Hi

I'm searching information about okrasa Heads.
By reading Oettinger old ads, I learned that 2 different kind of okrasa heads were available:

- Special alloy heads, for 7.5:1 compression
- High temperature and special alloy heads for 8:1 compression.

Maybe the first heads are older and the last ones were all for 8:1 compression !?

My questions are:

How could I recognize one of them ???
Do you know the meanings of the writings next to "Okrasa" name ?

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I have asked the meaning of the inscriptions in the cilinder heads some years ago at Oetinger.

The only anser they gave me was the meaning of the inscription S42.
The S stands for super fuel, and the 42 is the volume of the combustion chamber in kubic cm.

The meaning of the inscription just under the Okrasa inscription, they thought it was something of a production code but did not know the correct meaning of them.  9212.jpg You have insufficient rights to see the content.

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Here are other kind of okrasa Heads:

 9220.jpg You have insufficient rights to see the content.

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next  9222.jpg You have insufficient rights to see the content.

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and  9223.jpg You have insufficient rights to see the content.

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and another one  9224.jpg You have insufficient rights to see the content.

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Looks like the 0.15 stands for the 30Hp cilinder heads and the 0.16 for the 34Hp heads.

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this is mine.
I have no idea if the 30 hp kit and 40 hp kit have different Compression ratio.
What I do know is that my nos Kit includes 4 small rings with the diameter like the cilinder. Those are ment to be put between the case and the cilincder to overwin the higher crank taps.

Even the date in year is stamped in my head, the aloy ones from Okrasa, not the one with this small brain...
:roll:
greetings  9239.jpg You have insufficient rights to see the content.

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the rings are here above the intake manifolds.
You only see 3 rings....
:roll: There is one missing . But that is the easy part to find.... :lol:  9240.jpg You have insufficient rights to see the content.

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For the compression you have only to look at the stamping between the two intake valves, then it is easy to calculate your compressionratio.

The formula is in the pic. V1 stands for the volume of one cilinder on a 1200cc engin thats 298cc and V2 is the volume of the combustion chamber on a 30Hp engin about 53cc.
In this case you become a compression of 6.622:1

The moste Okrasa cilinder heads have a volume around 43cc, the compression with the original stroke is then 7.9:1

When you use the Okrasa 69.5 crank and the rings the compression rises also.
 9241.jpg You have insufficient rights to see the content.

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Here is the ad where I read about different kind of Okrasa Heads.
(See pink part of text)
Here is the bigger pic:
https://www.oldspeed.ch/pages/press-okrasa12.html 

Translation:

Up: "2 high output cylinder heads for 7,5 compression"

>>> so a standard tsv 1300/34 kit has 7,5:1 cylinder heads!

Down: "Volumetric ratio on our kits is 7,5:1 but it can be brought to 8:1 using our special alloy cylinder heads."

>>> 8:1 special alloy cylinder heads are an option!  9259.jpg You have insufficient rights to see the content.

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Apparently with the TSV-30 there where two different cilinder heads with different compresion ratios.
7.2:1 and 7.8:1

TSV-30 

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So we should be able to recognize 4 different okrasa cylinder heads... :shock:

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Some history I found in diverse magazines from the 80s

- the first series was 25 Hp heads that got 1 bigger inlet port, twin solex 28 mm carbs, on hand built intake and mushroom filters
- In 53 the dual port head was born for 25 hp engines
- in 54/55 the 36 heads were born but with only 1 carb a 28 or 32 mm ? the dual setup caused to many problems. compression was 6.8/1 with 30 or 38 HP
- 56 brought the new dual carb setup with 32 bpic , knecht filters fuel lines. compression was 7.2/1 and hp 41
-57 the 64 stroker crank was made for 1200 cc and a 69.5 for 1300 cc
this last kit gave 44 Hp.
- A special Cast auluminium cilinder head was constructed to use on Weber carbs. this gave 8.0/1 compression . It used high octane race fuel and only a handful were made

to mach 1:
The heads in my kit I have are made in 63. the fram filter bears no sr nr but the filterhouse is F827 and filter c827

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I have a copy of an old article that says the 8:1 ratio was what was sold here in the states.

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My heads are stamped on the other side with a (S) and (40).
This works out to 8.45 to 1 compression.
My question is, I also have the Okrasa crank, and a choice of stock pistons and cylinders, or 77mm dome top p/c's.
If I run the dome top pistons will my comp. be to high to run pump gas?
(92 octane for premium)

Joe

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