mile radius. So I was expecting way more then "ok". I was expecting perfect, and even though I was told by them to just go ahead and assemble I wanted to check clearance myself even if only with "poormans plastigauge". So I am pissed and I will be having a serious discussion with them Monday morning. There will not be any more $$$$ coming out of my pocket as far as this ckearancing issue goes.
 
Questions;
Does anyone think that 110 torque PLUS 90 deg is a little snug for main bolts?

Are you oiling the bearings before checking clearance?

Are the other mains installed and torqued?

Have you checked with crank in another position?
 
dartjack said:
Questions;
Does anyone think that 110 torque PLUS 90 deg is a little snug for main bolts?

Are you oiling the bearings before checking clearance?

Are the other mains installed and torqued?

Have you checked with crank in another position?
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Never torqued to 110ft/lb plus 90deg? My paperwork with ARP studs said to go to 110. All main caps torqued at once. Then I got a thou clearance so I re did check at 90 ft/lb and still had a thou clearance. I mention in a previous post I will be trying in 90degree increments.
 
Rodzilla said:
I just paid $4500 at the best machine shop in a 500 mile radius. So I was expecting way more then "ok". I was expecting perfect, and even though I was told by them to just go ahead and assemble I wanted to check clearance myself even if only with "poormans plastigauge". So I am pissed and I will be having a serious discussion with them Monday morning. There will not be any more $$$$ coming out of my pocket as far as this ckearancing issue goes.
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Did they align hone the block following the install of the main studs? Did they have to fix the crank journals at all?
 
Align bored and honed, I'm running billet main caps from MRL Performance. No fixing reported, balanced crank and polished according to my invoice.
 
Sounds like the caps might not be proper size. Also curious why the had to polish the new crank.
 
Caps had to be cut down, I don't want to try to repeat info cause I was clueless in the first place as to why they weren't working...lol. Polishing was done I assumed in order to meet the required clearance.
 
All caps have to be fitted to the block, and then the main bores re-cut and honed. So that's all normal. I'm just curious why the crank would be re-polished. My money's on the main bores, but I am curious about the condition of the crank. I'd definately want to be present when they do thier measuring.
 
dartjack said:
Questions;
Does anyone think that 110 torque PLUS 90 deg is a little snug for main bolts?

Are you oiling the bearings before checking clearance?

Are the other mains installed and torqued?

Have you checked with crank in another position?
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This is a very good question.

See milodon says 85ftlbs w/light oil for their main studs, and now im reading that arp wants 110ftlbs w/moly lube...

I have already run one of my motors with 85ftlbs on the main studs with no issue, but it makes u wonder...
 
moper said:
All caps have to be fitted to the block, and then the main bores re-cut and honed. So that's all normal. I'm just curious why the crank would be re-polished. My money's on the main bores, but I am curious about the condition of the crank. I'd definately want to be present when they do thier measuring.
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Not to sure, the whole rotating assembly was balanced, anything to do with that? I'll be on the phone tomorrow with shop to see. How do most guys check clearances, with bearings dry or a light film of lube? I don't think torquing dry would be good? I put a miniscule film on top bearing and and nothing on cap bearing. I also have .008" play at thrust bearing.
I checked all my rod bearings today and I have .001" to .00125 clearance on those. Too tight as well. Torqued to 63 ft/lbs as per Eagle specs.

I have only had 2 pistons in at once at the most because I have clearance issues at the Stud girdle and rod bolt to bottom of cylinder, not all but I need to do some clearancing yet. But with 2 (no rings) in I can turn the crank super easily, no binding or seeming tight with the thou of clearance I measured.
 
Rodzilla said:
Not to sure, the whole rotating assembly was balanced, anything to do with that? I'll be on the phone tomorrow with shop to see. How do most guys check clearances, with bearings dry or a light film of lube? I don't think torquing dry would be good? I put a miniscule film on top bearing and and nothing on cap bearing. I also have .008" play at thrust bearing.
I checked all my rod bearings today and I have .001" to .00125 clearance on those. Too tight as well. Torqued to 63 ft/lbs as per Eagle specs.

I have only had 2 pistons in at once at the most because I have clearance issues at the Stud girdle and rod bolt to bottom of cylinder, not all but I need to do some clearancing yet. But with 2 (no rings) in I can turn the crank super easily, no binding or seeming tight with the thou of clearance I measured.
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When you use platigage all surfaces MUST be oil free, oil will give you a false reading.
 
66 Dartman said:
When you use platigage all surfaces MUST be oil free, oil will give you a false reading.
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Exactly! Oil can take up a lot more room than you think. Without oil you may have .002~.003" clearance. And I agree with ramcharger's earlier statement that with your build you should shoot for .0025" clearance. Even .003" is fine. I wouldn't go any tighter than .002" for sure. Even though you say your not going to race it your description of it being a stroker that will make up to 600 hp and turn 6800 rpm that's an area that requires looser than normal bearings. Not as loose as a race engine but definitely a lot looser than a grocery getter. Don't worry about torqueing it down with no oil on the bearings. Won't hurt anything.
 
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