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

[Gasoline Fumes]

Originally Posted by ultimx

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.

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.

[Starsky]

very cool!

[arcosine]

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.

[Christ]

Originally Posted by Gasoline Fumes

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.

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.

[ron]

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

[ERTW]

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

[Lotusrk]

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.

[Frank Lee]

Originally Posted by orangustang

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.

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.

[ksa8907]

Originally Posted by t vago

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.

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.

[mechman600]

Originally Posted by Lotusrk

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).

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?