Crank Measuring part 2

Posted By: Moparnut426

Crank Measuring part 2 - 01/29/09 02:08 AM

So I asked about plastiguage earlier, wasnt really happy with my measurments as far a s accurate. So, i used a mic, my crank measures at 2.125 pretty much on the dot. K1 stuff is nice, I dont have an inside mic so I measured them with my digital dial calipers whick I tested with my mic, and its spot on, I had it calibrated erlier this year at a machining shop in town. The rods measure 2.250 without a bearing in it, and each bearing half measures .062. If I add the .062 together it makes .124, that added to my inside measurement of 2.250 makes 2.374, now take that measurement minus the 2.125 i end up with .249. Is this more accurate than plastiguage because I hit .25 almost on the nut. Its a lot of math, and a bit of hassle, but without a dial bore gage its all I have for now. Would you guys consider this an accurate enough measurement, and run it or should I buy a dial bore gage?

or is my math totally messed up? I am not known for my math skills so Im just asking it this will work, dont rake me over the coals if Im wrong.

Kasey

Posted By: dusturbd340W5

Re: Crank Measuring part 2 - 01/29/09 02:11 AM

I will bet that every one will say get a bore gauge the way you are doing it has to much chance of measurements stacking up.

Posted By: Moparnut426

Re: Crank Measuring part 2 - 01/29/09 02:14 AM

Kinda what I thought too, but all my measurements were very to the number, and not to an odd decimal. We will see.

Posted By: RonP

Re: Crank Measuring part 2 - 01/29/09 02:21 AM

Quote:

So I asked about plastiguage earlier, wasnt really happy with my measurments as far a s accurate. So, i used a mic, my crank measures at 2.125 pretty much on the dot. K1 stuff is nice, I dont have an inside mic so I measured them with my digital dial calipers whick I tested with my mic, and its spot on, I had it calibrated erlier this year at a machining shop in town. The rods measure 2.250 without a bearing in it, and each bearing half measures .062. If I add the .062 together it makes .124, that added to my inside measurement of 2.250 makes 2.374, now take that measurement minus the 2.125 i end up with .249. Is this more accurate than plastiguage because I hit .25 almost on the nut. Its a lot of math, and a bit of hassle, but without a dial bore gage its all I have for now. Would you guys consider this an accurate enough measurement, and run it or should I buy a dial bore gage?

or is my math totally messed up? I am not known for my math skills so Im just asking it this will work, dont rake me over the coals if Im wrong.

Kasey

Your math is wrong

Crank 2.125
Rod big end 2.250
bearings .062 + .062=.124
SHould be Rod 2.250 - .124 = 2.126
Rod 2.126(with bearings in) - Crank 2.125 = .001 clearance

Posted By: TS3303

Re: Crank Measuring part 2 - 01/29/09 02:22 AM

yes your math is screwed up. I doubt you have .25 clearance with plastiguage, check your decimals. The rod bearing makes the bore smaller not bigger, subtract the bearing thickness from the bore. 2.250 - 0.124 is 2.126 which would give you .001 clearance. Those numbers are no where near accurate enough. You need the tools to measure accurately to 1/10's (.0001) for them to have any value.

Posted By: Moparnut426

Re: Crank Measuring part 2 - 01/29/09 02:23 AM

Ok, my math has always sucked. With the plastiguage it was dead on .002.

Ill get a dial bore gage coming tomarrow.

Posted By: MR_P_BODY

Re: Crank Measuring part 2 - 01/29/09 02:25 AM

Put the bearings in and torque them down and TRY to
get a reading with your calipers(should use a bore
gauge)subtract the crank numbers from the bearing ID.
Or take the block, crank and your rods to your local
machine shop and have them measure it(which this
would be better)

Posted By: Moparnut426

Re: Crank Measuring part 2 - 01/29/09 02:34 AM

I planned on doing that when I take the whole thing to the machine shop to get ballenced, I like doing things my self as I love to learn. I have taken many engine machining classes, and I have resized rods, and bored blocks, but I used the schools "correct" tools. I havent touched any engine machining tools or equipment in 9 years so Im a little rusty.

Im having Kecks machine do the block work and balencing.

Posted By: Moparnut426

Re: Crank Measuring part 2 - 01/29/09 02:35 AM

Quote:

Put the bearings in and torque them down and TRY to
get a reading with your calipers(should use a bore
gauge)subtract the crank numbers from the bearing ID.
Or take the block, crank and your rods to your local
machine shop and have them measure it(which this
would be better)

Also I didnt want to put the bearings in the rods because my caliper is pretty sharp and I didnt want to knick up the bearings. I have a bore gage coming from Ebay.

Thanks guys!!

Posted By: Quicktree

Re: Crank Measuring part 2 - 01/29/09 02:44 AM

I would take it to a machine shop and have them check it before buying those tools for a 1 time deal.

Posted By: Moparnut426

Re: Crank Measuring part 2 - 01/29/09 02:48 AM

Well I have needed them for more than this engine, I have built a lot of engines and wanted more accuracy. I have always relied on plastiguage, but have always been a littl leery of it. I have A LOT of money invested in this, and dont want any unforseen explosions. This block is window free, and dont want any installed for a long time.

Kasey

Posted By: B G Racing

Re: Crank Measuring part 2 - 01/29/09 02:34 PM

If you don't have a good inside mic or bore gage,then buy your self a set of snap gages and measure your bore with your outside mic.