Nova .28

[David Ashcroft]

I measured my Mod Nova 28 on the metric engine programme ,and got 185exh
Rotor opens 219 ATDC and Rotor closes at 65 with a totel open duration of 206.
The blowdown is 31.7 as expected because this engine was modded to rev.

What surprised me though was the button CC volume of 0.37cc !! with the plug in,,which will end up with a trapped CR of 7.6 that's without a any shims and .0.16" clearance ,I not sure why the button was enlarged so much,,although this is a converted car engine to run low 25% nitro.

New button in the making..
.

 

[Gary Lauer]

I also have a 28 marine and without any shims have .012 clearance. How do you make that smaller? sand the top of the cylinder?

 

[David Ashcroft]

I also have a 28 marine and without any shims have .012 clearance. How do you make that smaller? sand the top of the cylinder?

Don't Sand the cylinder..

 

[David Ashcroft]

I am currently having a new Head Button machined now with a smaller bowl cc..

 

[David Ashcroft]

Engine now ready,new mod button ,9mm carby,,os needle ..

 

[RonShaw]

I measured my Mod Nova 28 on the metric engine programme ,and got 185exh
Rotor opens 219 ATDC and Rotor closes at 65 with a totel open duration of 206.
The blowdown is 31.7 as expected because this engine was modded to rev.

What surprised me though was the button CC volume of 0.37cc !! with the plug in,,which will end up with a trapped CR of 7.6 that's without a any shims and .0.16" clearance ,I not sure why the button was enlarged so much,,although this is a converted car engine to run low 25% nitro.

New button in the making..
.

David,
The larger bowl is for the lower nitro. Higher nitro requires less bowl volume/more compression. .22-.24 better for high nitro in your .28. What volume did you settle on for your new button? Let us know how it goes. Thanks.

 

[David Ashcroft]

David,
The larger bowl is for the lower nitro. Higher nitro requires less bowl volume/more compression. .22-.24 better for high nitro in your .28. What volume did you settle on for your new button? Let us know how it goes. Thanks.

Button now .23cc

 

[RonShaw]

Button now .23cc

Perfect. Keep us updated.