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Turbo bypass valve

 
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knobby  



Joined: 23 May 2011
Posts: 41
Location: Cincinnati,Ohio

PostPosted: Fri Oct 26, 2018 9:34 am    Post subject: Turbo bypass valve Reply with quote

I just got my turbo back from Majestic and have to replace the bypass valve gaskets myself because they thought that they were NLA!
Anyway I need help with the piston orientation.
I think the piston crown faces the opposite side to the vacuum elbo.
There are two slots on the crown and I need to know if they need to be oriented in a specific way or doesnít matter.
Also a slot cast that is visible from the underside of the piston.
Any help appreciated as Iíd really like to get this right before installing it this weekend.
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81 RED 931 S2(daily driver),81 WHITE 931 S2(not currently drivable).
Cincinnati,Ohio
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924RACR  



Joined: 29 Jul 2001
Posts: 8236
Location: Royal Oak, MI, USA

PostPosted: Fri Oct 26, 2018 10:46 pm    Post subject: Reply with quote

Per the parts manual, the piston looks to be installed with the flat face opposite the inlet elbow (boost sensing line from intake), or facing the RHS of the car... and the spring on the LHS of the car/on the vacuum elbow side... make sense? Sounds like what you were expecting for orientation.

Can't offer any ideas regarding rotational orientation, sorry.

Definitely want to get that sorted now; I made the mistake of getting it backwards, and had to fix in-car, which sucked (but was just barely doable)...
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Vaughan Scott
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'79 924 #77 ITB racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1903
Location: Somerset, UK

PostPosted: Sun Oct 28, 2018 1:15 am    Post subject: Reply with quote

Not aware of orientation of the slots. I donít believe it matters. Had mine in and out twice and did not consider this. There is nothing to stop the piston spinning except spring friction anyhow.
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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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knobby  



Joined: 23 May 2011
Posts: 41
Location: Cincinnati,Ohio

PostPosted: Mon Oct 29, 2018 2:02 pm    Post subject: Reply with quote

I eventually spoke to the tech at Majestic who confirmed that the rotational orientation of the piston slots was vertical when he disassembled the turbo but John stated that it did not matter.
Any way I installed it this weekend and am very happy with it!
Thanks for your replies,much appreciated!
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Cincinnati,Ohio
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