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Overhaul Porsche 931 S1 engine
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MOTANUL  



Joined: 19 Nov 2018
Posts: 157
Location: ROMANIA BUCHAREST

PostPosted: Wed Dec 23, 2020 5:21 am    Post subject: Reply with quote

Carrera RSR wrote:
Use Total Seal piston rings.


I have already written to Total Seal. But I did not receive any answer. I later wrote to another member of the sales team - he didn't answer either.


It is possible that the size of the piston on my car is atypical (86.75) and they don't have piston rings for this size.

I managed to buy connecting rod from Romania.

Ref. the Piston rings 86.75:
It is still not 100% clear to me if the pistons rings of the Porsche 924 S2 are identical in size to those of the Porsche 924 S1. I found to buy Genuine piston rings for porsche 924 turbo S2 (86.75 mm).

For main bearings I have: https://www.mespiecesauto.com/en/produit/coussinet-porsche-924-046105501-0406105561-046105591-046198451/

I receive an answer from mittelmotor.de. They have everything (piston rings, connecting rod, main bearings) for 700 euro.


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1980 Porsche 924 Turbo (931) diamond silver metallic/helios blue metallic
sold Porsche 924 NA 1979
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bureau13  



Joined: 07 Sep 2017
Posts: 357
Location: South Florida

PostPosted: Wed Dec 23, 2020 2:50 pm    Post subject: Reply with quote

Maybe a ROW vs US thing? I THINK I read that the US cars had slightly lower compression than the ROW cars, although I don't remember if that were only particular years, or what the numbers were.

MikeDanger wrote:
are you sure s2 is 8.5:1?? thought it was 8.0

944 turbo is 8.5

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1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2194
Location: Somerset, UK

PostPosted: Wed Dec 23, 2020 4:19 pm    Post subject: Reply with quote

MOTANUL wrote:
Carrera RSR wrote:
Use Total Seal piston rings.


I have already written to Total Seal. But I did not receive any answer. I later wrote to another member of the sales team - he didn't answer either.


It is possible that the size of the piston on my car is atypical (86.75) and they don't have piston rings for this size.

I managed to buy connecting rod from Romania.

Ref. the Piston rings 86.75:
It is still not 100% clear to me if the pistons rings of the Porsche 924 S2 are identical in size to those of the Porsche 924 S1. I found to buy Genuine piston rings for porsche 924 turbo S2 (86.75 mm).

For main bearings I have: https://www.mespiecesauto.com/en/produit/coussinet-porsche-924-046105501-0406105561-046105591-046198451/

I receive an answer from mittelmotor.de. They have everything (piston rings, connecting rod, main bearings) for 700 euro.




Have you pulled the pistons to check size? Usually 86.5 then 86.95
Have checked the bores for wear?
S1 and S2 rings are the same
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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MOTANUL  



Joined: 19 Nov 2018
Posts: 157
Location: ROMANIA BUCHAREST

PostPosted: Wed Dec 23, 2020 8:36 pm    Post subject: Reply with quote

Carrera RSR wrote:

Have you pulled the pistons to check size? Usually 86.5 then 86.95
Have checked the bores for wear?
S1 and S2 rings are the same


86.75 is my size - repair stage nr.1. An atypical dimension on the verge of extinction.

Bores wear 0.01 mm

S1 and S2 rings are the same: Very happy

After a thorough cleaning, the cylinder head looks like new. The engine block, on the other hand, looks worse - it's very rusty.



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sold Porsche 924 NA 1979
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MOTANUL  



Joined: 19 Nov 2018
Posts: 157
Location: ROMANIA BUCHAREST

PostPosted: Mon Jan 25, 2021 6:52 pm    Post subject: Reply with quote

I managed to find a Thermostat that opens at 80 degrees instead of 87 (OEM).
I managed to find a thermoSwitch that works between 87 and 82 degrees instead of 92/87 (OEM).
My car is 924 turbo with AC / 1980 and has 2 fans. Can you confirm that the small fan only works when I turn on the AC?

I thought it would help a lot to cool the engine when I'm with the car on the track day for example. Do you think this is a good idea?


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MOTANUL  



Joined: 19 Nov 2018
Posts: 157
Location: ROMANIA BUCHAREST

PostPosted: Fri Mar 05, 2021 5:17 am    Post subject: Reply with quote

I started reassembling the engine. The turbocharger has been rebuilt.
k-jetronic and injectors - work in progress.




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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2224
Location: MI

PostPosted: Fri Mar 05, 2021 8:26 am    Post subject: Reply with quote

MOTANUL wrote:
I managed to find a Thermostat that opens at 80 degrees instead of 87 (OEM).
I managed to find a thermoSwitch that works between 87 and 82 degrees instead of 92/87 (OEM).
My car is 924 turbo with AC / 1980 and has 2 fans. Can you confirm that the small fan only works when I turn on the AC?

I thought it would help a lot to cool the engine when I'm with the car on the track day for example. Do you think this is a good idea?



I lowered my engine temps and I like it a lot..
I forget what fans do what as oem, but that combination should work..
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Mike9311  



Joined: 14 Dec 2004
Posts: 1102
Location: Chicago-ish

PostPosted: Fri Mar 05, 2021 11:44 am    Post subject: Reply with quote

Not 100%, since its been a long time since I drove my 80, but I think you are right about the fans. Both only run with AC
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peterld  



Joined: 10 Dec 2006
Posts: 834
Location: Noosa Heads QLD Australia

PostPosted: Fri Mar 05, 2021 7:45 pm    Post subject: Reply with quote

Looks lovely.........
However I must draw your attention to that gasket on the turbo flange.......with the square hole cut in the centre oil passage.
That gasket with the square inner hole must be something that comes in a kit that turbo rebuilders use. It was on my rebuilt turbo as well, and I gave it no thought, using it along with the o-ring..........bad/bad/bad! The o-ring distorted, the gasket leaked profusively.
A subsequent check of the PET revealed that both turbo oil flange fittings use NO gaskets, simply relying on o-rings.

I'm not saying don't use it....just check fittings carefully.
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Fri Mar 05, 2021 11:13 pm    Post subject: Reply with quote

I would not use that gasket; my last turbo rebuild came with it too, but it's not right - just the o-ring.
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Mike9311  



Joined: 14 Dec 2004
Posts: 1102
Location: Chicago-ish

PostPosted: Fri Mar 05, 2021 11:58 pm    Post subject: Reply with quote

Nice save guys! I didn't even see that gasket because I wouldn't think to use it either. I was more looking at the fact that he has a nice 6:10 housing
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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MOTANUL  



Joined: 19 Nov 2018
Posts: 157
Location: ROMANIA BUCHAREST

PostPosted: Thu Mar 11, 2021 12:39 am    Post subject: Reply with quote

Fasteddie313 wrote:

I lowered my engine temps and I like it a lot..
I forget what fans do what as oem, but that combination should work..


I will first check how the water temperature is after the engine repair (I removed a lot of rust from the engine block and radiator). If the second fan is also needed to maintain the water temperature, I will make the modification to the electrical installation so that I can turn it on if necessary).
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1980 Porsche 924 Turbo (931) diamond silver metallic/helios blue metallic
sold Porsche 924 NA 1979


Last edited by MOTANUL on Thu Mar 11, 2021 12:46 am; edited 1 time in total
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MOTANUL  



Joined: 19 Nov 2018
Posts: 157
Location: ROMANIA BUCHAREST

PostPosted: Thu Mar 11, 2021 12:41 am    Post subject: Reply with quote

924RACR wrote:
I would not use that gasket; my last turbo rebuild came with it too, but it's not right - just the o-ring.


Before, he only had that o-ring and no oil flowed at this joint. I already ordered that o-ring (I thought it was better to put a new one - not to reuse the old one).
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sold Porsche 924 NA 1979
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MOTANUL  



Joined: 19 Nov 2018
Posts: 157
Location: ROMANIA BUCHAREST

PostPosted: Thu Mar 11, 2021 12:44 am    Post subject: Reply with quote

peterld wrote:

A subsequent check of the PET revealed that both turbo oil flange fittings use NO gaskets, simply relying on o-rings.


OK. Thank you - I will do so.
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MOTANUL  



Joined: 19 Nov 2018
Posts: 157
Location: ROMANIA BUCHAREST

PostPosted: Mon Mar 29, 2021 6:17 pm    Post subject: Reply with quote

The engine is back! (I hope for good ).


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