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MaxDiesel

Time for a top end rebuild... part 2

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Many have built single plug motors using these. Some are getting close to 100 bhp / litre.My own single plug 3.0 engine uses very similar Wossner pistons and is starting to yield strong results.

Any more info? Sounds interesting...

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Got back down the garage this afternoon to build up the cylinder heads - its one of those jobs that takes a while but you just have to work through systematically...

 

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Took me a while to find the 'safe place' I'd put the bits for setting the compressed spring lengths:

 

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I made the bits copper pipe to exactly the minimum compressed spring length - can use them to quickly check if more/less shims required under the spring seat

 

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Then fitted the valve stem seals - used a bit of assembly lube to help get them on smoothly and squarely. Drifted them on with a short length of steel tube that fits snuggly onto the metal case of the seal

 

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Then fitted the springs

 

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All done :)

 

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Hopefully get the pistons and cylinders on next weekend...

 

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Got onto the pistons and cylinders today:

 

Last time I rebuilt the engine I fitted the pistons onto the rods first and then fitted the cylinders (as per Bentley manual) - it was pretty fiddly using a ring compressor in the middle of the head studs so this time I've tried it the other way (as per Wayne Dempsey book):

 

Rings compressed, bore oiled:

 

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Its a lot easier getting the piston into the bore on the workbench - probably less risk of snagging a ring too:

 

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First one in no problem:

 

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All ready to fit :)

 

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Fitting on the engine was fine - just need to remember the copper base gasket and to fit the pin circlip on the side you can't access first... getting the second circlip on is a bit of a fiddle

 

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First side done - used the same bits of copper pipe as last time to hold the cylinders down:

 

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All done - almost a 3.4 now.... :steering:

 

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Interesting thread as usual Matt, but I'm a bit perplexed about the gudgeon pin circlip comment. Are you fitting the piston / barrel to the insitu conrod, i.e. already on the crank, or are you fitting the conrod to the piston / barrel, then to the crankshaft?

 

Regards,

David.

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Interesting thread as usual Matt, but I'm a bit perplexed about the gudgeon pin circlip comment. Are you fitting the piston / barrel to the insitu conrod, i.e. already on the crank, or are you fitting the conrod to the piston / barrel, then to the crankshaft?

 

Regards,

David.

 

Yes - I fitted the assembled piston and cylinder onto the in-situ conrod. The first time I rebuilt the engine I fitted the pistons onto the engine then fitted the cylinders - this was the method shown in the Bentley manual.

 

Having tried both methods I'd definitely assemble the pistons and cylinders on the bench again and then fit to the engine.

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What type of head studs are those?

 

ARP - fitted during the original rebuild and still very shiny!

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Some more progress on the rebuild today - actually managed to get my teenage son helping which sped things up nicely.

 

Gave the cam carriers a thorough clean and check over - think I'm going to treat myself to a proper cleaning tank before the next rebuild... :whistling:

 

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All ready to go on:

 

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The sheet metal air guides were looking grubby so ended up rubbing these down and giving them a quick coat of VHT paint...

 

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Lifted the cylinders ~30mm to access the base gaskets and give them a thin coat of Loctite 574 - bit of a fiddle but recommended in the Dempsey book to avoid any chance of leaks

 

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ARP moly assembly lube on all the head nuts & washers

 

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Heads on and nipped up

 

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Cam carriers on for final torqueing of head nuts, then fitted the camshaft to check it runs smoothly

 

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Second side done - chain housings next, then rockers and cam timing... :unsure:

 

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Hello Max: very nice looking engine.What is interesting to me ,is that the way you put it together.I always put the pistons on rods first then the cylinders.I have tried your way and did not like it;-)(not saying it is wrong)

I also put together the cam housing and cylinder heads on the bench then onto the engine..it is just the way i was once taught by old mister from Zuffenhausen.

 

But after all ,nice job;-)

 

Ivan

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Hello Max: very nice looking engine.What is interesting to me ,is that the way you put it together.I always put the pistons on rods first then the cylinders.I have tried your way and did not like it;-)(not saying it is wrong)

I also put together the cam housing and cylinder heads on the bench then onto the engine..it is just the way i was once taught by old mister from Zuffenhausen.

 

But after all ,nice job;-)

 

Ivan

 

Hi Ivan,

Thanks for the feedback - I've tried fitting the pistons onto the rods first too but didn't like compressing the piston rings with the head studs in the way, maybe with the original Porsche ring compressor this it would be easier?

Interesting what you say on the pre-assembling the cam housing and heads on the bench... I very nearly did it this way but then went with the method in the manual as its how I've done it before. Will definitely try this next time ;)

Matt

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Hi Matt: before moving to Europe i have never seen it done,your way and never did read any manual i have to admit ;-)

Yes give a shut you will see how easy is to later slide on the tubes no head-ache;-)

 

Ivan

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Hello Max: very nice looking engine.What is interesting to me ,is that the way you put it together.I always put the pistons on rods first then the cylinders.I have tried your way and did not like it;-)(not saying it is wrong)

I also put together the cam housing and cylinder heads on the bench then onto the engine..it is just the way i was once taught by old mister from Zuffenhausen.

 

But after all ,nice job;-)

 

Ivan

Thats the way Ive been taught, Admittidly the ring compressor I used was a 1.5 inch ring secured with plyers that fitted easily between the ase and the cylinder. My hands are far too big to fiddle with the clips on the gudgeon pins if the barrels were already on. In addition assembling the cam carriers on the heads is the way porsche did it. But there more ways to skin a cat but the porsche way is the way I was taught allowed you to get everything lined up figure 8 the 574 and then plonk it on easy peasy then do the next one.

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Got back onto my rebuild this weekend after a couple of frustrating delays - my top end gasket set was missing the camshaft end O-rings :( and then found I need an extra cam gear shim which took my local OPC a few days to get...

 

Gave the camshaft O-ring and gasket a coating of Curil T - big thanks to Nathan (R2D2) for sending me his Curil T, it seems you can only buy this from Germany. The Curil T wasn't what I was expecting - green and very very sticky!

 

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And on

 

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Then set about checking cam gear alignment - started out with my wife holding the straight edge whilst I measured the distance to each gear.... she soon got bored with me measuring everything 5 times so I ended up making this

 

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This made life a lot easier and I actually got some repeatable measurements which showed I was just out of spec (0.05mm) on one cam gear and needed an extra spacer shim.... time to call local OPC

 

Then moved onto the cam timing. Started by setting up the DTI on no 1 piston using a 200mm extension on the DTI through the spark plug hole

 

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Then fitted an angle gauge on the front pulley and got a precise TDC by measuring the angle with the piston 5mm down both sides of TDC and setting zero degrees at the midpoint

 

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For what its worth this was the actual TDC point - so more or less as per the pulley mark

 

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Then set timing on number 1, managed to get this spot first time around 1.25mm and 0 degrees :D

 

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Torqued up the camshaft nut using the tool I made last time - think this has done at least four IB rebuilds now, happy to loan out again if any needs it.

 

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Then did number four, this took a couple of goes - found it useful to mark the pin holes I tried as I went along

 

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Timing done, and tensioners fitted

 

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Just waiting for the chain covers and cam covers to come back from painters now - I bead blasted and lacquered these last time and this didn't last well, so I've gone for 2-pack etch primer and matt aluminium paint this time around.

 

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Good work on getting TDC Max, my Z1 mark was bang on too. Surprised you didnt install the tensioners before you did the timing. Incidently the cam shims are the same as the shims for your fan pulley if you get stuck next time. Not that it matters hugely but Are the 3.2 cams not 1.4mm at 0 degrees?

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Good work on getting TDC Max, my Z1 mark was bang on too. Surprised you didnt install the tensioners before you did the timing. Incidently the cam shims are the same as the shims for your fan pulley if you get stuck next time. Not that it matters hugely but Are the 3.2 cams not 1.4mm at 0 degrees?

 

Thanks Dave. I did the timing with clamps on the idlers and then checked it again with the tensioners fitted and got the same reading... so next time I think I'll just fit the tensioners as you suggest.

 

I did wonder if the cam shims were the same as the fan pulley and checked the PET hoping they were - it gave me a different part number.... (I wouldn't put it past Porsche to have two part numbers for the some part though!)

 

Re the timing setting - I went with the Bentley manual specs which gave 1.25mm nominal with tolerance range of 1.1mm to 1.4mm. Is the OEM spec 1.4mm ?

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Hi Matt

 

Looking good.

 

1.25mm is the Porsche recommended ideal within the range 1.1mm to 1.4mm as you state above - so as per the other manuals.

 

There is a difference in the O/D of 2mm between those shims but they are interchangeable.

 

Also I thought the reason you time the engine with grips prior to installing the tensioners is because the tensioners are not fully loaded until the engine is cranked. I might be wrong.

 

cheers

Edited by R2D2

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Theres a lot of tension in those hydraulic tensioners as they are spring loaded as well as hydraulicly fed. When you pull the securing pin on them they dont half snap inro position. Id be worried id damage the camchain housing case using vice grips. Some guys use an early mechanical tensioner to achieve the same objective. Interesting to see you used that curil T on the o ring there max Ive always used 574. Although ive used the curil T on rear main seals and input shaft seals. Its great stuff. Ref the timing Ill have to have a look when I get home end of the month but as R2D2 has pointed out its well within range.

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Got my cam covers and chain covers back from the paintshop Friday, pleased with how they came out - took a couple of attempts to get a sliver that didn't look too 'bling'... just wanted them to look like clean aluminium:

 

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Forgot to say in last update - I re-used the low-cost rocker shaft seals I came up with last time as they had sealed well to date. For anyone else who want's to try this its just two standard size O-rings, one inside the other:

 

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Fits like this:

 

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The O-ring sizes I used are as follows

 

Inner: 1.6mm section, 12.1mm ID
Outer: 1.6mm section, 14.1mm ID

 

Total cost for an engine set is less than ten quid.

 

Back to engine assembly... started bolting the newly painted bits on which was satisfying after all the accurate measuring and setting stuff

 

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And chain covers and oil lines on

 

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Next heat exchangers - the wires coiled up are individual cylinder thermocouples.... fitted these a while back when to help diagnose a running problem

 

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Nearly there

 

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And done, more or less:

 

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Waiting for the throttle body to come back from being bored out +3mm - hopefully back by next weekend.

 

Got a few more winter jobs to do before the engine goes back in - one driveshaft needs rebuilding and the fuel tank's coming out for refurb or replacement depending on what I find... neither jobs I'm looking forward to but both need doing before I can start the run-in.

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