deck height

[zxdillan]

could anyone tell me what the optimum deck height is? ie piston to head clearance inside the combustion chamber. lots of threads about pistin to head clearance ie squish, but non about deck height, please help!!!

[mick41zxr]

Deck height generally refers to piston to head clearance. You also need to check piston to valve clearances, which are listed in the kit manual which is on this site. After that you play with chamber volume for compression ratio as there is no set ideal height for the combustion chamber. This is often dependent on piston crown design. A good & I mean good tuner will have their preferences on how they like a chamber to be set as valves & port bowls can be manipulated for different tunes. That being said the 400 has a pretty good design standard.
A good reference is to look at the kit manual for the 750's which are available on the net. The 400 manual also lists the basic porting required.
Regards,
MB

[rmkd177]

As Mick says 'deck height' usually refers to piston to head clearance. And again usually the closest point is the flat areas on the circumference of the piston (squish) the old fashioned...in accurate way was to place small strips of soft solder on those areas and rock the piston about tdc till your satisfied it has compressed to the 'gap' between the two.However with more accurate measuring equipment available its not as common to use the solder technique. So back to the question...optimum...has a few variables, which are affected by...basicly...piston weight...maximum revs to be used and type of con rod ect. My ball park figures are 0.61mm for stock pistons at 16,200rpm with 1208 conrods, down to 0.5mm with stock pistons 14,500rpm again with 1208 conrods. If you are accurate with your measurements and competant on a lathe or milling machine then these figures (in my experience) will work perfectly. However if you question your skills the best way to check your accuracy is to run the motor for a while then remove the plugs and inspect the piston crowns with a 'boreascope' which im sure some friendly mechanic will lend you.