Bore gage recommendations

[stownsen914]

I have a couple engine rebuilds to do in the next couple years, so figured it would make sense to invest in good quality bore gage to measure crankcase bores and cylinders. I'm looking for some recommendations on brand and features, e.g.

Accuracy - do I want .0001"?
Depth - I assume I'll need 10" to get to inner bores when measuring a crankcase?
Range - looks like 1.5" or 2" to 6" range is common and should be good for measuring crankcase bores and cylinders.
Anything else?

It looks like Mitutoyo may be one of the best brands, but cost upwards of $1000. I'm hoping to find something more reasonable if I can. Thanks!

[Anglocanadian]

I myself use a mitotoya because that's what we have at work, the Fowler bore gauge has a good reputation and price :
https://www.amazon.com/Fowler-Warranty-52-646-400-Measuring-Graduation/dp/B000XQ2T1E/ref=sr_1_1?keywords=fowler+bore+gauge&qid=1574633028&sr=8-1

[bpu699]

Originally Posted by stownsen914

I have a couple engine rebuilds to do in the next couple years, so figured it would make sense to invest in good quality bore gage to measure crankcase bores and cylinders. I'm looking for some recommendations on brand and features, e.g.

Accuracy - do I want .0001"?
Depth - I assume I'll need 10" to get to inner bores when measuring a crankcase?
Range - looks like 1.5" or 2" to 6" range is common and should be good for measuring crankcase bores and cylinders.
Anything else?

It looks like Mitutoyo may be one of the best brands, but cost upwards of $1000. I'm hoping to find something more reasonable if I can. Thanks!

Go on eBay. I bought a used matco good to .0001 for $100. Awesome buy, works great. You can get these things used cheap...

[Jeff Alton]

Your size range is correct. We have a Mitutoyo and a Darson. But like most thinks, many are produced in the same factory. You will also need a corresponding set of micrometers that span the bore ranges you want to measure.

Cheers

[Catorce]

You want the best bore guage that money can buy? Now let me tell you, I have a machine shop full of Mitutoyo stuff because I actually MAKE engine cases.

But the best bore gauge hands down, the gold standard is a Sunnen. It's long enough to measure every bore in the flat 6 case from one end. Accuracy to a tenth. And, it fits bores much easier than your typical point style dial bore gauge.

Mine was $1300, but this is a big boy tool.

You may not need it, but I do.

Sunnen GR2241

[dannobee]

+1 on the Sunnen gauge. It's the only one I've used for going on three decades now.

Since time is your friend, I'd keep an eye on flea bay.

[KTL]

You MUST have an indicator with a resolution of 0.0001" because 0.0005" is insufficient when it comes to measuring your cylinder to piston skirt clearances, which are VERY tight

Agreed you want one with a long reach to measure all the way into the case. But a way around that is to have a fixture/insert in the #8 main bearing location to replace the actual #8 bearing insert. You MUST have the #8 bearing fixtured in some way because the original bearing insert is sized on its outside diameter to align the case halves here.
It's really strange that Porsche did not align this end of the case with locating sleeves like the other end of the case at the #1 flywheel side. Maybe Adam/Catorce could elaborate on this since he has redesigned and built the 3.6 case.

A workaround for the long reach gauge is you can use a VW 1600 rear main bearing to replace the 911 #8 main and thus allows you to get the bore gauge head into the case at the main bores from the #8 side of the case. Thanks goes to cgarr for this trick

[stownsen914]

Thanks all.

Interesting KTL makes about the #8 bearing needing to be in place to measure the case. Didn’t know about that.

Scott

[Catorce]

Kevin,

You're right about needing the #8 bearing to align the back end of the case. The way we got around that is by sleeving the #7 bearing, so our cases, as stock come with FOUR sleeves, two on the #1 end, and 2 on the #7 end.

This came from the fact that we needed to align the case halves and then bore a hole through them both, which obviously could not be done with a #8 bearing in place.

If someone wants, they can get the whole thing shuffle pinned, but with four locating sleeves per case plus a #8 bearing, the case halves are really going anywhere.....

Porsche did not need to use more sleeves most likely because they had a massive fixture holding everything together while they bored. We also have a fixture, but we are much more limited in the machinery we use (i.e. we only have the one machine) than Porsche would have been, so they probably used a lot more fixtures than we do.

[KTL]

Thanks for sharing your approach to fixing the case Adam. I had forgotten that you sleeved the mains. I have that on my 3.0L case (#2 through #7, courtesy of cgarr) and it's a really nice feature to improve the stability of the mains and provides some help for the case through-bolts.