Turbo 3.6 Valve Spring Installed Length?
03-31-2023, 05:23 AM
#1
Turbo 3.6 Valve Spring Installed Length?
Morning, I wondered if a struggling engineer could ask for help?
I'm trying to analyse the 964 valvetrain, cam and rocker options. I have 964 parts, NA and Turbo cams, measured the geometry of the heads etc and it's starting to look interesting... but I keep getting screwed over on the details. My GF has a 993 and I have the manuals for it it appears that they changed the springs and rockers (hydraulic) on that so it's no use... I then bought a full 964 manual but that only deals with stock Carrera...
I'm trying to avoid having to buy another workshop manual just to find out the installed lengths of a Turbo 3.6... could anyone tell me those numbers? ( I've just ordered a "Porsche 964 Technical Specification Book" but I dont know if the numbers I need are in there either!)
Also, the parts catalogue says the Turbo 3.6 uses the same springs are Carrera (different head, valve, guides...) parts 901 105 901 50 or 51 - is that the case in folks experience here??
So far the results look decent for the Carrera (apart from a few nasty wear spikes on the follower wear the oil entrainment passes zero) but the Turbo is looking a touch light on spring cover if I use stock spring lengths....
I'm trying to analyse the 964 valvetrain, cam and rocker options. I have 964 parts, NA and Turbo cams, measured the geometry of the heads etc and it's starting to look interesting... but I keep getting screwed over on the details. My GF has a 993 and I have the manuals for it it appears that they changed the springs and rockers (hydraulic) on that so it's no use... I then bought a full 964 manual but that only deals with stock Carrera...
I'm trying to avoid having to buy another workshop manual just to find out the installed lengths of a Turbo 3.6... could anyone tell me those numbers? ( I've just ordered a "Porsche 964 Technical Specification Book" but I dont know if the numbers I need are in there either!)
Also, the parts catalogue says the Turbo 3.6 uses the same springs are Carrera (different head, valve, guides...) parts 901 105 901 50 or 51 - is that the case in folks experience here??
So far the results look decent for the Carrera (apart from a few nasty wear spikes on the follower wear the oil entrainment passes zero) but the Turbo is looking a touch light on spring cover if I use stock spring lengths....
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Bobley (03-31-2023)
03-31-2023, 02:05 PM
#3
Interesting, that's the same as stock Carrera then. Seat pressure works out at 268N inlet and 312N exhaust. That means the valves will be getting a bit on edge by 7000rpm...
Seat pressure is usually a function of the reciprocating mass for NA engines and then you need to accommodate gas pressure on Turbos to account for the large pre turbine pressure trying to blow the exhaust valve open. 1.5 Bar (guess) will put about 180N load on the valve...
Having a big preload will muller your followers though...
Seat pressure is usually a function of the reciprocating mass for NA engines and then you need to accommodate gas pressure on Turbos to account for the large pre turbine pressure trying to blow the exhaust valve open. 1.5 Bar (guess) will put about 180N load on the valve...
Having a big preload will muller your followers though...