Xflow piston to deck clearance

[Taran Las]

Can any of you knowledgeable people tell me what the minimum piston to top of deck clearance for a xflow should be.

 

Thanks

 

Phil

[cdg]

Phil,

The last x-flow that I built (for myself) had a clearance of 0.25mm to the top of deck, using an Ajusa competition head gasket.

 

If you are using a copper asbestos type, perhaps 0.5mm would be safer.

I know that some engine builders actually have the pistons slightly proud of the block in order to get as much compression as possible, but it sounds a little extreme to me and must surely depend on the compressed height of your gasket.

 

Chris.

[oilyhands]

As a rule of thumb, the minimum clearance between the top of the piston and the head face should be .030 (.75mm) to .040(1mm), the extent of protrusion from the block (if any) will, as Chris has mentioned, be dependent on compressed gasket thickness. If the piston is flush with the block face it should be OK. Bear in mind that reducing this working clearance will have an affect on the valves proximity to the pistons too.

 

Oily

[Casbar]

Just gone through this exact problem with my engine build.

 

If you are using a comp gasket (Ajusa) this will give 50thou.

 

You can run the pistons upto 10 thou above the block face. To be safe, I have gone for a flush fitting. Bear in mind, there will be some rod stretch. Also be sure to dry build to check for valve clear.

 

If you need to machine the pistons, be careful about compression ratio's.

[Taran Las]

Thanks guys, Looks like I have some serious measuring to do over the winter.

 

Regards

 

Phil