Disabling intake and exhaust valves (going to 8 valves in a 16-v head)
 

My original plan was to install a CRX HF camshaft along with the roller rocker arms in my 16-valve Civic Wagon. The HF torque peak is something like 2500 RPM lower than my engine. The HF has only 8 valves, but it's pretty clear that the head is very similar to the 16v head. There are blank spaces where the valves would be.

http://img.photobucket.com/albums/09.../crxhfhead.jpg


Unfortunately (and surprisingly) the HF cam has larger lobes that hit the 16v head, so I was unable to install the HF cam. So what I ended up doing was just using the spacers that are used on the HF in place of the missing rocker arms.

http://img.photobucket.com/albums/09...6to8valves.jpg


So far I like it. It's more responsive and torquey at the very low RPM I usually drive at. I kept overshooting my 2000 RPM shift point. But it will not make it to redline in second gear anymore. It's probably not an ideal setup, since the camshaft wants to make midrange power and the valves won't let it. I'm hoping for an increase in MPG, time will tell.

Not surprisingly, the exhaust is much quieter now. :)

Interesting! Looking forward to seeing your results.

Cool! You mentioned this at GGP. Nice to see it come to fruition.

More torque down low is usually a good thing for the light-footed.

Subscribed for updates.

good idea. i'll be curious how it works out!

I was really hoping to use the HF cam too. Or "diesel cam" as I had been calling it. :D

It seems to make the most difference at part throttle and at low RPM. I probably lost 20-30 HP at the top end, but I wasn't using it anyway. :)

Why not just swap the HF head on? It doesn't take long, and you get the proper intake manifold to deal with the required higher air velocity at lower speeds, as well as slightly larger valves than the 16V heads have, which allow better flow at low RPM.

And you can use the HF cam. You can also use your stock electronics to run that head, as long as you only use the head, and don't try to incorporate the recirc valve on the intake manifold.

I also have a complete HF swap I'm selling, if that's something you're interested in. It's currently in Johnson City at a buddy's house.

I would swap the whole head, but the one at the junkyard has been sitting for at least a year with no valve cover or hood. Might be OK, the cam was fine. But it's missing the injectors and possibly other parts. I saw your ad and I'd buy your swap if this poor Wagon wasn't so rusty. I'd look for a better shell, but like Darin, I'm suffering from TMP. :)

I'm tempted to swap in the HF trans, but I'm scared of gearing that tall in a heavier Wagon that I use like a truck. I'm often wishing for a shorter first gear.

The first gear is the same, the final changes it a bit. With the added low-end torque of the HF swap, you'd probably be net about the same.

One problem I had with the HF's gearing was that, even in my +100 HP sedan (~120HP at that time, IIRC), I couldn't pull anything except 3rd gear up long hills, and accelerating past 60 or so was just wishing in a bucket (on those hills). I was also running 205/40ZR16 street performance tires and hadn't done much else to the car at that point.

For the record, I'd entertain trades for the swap as well, if you know anyone that's interested in it.

The HF 3rd gear is slightly taller than my current 5th gear! First gear with the HF final drive is about halfway between my 1st and 2nd gears. I can take off in 2nd gear now on flat ground, but it would kill my clutch on a hill. I might try the HF trans, I keep thinking about it.

I don't have much to offer in trade. Have any use for a Chevy 350? :)

I had no idea that you could run a 4-valve head with a 2-valve cam! I'm very interested!

Amazing! Man... makes me want to start looking for 1.8 cams for my 2.0 again...

I'm actually still running the 16v cam, just half of the rocker arms. The cam swap was not possible due to the cam lobes hitting the oil retaining wall on the cylinder head. I don't know how different that wall is on the HF head. I probably could notch my head a little to clear the cam.

A video!
http://www.youtube.com/watch?v=JJ-JhKniuVM

The 8V cam probably has significantly higher lift than the 16v cam. Curious to see how this comes out, the FE system will still assume 16 V and the associated airflow and fuel accordingly. Maybe the decrease in power will improve driving habits more than anything, although I would accuse my 106 hp 16v Civic of being too powerful.

Unfortunatley, I have no use for a 350 LOL.

Anything diesel laying around? Or bikes, scooters, etc...

I wonder if you would be able to achieve better efficiency by leaving the second exhaust valve functional, like the first stage on the 3-stage VTEC engines. If I had a SOHC rocker-arm setup like yours, I would think it worthwhile to play around with disabling one intake valve, then one exhaust valve, then one of each, and see which works best. They all seem like they would have their advantages, but I'm not sure which one seems the most advantageous.

2 intake, 1 exhaust = increased EGR effect from decreased exhaust flow, but higher VE from better intake flow
1 intake, 2 exhaust = lets less air into the engine for reduced consumption, but removes some exhaust restriction for better performance
1 intake, 1 exhaust = less total flow, still balanced like the 4-valve. Definitely way less power with the 4-valve lift, as you've seen.

I'm not sure which of these would result in the best fuel economy. As I said, there's some reasoning to support each concept, and it probably depends on your driving style.

SUBSCRIBED. Great thread. Finally, real world testing of an idea the rest of us are too scared to try!

Unfortunately, the 1ZZ-FE in my wife's Toyota has a shim under bucket valvetrain, so no rockers to omit.

I might have a junk 16V head laying around if you want to practice clearancing it for the HF cam... You can have it if you want.

I have a few old mopeds....


Thanks, but I actually have a spare head I can play with.


I've been wondering the same thing. :)


It's running in closed loop, but I don't know if that can fully compensate for the reduced airflow.

Any more news? I noticed you posted a fuel log entry since doing the valve work (and your new side skirts):

2nd best tank for you so far - 60 mpg.

My current tank isn't looking great at around the halfway mark, maybe 50 MPG. But that's with a lot of almost-normal driving on a trip. I'm planning to fill up so I can start over. It's hard to test mods with no MPG readout, especially when most of my percent above EPA comes from driving style. But even 50 MPG is impressive for a car that used to get 38. I should drive a tank without hypermiling to see how the mods alone help, but I don't think I remember how to drive normally. :)

I do wonder if it's running rich with less airflow. But then I wonder if there really is less airflow. Obviously there is at 5000 RPM and full throttle, but at 2000 RPM with the throttle barely open, I'm wondering if the throttle plate is more of a restriction than the disabled valves.

I was back at the junkyard and looked at the HF head. It doesn't have much of an oil retaining wall like my 16V engine. I guess with roller rockers, the cam doesn't need to sit in a pool of oil. So I could cut away the part that interferes with the cam lobes, I just need to figure out how to do it without getting metal pieces all over the head and in the oil.

subbin'. Very cool.

Hm... I might try this on my wife's car. She's been wanting it to get better in-town gas mileage (it currently gets 19 MPG). If I can get about a 25% improvement, that'd truly be awesome.

What car and what type of valvetrain? I think you want to keep the oiling system as it was with all the valves. The spacers I used cover the now-unused oil holes in the rocker shafts for the deleted rocker arms. Leaving those holes open could potentially affect oil pressure in the head.

The car is a 2002 Sebring Convertible GTC with a transplanted Chrysler 3.5L V6 engine. It is a SOHC design with 24 valves. For each cylinder, there are two separate intake valve rocker arms, and one combined exhaust valve rocker arm assembly.

If I were to do this, I'd probably go to a junkyard to find a head from a junked 3.5L engine, and get measurements of the pivot shaft, so I can find or fabricate spacers to block off the oil holes as you mentioned.

If you wanted to reduce the valve number, just remove the rockers to 1 of the intake valves (3 valves/cyl) and you are done. You won't even need to pull the heads. Just block the oil holes as noted above.

It wouldn't breathe very well then, but that cuts down the air (and fuel) flow.

Taking out a rocker arm isn't ideal. Epoxy would do wonders

Except JB weld breaks down under constant exposure to petroleum products.
Not to side track, has anyone tried re grinding a V-Tec cam for econo ?
Basicaally a custom cam grind to mimick the 1st and 3rdd stages of the unobtainable 3 stage engine ?

My vote is for the 1 intake and 2 exhaust setup.

Don't forget to re-index your plugs towards the single intake valve.

Wow that's a pretty nifty idea. What did you record without the mod on highway? Shouldn't it be tuned to maximize your changes? Curious to see what afr's your running with that mod. Most def subscribed.

That should work just fine. :thumbup:

It'll probably takes months to see how much this is helping me. If my average goes up, I'll be happy. I am considering buying a wideband AFR meter.

very cool!

I did this back when I had an 84 accord, 12 valve engine. The car idled better, got slightly better mpg, about 2 mpg better, warmed up faster, had more heat and of course less power.

Running rich, no. The ECM is perfectly capable of adjusting fuel flow to compensate for the lower airflow. It's when you start flowing too much air that's the problem. Don't be surprised, however, if you get random TPS code once in awhile. Just reset it and go about your day if you do.

To clearance the head, if you're SUPER careful, you can do it without pulling the head off. Stick paper towels in the oil holes, put grease on them and leave a nub with which you can pull them back out. Clean all the excess oil from the head so you end up with a clean, oil free area. Once you clearance the area you need, put a paper towel around a tongue depressor or something and spray liberally with WD40, and thoroughly clean everything in the head. Pull the papertowels out of the holes, then dump a quart or two of either kerosene or diesel to rinse everything up. If there are still metal flakes, clean them out again and rinse again. If you don't see any, clean out the fluid, pour about half a qt of oil all over the head, then change your oil.

Honestly, if you don't need your car for a day or so, it's almost easier to pull the head, clearance it, then put it back on. The whole head gasket job only takes about 3 hours if you're meticulous about it, and you can probably clearance the 8 areas you need to in about an hour or so.

what mpg do you think a 96 accord would do with a 3 valve system i can grind down the cam lobes easy enough it gets 33mpg now on the hwy now 240000mi on engine, no rust ca. car

I vote 2 valve. I reason that if 4 valves is tuned to make peak hp at 6000 rpm and peak torque at 4700 rpm, then 2 valves will tune to half that (for the 2.4 ecotec). peak VE will now occur at 2350 rpm - which is my cruise rpm. It will make more power at that rpm than stock - which you confirmed. Polishing the ports and chamber always help. Also, running one exhaust valve means there are fewer hot spots to cause knock. 2 intake valves cause a tumble motion, while a single valve causes strong swirl - potentially better against knock.

I would also reduce the intake manifold runner area by 50% to boost VE. A 6" runner will actually help. A turbo will boost FE and regain the top end. My .02

Easy way to alter cam grind
 

I learned from my econo-minded father to lower the rpm of maximum torque by increasing the valve clearence. This reduces duration (number of degrees the valves are open), reducing valve overlap to a minimum. Disabling half the valves on a 16 valve head drastically reduces the flow potential which would be counter-productive to torque and horsepower. We have altered lash from the stock .010" intake and .012" exhaust up to 1/4 turn intake and 1/3 turn exhaust. I have not checked this, but this might translate to approximately .030" and .036" or slightly more. The increase in valve lash might be considered drastic by some, but works well with a minimum of noise and no observed increase in cam wear over very long mileage (150,000 miles). Maximum torque is moved to a much lower RPM, in the case of 2 Toyotas, about 2,000 rpm.

Hey, I have that on my 24v Sable! I did it by staying under the rpm where the secondary intake butterflies open up. It also has 2 in., 2 ex., but that is for misbehaving.

please, don't neuter such an amazing engine. if you want more torque, port-match the intake and exhaust and maybe try an intake plenum from a charger/challenger.

I asked about this years ago on this forum and got an answer (which I agreed with at the time) about wear being an issue. You have obviously proven otherwise. I think increasing the lash is a far superior "tuning" method because it alters the valve duration, unlike simply disabling valves. Unfortunately, my Matrix has direct actuating lifters and are adjusted by using different thickness of lifters, and I am quite sure that a sufficiency "thin" lifter isn't available for such and endeavour. And I don't feel like lathing them - my wife wouldn't be impressed with me tinkering with her car.

Do you have any MPG figures to disclose?

Wow...thanked in your first ever post! Is that a record?