Exhaust valves

[918_gsx]

Just pulled my head off. Anyone else seen exhaust valves coked up like this just on the first 3 cylinders? First thoughts were that I was running lean. But I'd have all 4 valves discolored together wouldn't I? Just curious for some experience feedback.

 

[GRAVEDIGGER]

Number one cylinder is always the lean one on our cars which is what you're seeing on yours too. The way the air enters the throttle body and flows through the intake always creates a slightly leaner condition on cylinder one as it flows into the engine, because of the extra air entering that cylinder. This is why it's desirable to put the exhaust temp bung in the number one exhaust runner when monitoring exhaust gas temps... So you can monitor the leanest cylinder.

 

[918_gsx]

Thank ya very much. I will get that done then. And might I say...what b*%#ch to get the head off!

 

[Sirnixalot]

^ try getting the head off a GTi-R and you will see what hard is

 

[918_gsx]

Haha. I bet. The HARDEST part was getting the damn lower timing cover off. Gayest setup ever

 

[RipperXX]

Did you notice the engine burning any oil before you tore it down?

 

[918_gsx]

No, I didn't

 

[BogusSVO]

I have seen that before... some of the cause will be to wide of a valve seat.. when the seat is too wide you get more heat transfer from the valve to the seat, when that happens the valve will not heat up enough to burn the deposits off.

Another cause can be short trips, that do not get the engine up to op temp. same thing, the valves will not heat up enough to burn the deposits on.

 

[RipperXX]

Interesting, so do you think this issue would be more prone in engines using oversized valves or sodium filled exhaust valves?

 

[BogusSVO]

Ripper..... neither...... I will say it it is due to the "point of contact" between the valve and the seat

sodium filled valves have been used for a long time (350 chevy, 427 Ford) mainly in HD trucks to keep the valve stem form having to much thermal expantion and gaulling a valve/guide.

with an over sized valve, you will have an over sized seat.... whaen I was trained to do valve jobs years back, Seat width was stressed, to thin a seat the valve runs hotter and stands a better chance of a valve burning, too wide a seat and you get deposit build up from the valve being too cool.

too keep this from being a thead jack.... PM me if you like to talk some more about this topic.

 

[crazyquik22023]

^ try getting the head off a GTi-R and you will see what hard is

Aren't those the SR20 motors?

 

[Rideit636]

Are you getting that head cleaned up or worked on at all? I would pull those valves and clean them really well with a wire wheel, clean the seats, lap them in and see if you need need to get them ground and get the seats cut. I can almost guarentee there's. A bunch of crap between the valves and the seats. Or if budget isn't an issue, get a set of engnbldr valves and have your seats cut.