Sleeve shimming

[David Ashcroft]

When shimming sleeves for timing adjustment ,how much does timing change in relation with shim size eg:exhaust 186 + .003shim what would the exhaust timing be now ?

David

 

[dwilfong]

David it depend on the eng.

stroke and rod length will make it different for every eng.

 

[David Ashcroft]

David it depend on the eng.

stroke and rod length will make it different for every eng.

Ok bluehead 91vac. If that helps

David

 

[David Ashcroft]

Would someone perhaps done this on a cmb 91 rs or any engine for that matter and know how time timing changed in relation to what shim thickness was used..I am really just trying to see timing change to shim thickness ratio approximately

 

[steve wood]

all motors vary. example, if you have 10 rs 91's, and measure them up you can find as many as 10 different timing numbers in the sleeves.rotor timing varies also,but doesn't seem to be as much,they must be easier to make.

on an rs 91, a .003 shim changes the exhaust, boost, and transfer numbers by 1°. a .010 shim changes the numbers by 2° on the exhaust,and 3° on the boost and transfer ( all numbers from mwd's program)

 

[Ian Inverarity]

David, it is not quite as simple as a certain shim will change the timings by a certain amount, you need to look into the geometry and maths.

Do you know what timings your VAC91 has now? VACs I have measured have transfers around 136-137, that would be considered high already.

 

[David Ashcroft]

all motors vary. example, if you have 10 rs 91's, and measure them up you can find as many as 10 different timing numbers in the sleeves.rotor timing varies also,but doesn't seem to be as much,they must be easier to make.on an rs 91, a .003 shim changes the exhaust, boost, and transfer numbers by 1°. a .010 shim changes the numbers by 2° on the exhaust,and 3° on the boost and transfer ( all numbers from mwd's program)

Thanks Steve that is just what I wanted to know.

 

[David Ashcroft]

David, it is not quite as simple as a certain shim will change the timings by a certain amount, you need to look into the geometry and maths.

Do you know what timings your VAC91 has now? VACs I have measured have transfers around 136-137, that would be considered high already.

..
Ian yeah mate there are a lot of calculations I am aware perhaps bit over my head ha..No I don't know the measurements at this time ,,but yes 136-137 is high

David