BelowRadar

So, as part of the continuing saga of my mystery misfire, I finally took the car to a professional on Honda engines.

After some diagnosis, it turned out that cylinder 2 has 120psi compression versus 225/230 on the others. Strangely, the car produces 210WHP on the dyno !?!? (All stock powertrain)

This is a stock, NA AP1 (F20C) motor with 77,500 miles. I bought it at 48,000 miles.

My mechanic said that a valve on cylinder 2 was "all the way down" when he went to adjust it, which is an unusual condition. (Apparently they start to come out of spec by loosening up, not tightening) It was also stuck, and required an unusual amount of force to bring it back into spec.

So, my head is now in the process of being disassembled to figure out what's wrong.

While I am paying for 8 hours of labor to take this head off and put it back on, I am considering doing the following things: (Advice please!)

1. Replace all valve retainers with the stronger AP2 part. (Just intake?)
2. Replace timing chain tensioner
3. NIXED - Maybe - Replace engine block studs with ARP studs?
4. Maybe - Replace timing chain?
5. Maybe - upgrade to AP2 Valves?
6. Replace serpentine belt (Why not)

Obviously, I will also be fixing whatever the problem is on cylinder 2. My mechanic is going to take the whole head off, bathe it, and send it to a machine shop to make sure the seats are OK.

My question to the community here is this: I am in way over my head, and learning about engines as I go along. I'm no slouch - but I'm an EE not an ME. Can y'all offer any advice on this problem, and what I might have done while the head is off? This is looking like it's going to cost me around $1500 (Rental car and all) before it's all done, so I want to make damned sure I am doing this right.

Thanks!

UPDATE 1: Head has been analyzed by the machine shop - they say that Cylinder 2's exhaust valve seat was "cracked" and "mushroomed" so that the exhaust valve was not properly sealing against its seat (hence the low compression). Neither the machine shop or Colin can come up with why this happened except possibly a bad seat that eventually gave up. They're going to put a new seat in there (apparently seats are steel - the head is aluminum) and "re-grind" all the other seats so the valves are sealing perfectly. This is all pretty scary-sounding to me so I am just repeating what they've told me.

PrimoGen

you should bite the bullet and do new valves and retainers while the head is off and apart. get upgraded ones like Ti

depending on available cash and I forget which side this applies to but, i would do the AP2 cam upgrade on the appropriate side (exhaust or intake...i forget)....just for a little more umph!!!

dantediss

I understand the whole its lighter and more expensive..therefore better mentality...but DO NOT REPEAT DO NOT get ti retainers,.. they wear out fast so unless you like spending $$ just do the ap2 ones

dantediss

ti retainers are great for cars that track and race and have motor breakdown and buildups constantly. plus ti and aluminum dont mix well... they tend to fuse together not good if the ti fractures

BelowRadar

Thanks for the input, guys. One of my questions is whether or not to change out the "good" valves or not. I tend to think of it as preventative maintenance, but my ME friend tells me if they still measure up then not to change them.

raymo19

I would replace them all. It's one of those "while the patient's open" deals. How many miles on the motor?

BelowRadar

77,500 miles. I will update the first post as well.

dantediss

def upgrade or replace anything you can while the heads off.. no need to pay twice, im sure billman will chime in but he says its a big no no to switch to ap2 springs..retainers are fine though

spectacle

Did you take the car to Collin?

We told you it was valves

ChefJ

If you plan on leaving the motor in stock form I would recommend agains getting ti valves. Retainers are a different story but the ap2 retainers will do a fine job. The ap1 retainers are known to have issues even with the most minro over rev.