Leaking exhaust valves

[PeteyDaMan]

Hey all,
After doing a leak down test on my 512 and having poor results on a few cylinders I decided to take the heads off to see what's what.

I found some odd deposits on the combustion chamber. They're not gouges or pits and wipe off but what caused it?

I tested a few of the valves and found the exhaust ports to be leaking badly. What caused this?

The heads are Eddy Performer RPM's and only have about 1500 miles on them (granted some of it was pretty hard miles).

Here's some pics and a vid showing the leak

 

[Wietse]

What is the fuel ratio looking? If fat it could leave deposits, if too lean things get too hot really fast.
As you mentioned, deposits that wipe off and no physical damage i would guess it ran pig rich maybe?

Check and see how the valve sealing area and the valve seat look like, any damage could be of lean mixture?

 

[Rebelrouser]

Hey all,
After doing a leak down test on my 512 and having poor results on a few cylinders I decided to take the heads off to see what's what.

I found some odd deposits on the combustion chamber. They're not gouges or pits and wipe off but what caused it?

I tested a few of the valves and found the exhaust ports to be leaking badly. What caused this?

The heads are Eddy Performer RPM's and only have about 1500 miles on them (granted some of it was pretty hard miles).

Here's some pics and a vid showing the leak



View attachment 1509218

Not sure of the deposits but I can tell you most likely those exhaust seats leaked when the heads were new. I been grinding valves since 1975 and I have a vacuum tester to make sure my valve jobs hold vacuum. I have found a lot of brand-new heads that the seats leak. They are using cutters to make the seats, and in a production environment they simply are not good enough. I take them apart and touch with a stone and they hold vacuum. Ask most performance shops that use cutters for seats, most touch with a stone, after cutting the profile, so they seal. On new cast iron heads, they are heat treating the seats after cutting the seats, it looks like, and they leak as well. I also never trust spring pressures on new heads they are all over the place as well. I see guides too tight also.

 

[Wietse]

Not sure of the deposits but I can tell you most likely those exhaust seats leaked when the heads were new. I been grinding valves since 1975 and I have a vacuum tester to make sure my valve jobs hold vacuum. I have found a lot of brand-new heads that the seats leak. They are using cutters to make the seats, and in a production environment they simply are not good enough. I take them apart and touch with a stone and they hold vacuum. Ask most performance shops that use cutters for seats, most touch with a stone, after cutting the profile, so they seal. On new cast iron heads, they are heat treating the seats after cutting the seats, it looks like, and they leak as well. I also never trust spring pressures on new heads they are all over the place as well. I see guides too tight also.

Just out of interest, do you mean that after machining those edges are too rough?
The sharp edge is not allowing a good seal between valve and seat?

 

[Charged440]

Were these heads run right out of the box?

 

[PeteyDaMan]

Were these heads run right out of the box?

Yep

 

[PeteyDaMan]

What is the fuel ratio looking? If fat it could leave deposits, if too lean things get too hot really fast.
As you mentioned, deposits that wipe off and no physical damage i would guess it ran pig rich maybe?

It was running between 11.5 and 12.5 depending on load so on the rich side but not crazy

 

[PRHeads]

My suggestion would be to pull the heads apart, wire wheel the deposits off the valves, and carb clean/scotch-brite the deposits off the seats.
Mildly lap the valves, clean everything again, and retest.
If you still get similar results, the heads need a trip to the machine shop.