OS91 Viper

[freddyferris]

Hi!
I finaly got my motor! Yeah!!! Rocks looks realy good!!!!

Got the set from OS... And they give a OS8 and a OS A5... is the combination OK? Or schould i take 2x OS A8 ?

thx

Fred

[DavidH]

That combo of plugs OS 8 and A5 will work fine.

David

[freddyferris]

Do i need anything els head shims or somthing?! (wildcat30)

Fred

[DavidH]

I don't know how OS has shimmed the Viperhead.
Here in the US with CP 30% we use .016 in shims. 2 X .008 shims .
For 30% Magnum .024 in shims 3 X .008 shims.

I would think with the WC 30% you will probably need .016 shims 2 X .008

James probably informed OS how much to shim the Viperhead when he supplies them to OS.

David

[freddyferris]

hum ok... i'll put ashim morefor the break in period.. schould be better no?

Fred

[DavidH]

You will need .016 in shims to run 30% fuel.
Check and see if the head has 2 X .008 shims from the factory.

Shimming anymore is just going to lower the compression more.

Now another to take into account. I don't know if OS changed the piston in that motor, that would make a difference in how it would be shimmed also.
I remember reading something in the description of the motor about a different piston than the other OS 91's.

David

[r/c_outlaw]

.024 seams like alot of shim....i use the 4 shims ( 2 packs from omi) to get .024
.....is that right or am i adding it up wrong... using 30% curtis blend wildcat viper head and big bore mod

thanks

[bono1]

Two eights and two fours should give 24. I used that combo with one engine and I used three eights with the another and all is good. Any combination should give the same results.
Sam