valve lapping process

[GregT]

I use a short piece of hose (breather hose works well) pressed over a bolt head that is chucked into my cordless drill. No suction involved, just friction. However, since you need to apply a bit of pressure to take advantage of that friction, it also applies that pressure to the valve face, making it VERY hard to turn. I just press on the valve stem with my finger, then turn the drill on and spin the valve. Light pressure is accomplished by allowing the valve to seat lightly while spinning.

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UK magazines in the 70's advertised a tool which mounted in a drill and held the valve stem. And had a planetary gear train which spun it a couple of turns one way then the other...Clever.

[rapidray]

Ok guys, I build a lot of heads. I also do the valve jobs with a Serdi. I only use FINE Clover Lapping Compound & I only use it LIGHTLY, to confirm that the seats are all concentric and full contact. If you are lapping to "FIX" a seat, you NEED A VALVE JOB DONE!!! All the valve jobs WILL seal on fire up if they are concentric & making full contact. Half the time I am just checking with machinist dye & spinning the valve and it shows me the contact pattern.
Ray.

[chuck hahn]

I don't have dyes, but a fat black permanent marker shows the pattern very well too.

[hannibal]

I read not use a drill as you can't feel what's going on with the valve. No tips or tricks just a good amount of patience with the suction cups. Never checked the pattern though so not sure how well my valve lapping turned out.

[sharpy]

Ok guys, I build a lot of heads. I also do the valve jobs with a Serdi. I only use FINE Clover Lapping Compound & I only use it LIGHTLY, to confirm that the seats are all concentric and full contact. If you are lapping to "FIX" a seat, you NEED A VALVE JOB DONE!!! All the valve jobs WILL seal on fire up if they are concentric & making full contact. Half the time I am just checking with machinist dye & spinning the valve and it shows me the contact pattern.
Ray.

Yep what ray said. do it rite or not at all

[glib]

Ok guys, I build a lot of heads. I also do the valve jobs with a Serdi. I only use FINE Clover Lapping Compound & I only use it LIGHTLY, to confirm that the seats are all concentric and full contact. If you are lapping to "FIX" a seat, you NEED A VALVE JOB DONE!!! All the valve jobs WILL seal on fire up if they are concentric & making full contact. Half the time I am just checking with machinist dye & spinning the valve and it shows me the contact pattern.
Ray.

After reading your post, I did a search for fine clover lapping compound. Found various grits but not “fine” specifically. Would 600 be good? (1st timer—actually on Nissan 300zx heads).

[rapidray]

Yes on the 600.
Ray.

[red1100]

I’ve done many lapping jobs with a drill and compounds, 426 Hemi,440 and 383 Mopars,64 327-365hp Vetteand others, but only on heads that had a good valve job already. I just did my one owner,me, 95 Jeep Cherokee 4.0 with 245,000 miles and guides still within spec. Had a blown head gasket due to stuck thermostat. I used a slow speed reversible drill a rubber hose on the upper valve stem and permatex compound. Slow and consistent speed, reverse every few minutes got all twelve seats in beautiful shape. Pushing the valves all closed no springs,and filling the ports with water showed no leaks at all nearly 8 hrs later. Drained and filled ports with carb cleaner and another check in about one hour again no leaks at all. Reassembled and it runs smooth as silk.