Author Topic: Crank turns hard in new short block  (Read 1049 times)

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bsprowl

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Crank turns hard in new short block
« on: February 03, 2025, 01:41:58 PM »
As I said in a the cam card thread, turning the crank takes 35 ft-lbs for break away and 30 or so to turn.  And there is more grim in the cylinders that I like so I pulled the pistons and rods out.  Almost all of the pistons have dirt completely around the outside above the top rings.  THe bearings have a date of 2021 on them so the short block was not assembled before that.  I was told it was done in the 2018 time frame.

THe crank spins easily with only the cam and timing chain installed; 10 inch pounds for break away.

My questions are what is the torque for the rod bolts; they are labeled SCAT 44 ARP 8740.  Also what should I use for lube? They have a light coat of moly on them but it looks dry.

Someone, Blair maybe, told me that these bolts should be upgraded if I was going to do some serious racing.  That is my plan so what should I buy?  Years ago, a bolt change required a resizing of the rod is that still true?




blykins

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Re: Crank turns hard in new short block
« Reply #1 on: February 03, 2025, 02:06:52 PM »
The 8740 7/16" bolts torque at 64 lb-ft with ARP lube.  If you change bolts, rods should be measured for size. 

If everything freed up when you pulled the pistons/rods, make sure the rings are gapped correctly, make sure the rod bearings don't hit the radii on the rod journals, and make sure the rods are facing the right way. 
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bsprowl

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Re: Crank turns hard in new short block
« Reply #2 on: February 03, 2025, 05:32:40 PM »
The radii and and rods orientation seem to be OK.  I'll look again to verify that.

If I have to check the rings I've got a problem.  My vision is really poor with and my hand-eye coordination sucks at best at detailed work as I'm ageing out.  I just watched couple of videos and discovered that they make ring fillers; I did it back in the day with a hand file.  Maybe it won't be that difficult. 

Now I have to determine the gap I need.