2.7 Rebuild – To bore or not to bore and other questions

[draw]

Time to measure rod journals and oil clearances...

I measured all of the rod bearing journals. All 6 came in at 51.976mm and the spec is 51.990-51.971. Ok, good...



Surgical cleaning of each rod and the bearings. Torqued them to 50 ft-lbs per ARP spec. (I'll be using a stretch gauge when I bolt them up for real).



I set my micrometer to 52.000mm and zeroed out my bore gauge...



Used bore gauge to measure vertical clearance...



And the results...



Oil clearance is definitely on the "loose" side. Too loose? Not much I can do about it at this point. Looks like a 20W-50 oil will be required for sure...

[draw]

Time to measure the main bearings and oil clearance...

Measured the main journals on the crank. Spec is 56.990 - 56.971...



Ok, good. Time to measure the oil clearances...

Inserted bearings into the case...



After putting the case halves together, I realized that I installed the wrong stud. Took it apart and put in the correct stud, then bolted it up and torqued everything to spec.



Installed the extension on my Mitutoyo bore gauge so I can reach all the bores...



Set my micrometer to 57.000mm and zeroed my bore gauge...



And here's where things went south...

Measured oil clearances for #7 at 0.115mm, #6 at 0.132mm, #5 at 0.131mm, and #4 at 0.139mm. Then I stopped...this can't be right, can it? As a crosscheck, I set the micrometer to the size of the journal, zeroed my bore gauge and measured again. Same results. I checked my micrometer against the standard. Still good. Checked the micrometer against a 2.000" gauge block. Bang on. The bore gauge is accurate to +/- 2µm. WTF???

Maybe the case wasn't lined bored correctly? So, I took everything apart, took out the bearings, and bolted it back together. Spec for the case bore is 62.000mm to 62.019mm.



It's all within spec, but on the "loose" side. The crank journals are in spec, but on the "loose" side. The result, loose + loose = too loose.

Not sure what to do here. Run it? Buy some Calico coated bearings?

Opinions welcomed!

[targa72e]

When you bolted the case together did you have the #8 bearing installed? The #8 bearing serves a important part to align the case halves. I could not get my bore gauge to fit thru the standard hole in the #8 and had to use a old one and machine the opening larger. I got lots of bad measurements until I used the modified #8 for alignment. Just a thought.

john

[PeteKz]

Ward, I was away for a couple weeks and now catching up. I think you are doing an excellent job as a first-timer. In fact, you're being more meticulous in measuring everything than I would, but I've built these engines before.

Those oil clearances are too much. What bearings did you use? New ones? Do you still have the old ones that came out? If so, try assembling with those and see what you get (as a first step, measure the thickness of the old bearing shells versus the new ones). BTW, I am a fan of reusing old bearings if they are not visibly worn and measure within specs because they have already proved themselves in service. Bearings are not supposed to wear in use. If they do, then either oil flow was interrupted or the oil had contamination in it. And, some new bearings have been measured out of spec.

Call whoever did your case work and crank work and talk to them too.

With larger clearances (but within specs), more oil will flow through the bearings. I consider this a good thing, since that's what cools the bearings. Builders of race engines usually shoot for larger bearing clearances for this reason. You also have a larger oil pump, so I think you will have plenty of excess oil flow. FYI, I'm using 5W-30 oil right now and have plenty of pressure with a Turbo pump (also larger capacity) in my 3.0 case. Don't go to 15W-50 unless your oil pressure is low, and then I would be thinking that something else is losing the pressure. Oil pressure should be at least 10psi for each 1000 RPM. A healthy 911 engine will reach 60psi long before it gets to 6000 RPM. If it doesn't, something is wrong.

[PeteKz]

Re stacking base shims: No problem. Use the Three bond stuff recommended on this forum, or the Permatex Mega Gray high-torque sealer. After having some pesky case leaks using 574, I've decided to use the Mega Gray or Three Bond on the case halves on future builds.

[draw]

Originally Posted by targa72e

When you bolted the case together did you have the #8 bearing installed? The #8 bearing serves a important part to align the case halves. I could not get my bore gauge to fit thru the standard hole in the #8 and had to use a old one and machine the opening larger. I got lots of bad measurements until I used the modified #8 for alignment. Just a thought.

john

Thanks for the comment, John...I appreciate it!

No, I didn't have the #8 bearing installed, but my case is shuffle pinned, so that should (hopefully) locate the case halves properly.

Originally Posted by PeteKz

It's always good to have more working time, just in case the assembly doesn't go together quickly.

Yes, for sure!

Originally Posted by PeteKz

Ward, I was away for a couple weeks and now catching up. I think you are doing an excellent job as a first-timer. In fact, you're being more meticulous in measuring everything than I would, but I've built these engines before.

Those oil clearances are too much. What bearings did you use? New ones? Do you still have the old ones that came out? If so, try assembling with those and see what you get (as a first step, measure the thickness of the old bearing shells versus the new ones). BTW, I am a fan of reusing old bearings if they are not visibly worn and measure within specs because they have already proved themselves in service. Bearings are not supposed to wear in use. If they do, then either oil flow was interrupted or the oil had contamination in it. And, some new bearings have been measured out of spec.

Call whoever did your case work and crank work and talk to them too.

With larger clearances (but within specs), more oil will flow through the bearings. I consider this a good thing, since that's what cools the bearings. Builders of race engines usually shoot for larger bearing clearances for this reason. You also have a larger oil pump, so I think you will have plenty of excess oil flow. FYI, I'm using 5W-30 oil right now and have plenty of pressure with a Turbo pump (also larger capacity) in my 3.0 case. Don't go to 15W-50 unless your oil pressure is low, and then I would be thinking that something else is losing the pressure. Oil pressure should be at least 10psi for each 1000 RPM. A healthy 911 engine will reach 60psi long before it gets to 6000 RPM. If it doesn't, something is wrong.

Thanks, I'm 44% German (Prussian, really) and I try embrace my "meticulous" side. Plus, I really wanted to get into the "nitty gritty" of everything to increase my knowledge.

The bearings are new Glyco and the old ones were trashed long ago. I "miked" the bearing shells, the results are in the following table (mm).



Yes, I will definitely need to experiment with the oil viscosities. Maybe my GT3 oil pump isn't going to be overkill after all...Ha!

Originally Posted by PeteKz

Re stacking base shims: No problem. Use the Three bond stuff recommended on this forum, or the Permatex Mega Gray high-torque sealer. After having some pesky case leaks using 574, I've decided to use the Mega Gray or Three Bond on the case halves on future builds.

Thanks for the feedback on the shims. I know it's done frequently, but it's not optimal. But it may not matter anyway. I've been agonizing over going with a 1.0mm shim and deck height of 0.79mm. Either way, Curil T2 will be used.

[PeteKz]

I'd go for the deck height of 0,79mm.

Glyco is the brand that had some quality control problems. I know you measured the diameter of the bearing shells installed in the case. I meant to measure the thickness of the shells themselves. Should be few mm, then compare to the old ones, but if you trashed the old ones, maybe you can find some others compare to. Or someone here has those numbers. They may be too thin, which would increase the oil clearance.

[draw]

Since I can be a doofus at times, I wasn't sure of my dial bore gauge'ing skills. Maybe my measurements were erroneous? I confirmed main bearing oil clearances with...Plastigage???

Put a strip of Plastigage on journals 1-7...



Torqued up the case, including the #8 bearing, and the results came out fairly consistent...







The results (estimated when in between sizes)...



Damn, I was hoping i was going to be wrong. Now what? Search the forum! I came across this post about HM Elliott...

Originally Posted by Ollies930

lvporschepilot, I do not have any personal experience with mag cases, but being .002" out of round would scare the crap out of me and I would probably try to have the case halves skimmed a couple of thou and line bored back to standard round. Probably expensive, but I would avoid the oversized bearings for .25mm oversized line bore at all cost, the oversized bearings (if available are ridiculously expensive, at least on 3.2/3.3/3.6 cases)

Tippy, I do not know the exact prices on the coatings and I do know that the mains would be more, but I had my rod bearings quoted with a double application of the pro stock/top fuel coating and removing the existing standard coating first at around $85 for the set, IIRC. Give them a call, they are very helpful and check out their web site
https://www.hmelliottcoatings.com/

I gave them a call to see what they could do to the bearings. They asked me what type of engine I have. When I said "Porsche," they started cracking up!!! He laughed because they're "doing them all the time now." I guess I'm not the only one with this problem.

Sent the bearings off today to get them double coated with their HM30 coating. This is supposed to take up 0.001" or 0.0254mm, which will get my clearance in the 0.100mm to 0.080mm range. Not great, but better. Now to wait 2-3 weeks for them to come back...

[PeteKz]

Ward, if you already sent them off in the mail, then too late. But I would want to find out why they were so far off in the first place. I don't like to apply band-aids if I can avoid it. I would want a clearance in the .0025" range (.064mm).

[Rosco_NZ]

Another way is to install oversized bearings and grind the crank to suit each installed and measured main bearing. In my case, both case and crank were ‘std’ but outer limits of spec, net result excessive clearance.

[draw]

Got the bearings back from HM Elliott with two coats of their HM30 coating. Total cost was $148.21.

Inserted them into the case and torqued it up to spec.



I checked the clearances with Plastigage and the bore gauge.



They came in tighter as expected, but still on the loose side. The #1 thrust bearing is on the tight side. I was expecting that, too since the case bore was on the minimum spec of 62.000mm.



I think this is as close as I can get without undertaking some additional machine work to the case or the crankshaft, which I'm not really excited about. I'm moving forward unless someone talks me out of it...

[PeteKz]

I won't talk you out of it. Run it.

[draw]

I wasn't happy about the loose oil clearances for the rods using the Glyco bearings, so I bought a set of ACL bearings.



I swapped out the Glycos and remeasured. While still not "perfect," the clearances have decreased from the 0.090mm range to 0.080mm range.



With that sorted, I moved on to installing the rods. Even though some people say that rod orientation doesn't matter, I followed this advice...

Originally Posted by Flat6pac

Having taken apart many factory assembled motors I face the crank with #8 to my left and the rods pointing towards me and I record the rod numbers, which are all facing up,
That’s the way I reassemble the crank.
Bruce

I torqued the ARP rod bolts to 45 ft-lbs, then went to the stretch gauge. The initial torque gave me about 50% of the stretch I needed, then I took it home with 12-point extra-long box end wrench.



And Bob's your uncle! My homemade crankshaft holder came in extra handy during the bolt stretching process. Also, by premeasuring each bolt and then adding the stretch value, it was easy to hit the desired stretch. I'm glad I followed the advice gleaned from this forum.



Feels good to make progress...onward!

[LukasM]

Hi Ward,

Nice progress indeed, almost ready for case assembly!

And good to hear that the coating helped enough to get the clearances within tolerance. How durable is the coating, compared to regular bearing shells?

What is your view on the case, did Olli's do a good job? I would have thought that they would align bore to the minimum specified size, since wear just opens up the bore over time, and you want to maximize service life. However I'm a novice when it comes to engine building so maybe I'm overlooking something.

Cheers,
Lukas

[jkkarrow]

Nice headers,Fab engine!

[Rosco_NZ]

Seems Ollies bore to spec … my case was STD but on the high side, crank was STD but on the low side .. net result too much clearance.

[dedyplay]

Fabulous engine! Make sure the intake and exhaust ports are well opened!

[SiracHaile]

I had my case align bored and pined by Ollie’s. I measured my clearances with a dial gauge and plastigauge and they were loose .[emoji[emoji[emoji6]][emoji[emoji6]]][emoji[emoji[emoji6]][emoji[emoji6]]][emoji[emoji[emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6]]]][emoji[emoji6][emoji6]][emoji[emoji[emoji6]][emoji[emoji6][emoji6]]]]” across all mains. I called Ollie’s about it and they assured me it’s fine. So it’s together and once I get it running we’ll see what the oil pressure is at. But I thought I was the only one looks like it’s common.

[Herb_911_76]

Draw, thanks for your detailed report, very informative as I'm also working on a 2.7. FYI: Previous owner had Dilavar studs on exhaust side. All but 3 Dilavars had snapped while all steelies on the intake side were fine and tight, despite a lot of rust. Novice advice requested: Your bearing trouble has me reconsidering splitting the case. It wasn't leaking, except a bit of sweat around both shaft seals. Are there any pointers that can help me make a decision? I don't know the exact mileage (intermittent odometer), but should be around 80k miles. Cylinders still have cross hash and also Pistons are dead nuts in spec, valve guides are worn... Sorry didn't mean to hijack your thread.

[draw]

The planets finally aligned, and I got the case closed!





I added a very thin schmear of Threebond 1211 to the #8 saddle and inserted the dowel pin before dropping in the crankshaft...





Yes, I will be moving the ground strap!





Celebrated with a German beer...



Onward...