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924 Turbo valve springs tech question

 
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Porscherally  



Joined: 20 May 2020
Posts: 6
Location: Istanbul

PostPosted: Wed May 20, 2020 5:39 pm    Post subject: 924 Turbo valve springs tech question Reply with quote

Dear Friends,

This is my first post in the forum. Hello to everyone. And wishing you healthy days during this very difficult pandemic days.

Can you please help me with the info as the title suggests?
I need the technical info for the 924 Turbo valve spring’s fitted height ( installed height ) and the seat pressure ( poundage ) @ installed height and @ various lift heights to check if the springs are OK to use during an engine rebuild.

Stay safe.
Regards.
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gegge  



Joined: 27 Jul 2007
Posts: 1077
Location: Sweden

PostPosted: Wed May 20, 2020 7:44 pm    Post subject: Reply with quote

Welcome!

Try the search function. Then you will find:

http://www.924board.org/viewtopic.php?t=28090&highlight=seat+pressure
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs
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Porscherally  



Joined: 20 May 2020
Posts: 6
Location: Istanbul

PostPosted: Thu May 21, 2020 1:29 am    Post subject: Reply with quote

gegge wrote:
Welcome!

Try the search function. Then you will find:

http://www.924board.org/viewtopic.php?t=28090&highlight=seat+pressure


Hi Carl,
Thank you very much.
I am not sure if I could have located that thread if you didn’t write. The link helped a lot but I still have a question and in fact two questions.
At the second page of that group buy thread, RC mentioned about the spring poundages for seat and also full lift. And if I understand correct, seat pressure @ stock installed height ( 42.34mm ) is 62 lbs and the recommended open pressure @ full cam lift is 223 lbs.
Again, if I understand correct these spring rate values for the springs from that aftermarket supplier which is OK but I am not sure if the quoted “ open pressure 223 lbs “ is with the stock Turbo camshaft or with another camshaft’s full lift.
Meaning that, should the 223 lbs poundage is created with the standard Turbo camshaft or some other profile?
Also, I would very much appreciate if you can share the stock Turbo camshaft lift figure if you have. I am trying to put an engine back together which had a rather hard life with the correct stock configuration.
Last but not least, do you happen to know if Ideola Garage is still in business or active or not ?
Many many thanks for your help.
Kerem
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gegge  



Joined: 27 Jul 2007
Posts: 1077
Location: Sweden

PostPosted: Thu May 21, 2020 2:39 am    Post subject: Reply with quote

This forum is great because there´s so much information left for free!

The 924 NA and turbo used the same springs and cam. A good turbocam by the way. Lift is close to 12mm and duration 223 @ 0,050", same profle as GT and GTS.

Installed seat pressure 62lbs and 223lbs (a lot!) at full lift. Installed height 42,3mm. Coilbind at 15,5mm lift. I wouldn´t worry about the springs as long as you don´t intend to rev past 7000 rpm. If so, install solid lifters.

Ideolas Garage is closed
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs
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Porscherally  



Joined: 20 May 2020
Posts: 6
Location: Istanbul

PostPosted: Thu May 21, 2020 3:06 am    Post subject: Reply with quote

gegge wrote:
This forum is great because there´s so much information left for free!

The 924 NA and turbo used the same springs and cam. A good turbocam by the way. Lift is close to 12mm and duration 223 @ 0,050", same profle as GT and GTS.

Installed seat pressure 62lbs and 223lbs (a lot!) at full lift. Installed height 42,3mm. Coilbind at 15,5mm lift. I wouldn´t worry about the springs as long as you don´t intend to rev past 7000 rpm. If so, install solid lifters.

Ideolas Garage is closed


Exacty, there is a vast amount of information here. I am trying to be acquainted with the forum and some of the subjects which I will need info. I am managing partner in a workshop and we are trying to do some work on my friend’s 1980 924 Turbo. Last time, due to a wrong downshift, the engine had bent valves etc, we are trying to rebuild the top end, new seats, new guides, new valves etc. And I seriously suspect about the valve spring’s condition as well. So I want to make sure they are OK.

You said that 62lbs and 223lbs a lot !!! But are these the figures that I should see with the usable springs (more or less) OR these figures belongs to that custom order at that thread ?

Pity that Ideola Garage closed. I have seen some well thought parts there.

We are considering fitting an IC ( stock engine and no modifications planned ) but apparently the “ air to air “ top mount IC which seems the easiest way but not much recommended ( versus the water to air top mount )

Many many thanks again.
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1099
Location: Washington DC area

PostPosted: Thu May 21, 2020 4:46 am    Post subject: Reply with quote

I bought some of the new springs a few years back and ran measurements for the stock cam (same in NA and Turbo). Although my data is gone, I recall that the new springs were a few pounds lighter at full cam height. I'm running them anyway in both race cars that I built with no problems. I rarely take my engines to 7000 RPM since the torque falls off drastically after 6500.
I've also seen that all 931 bent valve situations are a result of a mechanical overrev on downshift or belt failure. Not a spring issue.
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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gegge  



Joined: 27 Jul 2007
Posts: 1077
Location: Sweden

PostPosted: Thu May 21, 2020 6:29 am    Post subject: Reply with quote

Interferens engine and belt is a bad combo when pushing the envelope...
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs
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Porscherally  



Joined: 20 May 2020
Posts: 6
Location: Istanbul

PostPosted: Fri May 22, 2020 6:00 pm    Post subject: Reply with quote

Fifty50Plus wrote:
I bought some of the new springs a few years back and ran measurements for the stock cam (same in NA and Turbo). Although my data is gone, I recall that the new springs were a few pounds lighter at full cam height. I'm running them anyway in both race cars that I built with no problems. I rarely take my engines to 7000 RPM since the torque falls off drastically after 6500.
I've also seen that all 931 bent valve situations are a result of a mechanical overrev on downshift or belt failure. Not a spring issue.


Thank you very much.
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Porscherally  



Joined: 20 May 2020
Posts: 6
Location: Istanbul

PostPosted: Thu May 28, 2020 5:01 pm    Post subject: Reply with quote

gegge wrote:
This forum is great because there´s so much information left for free!

The 924 NA and turbo used the same springs and cam. A good turbocam by the way. Lift is close to 12mm and duration 223 @ 0,050", same profle as GT and GTS.

Installed seat pressure 62lbs and 223lbs (a lot!) at full lift. Installed height 42,3mm. Coilbind at 15,5mm lift. I wouldn´t worry about the springs as long as you don´t intend to rev past 7000 rpm. If so, install solid lifters.

Ideolas Garage is closed


Hi again,

I am still struggling with the 2 sets of original valve springs in hand. I am recording around 85 lbs installed and 235 lbs when I set them @ 42.30 mm which seems kind of high in comparison to 62-223 lbs figures mentioned in the forum.
Do you happen to know the Porsche factory installed height and poundages for the original springs ?
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gegge  



Joined: 27 Jul 2007
Posts: 1077
Location: Sweden

PostPosted: Thu May 28, 2020 6:37 pm    Post subject: Reply with quote

The NA and Turbo use the same springs. But there is a difference between the two. IIRC, the Turbo have a "rotocap" - a roller bearing that might shim the spring further than the NA washer.

Therefore seems your figures right from my perspective.
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs
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Porscherally  



Joined: 20 May 2020
Posts: 6
Location: Istanbul

PostPosted: Fri May 29, 2020 1:52 am    Post subject: Reply with quote

gegge wrote:
The NA and Turbo use the same springs. But there is a difference between the two. IIRC, the Turbo have a "rotocap" - a roller bearing that might shim the spring further than the NA washer.

Therefore seems your figures right from my perspective.


I understand your point But that rotocap is actually a very thick piece. It is 9.30 mm !!!
So, I am %100 sure that the mentioned aftermarket springs ( 62-223lbs @ 42.30 mm fitted height and @ cam lift ) is also calculated in with that thick rotocap.
But, one thing I have noticed, it has been said that aftermarket Australian springs had a slightly shorter Free Length so ; either the original springs will produce naturally a higher poundage if installed @ 42.30 or the original springs should be installed at a different height ( 43 mm ) so that they have less poundage.
But without really knowing the factory data it is a guess work. Naturally I am trying to avoid over stressing the valve train.
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