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Tonight i finally got some time to install the main bearings and take some measurements. Originally i was going to use plastiguage but i broke down and bought a set of mic's and a dial bore guage set from summit.
From my understanding of how this works, i first take a measurement of the crank journal i was about check using the mic. I then took the dial bore guage and attempted to find the smallest measurment on the mic and then zero'd the dial bore guage. I then torqued the main in 10 lbs increments until they reached 110 lbs. I inserted the dial bore guage and again looked for the smallest measurement... That number is my clearance.
I only measured the first 4 mains. Below is a pic of my numbers.
http://reitanfamily.com/gallery/d/11980-1/DSCF4288.JPG
My book talks about using plastiguage and says .002-.003 clearance "to be very good". I just wanted to make sure that my measurements above look ok. Another question i have is that the bearings are not perfectly round, if i take measurements closer to where the bearing halfs meet i get a diffrent measurement.. Still with in limits according to the .002-.003 limits.
Here's a pic of a main reading .0020, the papertowels just kept the dialbore guage lined up while i shot the pic :)
http://reitanfamily.com/gallery/d/11974-1/DSCF4286.JPG
Another Q, the dialbore guage is leaving these marks on the bearings, is that normal or should i be lubing these up first?
http://reitanfamily.com/gallery/d/11965-1/DSCF4282.JPG
Overall pic of the first 4 mains installed..
http://reitanfamily.com/gallery/d/11986-2/DSCF4290.JPG
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Bearings are not suppose to be perfectly round. Your clearances should be slightly more at the parting lines. This is to allow for a better hydrodynamic wedge [oil] to lube the entire bearing. It is also to allow for slight distortion when the main caps deflect. If the bearing were "round" the parting lines would pinch the journal and scrape the oil off which would allow the journal to grab the bearing...instant spun bearing. As for your clearances they should be ok for the smaller journal of the Chevy and the rpm limit of a jetboat but IMO they are on the low side. If it were a Ford with bigger mains I prefer something in the area of .0032" to .004" depending on use and rpm the engine will see.
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Your clearances are dependant upon what you have designed it for. Many racers throw the crank "on the low" to get more clearance. Street engines going for longevity, or engines designed to run very light oils are set-up with less clearance. And rverywhere in between. So one blanket statement upon where it 'should' be does not exist.
And the marks on the bearings are natural for this. Just take a bit of 2000 grit sandpaper and run it with a little moisture in the direction the crank will end up turning in the bearing to get the surface ready again.
But looks good to me so far.
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Got here late on this one but I see it's all taken cared of!.. :cool:
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Got here late on this one but I see it's all taken cared of!.. :cool:
Word :)
