944 Turbo S Engine Rebuild Thread

PSH · Nov 28, 2020

Looking pretty David...now if you were to machine a small 'V' groove between 1 and 2 piston rings you'd be able to increase boost with no blowby....the other trick is to machine small semi-circle along the bottom edge of ring 1. This encourages pressure behind the ring and again hold higher boost levels. The amount of holes required depends on bore size....I machined these holes in my son's Cossie engine, that required 5 holes. He runs at over 35 PSI. I didn't do the same in my engine as it already has the 'V' groove, probably as it's a 'full-race' piston.

Pete
BTW, my ring gaps are given in my engine build thread..these were caculated using a formula used in racing and then confirmed as correct by IASA's tech department for the intended power/heat output.

Dan944t · Nov 28, 2020

Eldavo said:
ARP head studs and nuts, new Porsche washers. The ARP washers are too thin and flimsy so used new OEM ones that I scored on one side to prevent them turning.

Head studs were installed with Locktite to hand tight only so that they protruded 72mm from the deck. In some cases they were pretty much bottomed out, in others a turn or so back so you should be fine.

cheers dave, i pulled my photos up and i set mine to 72 also. what locktite did u use on them?

i bought some but will have to dig out what number i bought. think i got that loctite number from you Pete possibly ??

anyhow i’m deffinately fitting them with locktite this time round fitting head back on, and i’m going to torque head up twice and ruff up the bottoms of my new washers i think

https://imgur.com/a/UOeoCtn

Eldavo · Nov 28, 2020

I’m not searching through 522 pages of your build thread to find your ring gaps, which will probably be not a million miles off mine and are, of course, piston dependent too.

Also, given the "issues” I’ve had - there is NO WAY I’m modifying these pistons at all in any way, shape, or form [

]

Not sure where this belief that I’m going to be running crazy high boost numbers come from either?

Dan - no idea what Locktite they used sorry. My garage drawers have blue and red, the Porsche Specialists have a whole shelf of all different flavours for different things.

Dan944t · Nov 28, 2020

no probs Dave, got the stuff tucked away in my workshop/garage can’t remember the number but it’s meant to be for parts of the engine that are prone to coming loose due to vibrations , so that’s what i’m gonna use this time round. if i have further problems after with my water jacket preasurising again i will go to APR studs then we’ll have to see? hopefully i won’t cos i’m now getting bloody cheesed off with it and just want to enjoy it, but that’s the danger of modifying as a few of us know too well ?? keep up the good progress mate ????

blade7 · Nov 28, 2020

Eldavo said:
Also, given the "issues” I’ve had - there is NO WAY I’m modifying these pistons at all in any way, shape, or form []

Go on, stick some of that ceramic gook on the crowns. It'll look pretty in the build pics, well until it falls off

.

PSH · Nov 28, 2020

522 pages...????..page 4 sir, page 4.
...

James0 · Nov 28, 2020

Some impressive attention to detail.
As far as head studs, on my block the 16v studs were too long and the 8v studs would be way too short if wound all the way in, I set them to the right height and added thread lock.
Can't remember the thread lock I used but it wasn't any kind of unicorn tear stuff. Been fine for over ten years and many miles, standard boost level but high compression.

Eldavo · Nov 28, 2020

PSH said:
522 pages...????..page 4 sir, page 4.
...

Come on, don’t keep us all in suspenders . . . . what were the numbers (for a completely different piston)? [

]

PSH · Nov 28, 2020

Ok...

Quote:

Porsche gap average is:
1st: 0.30mm
2nd: 0.30mm
oil: 0.45mm

using the formula for a modified street/drag strip engine, an engine of my bore will work out at
1st: 0.48
2nd: 0.53
oil: 1.49 ( I didn't like this gap at all and question it's validity but that's what the formula adds up to)

But I adjusted these setting to what makes sense in my head for the job in hand so have decided on the following:
1st: 0.45
2nd: 0.50
oil: 0.55

Once I had decided on these settings I sent my findings to IASA with details of the ouput planned for my engine and was very happy to get a green light back from them this evening.

End quote:

While looking this up I also remembered machining up an extra dowel for the girdle...IIRC Porsche only fitted one at the rear...there's probably a lot of other small tweeks that I did internally to the engine..my memory fails me today though.

Pete

blade7 · Nov 28, 2020

Eldavo said:
PSH said:

522 pages...????..page 4 sir, page 4.
...

Click to expand...

Come on, don’t keep us all in suspenders . . . . what were the numbers (for a completely different piston)? []

Now look what you've bleedin done.

Just kidding...

Eldavo · Dec 4, 2020

Slight delay, the piston ring compressor had a slight flaw to it and caught on one of the oil rings. Ordered a new set of rings that will be here Tuesday and picked up a coated Wiseco tapered ring compressor.

Eldavo · Dec 4, 2020

Got a bit sick of double nutting the exhaust studs to remove them so these arrived in 3 days from Rennbay via FedEx. Hex socket in the end of each stud.

Eldavo · Dec 4, 2020

Also, swapped the steam vent attachment over from my other head too:

Eldavo · Dec 4, 2020

And last but not least, tapped the oil pan for a Bosch temperature sensor underneath the oil level sensor to display oil temp on the screen via VEMSDisplay as well.

Eldavo · Dec 4, 2020

With the windage tray removed for easy access for the hot parts washer I grabbed a pic of the oil baffle trapdoor for anyone interested in how it works/where it sits.

Dan944t · Dec 4, 2020

nice one!

dlknight · Dec 8, 2020

Eldavo said:
Got a bit sick of double nutting the exhaust studs to remove them so these arrived in 3 days from Rennbay via FedEx. Hex socket in the end of each stud.

Very nice - I'm going to have to make a dent in my wallet for a set of those I think...
EDIT - that is enough ebay for me tonight!

found some very sexy SFR exhaust manifolds whilst searching for exhaust manifold studs...

Eldavo · Dec 8, 2020

Yeah the SFR stuff ”looks” nice but fitment is supposedly hit and miss and actually getting hold of the stuff takes an age and is a bit of a roll of the dice.

Going to have a chat to my exhaust man about potential costs of knocking up a set of new manifolds and a crossover - watch this space.

You could probably put the exhaust stud kit together yourself for less but I couldn’t be bothered measuring and sourcing bits separately, for less than £50 delivered it was an easy decision.

Replacement ring pack turned up today but rather than a picture of a box here’s one of my birthday present steering wheel that I finally got around to fitting today: