Thread: Another build question

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Originally Posted by erik erikson

Corner to coner with a straight edge.
If I find .004 or more with a feeler gauge it is time to deck the block.
There are a few people that will disagee with what I said.

I'm not gonna disagree with you Erik, but that isn't exactly what I had in mind. What I was referring to was.....are the decks square with the crank?

Jim, here's how I do it. First, get the pistons you will run. Clean the block up so you and the machine shop owner won't get greasy handling it.Take the pistons, rods and the block to the machine shop and get the block bored and honed for those pistons and rings. DO NOT HAVE NEW CAM BEARINGS INSTALLED YET. You're gonna hot tank the block later and the caustic soda will eat the cam bearings. Have the rods resized and fitted to the pistons. If you're gonna get the crank turned, do that next. Now take the rod/piston assemblies, crank and block back to your shop. If you're good friends with the machine shop owner, he may let you do this at his shop so you won't have to haul the parts back and forth. Most shop owners though, will not want you to do your own work in their shop for reasons of liability. Plus, you'll be in their way.

Mount the block on your engine stand. Roll it over and install the crank on oiled main bearings. This is a good time to plastigage the bearings if you're gonna do that yourself. If you're not gonna check them, you don't need to torque the mains down, just give them a moderate tug on your ratchet handle. Otherwise, have the machine shop mike the bearings and take their word for the clearances. Now, choose any piston/rod assembly and install it (less piston rings) on #1 rod journal on oiled bearings. Roll the block over and mount a dial indicator on the deck. Bring the piston to approximate TDC and pre-load the dial by about 0.200". (adjust the dial/plunger on the stand so that the plunger moves up about 0.200" against the piston crown with the piston at approximate TDC). Now, jockey the crank back and forth until you see absolute TDC on the dial. Now, place a depth mike on the deck and let the spindle slide down the cylinder wall until it contacts the crown of the piston at the wall. Do this at the 3:00 O'Clock and 9:00 O'Clock positions of the piston as you're standing at the side of the block. If you check at the Noon or 6:00 O'Clock positions, the piston can rock on the wrist pin and give you an erroneous reading. With the block deck free of oil, write the measurements on the deck with a Sharpie. If you get measurements that are very much different side to side on this one piston, then the rod is probably bent. Disassemble the rod/piston from the crank and assemble another one in the #1 hole and check again.

Using this very same piston/rod assembly, disassemble it from #1 cylinder and move it to #7 cylinder. Repeat the above procedure to find the piston deck height on this #7, then move to #2 and #8 so that you will have measurements on all four corners of the block.

If by some act of God the decks are square with the crank, thank your lucky stars and go buy some lottery tickets. If not, you will have the measurements to give your machinist who can then cut the decks to square. You will also know the piston deck heights of all the holes so you can make a revised decision about cutting the decks for matching up the gaskets for 0.035" to 0.040" squish. If you decide you don't have to cut the decks, then follow Eriks advice about checking to see if the decks are flat before you take the block back to the machine shop. If the piston deck heights are square and the decks are flat, go back to the store and buy some more lottery tickets.

On this trip to the machine shop with the block, have it hot tanked and replace the cam bearings.

Oh yeah, last thing. If you did find bent rods, have the machine shop straighten them or replace them with new rods. www.summitracing.com has Eagle SIR rods for $235. per set.

An afterthought: If you can't buy, beg, borrow, steal or rent a depth mike, you can use the slide on the end of a 6" dial caliper to measure depth. The slide has a little scallop cut into it. You want to position that scallop right next to the cylinder wall so that the very end tip of the slide contacts the piston crown. If you can't buy, beg, borrow, steal or rent a dial indicator, you can check for piston at TDC by using a straight edge held on end across the bore and slip feeler gauge blades between the straight edge and the piston crown right next to the cylinder wall. Move the piston up and down with the crank snout until you get the thinnest blades to go in snug.