So I just adjusted valve clearances on a family members 2015 crv as it passed 100k miles.
What I would like to learn is how do these assemblies wear?
All of the intake valves were out of spec tight, all of the exhaust valves were out of spec loose. This cam cover had never been off. Decent oil change history but not all synthetic.
What the internet and my experience say is (in Honda’s) the exhausts get tight with wear and the intake loosen up. One notable difference with this 15 Honda is the intake is on the back (firewall side) and I believe the engine rotates clockwise.
My current theory is the chain tensioner is on the intake cam side opposed to the traditional exhaust cam side, would this cause the flip flop of wear patterns?
Or is this just one of those online “facts” that gets repeated endlessly and I always just had a Honda that matched the pattern.
ideas/experiences?
I don't know about Honda's, but from my air cooled VW days, if the exhaust valves were too tight it meant the valves were stretching and would eventually break. I have seen pictures of pistons after the head broke off an exhaust valve and destroyed the piston, cylinder, and head. I doubt that's helpfull in your case though.
I have never once seen a Honda wear the exhausts loose. Always tight. The exhausts are generally ALWAYS the reason for the weird mid-warmup idle/light throttle misfires at about 160-220k miles. I've never seen it not be. They would leak juuuust enough for it to only hurt compression at low cylinder pressures, and only in the time the valves heated up but the head was still relatively cold.
The seats on the heads and the valves (mostly the valves) wear and so the valve tip recedes upwards, closing the gap.
Also... when I would ever adjust the valves, I'd go to the loose end of spec, and if they were a thou over... eh, it'll be just fine. Better a hair loose than tight.
Really have to be careful adjusting them, too, because it is very easy to open the valve slightly with a feeler gauge. Go/no-go gauges are your best friends here.
Pete. (l33t FS) said:
I have never once seen a Honda wear the exhausts loose. Always tight. The exhausts are generally ALWAYS the reason for the weird mid-warmup idle/light throttle misfires at about 160-220k miles. I've never seen it not be. They would leak juuuust enough for it to only hurt compression at low cylinder pressures, and only in the time the valves heated up but the head was still relatively cold.
The seats on the heads and the valves (mostly the valves) wear and so the valve tip recedes upwards, closing the gap.
Also... when I would ever adjust the valves, I'd go to the loose end of spec, and if they were a thou over... eh, it'll be just fine. Better a hair loose than tight.
Really have to be careful adjusting them, too, because it is very easy to open the valve slightly with a feeler gauge. Go/no-go gauges are your best friends here.
Have you adjusted a 15 reverse flow earthdreams engine? I had a crz and have a Acura k24 and they are as you described.
Im not talking huge amounts, but all 16 valves were out and in the opposite way I expected.
