Main bearing cap wiggle

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nothingbutdarts

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#4 main bearing cap just slides into the block & actually you can hold the 2 sides of the cap & slightly twist it just a very small bit. The other 4 caps you have to lightly tap them into the block. Is this #4 cap OK?
 
could you knurl the edges or would it have to be align bored again? Maybe bolt it up, torque it down and take a punch and tap some knurls at the base of the block?
 
Is it possible someone swapped that cap out of a different engine? I would start by checking VERY VERY carefully for burrs/ dirt/ etc
 
Is this an engine you’ve used or one that an engine or block you’ve picked up and started work on? Did you disassemble it from a complete engine? If so, how did the crank and bearings look on number 4? Any evidence of micro welding on the cap or block parting line?
 
nothingbutdarts said:
Is this #4 cap OK?
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As is, No it's not. This engine had to of had a bearing strain/stress/failure issue in order for the main cap to "shrink". If it was a SBC 283-327, W chev 348-409, chev 230 250 292, this is common,old age, BUT a SBM with a shrunk cap has had an issue. Can it be fixed? Yes.
As is, without corrective measures, it will pinch the side clearance of the bearing. The cap needs to fit tight in to its saddle.
 
This is "Toms" Hemi, PIC 2 , that's had a bad day with a crank. So bad, that if you look at the colour of the main caps, some are actually "substitutes", **** Can be fixed. Yes, that's a sawed of oil pump section. For eg, on a SBC that alone will change the shape/ size of the rear main by .0009 thou.
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Yes, an engine I used, years back it spun a rod bearing on 7 and 8 journal & got tight, it has been sitting a number of years since then. I believe it spun the bearing because of the oil filter adapter gaskets being put on incorrectly & dirt getting in the oil. The bearings in # 2 look the same as in #4. This 340 has been sitting since I pulled it out around 1988 and I don't remember much about it anymore. I dropped the crank out of it a couple weeks to see if I could get the crank repaired. I'm quickly changing my mind about it.
 
nothingbutdarts said:
#4 main bearing cap just slides into the block & actually you can hold the 2 sides of the cap & slightly twist it just a very small bit. The other 4 caps you have to lightly tap them into the block. Is this #4 cap OK?
Click to expand...

Torque it and measure with a dial bore gauge. Then correct with staking each side of the register of the block and measuring over in over till you get it right.
It will feel smooth across the cap/block parting line when its right.
 
You can spread the #4 cap carefully using a press to get the snug fit. Block will then need to be align honed.
 
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