Assessing an unknown engine

[RobFrost]

In the preparation for assembly I've been unbagging engine parts, removing tape over openings, rewashing items already washed... Time to mount the case on the stand again soon. One thing holding me up is I'm unsure which bell housing holes take studs and which take bolts, and what lengths. I guess and good close peer at the parts diagram is in order.

It's more apparent than ever after rewashing the con rods, which is the replacement one. I assume it's off an S as I believe the black surface is the nitriding, which wasn't done on the E rods.





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[RobFrost]

I have it on good authority that every engine builder worth his salt wipes down all his surfaces with [checks packaging] HUGGIES before embarking upon final assembly.



Along with clean up, I'm starting to get everything set out.







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[RobFrost]

Next dilemma... I may have mentioned one of the rods is the black sheep of the family, so to speak. Well it's around 10g heavier than the others. 10g is the limit. But i notice all the others are within 1 or 2 grammes of each other, so maybe they've been balanced carefully.



I notice four of them have been machined around the larger journal, which may have been to bring their weight down to match the lightest. But the black one has no such machining. I'm wondering if this is where I can remove a few grammes of material to bring them closer to uniformity?




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[RobFrost]

I've measured all the big end journals to within spec, and they're all consistent, but it seemed sensible to confirm the clearance is correct. So I picked one and measured the clearance both at the end of the con rod and at the side, with plastigauge.



I torqued it up using the old con rod nuts and bolts, not the new and it came out spot on at between 0.05mm and 0.04mm.



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[911hillclimber]

Ref rod weight equalisation Rob.
I would think that area is a good one to 'loose' some weight from.

As a side note, on the fab Corrillo roads in my Lola's 3.2 I asked the supplier why there were no balancing marks on any of the rods. He laughed and said after balancing the set the marks and scratches were all polished out so it seems no balancing had been done. but did not say where the balancing had been made, but they are 9,000 rpm rods!

[PeterK]

Of course. When you get really picky, you need to balance (relieve weight from) the rods at both ends. Is the little end too heavy relative to the rest, or just overall weight

[chris68]

Hi Rob,

Hope you're well.

... to get really really picky, it's a good idea to get the crank, flywheel and clutch cover dynamically balanced as a rotating assembly.

Not sure how necessary this would be. Depends on how hard you want to rev it. Plus, I assume Porsche did a pretty good job of balancing individual items in the first place??

Cheers

[911hillclimber]

Well worth reading the excellent Bruce Anderson Performance Handbook on rods, page 122 and placement of rods in the right place to balance things out ON ASSEMBLY of the engine.

[RobFrost]

Well worth reading the excellent Bruce Anderson Performance Handbook on rods, page 122 and placement of rods in the right place to balance things out ON ASSEMBLY of the engine.

Hi Graham. I found that on page 144 of my edition. He refers to cylinders 1 and 3 as the back of the engine, by which I'm guessing he means the flywheel end, nearest the front of the car. If I understand that correctly, he says use the heavier con rods nearer to the flywheel.

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[911hillclimber]

I followed his advice when I rebuilt my first 911 engine, a 2.4S with E cams and mech injection.
(iirc there is a clear diagram in the book as to cylinder number and flywheel position Rob).

What an engine that was, sold it running for £1000 in '93 to help fund my 3.2 for the 911.

Sold to a DDK'r in Ireland. (but before DDK existed).

[RobFrost]

A couple of people over on Pelican were a bit sniffy about shaving 10g off the con rod, but a couple of others said they had done it and had no problems. So I got the overweight rod down to the machine shop and shaved a fraction of a mm off in the same place the others are machined. If only it was so easy to shave a little off my own big end.

Porsche spec is to be within 10g of each other, and all are now within 1g of each other on opposing cylinders.



The block is now back on the stand ready for assembly and it received another good wipe down, blow off with the air line.



Everything set out ready to go.



And I got the con rods installed and torqued up. All seem nice and tight and moving freely.







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[PeterK]

Very satisfying to be actually building up the engine, after all the preparation and fettling.

[911hillclimber]

Joining the cases, The Exciting Bit.
Be super careful about the rings on the through bolts Rob, so very easy to snag one.
Looking forwards to progress reports.

[RobFrost]

I decided to fit RSR rocker shaft seals to this engine.

Tiny little o-ring, £5+VAT.

24 required.

So I bought one and measured it. One 1.5mm thick viton sheet and two hole punches later...



Easiest £120 I ever made.

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[911hillclimber]

I tried fitting those designs for the Lola, imho quite useless, ripped sliding them into place, hope you succeed!