10 replies to this topic

[087dave]

Hi all

I have gotten my big valve mg metro cylinder head back from the local machine shop.

They carried out the following work,

Bare skim off the face
Resurfaced the seats as they had pitting on them
I wanted to keep the original leaded seats
Recut the valve faces

So my questions would be when I rebuild it is,

Do I "dry" grind the valves into the seats?if so for how long? Would u use engineers blue?
Do I oil the valve stems? For when the stem will be against the guide
Do I put grease on the oil seals for the valves?

Thanks

[gazza82]

Grinding paste: coarse then smooth until seats look grey and same across all eight seats and valves. Using blue might help show high/low spots.

Not sure about oil on stems ... Been a while since I rebuilt a head but don't remember. I'm doing one now but not at that stage.

Again not sure in seals but I'd assume dry assembled.

[Fast Ivan]

I would use a very fine paste followed by a very very fine paste, as the seats and valves have been re cut

small amount of oil on the valves

not sure about grease on the seals but I haven't used any before

[Dusky]

I do use oil , especially when grinding in the valves.

[Fast Ivan]

I do use oil , especially when grinding in the valves.

 

I meant use the oil for assembly, I should have been clearer

[gazza82]

I guess it may depend how long it is before it is used and conditions you store it in.

 

If it's going straight back on and run, it probably doesn't need anything .. and remember the seals are there to prevent oil getting to the stems/guides.

 

If it is to sit, a smear of grease or engine rebuild lube will protect the surfaces a bit especially if in a cold and damp garage. As any of my components are assembled they are getting  a smear of 'Lubricate' on the bare metal faces and cling-film wrapped to store as it will be many months before they go on the car.

[087dave]

Ok tks for the replies

Do u guys see anything wrong by dry grinding the valves
Into the seats?

[Bubblebobble]

It wont really achieve anything without a abrasive paste , apart from sore hands ! 

[087dave]

I always thought grinding paste was made to get mild pitting out of
Valves and seats....thing is the valves and seat have been recut and have a nice smooth finish on them...correct me if I'm wrong

[Fast Ivan]

You'll need a paste, a very fine paste followed by a very very fine paste to get the best seal

[Bubblebobble]

I always thought grinding paste was made to get mild pitting out of
Valves and seats....thing is the valves and seat have been recut and have a nice smooth finish on them...correct me if I'm wrong

The paste it used to wear the two parts together so you get a perfect seal , the parts working back and forth against each other bedding in .