Anyone ever done this and what were your results? I know there would be a loss of combustion efficiency but that doesn't always result in power loss.

This is more theoretical thinking out loud but here is the reason I ask. If you were to revise the left or right spark tube to instead exit the cylinder head at what would be the center of the spark plug tubes at the top of the cylinder head, you be much more free to get the valvetrain geometry more correct. Given there is already some misalignment in the z axis that can only be modified with offset lifters or adjusting the lifter bore spacing, you could at least get both pushrods in line with the lifter bore angles in the x-y plane. Also, it definitely seems like Steel rockers give you best chance to get the most clearance as well since you don't have to use as much material to make them work well.

You couldn't go to a single plug centered, the valves would be in the way or would have to be very, very small.

Not centered in the chamber, only centered at the top.

I tried running just 1 plug on my 03 hemi and I couldn't tell any difference. I did hook them all back up but I am not sure it makes any more power, I heard it was for emissions reasons.

Nah, i'll just run all 16 and no plug wires.

Given the huge expense Mopar has spent over the years in development and production, I have to say they had to have seen an overwhelming benefit of the dual plug design. Whether that benefit is in power or emissions, I have not determined, but whatever it was had to offset quite significant cost increases. A

s I am in production of vehicles, I know those engineers had to make quite a case to management/penny-pinchers to get those extra 8 spark plugs per car, the added raw materials into the head and a coil to handle both plugs as well...and they won. I'll carryover their lessons learned and just run the 16 plugs, if it's just for emissions...well that's fine too. The cost is insignificant.

But I wouldn't see any overly ill effect of running just one. We have ran one for a long time in tons of different chamber configurations.

Interesting thought.

Wonder why BES would waste money putting 2 distributers on his prized Hemi engines.

I think it is part of the reason they dont need so much lead. Ask any Fuel team out there the same question.

Google Nutter racing engines. They have done this with a GM computer.
Matt

A thread from many years ago:

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/146518/1.html

Greg

A little column A a little column B.

The flame front can only travel so fast. Putting 2 plugs in the chamber the flame front doesn't have to travel so far (there is no "penalty" for the flame fronts crashing together) so you get a more complete burn which is good for both performance and emissions.

The center plug is one of the benefits of the original HEMI design. For instance, if you have a 4" bore the flame front only has to travel 2" in any direction, with a wedge head, with the plug to one side of the cylinder, the flame front may have to travel up to 3.5" in one direction.

As you can imagine, at higher RPMs the ability of the flame front to travel to the edges of the cylinder become more critical as there is less time to complete the burn.

I suspect that they couldn't fit the plug in the center of the chamber without sacrificing valve size, so the nested a plug between the valves on either side. It probably didn't add too much to the cost of the coil packs, and at the volumes they buy spark plugs that probably wasn't a big deal either.

I tried it with only one plug. No difference in 1/4 mile times. I was running 10.2 at the time.