minimum clearance valve to piston aaz

[mk3pete]

hey all just wondering if you guys have some advise and info for the build im creating!? il post up a build thread one day, i have heaps of progress pics.
basically aaz fresh everything, holset, ported head and custom grind cams, h beams, girdle just to name a few
i have new 1mm oversize pistons which are protruding .025 thou.
i have a new 3 notch hg and im hoping someone knows the thickness of it? as im a bit unsure how to accurately measure it?
my engine machinist tells me i need a minimum clearance valve to piston of .060 thou?
not that i dont believe him but id like to know an opinion from someone here with experience.

[theman53]

The bore diameter is to be .0012" over the size of the piston.
 
The protrusion of .025" above the deck is under a 1 notch gasket. The 3 will be way too much...this is all in the Bentley manual

[mk3pete]

The bore diameter is to be .0012" over the size of the piston.
 
The protrusion of .025" above the deck is under a 1 notch gasket. The 3 will be way too much...this is all in the Bentley manual

yes fair enough my thoughts on running the 3 notch is to lower the compression. il be running 35 to 40 psi with an 11mm pump from diesel maken.. when he decides to finally build it for me. been waiting very patiently haha
australian climate isnt that cold so not worried about cold start issues

is there a rule of thumb calculating cr depending on hg choice?

[theman53]

Yes the rule of thumb is in the Bentley, run the 1 notch. If you want to lower CR do it in the precup. 35 to 40 is not a big deal and all you will do is reduce the efficiency of the burn by adding thickness to the HG. The precup was designed for 75hp and in an economy car...add the thicker gasket and your flame travel will look like a tick

[Alleslowbuged]

Hi,

sorry for using your thread.

@theman53
What du you mean, with "do it in the precup"? Are there alternative precups available which could be swaped, which are designed for higher peak power? If yes, do you have part numbers availabe and can state how much the compression rate will be reduce?

Best Regards
Alleslowbuged

[theman53]

no, port them