944 Turbo S Engine Rebuild Thread
- Thread starter Eldavo
- Start date
Some more progress from yesterday, apologies in advance for the multiple posts but you can only attach one picture per post if hosting it on the forum and as I post from my phone I can’t be chewed on with hyperlinking to external hosting etc.
Anyway, time to set the ring gaps. As the mechanic pointed out, every set of Porsche pistons they get come with the rings pre-gapped . . . apart from mine!
There‘s no real shortcut to it, just time intensive of trim, fit, align, measure then rinse and repeat until done.
Did the maths on the ring gaps using the Wössner formula and it tied in perfectly with those from a friend’s engine builder bible that he used for building his race car with the same pistons and liners. Erred on the side of caution again, loose runs and tight doesn’t.
Anyway, time to set the ring gaps. As the mechanic pointed out, every set of Porsche pistons they get come with the rings pre-gapped . . . apart from mine!
There‘s no real shortcut to it, just time intensive of trim, fit, align, measure then rinse and repeat until done.
Did the maths on the ring gaps using the Wössner formula and it tied in perfectly with those from a friend’s engine builder bible that he used for building his race car with the same pistons and liners. Erred on the side of caution again, loose runs and tight doesn’t.
Next up was fitting the crank girdle, due to the oil scraper I have and the support bracket welded onto the oil pickup tube there’s an order that everything has to go in so that it all works as it should.
Dry fitted and worked out what the tricky bits were before final assembly. There is an oil passageway between the block and the girdle that must be air tight so the correct Locktite anaerobic sealant was rollered onto the surface before final fitting.
Dry fitted and worked out what the tricky bits were before final assembly. There is an oil passageway between the block and the girdle that must be air tight so the correct Locktite anaerobic sealant was rollered onto the surface before final fitting.
With everything torqued down to the first step, the rubber mallet comes out to ”massage” the position of the girdle fore or aft so that there is a seamless transition between the two parts at the front of the block where the oil pump sits. Otherwise it will never seal properly, leak and introduce more aeration into the system.
Final torque settings, double checking the front fit and leave it to sit overnight.
Parts of note: crank has been polished and balanced, oil pickup tube has a strengthening bracket welded on and a skirt around the pickup to reduce aeration. Ishihara Johnson Steel and Teflon crank scraper with windage shield mesh.
Final torque settings, double checking the front fit and leave it to sit overnight.
Parts of note: crank has been polished and balanced, oil pickup tube has a strengthening bracket welded on and a skirt around the pickup to reduce aeration. Ishihara Johnson Steel and Teflon crank scraper with windage shield mesh.
These should be going in today!
Wössner uncoated forged pistons, BW Forged rods with ARP bolts, ACL race rod bearings, and of course . . . 12 laboriously gapped rings! Guys had a local engineering firm fab up a custom made taper-fit piston ring compressor/installation tool last year so that will be getting dusted down for another use.
Wössner uncoated forged pistons, BW Forged rods with ARP bolts, ACL race rod bearings, and of course . . . 12 laboriously gapped rings! Guys had a local engineering firm fab up a custom made taper-fit piston ring compressor/installation tool last year so that will be getting dusted down for another use.
924Srr27l
New member
blade7 said:
Alusil (use) Piston rings have to be barrel shaped on the outer faces to prevent sharp upper or lower edges from ripping the exposed silicon crystals out of the aluminium matrix.
Conventional rings for iron bores are usually taper or parallel faced to assist in oil scraping and compression sealing.
My Wossner's tap from cold for about a minute....
R
Dan944t
New member
nice one Dave, ive gone through all this few years back myself as you may remember when you were conviderung the steel linners like mine.
what ring gaps did you go for Dave i’m interested to cross reference them with what i decided to go for when i gapped mine?? i also went with the cautious route of bigger is better as not to heat up and close up. be very interested to know what you went for in the end with compression ring and scrapper ring?
atb
Dan
what ring gaps did you go for Dave i’m interested to cross reference them with what i decided to go for when i gapped mine?? i also went with the cautious route of bigger is better as not to heat up and close up. be very interested to know what you went for in the end with compression ring and scrapper ring?
atb
Dan
Hit a little snag today in that the tapered piston ring compressor we had made last year was for the 100.5mm pistons and was too big for the 100mm pistons.
A phone call and then a trip round the corner to see Steve the Engineer and a 100mm one was added to the tool collection!
A phone call and then a trip round the corner to see Steve the Engineer and a 100mm one was added to the tool collection!
Dan944t
New member
just managed to scroll through my phone camera and find my build and i went with 0.45 and 0.55 so seems i did ok ????
what head studs ave you used Dave i went with new standard in the end but i did buy APR but got rid after a conversation with Linsey Racing put me off and told me to 100% go standard for up to 600bhp so i went standard in the end! seems to be a controversial subject that?
did you or who ever put any lock tight on yours? and did they bottom out or bottom out them turn back a turn or two? ( these couple of things left me feeling uncertain if i did the right moove if im honest, had mixed opinins) i ended up bottoming out then turning back a turn on the studs no loctite.
Although heads off at moment and i’ve remooved most of the studs again to get straight edge on the block so may refit studs with lock tight not sure? porsche did it but Serdi uk said not to bother so i didn’t , but might this time on rebuilding back up for my piece of mind not to lift under boost? which is stilll a bit of a mistery of why combustion gases was entering my water jacket.
your builds going well mate.
on another note i’m gonna try a holset turbo in the summer with a 3” full system which i wilo be building myself so hopefully i can unleash some of my engines potential till further upgrades to the electronics ( need to save up though)
what head studs ave you used Dave i went with new standard in the end but i did buy APR but got rid after a conversation with Linsey Racing put me off and told me to 100% go standard for up to 600bhp so i went standard in the end! seems to be a controversial subject that?
did you or who ever put any lock tight on yours? and did they bottom out or bottom out them turn back a turn or two? ( these couple of things left me feeling uncertain if i did the right moove if im honest, had mixed opinins) i ended up bottoming out then turning back a turn on the studs no loctite.
Although heads off at moment and i’ve remooved most of the studs again to get straight edge on the block so may refit studs with lock tight not sure? porsche did it but Serdi uk said not to bother so i didn’t , but might this time on rebuilding back up for my piece of mind not to lift under boost? which is stilll a bit of a mistery of why combustion gases was entering my water jacket.
your builds going well mate.
on another note i’m gonna try a holset turbo in the summer with a 3” full system which i wilo be building myself so hopefully i can unleash some of my engines potential till further upgrades to the electronics ( need to save up though)
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.
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.
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