Pray

iTrader: (7)

I just disassembled my L33 with 799 heads to do some work on them. I thought the engine was down on power and econemy so I figured a tear down was in order. What I found on the exhaust valves and seats shocked me. The were "rusted" and pitted so bad that there is no way they were sealing. It had the normal white/gray carbon build up but it looked like someone poured dirt and water in the exhaust valve and let it sit for a year then started it up and went WOT. The intakes looked perfect and the pistons, cylinders and everything else look fine. It was pretty much uniform on all exhaust valves. My machinist said they neede alot of work to get right. I tried lapping them back in to no avail. They were jacked up.

This engine has about 85,000 miles on it. I have put about 35,000 on it since I had it. I take really good car of the motor but it didn't seem that the previous owner did. How does this happen? I drive it every day when I am not out of the country and when I am gone my wife drives it once a week or so. Has anyone else seen this before?

My biggest concern now is one, it comming back and two the valves being sunk and effecting flow once the complete valve job is done. I don't want to do all this work and spend all this money just to loose HP.

01ssreda4

iTrader: (96)

I've seen a similar condition to almost every head that I've hand lapped the valves in on. The exhaust valves have pitted sections. The only thing I assumed was that it was from moisture in the exhaust, whether it be from the environment or the combustion process.

Pray

iTrader: (7)

That's crazy. Do you think it caused sealing issues in the motor before you got to it?

RonSSNova

iTrader: (3)

Photos would be cool.
That said, new valves are probably not too expensive, and neither would be touching up the seats.
Makes a guy wonder about fuel addatives the companies use these days along with the E10 blend most of us get to run.
I should pop a valve out of the heads I just removed from my 80K mile Vette and see what they look like.
Ron

bartmanC5

iTrader: (3)

I bought some 18k mile LS6 heads, and here are the before-and-after lapping pictures. Pretty much as the OP described, intake valves were almost pristine with a great seal. However every exhaust valve and seat both looked corroded. Mine cleaned up nicely with some lapping. I just lapped all the exhaust valves and didn't touch the intake ones.

I'd be curious if you tried a compression test on them before pulling? I read that there is a 1* difference in angle between the seat and the valve, so the actual contact area should be fairly small.

Todd

Before (wire-brushed the valve)


After

3rdCoastPowerSports

iTrader: (5)

notice the oil on the freshly lapped valve and seat to prevent corrosion. bartmanc5 nice pics

Pray

iTrader: (7)

Mine looked like that but alot worse. You can still see some pitting after your lapping. Mine were alot more pitted after lapping. I am having a three angel valve job the valves done with a back cut, and the head's milled. I did a little clean up on the heads and I am having them flowed. I only want to do this onece. But it does make you wonder about what is in our fuel.

bartmanC5

iTrader: (3)

Thx man. The oil was from the oil-based lapping compound. I wiped down with brake cleaner to remove all the grit, then put fresh motor oil down during reassembly. The intake valves must get a wash-down with the cool charge and fare much better than what the exhaust valves have to deal with. I guess as long as they seal up, they're doing their job.


The 3-angle valve job with backcut should clean it up nicely and improve your low-lift air flow. Depending how much material they remove between the VJ and milling, you will probably need different length push rods.

Pray

iTrader: (7)

I told them to stay with 64cc's and only mill the heads to flatten out the deck and get me back to 64cc's. I don't think I removed much material from the chambers when I reshaped them. That is a good point that I will take into consideration when I re-assemble.

sfc rick

Mine looked that bad when I first pulled the heads and after I lapped them still could see some pitting. But my heads had 90,000 miles on them. A year later I pulled my heads and sent them off for a 5 angle valve job and a little mill. That valve job really made a BIG difference in power!

LS1MCSS

iTrader: (18)

What you're seeing here is normal to every engine I have ever torn down that had over 50K miles on them. It's typical and nothing to get excited about. Just get a valve job done, put it back together and roll on.