2016 SJ 760 conversion

J

Joel Cleveland

Location
Abq NM
I have a 2016 SJ that I want to slap a 760 cylinder on for IJSBA lites class. Does anyone know if the 62t cases in the newer SJ's accept the 64x cylinder without have to grind or machine the cases to fit? Do I run a regular 760 head gasket? Or can I go thinner than stock for more compression?
 
N3vrSat1sfied

N3vrSat1sfied

Military Member
Location
Fort Worth, TX
I have the info somewhere I know your cases are fine. They have a few different 760 cylinders though. I know the one labeled 62T Y1 is max bore of 85mm so you dont want that one. Cant remember which one you need of top of my head
 
V

Vortex

Location
Southeast
Pretty sure you do have to machine the cases to fit the larger 760 sleeves. Rules say no internal mods of any kind but they make an exception for the 760. It's under the '"if no oem sleeve is within x percentage of the class limit" clause. The gasket thickness change would not be allowed.
 
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Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
I could be wrong. Bit I believe the sleeves on the 760 cylinders will fit without modification to 62t cases. This is why you cannot go but to 85mm bore. 1mm overbore whereas a 61x cylinder can theoretically be bored to 84-84.5. If you install big bore sleeves in a 61x you can go beyond 85 but you have to punch out the cases

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V

Vortex

Location
Southeast
Now you might be able.to put a 62t cylinder on a 62t case and bore that cylinder to 84mm. That's a different cylinder and sleeve than 64x 760
 
37

37

Precipitation Hardened
Location
Indy
08+ SJ comes with 64U cases (single pulse 760 casting). No machining necessary on 08+ skis unless they don't have their original motors.

If your engine ID decal says "64U" then a 760 cylinder will bolt up without needing any machining. The cases are stamped 62T but have a 64U decal. That's where all the confusion happens on these conversions.

This is one of the selling points of the 08+ as a race ski.
 
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37

37

Precipitation Hardened
Location
Indy
701 and 760 base gaskets are the same.

The rules make you keep your stock 701 head, so run an OEM 760 head gasket either as-is or with a layer removed to get the compression you want. A 760 gasket with 2 out of 3 layers should get you in the ~175 PSI range if memory serves. Your pistons are below deck at TDC so there's no harm in running the 701 head. It's not ideal but those are the rules.
 
37

37

Precipitation Hardened
Location
Indy
tomski said:
You can use the 760 head if you build a bracket to mount the pipe.
If you remove a layer from the OEM 3 layer gasket you are under the minimum head gasket thickness.
Click to expand...
Did Lites rules change to allow OEM 760 heads? I just looked again and am not seeing where they're allowed.

As long as displacement is under 780cc, head gaskets can be a minimum of 0.675mm/0.027" after the -10% tolerance. Base gaskets must be between 0.80mm/0.032" maximum and 0.45mm/0.018" minimum per the tolerances.
 
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N3vrSat1sfied

N3vrSat1sfied

Military Member
Location
Fort Worth, TX
IJSBA rule book is very clear and easy to understand....... j/k

I had to ask all these questions when I built my lites SJ. glad we have a thread with all this info. OP check out my SJ build thread for some other rules we discussed in there.
 
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