A little trick I use to grind (lap) flathead valves

[125ccCrazy]

I don't know if anyone has done this when grinding valves in a flathead engine but it works great... Take an old lifter from any flathead or ohv engine, clean the head of it with acetone or rubbing alcohol, clean the valve head from any carbon and wipe clean also... Now take some quick set epoxy, mix a small amount of epoxy and coat the head of the valve while in the block or a vise, gently set the lifter on the valve (head to head), let the epoxy set about an hour, chuck the lifter in a cordless drill, slip the valve in the block with some oil on the shaft, apply some valve grinding compound to the seat and using the drill on slow grind the valve applying fresh compound as you hear the grinding noise getting quieter, periodically check both seats until both the block and valve have a nice grey seat.... This works much better than one of those handheld suction cup lappers and NO blisters LOL..

I also use a cordless drill when doing OHV heads..

when done grinding the valve sin teh flatheads just pop the valve and lifter apart, take a putty knife or a carpenter knife to scrape the glue off... it will peel off pretty easy...

 

[mybiz]

I always thought those suction cups with the wooden handles was made for doll house toilet stools.:lol: Your way is much easier. I havent done it but helped an old timer do the same.:wink:

 

[125ccCrazy]

I always thought those suction cups with the wooden handles was made for doll house toilet stools.:lol: Your way is much easier. I havent done it but helped an old timer do the same.:wink:

LOL doll house plunger.... This works really well.... I have done several heads for cars and trucks using a drill (electric)... when I got done I had nice seats on the valves and heads and no leaks...

The trick to doing this on the flatheads is to hold the drill straight up and not to cock it or it will break the glue loose and the lifter will pop off the valve... This could also be done in a drill press if you can gear it down low enough to run it at a slow speed...

 

[mybiz]

Id have to use a drill press now days id go through a lot of epoxy using a hand drill. I do have a 5HP briggs that needs the valves cleaned up I havent pulled the head yet. but there is something going on with the valves you pull the rope and now 99% of the time it acts like the valves are stuck open. Just hope ones not bent or worse. But when it fires up its got good compression.

 

[jimh]

Good idea. If I use a drill on OHVs, I always put a piece of plasic tubing on the stem to keep the chuck marks off the stem. Never thought of doing the flatheads that way.

 

[125ccCrazy]

Id have to use a drill press now days id go through a lot of epoxy using a hand drill. I do have a 5HP briggs that needs the valves cleaned up I havent pulled the head yet. but there is something going on with the valves you pull the rope and now 99% of the time it acts like the valves are stuck open. Just hope ones not bent or worse. But when it fires up its got good compression.

If you use a drill press you'll need a variable speed so you can run it fairly slow, if you go too fast it slings the compound off and polishes the seat more than grinding it.. With that Briggs it sounds like the valve guide(s) are worn out, most likely the exhaust... it's common on the briggs flathead 5hp for the exhaust guide to wear to the point where the valve cocks sideways in the guide and the valve spring cocks on the stem and over time the stem gets worn on an angle...kind of hard to explain but I'm almost willing to bet thats what happened or there is carbon stuck to the seat..

Good idea. If I use a drill on OHVs, I always put a piece of plasic tubing on the stem to keep the chuck marks off the stem. Never thought of doing the flatheads that way.

The tubing is a good idea, I haven't done that yet but I don't clamp the jaws down too tight, just enough to hold the stem but added protection surely won't hurt anything..I have done heads before that I couldn't get the drill down in the head far enough to grab the stem so I used a piece of rubber or silicone hose that fit the stem tight, slip it over the stem and chuck the other end of the hose in the drill to make sort of an extension... I believe that was on a Yamaha 80 moto4 and on trail 70 style heads...

 

[mybiz]

I'm more of a Tecumseh guy than Briggs. I do have 2 variable speed presses and a CNC. Also a lathe so i can do lots tinkering. I kind of had an idea carbon build up had something to do with the problem. My first thought was maybe a chunk got stuck under a valve.:hammer:

 

[oldfatguy]

I use a rubber suction cup that has a stem to chuck it in the drill press,it was easy to make.They do sell replacment valve guides,the correct reamer is hard to find.

 

[Jay Wrix]

Use toothpaste for the final finish, works great

Oh, but it has to be the paste, not the gel

 

[badtec]

I don't know if anyone has done this when grinding valves in a flathead engine but it works great... Take an old lifter from any flathead or ohv engine, clean the head of it with acetone or rubbing alcohol, clean the valve head from any carbon and wipe clean also... Now take some quick set epoxy, mix a small amount of epoxy and coat the head of the valve while in the block or a vise, gently set the lifter on the valve (head to head), let the epoxy set about an hour, chuck the lifter in a cordless drill, slip the valve in the block with some oil on the shaft, apply some valve grinding compound to the seat and using the drill on slow grind the valve applying fresh compound as you hear the grinding noise getting quieter, periodically check both seats until both the block and valve have a nice grey seat.... This works much better than one of those handheld suction cup lappers and NO blisters LOL..

I also use a cordless drill when doing OHV heads..

when done grinding the valve sin teh flatheads just pop the valve and lifter apart, take a putty knife or a carpenter knife to scrape the glue off... it will peel off pretty easy...

I was always under the impression that you need to spin it both ways, back and forth, lift, turn a little, start again.

Id have to use a drill press now days id go through a lot of epoxy using a hand drill. I do have a 5HP briggs that needs the valves cleaned up I havent pulled the head yet. but there is something going on with the valves you pull the rope and now 99% of the time it acts like the valves are stuck open. Just hope ones not bent or worse. But when it fires up its got good compression.

If it runs good after it finally starts, I wouldn't think that the valves are stuck open. I could be wrong...I was one other time. LOL. Scott.

 

[65ShelbyClone]

I use some RTV to glue a junk valve on top of the valve getting lapped.

 

[ProfessorJWN]

Seat Grinders

I guess I was "spoiled" growing up. We had a mechanical valve grinder and seat grinder.

We used to "triple cut" the angles on the valves and seats to get a very positive seal.

Seems like we "necked" the valves too to make them more "aerodynamic".

Also ground the cam on the Briggs flathead (bascially shortened the duration, and tack welded a taller lobe on the lobes (with an arc welder), so the vale opened really wide and closed really quick.

Also drastically ported the intake and exhaust port with the die grinder (you could look up through the l-head witht he valve out and see the top of the piston, so we called it a "Y" head.

Finally pulled the head gasket and used high temp RTV exhaust silicone for a head gasket.

That 3hp would spin the rear tire in gravel with two of us riding it (with a very generic centripetal clutch, no CVT)

It would do about 40mph flat out. On 125 octane racing gas.

Dad and Uncle tractor pulled, so there was always lots of great fuel choices!

We knew back then about 60/40 ethanol Gas mix. Runs great, and smells good too. (that was in the 70's)

 

[Jay Wrix]

triple cut valves, I have that, I have access to all the Sioux mechanical valve grinders, and the grinders for the block, I really like the difference, but I always lap them by hand,

Could I get some more info on a "y" head, I cant quiet see it yet

 

[fast tote goat]

I all ways lapped them the old fashioned way by hand back and forth, also have and old crank one that has a suction cup that goes back and forth as you crank it, however I do'nt think it really matters how you do it as long as you get a nice solid grey even line on both valve and seat. Sounds like an allright idea though.

 

[Cyanide]

man i wish i would have thought of that:censure: