Race Engine Forum UK

Hello Guy,

I read the 1rst book and found your recommendation for valve to piston clearance during overlap.
But what are the figures for the valve to valve clearance? I mean if you increase the intake valve size diameter you have this dimension decreasing so what is the limit to respect?
It is for the R5 Alpine engine built by a friend (the intake valve going from 38.5 to 41.5 mm) as we discussed previously concerning the head prep.

Thank you,

Robert

hi Rob

the minimum valve - valve I would tolerate at 'new build' is 0.020" (0.50mm) but much depends on valve-guide clearance, my figure is based on my work. The more loose the valve-guide fit the more you need.

I would generally try to achieve 0.040" (1mm) at new build.

I hope this helps,

G

Many thanks !!

Robert