I'm curious on this one. Who still laps their valves? I don't hear much about it these days.

I've laped valves on old shovelhead harleys and it works good, no problems at all. I would do it if I had to on a stock SBC or something...

I would not ask if I already knew, but,

What is lapping valves?

you take a tool with a suction cup on one end of a stick, with the valve with no spring on it sitting in the head, you put the suction end on the big end of the valve and have alittle lapping grease between the seats and valve surface, then applying alittle force on the valve and turn back and forth to seat the valve.

i think the question is who doesn't do it?? i know every heads i rebuild or buy i take it apart and clean it and replace or clean up the valves and then lap them.

here is a link with an idea about it, http://www.powrgrip.com/cgi-bin/powrgrip/V1275.html

I use a piece of hose that fits over the stem of the valve then use my drill to turn the hose and valve so I don't have to use those suction cups. Works fast and you don't have to do it long or use much rpm.

i have heard of that, one reason not to directly attach the valve to the drill is you run the chance of pulling on it too hard and do too much damage, while with the hose it give you alittle flexibility

i have heard of that, one reason not to directly attach the valve to the drill is you run the chance of pulling on it too hard and do too much damage, while with the hose it give you alittle flexibility

yes you're correct plus you won't damaget the stem if using a hose. A lot faster than turning it by hand using those suction cups. I just apply a little pressure with a finger on the valve to keep steady pressure on the valve in the combustion side.

I was shown to use a little green permanent marker.. like a sharpie, right? put marker all over the valve on the sealing side, then spin it in the head, note the contact patch.. then lap it until it's uniform. IIRC. You can see a NOTICEABLE difference this way with the marker.

Done this many times. With old heads that don't have hardened seats I suspect it would be better than having them actually reground. As long as you get a good contact ring/patch on the valve and seat it should be good to go. Seems like you can make some extra power with cleaning and shining up the ports, smoothing out the valve bowls and putting a small back angle on the back side of the valve.

The last time I lapped a valve was after I "ker-thunked" one in my head and listened to see if it sounded right....

Do it and you will hear what I am talking about...

No good clear "ker-thunk", then lap it!!

"Shade-tree" as all git-out, but it works!!

pdq67

Done this many times. With old heads that don't have hardened seats I suspect it would be better than having them actually reground. As long as you get a good contact ring/patch on the valve and seat it should be good to go. Seems like you can make some extra power with cleaning and shining up the ports, smoothing out the valve bowls and putting a small back angle on the back side of the valve.


I do that to every set of heads I rebuild. Why throw away horsepower? On every single engine I have done this to it seems to get better gas mileage, and more power on the top side. I don't know anybody that wouldn't lap the valves when replacing them.

I was shown to use a little green permanent marker.. like a sharpie, right? put marker all over the valve on the sealing side, then spin it in the head, note the contact patch.. then lap it until it's uniform. IIRC. You can see a NOTICEABLE difference this way with the marker.


if you use the lapping compound you will see this also.

And one other, He, He!!! "shade-tree" deal here is that by chance you nick a seat, then just put a small piece of 500 emery or whatever paper between the valve and the seat and push down hard on the valve head while turning it so that the emery paper can reseat it!!

He, He!! Like I said, "shade-tree" as all get-out and works fine!!!

And, yes, it's a "feelie" thing again!!!

Just listen for the "ker-thunk" like I mentioned earlier....

And use a marker too to check seat fit!!!!!!!!!!!!!!!!!!!!!

pdq67

I have been lapping valves for over 45 years. Every engine I do. That way I know (visually) that they seat correctly.

Jim

we always do it just to make sure everything is correct.

can somebody rec a decent vavle spring remover that doesn't cost a tank of gas if possible? Thanks

can somebody rec a decent vavle spring remover that doesn't cost a tank of gas if possible? Thanks

Hammer and a socket? Now putting them back together, you didn't ask about that.

borrow it from the part store, i think they do that, but i bought my own along time ago.

I allways, always lap valves to check the seats. I have had shops do valve jobs with a few seats not making contact, so it's something you want to check even if the guys are competent. Everyone makes mistakes.

I also did a experimental valve job on my throw-away 301 Pontiac by sending the valves to be ground and power lapping them in. 50,000 miles and still going. I think full valve jobs are not needed as much now as in the past, esp with hard seats.

I use the lever type spring remover, cost $15 or less I think.

Stu how did you do the power lapping that sounds interesting.
Would like to try that on a junker motor.