Valve lapping question(s) . . . .

[Roadkill]

I've now got all the bits I need to re-assemble the engine.

But, although the engine is "relatively low" mileage, I was thinking of giving the valves/seats a quick lapping in.

First question (for someone who has an LT1 owners manual) -

Is it O.K to lap these valves ? - I know some modern engines can't be lapped.

Second question (assuming they can be lapped) -

I'm guessing I'll need to go through the whole rough / fine jobbie and not just be able to get away with a quick fine lap ? - Or is it a case of just eyeballing it and seeing what it needs ?

[Roadkill]

Nevermind.

[Cunning Plan]

What was the answer?  

[art b]

prob the fact, that most modern engines have hardened valve seats and ya cant lap em...

[Titsy]

Quoting: art b

prob the fact, that most modern engines have hardened valve seats and ya cant lap em...

They have hardened seats because they have aluminium heads... That doesn't stop you lapping them... But I shouldn't think they need any more than a fine grind given the low mileage...

[philoldsmobile]

get the valve in the head with no spring, and using a cordless electric drill, spin em on the seats with some grinding paste!

(in case you hadn't guessed, put the valve stem in the chuck!)

used to do it on 4 stroke Karts if they had been run a bit lean, and it worked ok.

[Roadkill]

Quoting: Cunning Plan

What was the answer?

I just read up about it t'is all.

I knew I'd be busy today but in the end found time to search the 'net for an answer.

Quoting: Titsy

But I shouldn't think they need any more than a fine grind given the low mileage...

I agree, theoretically . . . but we'll see . . .

Quoting: philoldsmobile

get the valve in the head with no spring, and using a cordless electric drill, spin em on the seats with some grinding paste!

I've heard that done before - yes - but today read that it's not recommended as it can leave high points (somehow) ???

Apparently it should be in the C/W -> A/C/W motion - and never more than 1/2 - 3/4 of a turn !



I think I'll use a bit of fine paste on a low-speed setting on the puny wickes drill and see how it goes . . .

[Titsy]

If you're going to use the drill method then I'd strongly recommend fitting a bit of hose between the valve stem and check to protect the stem and give it all a bit of room for error...

Last thing you want to do is wear your guides...

[art b]

ive done that, on pinto heads, folowing polishing and porting,
oil the stem and use forward and then reverse, on a batt drill,
a couple of revs one way followed by the same in the other direction,
slowly does it, works a treat,

[Roadkill]

To be honest, I'll probably start off the "old fashioned way" and see how I get on . . . . However the last time I did it on a straight-6 wasn't fun.

Admittedly I was a lot younger then but I came away with serious callouses on my palms.