Okay,

I am in the process of tearing down my BBC and before I bring it to the machine shop on Monday I am going to take some measurements, kind of a before and after. I want to measure deck height and here is what I have done so far:

1. Found TDC using the positive stop method (heads off)

2. Set up the degree wheel to read zero.

3. I have found TDC on the number 1 cylinder using the degree wheel.


Questions
1. Can I measure the deck height as is or should I also use a dial indicator and base to make sure the piston at TDC?

2. I am also assuming that I can rotate the engine every 90 degrees and measure the piston to deck height on those cylinders that are at TDC. Or do I need to do each cylinder separately using the positive stop method and or in combination with a dial indicator/base to locate TDC)


Also what else should I be looking for as far a bearing wear etc...?

The easiest way to measure how far down the pistons are in the bore is with a deck bridge and a dial indicator.

You simply set the bridge on the flat of the deck with the indicator on the deck and zero the gauge making sure it has some travel taken up so it can meaure further down the bore.

I then perfer to have the bridge stradle the bore with the indicator as close to being over the piston pin bore as possible. This helps take out some of the highs/lows from piston rock. You'll still measurure some piston rock, in the .002 to .004" range depending on the piston to bore clearance. With the rock measurements, I tend to average them out high and low to come up with the middle measurement.

I've yet to find an exact way to measure this and get 100% accurate measurements. When mocking up my new shortblock, I wrapped the new pistons (no rings) with tape around the ring lands in an effort to stablize the piston. It's helped, but the piston still rocked enough to have some differences in the measurements. I went over every piston three times till I was satisfied I got the most accurate/repeatable measurent for each.

Once the deck bridge/indicator is over the piston, simply rock the crankshaft to take that piston up to TDC. You can simply turn the crank and watch the indicator top out, then go down. The top out figure is your clearance.

Thanks, that’s what I thought. The only questions is that that the pistons that I am using are the TRW/Speed Pro L2308AF30 which has quite a large dome, with a machined flat area near the top of the piston so that is where I have been taking my measurements from, so I can assume I am going to have more piston rock and a less accurate measurement.

My pistons were a 50 cc dome JE race piston. There was small portion of the flat quench that wrapped around the dome which was above the pin bore, just big enough for the dial indicator to measure off of.

Thanks I'll take a look at mine, I have the same 50 cc dome.

I find it easiest to keep it simple, and not outsmart myself... a straightedge and a feeler gauge, and average it out for the "rocking".