Grinding In Valves

[floodys 4 1 Cars]

Dont know if this in the right bit but, when i used to do mechanics it used to be called grnding valves in anyhow, i used to use course paste then fine paste with a stick with a rubber sucky thing on the end, is this still the same way to do it? or is there a new kind of "tool" you can get? cheers

[j_turnell 137 3 Cars]

Thats how i've done it in the past, ok on an 8v, but takes a while on an mi, you can cheat and use a drill though.

[DrSarty 90 1 Cars]

It's called 'lapping' too.

 

It's something that needs to be done on all engines, not just XUs (i.e. TUs as well) so it could be in 'General Motoring' if you were really that fussed about it.

 

I'm a big fan of the wooden stick with rubber cups on - big on one end and small on the other. You can stick it on your forehead for laffs!

[Sandy 191]

Just use the fine paste unless it's severe and wash it all thoroughly after.

[floodys 4 1 Cars]

lol, i used to stick em on my head too!!! so, its the same old way!! think i may treat myself to a new rubber stick!! i know what my job is at the weekend!! 16v's lapping/grinding inc head sticking!!

[M@tt 77]

 

[DrSarty 90 1 Cars]

Now I like THAT!

 

Can it still be stuck to my head?

[Jrod 7]

I've got one of those, still ended up doing it by hand as it just seemed easier.

[petert 588]

Lapping in valves is very old school. Modern seat cutting machines, with carbide cutters, produce a mirror finish, negating the need for such laborious work.

Edited October 23, 2009 by petert

[DrSarty 90 1 Cars]

Lapping in valves is very old school. Modern seat cutting machines, with carbide cutters, produce a mirror finish, negating the need for such laborious work.

 

Would that mean then Pete:

 

i) That someone you paid to triple-cut valve seats would NOT have needed to lap in the valves

 

and

 

ii) If you paid someone to produce triple-cut valve seats and you told them NOT to reassemble the head, that you would not need to do it either, i.e. just fit the valves straight away?

 

The reason I ask is I'm unsure whether new or old (true) valves will seat fine in their swanky new seats properly. Isn't valve lapping a way of matching each valve to each seat perfectly?

[DamirGTI 342]

... even after cutting valve seats on a proper cutting machine (Neway , Peg etc.) i always fancy lapping them afterwards as it helps checking how well the valve cutting job turned out .. in a few occasions i found some errors on the seat contact surface after cutting the seats with Neway carbide cutters , so few seconds of lapping stored it perfectly ..

 

Damir

[petert 588]

Would that mean then Pete:

 

i) That someone you paid to triple-cut valve seats would NOT have needed to lap in the valves

 

and

 

ii) If you paid someone to produce triple-cut valve seats and you told them NOT to reassemble the head, that you would not need to do it either, i.e. just fit the valves straight away?

 

The reason I ask is I'm unsure whether new or old (true) valves will seat fine in their swanky new seats properly. Isn't valve lapping a way of matching each valve to each seat perfectly?

 

Provided the guides are up to spec., and the valves are faced on a quality machine, there should be no reason to touch the seats after using a quality machine such as a Serdi. My local head gurus have recently gone one step further and purchased a full CNC seat cutting machine (can't recall the name). You just draw in the profile of the seat you want, including top cuts, bottom cuts and throat, and after centering off the guide, the cutter comes down and does the rest, producing a mirror finish. Far better than a profile cutter like the Serdi. With either though, any valve can go in any seat.