I was wondering when I purchase new valves do I still Lapp them with the old seals with the grinding compound?

 

If you have to buy new valves, 99% of the time the seats will have to be re-cut at a machine shop.

Other then that, lapping in is the only way you can get the new valves to "seat" properly, you don't have much of a choice.

Using valve grinding compound also introduces a new problem, the carborundum grit gets caught in the seats and the valves and no matter how much you clean those surfaces, you can't totally get it out.
The grit gets hot an causes premature failure of the seats and valves.
This failure doesn't happen over night, but it does happen.
That's why a modern machine shop cuts the seats, they don't use stones anymore.

Also, lapping in valves at room temperature fit when the engine is cold, but not so well when things heat up. Things will work, but it's not ideal.
Typically the seat is cut to 44 degrees and the valves are at 45 degrees.

The British/Europeans like to cut their seats with 3 different angles to improve air flow into the engine, so the theory goes.

 

Ok thanks for the info now what if I'm trying to stay away from the shop I'm on a very low budget can I just apply some valve grinding compund on the new valve and Lapp it to the old seats?

 

If you have a tight budget, then lapping in is the only way to do it.
You'll need some Prussian Blue to make sure that things fit properly.

 

Ok now is the purussian blue the grinding compund?

 

No, it's applied thinly to the valve seat only after all the grinding compound is cleaned off.
After it's applied to the valve seat (I like to use my finger) the valve is put in place and rotated 90 degrees in one direction and then back 90 degrees in the opposite direction.
If you see an even coat of Prussian Blue on the valve, then you job is done.

You can also do it the opposite way to check the valve seat contact, put the Prussian Blue on the valve, there should be an even coating on the seat.

If the seat is in very bad shape (badly burned), you will see it.
Bad seats are usually quite pitted, but still can be used.
Other problems is if the seat has gotten so hot it's not round anymore.
If this is the case, lapping in doesn't usually help with this, the seat(s) will need replacing.

You'll know once you get in there.

 

Ok now I see!! So that stuff if pretty much used to just make sure everything sits in good right? And another thing how do I shine and smooth up my seats or will the valve grinding compound when I do the lapping take care of that?

 

The valve grinding compound looks after that.
I use plenty of lacquer thinner and WD40 with a tooth brush to clean off the compound.

And yes, the Prussian Blue is used to make sure everything fits right.

Some guys even take it outside with some soap and the garden hose, but you need a nice warm day and some compressed are for that procedure.
The soap and water are very effective of getting all the grinding compound out though.

 

Ok I appreciate that very much my first time doing this and it is very overwhelming but it's very interesting and a big learning curve for me!!

 

You'll be fine, take your time and check your work as you go along.

You have a 4 litre, the valves are very close together, look for cracks in the head there, apparently that is quite common for the casting to crack there if the truck has been over heated at one point.