Added work/cost to split the case?

[bpu699]

Ok, this is an offshoot of the other thread, just trying to get info...

Most every thread I see says not to split the case if you aren't having issues... Sounds like great advice. Some threads say its stupid not to look, as you are 80% of the way there.

Now, if you want to split the case to examine everything, just to make sure its ok, and then ASSUMING its all fine... what are we looking at?

If the main bearings are fine, and the crank is fine, is there any machining involved? Or, do you just button it back up?

If it all looks fine, do you still spend time to polish the crank, or just leave it alone?

If it all looks fine, any point in putting in new main bearings? These seem pretty cheap...


I think the security of knowing it all looks great would be peace of mind. But if it racks up a huge machine shop bill and parts bill, when there are no apparent problems, then what's the point...


Seems like with the rod bearings, if you play with those then even if they "were" fine you have now committed to machine shop work. Is examining the crank bearings the same?

Thanks

[Edoyle]

I'm at the same place in my teardown. Good engine but was sitting for 15 years without having run. The case studs and nuts are all rusted and the case has some aluminum oxide on the outside so wanted to clean everything, change hardware, check internals and re-assemble without replacing parts I don't need to.

Let's see what the pro's think..

[bpu699]

Yep...

The question for me is do I renew everything to "as new", or just fix what I have as it was fine to start with (broken head stud/1 cam with pitting)...

It would be nice to make everything brand new... but from the sounds of it hitting a $15,000+++ bill to rebuild the whole motor just doesn't seem to make sense. I track the car... I would be beyond crushed if I did a full rebuild on a motor that didn't need it and then buried the car into a wall...

If this were a show car, I would probably go nuts and do it all...

As it gets track time, I would love to put in ARP rod bolts/etc... But now you are getting into machining costs, etc...

If you can split the case, look at stuff, and if its ok put back together... than that's a no brainer...

[sp_cs]

My engine builder suggested 10 hrs addition Labour to split the case. I've gone a bit mad with Gt3 crank and pump, but crank balancing, main bearings were recommended on a standard rebuild. Rod bearings can be done with just a topend iirc

[Dpmulvan]

Neither one of you mentioned how many miles are on the motors or if it's a 2.7 3.0 et.

[bpu699]

Originally Posted by Dpmulvan

Neither one of you mentioned how many miles are on the motors or if it's a 2.7 3.0 et.

Mines a 60k 930 88...

Any attempt to look at the bottom end would for security purpose primarily, and possibly to reseal. I have slight weeping at the joint line...

Primary goal is regrind a cam and replace headstuds...

If opening the bottom end is a $500 endeavor, I am all for it. If its a $2000... probably not...

Slippery slope, I know...

[John McM]

When you are disassembled down to the short block it's not that difficult to go a bit further and split the case. Assuming it's just a reseal the gasket kit is not that expensive and the rest is labour.

What no one can answer is whether you are opening a can of expensive worms in doing so. If the goal is to understand what the condition of parts inside the case is, then what do you plan on doing with the answers? If the wallet is relatively closed and there are no symptoms/signs of issues then I'd leave it alone.

[Flat6pac]

You're so close to resealing old sealants and replacing wear items.
Intermediate shaft bearings are always showing wear, $35.
The chain rails become brittle, $50
Gasket set, bottom end. $60
You get to see the mains, factory, Porsche, aftermarket, but now you know.
Looking at the mains, tells you what the rod bearings look like because rod bearings are
Further down the oil system.
Remove the mains and number them as to their original location
Clean the case, reassemble
Bruce

[Tom '74 911]

In terms of splitting the case or not, I have only torn down 3 engines, so I am not an expert by any means. But... I have a hard time imagining taking an engine down to the short block & feeling like I had been able to keep all the dust, dirt & grime out of the case. The 3 engines I've taken apart were average dirty and it would have been darn near impossible to guarantee that none of it entered the case during disassembly...

[bpu699]

Originally Posted by Flat6pac

You're so close to resealing old sealants and replacing wear items.
Intermediate shaft bearings are always showing wear, $35.
The chain rails become brittle, $50
Gasket set, bottom end. $60
You get to see the mains, factory, Porsche, aftermarket, but now you know.
Looking at the mains, tells you what the rod bearings look like because rod bearings are
Further down the oil system.
Remove the mains and number them as to their original location
Clean the case, reassemble
Bruce

You make it sound so reasonable... I appreciate that... Resealing it if nothing else diminishes leaks

If you look at the main bearings, and find slight wear... Would putting in new bearings and leaving the crank alone be reasonable? Or leave the originals? I ask as grinding the crank and getting undersized bearings seems a huge deal... What about polishing the crank?

With rod bearings, not sure I get the mechanics of it. If you take a peek at them, and replace with new same tension style bolts...why do you need to resize them? How do they change shape or orientation, if nothing else is changed? If it needs to be done then so be it...but why?

When you take the crank out, you take it to the machines shop and they resize. Then, you have to undo the bolts, and retighten again on the crank. How is this disruption any different than taking them off, peeking, and putting them back on. In both cases, you undid them...

I absolutely understand that a resized crank is better than one that isn't... But then, shouldn't an unresized crank with new bearings by definition be better that whatever is in there right now?

What am I missing?

[Flat6pac]

You're running with 60k miles and no oil pressure problems. You open to reseal replacing consumables. You're replacing studs. A broken stud doesn't mean that the crank is wasted.
You no longer cut cranks, you send it out for repair. The repair keeps you at standard size.
Want more, get the extra drill on the crank for oil to center rods.
Don't polish the crank with old bearings reusing. The main thing is oil is the cushion between metals.
Bruce

[Optimusglen]

I only have experience with one engine, so this may not be normal, but my mains looked great and my rod bearings had wear.

If you split the case first you need to get everything inspected. If the crank is within spec you don't need to have it reground. If there aren't scratches you don't need to have it polished. If your crank is warped or really worn it's a better idea to buy a different crank that's in spec, sure you could get it machined for oversized bearings, but then you have to also buy oversized bearings (including #8, which is quite expensive) and pay for the machine work. Probably cheaper to just get a new crank that's in spec.

For mag cases I've read that often times the years of heat cycles will mushroom the mating surfaces slightly, so several aspects of the case must be inspected. Aluminum cases don't have those issues I don't think.

The rod bolts are stretch bolts, they stretch slightly once they reach final torque. So once you remove them they are garbage. New ones are something like $15 each from our forum sponsor. So, 15x12 is $180 right there.

Bearings wear, sure you can measure them and if they are in spec with no scratches or copper showing you could probably reuse them if you must, they're cheap enough that replacing them just makes sense though. Main and rod bearings are probably another $150-$180 on the cheap end. And don't forget about the intermediate shaft bearings.

If the oil looks good, and you weren't having issues before, and you know the actual mileage and have service history, etc etc, I would leave the bottom end alone. Check the cylinder base decks to ensure they're aligned and move on. If you have any sort of issues, like weeping split line, I'd tear it down.

[boyt911sc]

Originally Posted by bpu699

You make it sound so reasonable... I appreciate that... Resealing it if nothing else diminishes leaks

If you look at the main bearings, and find slight wear... Would putting in new bearings and leaving the crank alone be reasonable? Or leave the originals? I ask as grinding the crank and getting undersized bearings seems a huge deal... What about polishing the crank?

With rod bearings, not sure I get the mechanics of it. If you take a peek at them, and replace with new same tension style bolts...why do you need to resize them? How do they change shape or orientation, if nothing else is changed? If it needs to be done then so be it...but why?

When you take the crank out, you take it to the machines shop and they resize. Then, you have to undo the bolts, and retighten again on the crank. How is this disruption any different than taking them off, peeking, and putting them back on. In both cases, you undid them...

I absolutely understand that a resized crank is better than one that isn't... But then, shouldn't an unresized crank with new bearings by definition be better that whatever is in there right now?

What am I missing?

BPU,

I just delivered my 14th engine rebuild project for a Pelican part member. Bruce Abbott is one of my mentors and advisers for engine rebuilding. He has a lot of engine rebuilding experience that we could only dreamed about. I was in similar state of mind before with only a couple of engine rebuilds top end. Once you have opened or splitted ithe crank case for further inspection, you will realize later that there is nothing to worry about.

Learn to over come your fear and anxiety. As demonstrated earlier, if everything looks fine, resealing the case does not cost much specially if you are doing the work. You are over thinking this simple mechanical endeavor. BTW, got another motor to be opened this fall. I will give you a brotherly advise to get you started. Chose or select a mentor that you feel comfortable to talk over the phone or somebody nearby. I called Bruce or Mike B. or John W. every time I got in a situation that made me unsure what to do next.

Your first engine would be stressful and nerve wrecking at the beginning. But with all the help and assistance from this forum you will find out that there is nothing to worry about this wonderful experience. And enjoy the time doing it.

Tony

[eastbay]

Just to replace the by now rock hard rubber seal rings on the oil pump make splitting the case mandatory in my mind.

[Matt Monson]

What Tony said. You decided to keep the car and fix it. It's not a mag engine. Ignore everything that you hear about those old ones. This is well within your skillset and it's the most bulletproof IB car engine there is. Go in, check it out, clean up some things and replace some consumables. Odds are you won't visit a machine shop.

[JFairman]

Cleaning parts takes the most time during a rebuild and at 60,000 miles 930 exhaust valve guides will be worn out and ready for replacement.

The heads will need to go to a good machine shop with 911 experience to have the heads fully cleaned and refurbished. It's well worth the cost to do all this right.

Good luck and enjoy it!

[bpu699]

Looking forward to fixing it... Glad I didn't sell the car...

Got to motor and trans split, motor on the stand... Ready to disassemble...

Heads were supposedly done 5000 miles ago, with perfect leak down when I bought it...9 years ago...

The one pitted lobe I was surprised about... But easy fix...

If you cut 1 cam, do you have to do the other too as a set?

Car had very good oil pressure, just over 4 bar hot... 2 bar hot idle...

Will see what if anything needs loves...

[Matt Monson]

To the cam question, how well matched to the vehicle tune and set up is the SC grind? If Theres something better for your use and other mods now would be the time to change it.

[bpu699]

Matt, I like the cams as they are torque...nice on the track....

What one nonporsche mechanic told me, was you have to cut them as a set, or the lift duration won't be exactly the same?

I know nothing about cutting cams. But see lots of folks on here cutting or repairing just one...

I'm not looking for crazy horsepower. Just want dead on reliability...

[Matt Monson]

Just get it fixed then. I've had Web repair single cams for me before.