The Fordson Tractor Pages Forum

Afternoon everybody, i am at the moment lapping all the valves in (new) on an FL cylinder head. Ive got all new valves because the other ones are rusty and horrible, however it seems to me that the new valves protrude about 1mm out of the head towards the cylinders (the old ones are flush). Is this a problem? i.e will they hit the pistons? im thinking probably not because theres the thickness of the head gasket, then the recess in the top of the pistons.
Has anyone had this before?
Lovely weather by the way!

Hi Nick
Sorry I can't help with your question, but how do you lap the valves?
Mervyn

Hi Merv, well to be honest its a new experience for me too, i usually get the local engineering company that i take cylinder heads to for things like new valve seats, crankshaft grinding to do it for me, but as all the seats in this head seem ok, im attempting it myself.
From what i understand, you use grinding paste, which you can get in course and fine. You start off by grinding in course grit and keep a constant pressure on the valve. You use what only can be descibed as a small sink plunger to grip the end of the valve, and twist it steadily in between your hands. Once happy with the course you then go with fine to finish the surface off so it will seal properly.
Seems an easy enough job, but it seems by reading the manual, that i may need to machine the valves down by about 1mm to make them sit flush with the underside of the head.
Surely someone else has had this before?

What manual are you reading?

The height of the valve above the head is set by the valve seats. If you have had your head skimmed then the valves will protrude more. 1mm seems a lot although it will depend on your valve supplier and how near the specification he has made the valves and how the seats are cut.

You may be better to get the valves sorted by a machine shop who can cut the seats back a little. It will take a long time to grind them down with a grinding stick but you will have well developed forearms.

Yes, valves do protrude slightly above the head surface.

Thanks for your reply brian. The valves i got, were in the set you get when you buy an 'engine rebuild kit'. I can see the difference in the valves, basicly the end of the valve on the old ones (the face if you like) is about 2.5mm thick, whereas the new ones are about 4mm. So a neighbour of mine, who is a gunsmith, is going the measure each valve and mill them down to exactly the same size. I take it this will be ok? I have checked that the valves fit nicely, which they do, so hopefully it will work ok!

The problem you may have then is if the valves are surface hardened, you may remove the surface or coating by milling the valve head. Some modern valves do not take kindly to grinding in either, they are meant to go straight into seats cut perfectly.

Think I would have a word with your supplier before doing too much.

Thanks for the explination Nick, sounds like a lot of effort. I was aware of the stick method but was hoping that technology would have come up with a easier method by hand. As Brian suggests let the engineers do it by machine.

Careful now, If the valves are sodium filled, they also could blow apart if too much is cut away on a valve refacer and the sodium is exposed. When they blow, they turn to shrapnel.

Stellite valves need a specified stone to grind, and most manufactures do not recommend grinding these valves.

Find out what the replacment valves are made of before proceeding. Dandy Dave!

Well i spoke to A******* yesterday, where i got the valves from, and the bloke had never heard of the valves sticking out the head. And from what dave has just said, im a bit nervous of milling these valves now! Should i just persevere with grinding the valves in until they are flush? How thick are valve seats usually?

Hi Nick
Glad to see you are still having fordson fun I'm not sure on the seat thickness. But I think you are gonna have to go to a machine shop as Brian said before and get the seats cut if there is a clearance issue.
Too grind them by hand that much will take years. But im thinking you will be bored in a day ..

I Just thought of this on air cooled Belarus motors when the heads ground the clearance on valves to piston has to be checked. To do this the head is put on with plasticine or blue tack type stuff on the piston top where the valves are.
The motor is then turned. The head is then removed and the thickness of the indent in the plasticine is measured to check clearance. Its a bit of messing about but why not try this and see if they clear. if alls good then no need to spend more money. you could just put the gasket and a few bolts in to hold the head down while turning it im thinking.
Regards Robert

And the plot thickens, I suddenly remembered that i had previously bought another engine re-build kit for my other major, and didnt use the valves. I checked them against the ones i was trying to put in the head and they are alot thinner at the end of the valve, and they fit pretty much flush, may need to grind them in ever so slightly, so problem solved!
However I am a bit annoyed that these other ones are so different!

Glad to hear that you have it solved. Thinking this over for a day it crossed my mind to ask if your head had valve seat inserts install at some point? They could be slighty smaller than the original seats. Also, maybe the first set of valves you tried were taking in account for a head that the seats were cut in already. At this point I guess it will not matter. Dandy Dave!

Yes dave this is what im thinking, as i dont know what exactly had been done to this engine since it was built, it could well have seat inserts or something. But you would think that all the equipment thats sent out, would be the same, and to then have optional sizes of valves or something. But never mind, its sorted now.
On another note, anyone want to buy some big valves for a major??????????????

MS, there is, and has been for decades, a DIY 'machine' for lapping in valves. It fits into a power drill and has a reciprocating [backwards & forwards] motion. In the UK it's called EEZILAP , costs 38 Pounds and is sold by Moss Europe. In the USA the same machine is sold by Goodson, but, for some unknown reason, costs $165.
I would add that there is a proper technique to use when lapping a valve face to a seat. The valve stem should be lightly oiled and after every dozen backward and forward movements of the hands with a stick, as well as with the drill method, the valve should be lifted and twisted about a third of a turn. The face and seat surfaces should never be allowed to squeak as this cuts groves into the metal surfaces. To check for perfect surfaces coat most of the seat with engineers blue, or multi strokes with a soft lead pencil, and twist the valve on it's seat. There should be no circles, tramlines or pits.
Pavel