Exhaust Valves

[jeremy1375]

I'm currently doing a head gasket and replacing valve stem seals on the head. I've been doing a lap grind to check valve and seat conditions, The intake valves and seats look good. The exhaust seats look good, but there is light pitting on the exhaust valves. The pitting is light enough that I can hardly feel it with a dental pick.

I don't want to put any more money than I have to into this, but willing to spend some if it will increase the life of the head. I've considered either replacing the exhaust valves or having just the valves ground. Would it be worth it to do one of those or would it just be a waste of money unless the seats are cut also?

 

[sidewaystsi]

run it.

 

[Kapok6]

Do the valves leak? If not, run those bishes.

 

[miliman13]

Did you confirm the valves don't leak?
If so run her.

 

[jeremy1375]

The valves hold water without leaking. I don't really have a way to test them under pressure. Does holding water count for not leaking?

 

[miliman13]

It's the best any of us can use as a test.
Go for it.

 

[doghouse]

Gas or rubbing alcohol is what I use. Rubbing alcohol seems to get through spaces water fails to

 

[KilleRabbit]

Gas or rubbing alcohol is what I use. Rubbing alcohol seems to get through spaces water fails to

Rubbing alcohol?
Sorry if this seems like a stupid question, but wouldn't that be bad for seals?
Ethel Alcohol dries out rubber and certain types of plastic causing them to crack and/or become brittle. I haven't pulled the head off my DSM yet, however I know I never would have exposed the valve seals on my supra to alcohol as they would be ruined if I did so.

 

[miliman13]

Rubbing alcohol?
Sorry if this seems like a stupid question, but wouldn't that be bad for seals?
Ethel Alcohol dries out rubber and certain types of plastic causing them to crack and/or become brittle. I haven't pulled the head off my DSM yet, however I know I never would have exposed the valve seals on my supra to alcohol as they would be ruined if I did so.

This tells us alot....

No it won't; because there is no rubber in the chambers .

 

[KilleRabbit]

This tells us alot....

No it won't; because there is no rubber in the chambers .

I was thinking you were turning the head on its side and pouring into the intake and exhaust ports (which would reach the seals through the keepers) but i suppose if it were upside down and you poured it on the valves where the cylinders were this wouldnt be a problem as long as none of the alcohol leaks throuh and rides the valve to the seal.

 

[Kapok6]

Alcohol or brake cleaner. Trust me...either of those will find leaks.

 

[bastarddsm]

Even if it leaks a little bit, it's nothing. The amount is soo small over the duration of a cumbustion event you'll never know. The only importing thing with the exhaust valves is that they seat decent enough to transfer the heat out of the valve.

 

[90laserRSfwd]

Might seem a little unorthodox, but you could put the valves in a power drill, and "resurface" the seat part with some very light sand paper, then relap them. I've seen a few videos on youtube, showing how to do this. Not sure if it'll work as well as say, getting the valves and seats cut, but it'll def. save you a few bucks, as valve jobs these days are upwards of $200

If your pulling the head (or already have), I highly suggest at least getting it to a machine shop for a trip to the hot tank (VAT tank some call it). Checking and resurface if necessary. The last thing you wanna do is fix it half a$$'d and have to do the work twice..

 

[keltalon]

Yeah put thinner liquid and see how long it takes to seep through. As was mention above a minute pitting of the exhaust valves you will not notice at all.

 

[FlyinTalon]

Lap the valves in by hand. Make sure the seats in the the head are good and clean , then take a marker color in the back side of the valve then snap it down in the cylinder head. Next pull the valve back out and check the back side of the valve were you just colored it in, you should see a nice clean ring a round the valve were it's seating ,repeat untell you get good results. Hope this makes seen, I've done plenty of heads and most the time you can get away by just doing this.