Iskenderian Racing Cams for 40hp (34PS) Vintage Speed Okrasa

[SilverThing]

I've managed to get my hands on a couple Iskenderian (ISKY) cams and am considering using one for a 40HP vintage speed Okrasa build. I have an German old tuning book 'Jetzt mache ich ihn schneller" from 1965 that mentions Iskenderian cams so they definitely seem to be period correct.

How does one determine what compression ratio to use with a camshaft?

Here are the specs:
Grind 221 "Torquer"
Lift at the cam 0.330"
Timing events at 0.017" lifter rise:
Intake Opens (BTDC) 23 degrees
Intake Closes (ABDC) 57 degrees
Exhaust Opens (BBDC) 57 degrees
Exhaust Closes (ATDC) 23 degrees
Timing events at 0.050" lifter rise:
Intake Opens (BTDC) 4 degrees
Intake Closes (ABDC) 38 degrees
Exhaust Opens (BBDC) 38 degrees
Exhaust Closes (ATDC) 4 degrees
It comes out to 260 degrees of advertised duration and 222 of duration at 0.050 cam lift.

Grind 234-MAX "Broad Mid-Range"
Lift at the cam 0.374"
Timing events at 0.012" lifter rise (different from above):
Intake Opens (BTDC) 33 degrees
Intake Closes (ABDC) 67 degrees
Exhaust Opens (BBDC) 67 degrees
Exhaust Closes (ATDC) 33 degrees
Timing events at 0.050" lifter rise:
Intake Opens (BTDC) 10 degrees
Intake Closes (ABDC) 44 degrees
Exhaust Opens (BBDC) 44 degrees
Exhaust Closes (ATDC) 10 degrees
It comes out to 280 degrees of advertised duration and 234 of duration at 0.050 cam lift.

Thanks!
_________________
"I like how everyone likes talking about Zeke's Thing yet he's the only one that's ever seen it." - Katie
"I've seen pictures..." - Jeremy

[Alstrup]

Calculating DCR.
But with today´s fuel even a stock engine can handle much more static compression than it has stock.
The mild Isky you have is close to stock, so something like 7,5 on medium grade fuel would fine
The more agressive one would work its best at around 8,5. That´s not easy to get in a 36 hp. So you would want to get what CR you can and run it.

[SilverThing]

What sort of dynamic compression ratio should I be aiming for either regular or premium fuel?

And this is a 40 SAE HP Okrasa motor, not a 36HP. Sorry if 34PS caused some confusion; it is the German power output and accounts for losses from things like air cleaner, muffler, and cooling system, which the SAE number does not.
_________________
"I like how everyone likes talking about Zeke's Thing yet he's the only one that's ever seen it." - Katie
"I've seen pictures..." - Jeremy

[Alstrup]

My bad. I was assuming the old 36 because its the vintage forum . I appologize.
In this light my post doesnt make much sense.
The 34 hp 1200 is somewhat easier to get some static compression into. Also, if you swop rocker arms to the later stock 13/15/1600 version you get 10% more lift, which comes in handy. I would aim for 8 or just over with the torque cam .
And 8,5 - 9 with the second cam. (This cam will require you to use a dual sgl. carb induction.)
If you calculate via DCR you wou would want something around 7.

[SilverThing]

The plan at this point is 83mm kolbenschmidt big bore 40hp pistons and cylinders coupled with an original okrasa 69.5mm 40hp crankshaft and 40hp okrasa cylinder heads.

Carburetion hasn't been decided on yet. I have a pair of rebuilt Solex 32PICB as well as a pair of Zenith 32NDIX. I would need to find manifolds for the Solexes, which are supposedly different for the fresh air heater 40hp engines. The Zeniths have steel manifolds, but are from an early stale air heater 40hp engine so I am not sure if the would work with a later fanshroud or not.
_________________
"I like how everyone likes talking about Zeke's Thing yet he's the only one that's ever seen it." - Katie
"I've seen pictures..." - Jeremy

[SilverThing]

Did the 1500 engines of the pre-1966 type 3 and type 2 use 1.1:1 rockers?
_________________
"I like how everyone likes talking about Zeke's Thing yet he's the only one that's ever seen it." - Katie
"I've seen pictures..." - Jeremy