Any of you folks have exp. with a 3-angle grind on the B20 motor?

Last fall, Honda Motor Company granted me the amazing opportunity to do a valve job on the CR-V. (Turns out that the previous owner never had the valves adjusted, and when we got it at 120K, one of the exhaust valves was already screwed..).

In any case, since we were in there, we gave it a very careful 3-angle job. Nothing else changed, save the burned valve(s) and the valve seals / gaskets. Trouble is, I wasn't able to appreciate the full impact of the work, as the (previously discussed) ignition issues were apparently already in-play.

So with the ignition corrected, and even running on 4 or 5 month old gas, the improvement is fairly obvious to me. The power is notably smoother across the range, and more available at lower RPM. And once into the power band proper (starts @ ca. 3000 RPM on this motor), there is a small but clear bump in HP - the motor just seems to breathe better all-around, and rev more freely.

Best part, it didn't cost +anything+ except the additional time - that is, once you're committed to a valve job. Going forward, unless there is some major, rational objection - I'd say just do it, period. If you're really feeling frisky, get in there and buzz off the casting marks inside of the ports, too..

I didn't bother, but knowing what I know now, I'd have done it without another thought.

 

I'd be willing to bet you benefitted more from the compression bump of resurfacing the head

 

We didn't resurface the head. We did check it twice - first we did a set-up on the surface plate and indicated on it, then we used a trued stone to skim it. The head was very flat, so we stoned it a bit more to add a little fresh surface finish, then it went back together.

 

I'm surprised you got a noticeable benefit from just a valve job. How many miles does it have? It's pretty comin for people to put timing belts on wrong with one cam off a tooth. If that happened and then you put it back right, that would explain it.

I'm not knocking the benefit of a 3 angle valve job, just surprised you would notice it in a stock engine with nothing else done to complement it

 

the refurbed head I installed has a 3 angle on it. cant say I notice any difference really, I mean it runs better overall but my old head was burning coolant and shitty valves and all kinds of stuff.

 

A valve adjustment can do a lot if it was really messed up. Just did a valve job on my CRV, and it runs WAY better. Runs like 100 RPM less on idle and like 500+ less RPM on the highway. Not to mention it is a lot more quiet.

My valves were all over the place. Some were way loose while other were way to tight. Not even sure if they have been adjusted before...

 

yeah as long as you weren't already misfiring you might have saved it. mine ran great after adjustment but came back a few months later and was not fixable.

 

^^
i agree

If it were me, with the head off, I wouldve shaved the head for a little bump in compression, throttle response, and a little better MPGs.
Also, like said, cleaning up the casting marks would aid in better flow.

 

Yeah it wasn't misfiring or running badly, it was just louder than usual and made a loud clicking noise. Definitely recommend everybody to adjust their valves, not only for performance, but to save your engine. Unlike most cars, the Gen 1 CRV valves get tighter overtime. If they get too tight it can start burning valves and cause a whole heap of expensive trouble!

 

Theres a saying:

Better to hear them (loose) then burn/replace them (too tight)


EDIT: Changing that tiny exhaust piping should let it breathe better also.

 

You need to reexamine that statement - it's factually flawed.

The engine RPM to wheel-speed relationship is a function of fixed gear ratios, and nothing else.. (excepting the possibility of abnormal slippage in the driveline; e.g. clutch or converter slipping).

There is no engine modification or adjustment of any sort that can change the RPM at which the engine runs in a given gear, at a given road speed. That can only be accomplished by changing the transmission or final-drive gear ratio(s).

 

Eh not 100% true in my case. My particular model is the 4 speed automatic

With adjusted valves, I have increased power. Therefore the torque converter has more to work with, and can allow shifting at lower RPMS.

Of course when it is locked up at higher speeds, what you said applies. So I guess "highway speeds" really wasn't the best choice of words, but like normal driving before the torque converter locks up.

Just my two cents from driving around town comparing what it used to do to what it does now.

 

Isn't torque converter lock-up a function of RPM, rather than a function of power (torque & RPM integrated)? I honestly don't know, automatic transmissions are a very weak point for me. But it's much easier to monitor RPM than torque.. much, much easier.

Sure, and in fact it applies any time the driveline coupling - be it a conventional friction clutch or an advanced hydraulic-electric torque converter - is 'locked up'.

 

Too loose, and the cams, followers, lifters, valve stems, pushrods (if you have them) etc. can become battered from the excessive play.

Severely too tight, as in held-open, and the valve faces burn through.

Slightly too tight, and the oil film gets squeezed out, resulting in accelerated wear (galling, etc) of all of the previously mentioned parts working surfaces.

Generally speaking, I run the valves on the wider spec in cars (I don't want to have to go in there a lot to see if they've tightened up), and on the middle-to-tight side on bikes (I want the performance, and I expect to go in there frequently).

The only exception on the bikes side is BMW and Guzzi big twins.. run those middle or wide. It won't hurt, and it seems to slow down the tendency of the valves to recede over the course of many miles.

From what I've been able to gather, if it's a B20 and it has clocked more than 30K road miles, the valves NEED to be checked. It takes about an hour to measure them, and around another 5 min. per valve to adjust, if needed.

A lot of legacy engine designs suffer from valve seat and/or valve face erosion. Ultimately, this manifests as valve recession, and a progressive loss of valve clearance. Once the clearance drops to nil, you have a stuck-open valve that will swiftly and surely burn out.

 

worst case it only cost me around 450 to do my head. without timing stuff, my bottom end was actually rebuilt before i bought mine. im planning to do my valves every 10k now just to be extra safe. i have a ton of gaskets and im basically a pro valve adjuster at this point, might as well.

 

Seems like overkill to me, but if you sleep better at night..

Just don't forget the other, frequently overlooked services - like changing out the brake and clutch fluids, the PS fluid, and so on.

Brake fluid is cheap, and it has a surprisingly limited service life.