Valve Seats

[Richie-Van-GTi 71 2 Cars]

After a bit of advice on valve seats. Can a standard gti6 valve be simply ground back by 0.5mm by a usual machine shop that does skimming etc? I know I will then need to add 0.5mm shims to the springs to compensate. Just unsure if its the seats can be ground or something below needs changing.

Thanks

[welshpug 1,657]

they can, though im not sure by how much, sandy can probably tell you or maybe PeterT.

 

need to be careful you dont run out of travel on the tappet though I think there may be a few mm in them.

Edited August 27, 2015 by welshpug

[Richie-Van-GTi 71 2 Cars]

Its going onto solid lifters so theres no concerns there. They will be made once the head is assembled and I get cams back from Peter. Looking about 0.5 stainless isnt too hard to find and have laser cut

[Tom Fenton 1,542]

Just make sure its hard enough, standard stainless would be too soft I think? And may just flatten/mushroom.

[Richie-Van-GTi 71 2 Cars]

Its going onto solid lifters so theres no concerns there. They will be made once the head is assembled and I get cams back from Peter. Looking about 0.5 stainless isnt too hard to find and have laser cut

[Richie-Van-GTi 71 2 Cars]

Stupid phone double posting.

Im thinking put them under the existing shims to ensure even pressure on them so any compression would be negligible.

[Tom Fenton 1,542]

Regardless of where you position them, they will still have the full spring force on them at full lift. If they are not hard enough they will squash which then defeats the object of putting them there.

[Richie-Van-GTi 71 2 Cars]

Under the existing thicker shim the force of the spring is spread across the full surface area. Directly under the spring the force would all be concentrated on the spring end surface area which is much smaller. I honestly dont think stainless steel at 0.5mm will compress enough in that environment to create any notable difference. Temperature will cause larger fluctuations in spring rate then the squish of the stainless.

[petert 586]

The combined seat/valve reconditioning process might be a total of 0.5mm. Regardless of the final result, you need to test spring height accurately if you're planning to rev the tits off it. If you don't have a spring tester and/or know how to set spring heights, my advise would be to leave it with a professional.

[Richie-Van-GTi 71 2 Cars]

I dont intend a higher than normal rev limit but i have now given the head to a machine shop with all the valves and explained what needs doing. Also buying another good unskimmed head so I have options.