8000 rpm/300 bhp 3.2 rebuild

[911hillclimber]

I used that first equation and got a CR of 5.3!
I'm happy with what I have estimated, CR in the 11's.
The measurements I have are only estimates using water and cooking measuring jugs with increments of 100cc so could be out so far to make a calculation more a guess, so no value flogging it any more.
Burrette on it's way.

There is also some jargon, USA v UK here which only makes it worse. The JE data give piston volume as the whole piston, not the dome.

As I said yesterday, this engine is what it is, I can't change anything by machining, or rather I don't want to.
I'm no race engine builder, and after this attempt I don't ever want to do this lot again, no fun from the start.

Should have left it alone and polished it or bought a big Boxster engine and installed that and it's gearbox, but that is my bad decision, not my first and not my last I'm sure.

[RobFrost]

I used that first equation and got a CR of 5.3!

Should have left it alone and polished it or bought a big Boxster engine and installed that and it's gearbox, but that is my bad decision, not my first and not my last I'm sure.

Hopefully when you're tearing up the tarmac and others eating your dust, you'll derive great pleasure from the sound of that 8k, knowing you built it yourself.

By the way - in my estimate made from the photos and from measurements you took, I used swept volume divided by unswept volume. That should have been (swept + unswept)/unswept. Therefore correcting this error brings my estimate to 11.69:1 instead of 10.69:1.

[Bruce M]

Can’t offer much advice but a couple of points.

Your piston dome is approx 47cc, so I assume the accurate value is 46.46cc or whatever the figure you mentioned was supplied with your pistons. That is not in cu-in and it is not the whole piston. It’s the volume of the dome above the upper/outer edge.

Water weighs very close to 1gram per 1ml. Caveat: It’s temp dependent and minerals in solution also change the actual value. However it’s pretty accurate.
So get a little jug on good scales. Zero the scales. Add 100g of water. Re-weigh the full jug and write down the weight. Use the water to fill the combustion chamber (plastic disc with hole makes it more accurate). Weigh the jug with remaining water and subtract from your noted value to calculate the amount of water in grams/ml needed to fill the chamber. Obviously avoid any spilling

[911hillclimber]

Rob, bets are on 11.6 ish. I trust JE have worked it all out on virgin dimensions of Porsche parts.
Mike, yes that sounds good and I will do the real calc and measures when the burette arrives, but for now I'm going to gap the 12 rings using Peter's grinding wheel.

Thanks for the interpretation of the JE details. Irritates me when units are mixed.

I was bought up with BS 9000 (?) way back in 1969, so long ago but the bible for doing engineering drawings. I remember the details well, just not the number!

Thanks also to the pm's and texts I've had to keep me going!

[Bruce M]

Did a fag packet calc based on the numbers above & assumed head CC of 90. With a 1.67mm deck the ratio was well below the figure quoted for the piston set but obv don’t take that as gospel! Is it possible to ditch the cylinder base gasket & use sealant instead to reduce the deck?

[911hillclimber]

It needs precise measurement of the key volumes for that I think, never read about anyone doing that, BUT, with the case sealent used see no reason but one why not. The machined surfaces are very true and fine finish.
Dempsey say seal the base copper gasket with sealent just before assembly, but I ignored that last time and all cylinder bases were oil tight.

The one BUT is the deck height. You could drop the barrel by the gasket, 0.25mm but the piston then rises in the barrel to the head mating face. Demsey and others go on about this being a min of 1.5mm measured to his book method and I have 1.67mm with a 0.25 gasket, so in theory could remove the 0.25 but be in the danger zone of the piston at 8000 hitting the head...…

I would rather sacrifice the CR and have good deck clearance!

Spent hours this afternoon doing the rings which are going well with a few niggles but found a real problem (of course).

Positives of the Day:
Gapped the rings using Peter's grinder which works a treat. This grinder is a luxury compared to needle files. You made me smile Peter!
One piston at a time matched to the barrel. Done 4 , 2 to go. All gaps were too tight, so managed to tweak then bang on.
Top ring has to be 17 thou, second ring 6 though wider, so 23 thou.
Generally the top ring as supplied was 12 to 15 thou and the second 18 max.

The real sod is getting the oil control ring set in, what a game but my skill is getting better with practice and no swearing. Patience is not my middle name but you just have to take your time.

Negative of the Day:
The C clips to retain the wrist pins are HUGE compared to the Porsche items. So thick and REALLY difficult to get into the piston grove.
My home made (from soft duralumin) was ovalized by the resistance to fit the clip. I did get one in place but silly effort.

Asked the piston supplier if the clips were correct and they are. He wished me luck.

There is no way you an fit these clips when assembling the engine using fingers and a screwdriver. I know I can fit 6 beforehand but they are murder with the piston in a vice!

Going to remake my Stompski knock-off tool in steel and see if that works. I doubt the Stompski tool would grapple with these clips.

The bad weather continues here, so should get Saturday to finish the cylinders and a bit more. Doubt my steel will arrive.
Will also contact the rolling road man to see how he feels about th Clewett ignition system, the simple (cheap) one.
It should at least bolt on and work, right?

[andytat]

I have experience of the JE piston pin circlips and found the only
tool up for the job is the Stomski Racing one. Not sure what they
are made of but they had no problem and after several sets of
pistons are still unmarked. I got mine from Ian Heward at The
Porsche Shop, Hartlebury Trading Estate.

Best of luck Graham

[911hillclimber]

Interesting Andy, just down the road from me too!

I have Peter's Stromski clip tool, too small for the 3.2 pin but it is stainless steel. This is why I'm hoping my diy version but in steel will do the trick.
Why JE use such wire beats me.
Just another thing to resolve!

[andytat]

JE certainly don't want the clips popping out that's for sure.
A steel tool should do the trick I think.
Best of luck Graham.

[911hillclimber]

Made my steel version of the Stomski tool, works well but difficult to machine to 3 thou.
However, the clips are simply stupid and a bitch.
One got away today at hypersonic speed, but found in my socket set.
I dread fitting the 6 clips to the Pistons whilst in the engine.
Hope to order 2 spare ones tomorrow...

[PeterK]

Plenty of cling film over the holes Graham !

[911hillclimber]

There is a better way I think, fresh stockinette down the holes, if the clip goes AWOL it will snag (maybe) on the cotton.

A full 6 hours in the garage today, and much done.

The 6 piston clips were irritating me, so assembly of the pistons/barrels/clips etc weighed heavy on my mind through last night.

Still, all went well!!!

I tuned my Stomski knock off tool and all 6 nasty clips went click into place. Amazing to say the least.
The trick is to machine the outer sleeve to 5 thou smaller than the wrist pin, machine the inside dia as thin as you dare go and still have some wall thickness, I got down to 15 thou.
Press painfully these thick wire clips in, tilt at an angle and get the open ends into the piston groove, mostly done blind, adds so much to the fun.

All in and the cylinder down and clamped in place.

The ring compressor is unbelievably good, never will I use anything else.
Oil ring gaps at 12 noon, second ring gap at 9.00 and the top at 3 o'clock.

Buoyed by this lot, carried on.

Heads on after a final clean of the mating surfaces yet again, all loosed on, barrel nuts greased with assembly lube from ARP and loosed down. Cam carrier prepped, oil tubes in and torqued down a treat followed by the head torques.
Cams install ok and rotate a treat on both sides.

Slowly all the holes are filling up!

Out walking tomorrow for some Shropshire air and hope to shim the cams and even time them on Thursday.
Rocker shaft seals arrived today.
Ordering the Clewett ignition tomorrow.

[wadsworthi]

Excellent progress, enjoy your Shropshire walk!

[Hugo 356]

Sharing the highs and lows of this build I feel like we need to be there at the first firing. Any chance of a live stream when the time comes?

[911hillclimber]

I can do one like this?
red line at 6300, 8K should be good.

https://youtu.be/c8pzuNoSi0w