Can any expert helping me as well?

My car very well handled with 150.000 kms, never raced, consumes a lot of oil. We believe is due to fail on valve crank parts
we were going to replace on this operation.

The compression test gave allegued low result, here is the test in BAR measures
https://www.s2ki.com/forums/s2000-un...1190696/page6/

The engine lacks of carbon and waste, the mechanic said.

thanks!

 

Got a call from the machine shop today with good and bad news. He said the exhaust valve guides are shot, and 4 of the exhaust valve seats are trashed (forgot to ask but guessing they are the same spots where the valves were super tight before adjustment). I'm told that the exhaust valve seats are beat up bad enough that they can't be repaired. That being said, is there something from Honda or the aftermarket that can replace the stock seats? I guess I'm not familiar with them, if they can be removed or if the seat is machined into the head. Hoping to avoid buying another cylinder head if at all possible.

The good news is he said he's pretty certain that my compression issues are head related. Gives me a little more hope that the bottom end will still be alright.

 

The seats are replaceable, but keep in mind the labor cost of this and all associated head work, and bounce that off of what you may find in a good used head. It may make more sense to pick up a used head for $300-$600. I would also want a little more re assurance that the cylinder condition is good before investing further. You should thoroughly inspect all the cylinder walls for any scoring or signs of irregular wear, measure all the bores and bounce off oem spec, make sure not ovalized. If prior to tear down, the leak down test showed air escape from either header or intake manifold ie meaning valves hen yes fair chance that was the issue, however you could still have poor cylinder sealing as well so always best if you could have correlated a lower compression reading along with known damaged valves. You do have known bad valve seats, so can you correlate the lower cylinder compression to those?

 

I will still measure the cylinders and see if they are round or not. There are some vertical scoring marks toward the tops of the cylinders, but only on the exhaust side. Most of them cannot be felt by a fingernail, but there are some that can be felt. They are very short though too, they definitely don't run the length of the cylinders. I can post a few pics of those too.

@s2000Junky any idea who sells replacement valve seats for these things? Thanks for all your help and insight!

 

You will get some level of oil burn/usage from these upper score marks, and based on the black flaky soot on the combustion chambers, you have (likely some from worn guides as well). Its not uncommon with F20's, but discerning how severe the scoring is key in deciding what you are willing to address and what you are willing to live with. You should have some idea by the amount of oil you were using prior to tear down. Some minor scoring in just the upper portion is acceptable usually if you are not able to catch your finger nail on it. If you are, your rings are not going to be able do their job fully and I suspect wear rate will be more rapid. I would get your mechanics opinion on this to see how he feels about addressing or not. Cost vs benefit analysis is what you will be doing here. It may make more sense to just accept it and button the engine back up and live with some minimal to moderate oil usage until it gets worse or you get sick of it, which ever happens first.

Sorry I don't on the valve seats. But someone here does, I know they have been replaced.

 

To be clear, the valve seats aren't replaced like taking one part off and putting on another. Its more like a knee replacement where they hack off part of your bone, and press in an artificial piece to try and do the same job.

The valve seats are just the head material with a shape ground into it. A shape the valve can seat, and seal upon.

When the seat is messed up, they try and grind off a little material to remake the shape.

When its too messed up for that, they grind a huge hole where the seat was, and press in a specially made part thats made to fill the hole, then grind a new seat into that.

Its a bit of a compromise, but it works. But as mentioned its a lot of labor.

 

You sure about this? Fortunately ive never had to go through that particular process of repair on this engine, but know some have done it on this forum. It also defies a bit of logic that the seats are just apart of the soft cast aluminum, rather then a hardened steel or iron seat. I don't know how an aluminum seat would get very far. Especially with the rpms/heat this engine produces.

 

valve seats are pressed in just like guides....

 

 

Is the bottom end ok? If not, maybe try to source a complete engine with lowish miles?