2.7 Crankshaft Question, and newbie intro

[Tbone425]

First off, I am brand new to the forum and hope I am following the correct procedure for this post. I just picked up a 911S with the 2.7 (literally from a barn). Has sat for the better part of 2 decades. No rust, really a great find from a project perspective. The motor was torn down already and I now have it sorted and laid out in my garage. I ordered the book authored by Wayne and it should arrive next week sometime. However Im trying to get a beat on some of the specs for the parts I have so I can start making my "needs" list. I have searched for Crankshaft specs but seam to come up empty for the 2.7. I want to know what the minimum specs are. Getting about 51.93-.94 across the rod journals and 56.92-56.94 across the mains. Trying to determine if this is a viable crankshaft. It appears to be in fine condition (to the naked eye, of course) Any help will be greatly appreciated.

[356RS]

Per the little spec book: Main bearing journals should be 56.990 to 56.971 for std. Rod journals: 51.990 to 51.971 for std.

[tharbert]

I'm not an expert concerning the numbers. I can say that it gets very expensive indeed trying to go non-STD. The STD bearings are cheap. The non-STD bearings are $600+. Whoever does the crank must also be able to re-harden the bearing surfaces. I PM'ed you a link you may be interested in.

[Eagledriver]

You are about to find out why most people don't rebuild a 2.7 engine.

-Andy

[BURN-BROS]

Since all the numbers are consistent, perhaps your Micrometer has not been verified with a gauge block.

[cgarr]

^^thats what I was thinking also when your measuring this close temps on a crank can change your readings too

[Walt Fricke]

After spending enough time reading on this forum, I have come to the conclusion that it may be worth while, unless you are a machinist or have similar skills which you use frequently, to send critical parts out to a machinist for measurement. Although my off-shore micrometer set did come with gauge blocks, and I bought an additional one to cover what I had didn't.

One of the guys who does lots of rebuilds would have a better view, but mine is that an undamaged crank, from a motor run with reasonable oil and filter changes and not abused, ought to be within spec for an awfully long time. It is the bearings which are designed to wear, so the harder crank journals can stay the size they need to be.

What did the bearings look like in this case?

Whatever you do, do not align bore the case to oversized OD bearings. Those are hideously expensive. Which is why the good machinists will shave the case a bit, and then align bore back to standard. Pretty clever.

And the #8 main (nose) bearing normally does not need replacement, because it is super well lubricated, does not take thrust forces, and is outboard of any rods, so it isn't subjected to those forces either. And it doesn't come in a main bearing set either, as those contain only 1-7.

Of course, if this crank had already been ground, that would be different.

[Tbone425]

Everything is laid out on my bench, the tropical climate here in Seattle might play a roll as well. Bearing all looked fine. No 'grabs' to speak of, was running strong and tight until it fell victim to the tensioner failing. PO knew what was happening and shut it down within about 10 seconds, with exception of chain gear that has just a couple more teeth than Walmart on a Saturday, it looks to be sound. Any sure fire way to tell if its been rebuilt? Everything appears to be much better of than I had expected. Optimism Andy, I think you meant to say I might be about to acquire a much deeper relationship with each moving part of my motor than people who don't rebuild 2.7's. Thanks guys. I'll be back a million times I'm certain. Anyone have machine shop in the Seattle area that is good?

[Jack Stands]

Lots of great machine shops, rebuilders out there (but check posts about Motormeister), so you can get all the help you may need. Check out Supertec's website for good information on the 2.7. Also, Wayne Dempsey's book on rebuilding a 911 engine demonstrates the procedure using a 2.7, so I'd study that thoroughly.

When in doubt, check with this BirdBoard. There's a lot of advice here (and some of it is even correct ).

[Tbone425]

Ya, I have been putting the horse in front of the carriage, trying to be patient in my wait for my books to arrive. Failing.

....should be here tomorrow and allow me to focus my OCD in a direction.

[Tbone425]

Walt, Wouldn't shaving the case cause fitment issues elsewhere? thanks again!

[cgarr]

Originally Posted by Tbone425

Walt, Wouldn't shaving the case cause fitment issues elsewhere? thanks again!

You need to bore the mains, I shaft and rear main seal areas normally don't have to take that much off the halves, there is a limit in which the case is junk.

[afterburn 549]

Most the time and usually.......the 2.7 can be polished and be fine.
There is a crank shop in Spokane that will polish it for you with loving care.
They did mine.

The updates...you need to send the case halves to a shop that dose them on a reg, basis, not your NAPA shop
shuffle pin, oil mod, ETC

[tom1394racing]

Your original question was regarding your crank measurements and the factory specs. Here is a chart I use for each crank that I check.



The new part limits are the black lines and the wear limit is the red line. I measure each journal twice at 90 deg increments.

If your measurements are accurate and consistent and if your journals look clean, your crank may have been ground to the undersize dimension.

[safe]

Originally Posted by tom1394racing

Your original question was regarding your crank measurements and the factory specs. Here is a chart I use for each crank that I check.



The new part limits are the black lines and the wear limit is the red line. I measure each journal twice at 90 deg increments.

If your measurements are accurate and consistent and if your journals look clean, your crank may have been ground to the undersize dimension.

Tom
How often is a crank worn beyond the limits from "normal" wear and tear, excluding spun/seized bearings?

[tom1394racing]

In my experience, I see it roughly 25% of the time on the early 2.0 cranks. The later cranks are almost always within the wear limits as long as there is no journal damage.

[Tbone425]

So I received my trio of books in the mail this week and bought a new micrometer. It Looks as though I have a couple things going in my favor (as of this writing). The case is a 7R which appears to be the best of the worst, the cylinders are The desire ones for reusing and for the most part look to be in good shape. The crank is std/std. However one of the cylinders is suspect. It has a couple pieces broken out of 2 gills about a quarter in inch wide for race one and another that is cracked. It looks to be fine otherwise. Is there a way to repair this one or is it dead?

So I need to start getting this stuff out to somebody who knows what they are doing. What would the collective recommend for machine work in the Seattle area? Any experience with Eastside Machine?

[Tbone425]

Does anyone have the contact info for the crankshaft machine person in Spokane?

Thanks

[afterburn 549]

I found them on the net.
S & J Engines Inc - Spokane WA 99201 | 509-838-3625

Advanced Engines - Spokane, WA High quality performance engines for hot rods, restoration vehicles, marine engines, and machine work

B & G Machine Inc Seattle, WA, 98108 - YP.com

these will get you started

[Tbone425]

So I thought I would post a pic for anyone interested in following this journey. Today market a big day as I packed up all my bits and headed off to the machine shop....