Valve seat grinding / lapping

johncusano

johncusano

Member
59A engine 1948 Ford. Stone ground a 45 then marked the cut with a permanent marker in 4 places,ground with a 30 stone till I get where a want the lap mark. But when I lapped the valve I only removed one of the 4 marker marks which was the top of the valve seat. Did I not cut the 45 enough or am I doing something else wrong,It's been a while since I did a valve job? Thanks for any help.
 
Is it possible the arbor was not perpendicular when grinding the 45? How is the pilot being centered and is it fitted tight? If the pilot uses both the tappet bore and the valve guide bore for centering it can be a problem.
 
JWL said:
Is it possible the arbor was not perpendicular when grinding the 45? How is the pilot being centered and is it fitted tight? If the pilot uses both the tappet bore and the valve guide bore for centering it can be a problem.
Click to expand...



Yes that’s the one I’m using. I would think that would be better. Why would that
be a problem.


Sent from my iPhone using Tapatalk
 
johncusano said:
Yes that’s the one I’m using. I would think that would be better. Why would that
be a problem.


Sent from my iPhone using Tapatalk
Click to expand...

Mine sets into the tappet bore and goes through the valve guide bore. Tight fit in both. I agree, it seems that's the good setup. Mine were very concentric on the sharpie pen lines. The lapping took only a couple seconds to get a good, even gray ring on each valve. Most likely 'beginners luck'. And perhaps the setup I bought was lightly used.
 
this was disscused recently, i too have the long pilot that seats in both bores, and thought that was the best. i too have had some motors that it fit fine, and some, like you that seemed off center. i believe its due to what the guy used to grind them in the first place. if he was crooked, the long pilot will not work. just my theory, hard to argue with JL, he forgot more than i will ever know
 
Are all valve seats behaving the same way or only one ?
If it was an offset lifter bore i would think only one side would be bad...so are both banks the same ?
 
I only did one it was late and cold in the garage so I stopped,the engine is still in the car so it is awkward to lap the valves, I will check the arbor for straigth ness and try the other that expands in the guide,I dont want to end up messing up a seat then i will be in big trouble Haha. Thanks for all the info!
 
Are you using the guide when lapping ?
Is it tight in the bore ?
Try rotating the guide 180 in the bore when lapping so it´s not the guide that is offset.
A bent valve would still touch the seat all around rotating it...
 
We measured one block where tappet bores were off center from the valve guide bores by about .008. I am not sure how that could happen, but it did. I have both styles of pilots but use the ones which are a tight fit in the guide bore and forget about the tappet bore.
 
JWL said:
We measured one block where tappet bores were off center from the valve guide bores by about .008. I am not sure how that could happen, but it did. I have both styles of pilots but use the ones which are a tight fit in the guide bore and forget about the tappet bore.[/QUOTE

Ok I will try that. Thanks.
Click to expand...
 
I guess it was the the long pilot that goes into the lifter bore and the valve guide either bent,or not bored correct.Using the other pilot with a split guide it seems to fit tighter.
 
While on the subject of valve jobs, I'd like to make a suggestion. On the exhaust valves, keep the seat on the top or outside of the valve as this is the only time the valve has a chance to cool. Also and very important. After grinding the valve, break the seat edge. I do this in a drill press with 400 paper.
This sharp edge can venture into a burnt valve.
 
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