I am building an engine and need to measure bore clearance. I have adequately sized Starrett inside and outside micrometers. Do I need a dedicated bore gauge, or will the inside mic do the trick?

If I need a bore gauge, what is a good suggestion for the very occasional builder? Eastwood (who normally offer quality stuff) has one on ebay for only $50!?!?!

http://cgi.ebay.com/ebaymotors/Dial-...spagenameZWD1V

There are also several Fowler brand gauges that are less than $100 (never heard of Fowler but that's no big concern).

Thanks in advance.

 

If you are not really strapped for cash, buy a bore gauge. Not only can you use it for piston clearance, but you can measure rods and mains as well.

The nice thing about a bore gauge is it is a relative measurement. That is, you measure the piston diameter with a micrometer, lock that setting, then zero your bore gauge to that setting. So even if the absolute calibration of your micrometer is off, you won't make a mistake on clearance.

All the other methods require an absolute measurement. That is, you measure the piston diameter, then measure the bore diameter and you subtract the numbers to get clearance. If you have a poorly calibrated gauge, you're dead.

Most, if not all machine shops use bore gauges to set clearances.

 

You have to use a bore gauge.

I used the next highest setting, set it to 0 with a outside mic and the clock and measure how much smaller the bore is. Then compare to the diameter of the pistons.

 

feeler gauge works best-
100% reliable
low cost

 

Most pistons are not measured at the tip of the skirt and measuring with a feeler gauge is not very accurate.

We use Sunnen bore gauges and setting fixtures to do the measuring with and mics to measure the pistons.

If your checking a block that was plate honed you may want to invest in a torque plate to check the cylinders!!

 

Another trick it to torque the head on the bare block using an old gasket and measure the bore from the bottom up.

 

I have a brand new Sunnen bore gage 2 inch to 8 inch as this cost 705 new and will sell it for 600 dollars. if intersted PM me

 

I use my inside mic, but measure it with the same mic that i use to measure the piston.......for the same reasons as described by Cris. I do the same for measuring the mains and rods as well. I have the inside mic setup so it's very hard to turn so it doesn't move when measuring with an outside mic. However, if i built more engines, i would buy a decent bore guage

Good luck.

 

An inside mic (a real inside mic not a SNAP GAUGE) will work if you have a good "feel" for how to use it. However its not the most accurate way of doing it unless that's the way you learned to measure bores and have been doing it that way for a long, long time. Feel is everything. I know an old machinest in NC that still bores and hones his blocks this way and can get within a .0003 to .0004 of round and taper on a good day. Usually its more like a half but thats pretty good considering what he is working with. Most people can't even repeat their measurement within a half using an inside mic. Like I said its all in your feel.

A dial bore gauge is much easier to use properly. Set your outside mic, insert dial bore gauge in to outside mic , zero dial bore gauge, insert dial bore gauge in to bore, measure bore perfectly to a tenth of a thousandth. Easy and fool proof.

Fowler makes pretty good instruments for the money.
Will

 

:o Sorry to contradict nearly everyone but it depends on what u want to measure for. If your checking bore taper, wear and prepping for machine then bore gauges are what u need. But to custum hone each piston to fit just an individual cyl then the long feeler gauges (foot long or longer) do the job best. I don't see how u could hand hone a single piston to fit the entire bore length without a feeler gauge. What i'm saying is the feeler gauge verifies the true clearance.: :

Hope this helps more than confuses u.
cardo0

 

What do you mean custom hone each piston??? Or am I missing out on some new machine shop process.

The pistons we buy are well with in .0002 of each other and they have to be measured at a certain place on the skirt, The piston skirts have taper and at the very tip of the skirt is the largest diameter of the skirt and thats not where you measure for clearance but using a feeler gauge to check for piston wall clearance it the very bottom of the skirt is where your going to get your measuremnt from as most piston manufactures want there pistons measured an .005 down from the bottom of the skirt with the piston up side down.

And you would have to buy feeler gauges in tenths not thousands to check for piston to wall clearance if that was the right way to check for clearance. At our shop we work in tenths not thousands.

Plus using a feeler gauge to measure piston to wall clearance you would have to keep the piston square in the bore which is hard to do with a tapered skirt and wedging a feeler gauge in between the piston and wall.

If your working in .001s an inside mike or snap gauges might work fine but if working in .0001s then a good set of bore gauges and a good set of mikes are in order.

And if your building a performance engine the block should be plate honed for the best ring seal and if your checking a machine shops work where the block was plate honed it should be checked with a torque plate using a good bore guage.

I which I could get away with using feeler gauges to check my piston wall clearance with as it would have saved me a few thousand dollars in Sunnen measuring equipment.

You should be using a good shop that does quailty work and one that has good equipment for doing performance work if thats what your looking for.

 

Actually it dosen't help at all, because you don't have a fricken clue.

Explain to me how you are going to get an accurate measurement with a flat feeler gauge "bent arount" in a round bore jamming the piston up against one side of the bore?

Come to think about it. Have you even seen a .002 or .004 feeler gauge? Do you know how flexible that is? - its almost like paper (a peice of printer paper is .004 on my caliper). Now try to slide a peice of paper about foot long and one inch wide down beside a piston in a bore. The absolute sheer stupidity of your statement is just amazing. Where-TF did you learn this crap the internet??

Even if this was the 1940's and piston manafctures still required about .008 of clearance in the bore and it had barrel faced piston skirts (which measure for clearance just down on the skirt from the oil ring land) , this wouldn't work worth a crap to accurately measure bore clearance.

And I though operating an inside mic properly by a novice engine builder was going to take some time for them to learn...

BLOCKMAN is absolutely correct. Modern pistons are so accurately machined there is no need to do anything but measure them to ensure they are the same and not a screw up from the factory. Every set I have bought in the past 15yrs was withing a tenth of a thousandths (thats .0001). Even TRW's mass prouduced junk was capable of comming within a few tenths. If your new pistons are so far off you need to bore each cyl individually to fit each piston you need to send that JUNK back and get a different set of pistons. This is not the 1940's. Those machine shop standards have LONG been surpassed.

Will

 

What do you mean custom hone each piston???
No i mean custom hone each individual cyl to fit only 1 numbered piston.

Or am I missing out on some new machine shop process.
No this hone machine practice is nearly 20 years old. I don't recall it's mfr but think it was SUNNIN. It had a long lever arm to work the hone by hand up and down on just 1 cyl at a time.

The pistons we buy are well with in .0002 of each other and they have to be measured at a certain place on the skirt
Yes pistons are very accurate diminsional nowadays but again this was nearly 20 yrs ago.

And you would have to buy feeler gauges in tenths not thousands to check for piston to wall clearance if that was the right way to check for clearance.
I did not ask to look at the feeler gauges myself but i can recall they very thin (and long).

Yes a block plate is a improvement but u tell me how many shops that advertize using a block plate to hone actually do? That plate will take additional labor and most low buck machine shops know the customer will never now the difference. Just a bit of reality here.

Well i'm not a machinist but that old method worked great in my GTO's motor - and i would use it again in a heartbeat.: : That machinist did a great job as those TRW forged pistons sealed up tight once the eng was warm and made NO noise at op temp. Just a little piston noise at start-up and warm-up as i expected from a forged piston set. And that motor was tight using no oil. The only smoke that motor made was tire smoke and it ran great on the street for several years.
I couldn't ask for anything more of that block work and was able to watch the machinist work with my own eyes. So any reckless bad-mouth that can't even understand how thin metal gauges can bend crackes me up. Then the bad-mouth accuses me as clueless when i have seen this method work with great results - clueless himself and doesn't deserve a response. But others may benifit from my experience here.

My apoligies for the late reply Blockman but i just don't have the computer surf time that i used too. Regardless i felt i should report my personal results to defend some good TRW piston products getting bad mouthed just because thier cheap.

cardo0

 

We use SUNNEN equipment at our shop and you used a SUNNIN to do your work, Hopefully that not a new type of equipment that I have not heard about.

So far all the years we have been building engines we have not had to hone a cylinder to fit a certain piston in a bore as the pistons we buy seem to be right to size.

We use a plate on all our engines we build and the blocks we sell as we have a good rep for what we do, We have them fill out a spec sheet to find out what they are using for gaskets and hardware and we duplicate every thing they are using on there finished engines.

NOW YOUR USING THE EXCUSE YOU DID THIS 20 YEARS AGO HMMMMMMMM

I did take the liberty of sending this link around to some engine builders and they got quite laugh out of it and the common response was WTF.

This is now 2008 and I really don't believe that anybody uses feeler gauges to check piston to wall clearance as just don't work that way just reread my post and look over rklessdriver post as your really need some education on engine building practices.

Here is a link to blue print machining a block I did years ago you may learn something or you may have some better way of doing this which I can't wait to hear if your using feeler gauges to check piston to wall clearance. http://www.chevelles.com/forums/showthread.php?t=93124

Again myself and alot of other engine builders got quite a chuckle out of this just keepem coming.

 

He never has. You will see some real gems that he posts from time to time. Like his lifters with oil pumps in them. And like:Now I have to go out and buy a piston honing tool, to keep up. Maybe it doesn't help because he wasn't talking to you. He was talking to "U". He had a clue, once, but I think it got lost rattling around in the empty space between his ears.

RACE ON!!!

 

I also sent this around some people. The general response was "WTF...is this guy serious?" Followed by snickers and laughter.

SUNNIN. That must be a HONNIN MACHINE right? I'll keep my eyes peeled for one... maybe they are on EBAY. Wonder if it's better than my Van Norman PS2V. I really kinda doubt it since my Van Norman doesn’t require me to use feeler gauges to check clearance.

CardoO this really isn't a fair discussion as you clearly don't know what you are talking about.

Please do yourself and the Corvette Forum a favor. Stop with the non sense mis-information.
Will

 

NOW YOUR USING THE EXCUSE YOU DID THIS 20 YEARS AGO HMMMMMMMM
Yes back in or around 1989 i did watch a machinist do this with a piston and feeler gauge to my block - with my own eyes.: :


Here is a link to blue print machining a block I did years ago you may learn something or you may have some better way of doing this which I can't wait to hear if your using feeler gauges to check piston to wall clearance. http://www.chevelles.com/forums/showthread.php?t=93124
When did i imply using a feeler gauge is the only way to measure bore clearance? Again i am not a machinst but using the feeler gauges is the best way i have seen and know of.
And i took a look at your link at chevelles.com and saw in the first picture that you waste a lot of money, time and effort on line honing a block. Well i just read (reviewed again) D. Vizard this morning (How to build a Performance sb Chevy on a Budget) and he states how line honing is usually a waste of money on most rebuilds. U seem to know how to spend a lot money on equipment but maybe U should read a little more and use the experience of others to save yourself and your customers a lot of effort and money.


So far all the years we have been building engines we have not had to hone a cylinder to fit a certain piston in a bore as the pistons we buy seem to be right to size.
Individual piston fitting and bore honing worked for me and if u can't believe it is your loss not mine.

This is now 2008 and I really don't believe that anybody uses feeler gauges to check piston to wall clearance as just don't work that way just reread my post and look over rklessdriver post as your really need some education on engine building practices.
First of all You need to re-read my post as i stated i am not a machinist and had a machine shop do the work on my Pontiac block.
And i did re-read Mr rkless post (as much as i hate to address him) and he makes a developing a feel with his bore gauges most important ("feel is everything") as he states most poeple can't repeat thier measurement well enough. But for some reason a feeler gauge ain't good enough - again his loss not mine.
Big deal, he can spell SUNNIN. I bet all his little friends can't wait for another spelling corrections post from thier spelling hero.
Telling me i can't share here what i have seen with my own eyes is more than stretch of authority (or lack of expertice or what ever) - I guess Mr. rkless conciders himself a moderator now too.

One more to help here,
cardo0

 

Oh i have a clue. And i recall that solid lifter issue. Well i'll state it here again: flapper valves in solid lifters behave like an oil pump. Does anyone here doubt this???

cardo0

 

Cardo
If you are dealing with a machinist that uses feeler gauges to check bore clearance you may want to find an other shop.

We are a performance shop and we line hone every thing that goes out the door and its not a waste of time and I can tell by your posts you don't own any bore gauges( AND I REALLY DON'T WANT TO KNOW HOW YOU CHECK THOSE CLEARANCES LOL.)

We buy a lot Dart blocks and those blocks come from Dart with the mains just under the low side of the spec so when a guy puts his crank in a Dart block thats not line honed and the crank binds up thats a waste of time line honing.

We deal with a lot of jobber shops in the area that don't line hone and from time to time they send us a block that they set the crank in and it binds up and from there they have to strip the block of the all the plugs and cam bearings and we line hone the block and they have to clean and install all the plugs and cam bearings again and when we prepare a block its all line honed and we don't ever get calls that they can't spin the crank in the block.

You have to remember we deal a couple hundred blocks a year and 99% of the blocks we prepare for engine builders and other shops that know what there doing and want their blocks line honed as it takes the guess work out. THATS WHY I DON'T LISTEN TO DAVE VISARD HMMMM. Number one Dave visard does not have a machine nor does he sell blocks that are blue print machined as I know the shop he works with in NC. Big differance here.

We don't cut corners at out shop and we have a dam good reputaion what we do and the product we machine.

Been doing this for 30 years now and I have a pretty good idea what works and what doesn't when it comes to block machining. I have seen it all but using feeler gauges to check bore piston wall clearances thats a new one for me and just when I think I have heard it all and you come out with this.

Well I have to tell you that you have made a lot of my friends laugh over this post. KEEPEM COMING!!!!!!!!

 

"U" mean I was wrong? "He had a clue, once, but I think it got lost rattling around in the empty space between his ears." "U" found that clue "U" once had floating around in that empty space? Yes! I doubt that. Oil is sent up the push rods by oil pump pressure. The flapper, or piddle valve, meters the oil flow to the upper engine. If it were a pump it would be a "flapper pump" lifter. What about the "edge orifice" or hydraulic lifters? Do only engines with one kind of solid lifter need valve train oiling? What about all the engines with hydraulic lifters?

You will have to excuse me for now. "But to custum hone each piston to fit just an individual cyl then the long feeler gauges (foot long or longer) do the job best." While I continue my search for a piston honing tool.

RACE ON!!!