I'm in the middle of doing an engine rebuild and I was going to replace the valve stem seals when I saw this:



It doesn't look good to me. I'm not sure what it is and what caused it. I'm curious what kind of options I have. I was thinking of just replacing the valves since I have the head off and I'm doing the seals anyway. That is, unless this can be cleaned up. I know there is a ton of carbon, but there appears to be damage to the valves on this cylinder, to me.

The motor is a D16Y8 that the PO swapped in P29 high compression pistons. It yields a stupid high compression rate (12:1+) and I'm pretty sure the PO's answer was to dump in a ton of fuel. I started the rebuild with the intention of just swapping the pistons for something around stock compression.

Just looking for advice on what to do and possible causes of this.

 

The build-up does look strange . . . I would try sandblasting the face and see if it comes off.

 

Fair enough! I have a sand blaster at work. I'll pull the valve and take it with me Monday. I was going to try a wire wheel, but I wasn't sure what it was.

 

A local machine shop should be able to jet wash it for you, stuff will probably come off if it is carbon fouling or similar.

 

Our local machine shop barely exists. It's 2 towns over and I'll be attempting to go there Monday. I'm not sure what they offer, but I will ask about the jet wash.

Thanks.

 

That stuff will (mostly) all come off in a sand blaster. Just buildup from fuel and burning oil

 

It had me worried because it was a strange silver color compared to the mucky carbon everywhere else. I actually took a brass wire wheel and cleaned up most of the valves at home. It took some searching, but I found a few videos and such that demonstrated how to clean valves. Mine don't look minty fresh, but they turned out alright.

 

The new P29's have a higher compression height than the originals so if they are new P29's with a Y8 head you're well over 13:1 compression. The deposits on the intake valves look like aluminium to me (the shape and consistency)

P29 pistons are not that great and will need AV gas or race gas to achieve MBTT, you're going to need 30ish degrees of timing to make MBTT and that's not happening at 13:1 comp on pump gas. You need to run lots of timing due to the pure **** combustion chamber design.

 

Preach it! I know! I removed the P29s. I'm going to stock pistons in the motor. I have zero aspirations of making this particular car fast. I really didn't know much about the P29s until I bought the car and started to clean some things up, such as the exhaust.

The valves actually cleaned up really well with parts cleaner, a brass wire wheel, and a scrub. Now I just have to find time to get to the machine shop during the week. Their hours are coincidentally the hours I work.

 

i was thinking about going the p29 rout with pistons in my y7mini me build but upon further research i that p29 would make far to high a compression ratio so i have thusly decided to go with pg6 pistons instead i should be somewhere around 11.5-1 c/r