Like the title says, I’ll be building a 370ci shortblock over the next couple of weeks. I won’t have any dyno numbers or track results as I don’t plan to actually put this in a car. I’ll most likely end up selling it locally or something, so I thought I would document the build and maybe help someone planning on building their first engine. I have invested in tools that most people probably wouldn’t, especially if they only plan to ever build one or two engines, but I will eventually compare bearing clearances as measured with plastigauge and compare it to measurements taken with OD micrometers and a dial bore gauge.

Parts List:
GM Gen III 6.0L iron block
Wiseco K398X3 pistons w/ pins, locks, and GFX rings
Scat 26125716 connecting rods w/ ARP 8740 bolts
GM 3.622” stroke crank w/ 24x reluctor

Last night was Day One as I started on the block by measuring the main housing bores with the main cap bolts torqued to OEM spec. The tolerance for the bore ID is 2.7509” to 2.7515”. I’m using a Mitutoyo dial bore gauge that was set to read zero at 2.7509” and marking on the caps how much bigger the bores are. All of the bores are within tolerance, with the #3 main bore being the loosest at 2.7512”. This is an important measurement that you usually wouln’t measure with plastigauge, which to me, justifies the cost of a dial bore gauge.



Next I checked the crank journal OD’s using an OD micrometer to verify what bearings I will need. The tolerance for the mains is 2.2247” to 2.2252” and on the rods, it is 2.0990” to 2.1000”. If the crank had been ground, the meaurements would obviously be lower. I check for taper and out of round by meauring in several spots around and along the journals. The journals all checked out within tolerance and less than .0001” taper and out of round.



The crank will need to go to the machine shop to get balanced, so I weighed the components to calculate the bobweight. If you provide the bobweight, most machine shops will charge you less since they don’t have to do it themselves. I’ll be using Wiseco 4.030” bore flat top pistons with Scat 6.125” I Beam rods and ARP 8740 bolts.



I still need the rod bearings to calculate the bobweight, so I’ll order them now that I’ve verified the crank hasn’t been ground and I will get the crank balanced after they have arrived. For now I’ll send the block to the machine shop to bore and torque plate hone the cylinders and the skim cut the deck surface.

 

Awesome Kent. Looking forward to the Plastigauge vs. dial bore/mic test results. I did this myself in the early 90’s and found the Plastigauge to be accurate, to within .0015”...but that was 26ish years ago.

 

Yeah, this is great. Thanks!

 

I've always been told Plastigauge sucks, but I've never really seen a comparison. I'll order the plastigauge with the bearings today so I can see for myself.

Thank you, I'm hoping people find this helpful for when they attempt to build a shortblock on their own.

 

how much? i just toasted my bottem end lol, my oil looks like a bass boat

 

Thanks for taking the time to show others what it takes.

 

+1, and looking forward to the plastigauge compare.

 

Here's a quick Plastigauge vs dial indicator video.

But don't let this detour you. I'm intrigued to see your findings. Sub'd

 

great video link! That is probably one of the best comparisons, explanations I have ever seen.