Valve grinding

**muddydigger** · 28th April 2007, 06:28 PM

Ok so back to this ere Disco. I was going to get the heads done proffessionally but the ball and chain says no way to expensive. So I have to do it myself. Ive looked extensivly on the net, and read a few books re porting. So Ive done a very mild bit of porting in the heads, just a little material removed to match the mufflers ect, nothing huge.

So to my dilema, I know that when resetting the valves it has to be a nice even surface all round, but do any of you go for a set method IE 1.5 mm surface? the hole of the beveled area?

So far ive got about 1.5 mm smooth even surface all the way round.

Do you think thats enough?

**Blknight.aus** · 28th April 2007, 06:48 PM

dont know where you are atm but we have a valve grinding machine and a seat finising set at work (ipswich)

How you finish the valves depends on whats more important to you...

hard sealing which will increase wear (small contact patch) but provide "sharper" valve action and self cleaning

soft sealing which provides longer life (larger contact patch) and valve cooling but are more prone to carbon fouling and hard starting when cold.

but which ever way you go, dont skim on the stems and the guides...

**shorty943** · 30th April 2007, 12:11 PM

Just like Dave says. 1.5mm seems like a very soft seal to me.

We were always taught the finer the seal the better the seal. But, superheated steam is a nasty beasty, so seals must be as close to perfect as possible.
With internal combustion engines, I would try for about 1 mm of nice clean smooth grey seal on valve head and seat. But, 1.5 will be Okay. This is not a racetrack vehicle. It's just that a wider seal can carbon up and cause the valve to be held slightly open, allowing the seat or valve head, or both to burn, in time. That is the operative scheme, it won't burn out tomorrow, it might last 5 or 10 years. The performance knife edge seal is great, if you pull the engine down after every race.
You have it right enough, I reckon.

Shorty.

**loanrangie** · 30th April 2007, 12:56 PM

When i did the heads on my 3.5 for the rangie, i just use some grinding paste and did a light lap just enough to help the valves seal and also some mild porting on intake and exhaust - basically just cleaning up the ports and matching them to the intake and exhaust manifolds. Combined with a bosch dizzy and a 350 holley it made the old 81' 3.5 4 spd rangie into a beast that could keep up with and overtake traffic.

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