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mittelmotor solid lifters

 
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Juho  



Joined: 03 Oct 2018
Posts: 377
Location: Finland

PostPosted: Wed Apr 14, 2021 4:07 pm    Post subject: mittelmotor solid lifters Reply with quote

I want to rebuild my head and want more revs (7k) i plan on using my 285 lift camshaft and mittelmotor solid lifters, anyone has used these and what do i need for head rebuild?[/i]
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safe  



Joined: 18 Mar 2017
Posts: 583
Location: Sweden

PostPosted: Wed Apr 14, 2021 9:56 pm    Post subject: Re: mittelmotor solid lifters Reply with quote

Juho wrote:
I want to rebuild my head and want more revs (7k) i plan on using my 285 lift camshaft and mittelmotor solid lifters, anyone has used these and what do i need for head rebuild?[/i]

Which camshaft is that? I see that they have a "Sport" and 3 different "Race".

440€ for a set of solid lifters, OMG, that is steep...You can buy them in Sweden for 80-90€....

But in essence you fit the lifter and camshaft, measure how thick of a lash cap you need for your desired valve lash and buy those...
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/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe
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Juho  



Joined: 03 Oct 2018
Posts: 377
Location: Finland

PostPosted: Wed Apr 14, 2021 11:00 pm    Post subject: Reply with quote

not camshaft from mittelmotor i have one already, can you link me those solid lifters??
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safe  



Joined: 18 Mar 2017
Posts: 583
Location: Sweden

PostPosted: Wed Apr 14, 2021 11:38 pm    Post subject: Reply with quote

Juho wrote:
not camshaft from mittelmotor i have one already, can you link me those solid lifters??

Sure!
https://www.acm.se/product/ventiltryckare-38-5-mm-porsche

I bet its the exact same as Mittelmotors,
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/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe
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Juho  



Joined: 03 Oct 2018
Posts: 377
Location: Finland

PostPosted: Mon Apr 19, 2021 5:56 am    Post subject: Reply with quote

is there source for valves and springs, the car is going to run 7000rpm all the time and i want it to be bulletproof
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 1227
Location: Maysville, Colorado

PostPosted: Mon Apr 19, 2021 7:25 am    Post subject: Reply with quote

The only 9mm stem valves I found in US were some by Ferrera that were a much larger size than our valves and would need a quite a bit of machining to work. SI used to make the 9mm valves, but no more. PSI makes the best commercially available springs but finding some other than beehive type to fit in our buckets might be tough. PAC Racing is second but most of their dual springs have quite high spring rates, more intended for roller cams. That is one reason I'm going to 7mm stem valves, others have used 6mm but a couple of trusted sources recommended against it for me. Many of the old air cooled Porsches use the 9mm stem(better heat transfer), but don't know about the length, old Alfas also, but I believe them to be too short.
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Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)
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safe  



Joined: 18 Mar 2017
Posts: 583
Location: Sweden

PostPosted: Mon Apr 19, 2021 3:29 pm    Post subject: Reply with quote

If you are changing springs and valves, change the valve guides to. Go to 8 or 7 mm and you will have a lot more to choose between.
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/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe
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Juho  



Joined: 03 Oct 2018
Posts: 377
Location: Finland

PostPosted: Tue Apr 20, 2021 12:46 am    Post subject: Reply with quote

are these avaible off the shelf, sorry i dont have any idea of rebuilding head
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safe  



Joined: 18 Mar 2017
Posts: 583
Location: Sweden

PostPosted: Tue Apr 20, 2021 1:12 am    Post subject: Reply with quote

Not what I know. Ask you local machine shop, it will be something custom, mist likely.
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/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 1227
Location: Maysville, Colorado

PostPosted: Tue Apr 20, 2021 2:15 am    Post subject: Reply with quote

I have Ferrera valves(7mm) high performance PAC Beehive springs($20 ea vs $12), Crower retainers and some RD Spring caps to fit Alfa adjusting shims and ACM/Parner follower buckets, and Ford 4.6l valve stem seals/spring seats. Cost so far about $800. The valves have almost doubled in price over a couple of years ago.

For machining the following is necessary:

1. Cut valves to length, cut the retainer grooves and reduce size of intake valve from approx 50mm to 40mm. Ferrera makes 40mm intakes in both 6mm and 7mm but supposedly the one i have flows better, as the back face angle is reduced from 20 deg to 12 deg.

2. Make new valve guides.

3. Make spacer shims to replace 931 rotators and set spring height.

4. Purchase the retainers and Alfa shims. The machinist will find some 7mm single groove retainers as the Ford ones are a triple groove and would be tough to machine without their special cutter.

Then mill the head to flatten it, and do a complete valve job.

Cost? I don't even want to know, but building a high performance motor can get expensive in a hurry. But, it does solve one of the major design issues of this motor which is the valve train weight. As a comparison, a fellow I know built his own Formula Ford motor about 4 years ago, all "stock" parts. The parts cost only was $6500, projected motor life is about 40 hours.
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Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)
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Mike9311  



Joined: 14 Dec 2004
Posts: 1678
Location: Chicago-ish

PostPosted: Mon Apr 26, 2021 1:45 am    Post subject: Reply with quote

I agree on cost. So far on my test build every step is $200 here $200 there and I am doing all the work. Really wish I would have bought all the valves when I bout individual test pieces. Prices easily doubled like you said

I like your idea of machining down of the valve to get that tulip shape. With the 6mm stem versions I am using I thought about machining the 46mm to 44 but ended up just following thru with the 42/38 combo. It would have been 42/36 but I wanted the special exhaust material plus if gives me room to fix some porting irregularities from the PO of the head I am using. Of course I could have machined it to 36

I am comfortable with the 6mm stems since they have a long history of use with Volvo's in DTM even though, like you, heat is a factor. So I have custom Beryllium free copper seats for the exhaust side. In the end I will be saving over 800g over the entire valve train. Crazy to remove nearly a kilo just like that so I choose different springs in totally the opposite direction of everyone else.

Once I am finished with the head fixture I'll post up a separate thread with all the details on the solid lifters as well.

Exhaust valve is in front, intake in back

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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
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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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11723
Location: PacNW

PostPosted: Mon Apr 26, 2021 2:30 am    Post subject: Reply with quote

Mike, I'm sure I speak for everyone when I say I'm looking forward to the day when you begin to take these projects a little more seriously.
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  • WeiBe (1987 924S 2.5t) - 931 S3
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Mike9311  



Joined: 14 Dec 2004
Posts: 1678
Location: Chicago-ish

PostPosted: Mon Apr 26, 2021 10:55 pm    Post subject: Reply with quote

What you should ask for is that I simply finish. I get asked constantly "don't you actually want to drive one of these things?" I do reply with a yes but I also say I love the journey.

Seriously though, I really need to follow thru.
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
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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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11723
Location: PacNW

PostPosted: Tue Apr 27, 2021 3:16 am    Post subject: Reply with quote

My white turbo project was bought in 2013 and just fired up a couple weeks ago, so don't be too hard on yourself!


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  • WeiBe (1987 924S 2.5t) - 931 S3
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