M42 valve seat specs

[teo97]

Hi to all of you! :) My name's Matteo.
I kindly need some information about M42 valve seat job.

My head suffered from crack in cylinder 2, from water passage to exhaust valve seat.
Also in cylinder 3 there's a crack between exhaust valves.

I have to cut it and weld. Then remake valve seat.



Some information:
Valve seat width

Intake mm 1.65 ± 0.25

Exhaust mm 2.0 ± 0.25


Ø valve seat

Intake, outer Ø mm 32.4

Exhaust, outer Ø mm 30.1


Ø valve diameter
Intake 33 mm

Exhaust 30.5 mm



I can proceed with valve cutters, but I need confirm. Which diameter of valve cutter should I use for intake and exhaust valve seat? Angle for both is 45 deg.
Maybe addressing this question to those who already have done this.

Many thanks.
Teo

[fresh_TD]

Just get good used head, instead. "Passion is timeless"

[bmwman91]

Repairing the cracked head is not likely to give a good long term solution since the cracks go all the way through, and a weld will penetrate only part of the depth. As fresh_td said, finding a good used head will provide much better results. These engines do not like to overheat, which is probably the cause in most cases, but I also suspect that maybe there were some issues with quality control during production (maybe a defect in one of the molds) since some heads seem to crack very easily, and some seem to have no problems ever.