dgz924s

Does anyone here align the plug to the intake valve? If so what method are you using to ensure it is aligned to the valve, marking the plugs or ?

Or does it even make a difference? 944 motor in my case...?TIA!

Geoffrey

You are talking about indexing the spark plugs. There is a tool that will help you index the spark plugs on the bench and then you can install them in the car.

Joe Weinstein

I would love to hear of any controlled tests that verified a difference. I am thinking that
spark is not delivered to the cylinder until after the intake valve has closed, and the
chaotic flow of the intake charge is well past any predictatable orientation.
Joe Weinstein

dgz924s

No actually in the car. I know a guy here who techs race cars/engines of domestic cars and sets up the engines by indexing the plug as you say it. He gave me a reason but I can't recall it. I figure if it is beneficial why not make use of it especially in a 944na.


Joe....I can see your reasoning..... Any others care to differ?

Matt Marks

I understand that on 2 valve engines to index the plugs you align the electrode with the exhaust valve (?) to get better fuel burn. Does the same apply to 4 valve engines?

Anyone have any hard numbers on this for either valve setup?

m42racer

There is always a great debate which way to face them. At least you are thinking about even indexing them. On Porsche 2V 911 type heads, the direction is always slanted towards the Exhaust. It takes some (dyno) testing to establish how far to slant them. The Cam Timing dictates the slant. Run the engine and look at the Intake side of the ground electrode. (I must add that all of this is only applicable with standard single ground electrodes. Those plugs with multi Straps or recessed ones do not apply here.) The side of the electrode will show fuel deposits higher on that side than the exhaust. Until you see an even color both sides, the direction can be adjusted. The more the Exhaust Cam is advanced the more slant towards the Intake Valve. The less Ignition advance the more the slant should goes towards the Intake valve. The opposite applies here to. Selection of the right plug end, plug gap, the corect heat range and indexing all make a difference. Its all the little things that can add up to a significant large difference. Reading the plug is the most important. Also, after spending all that money on Twin Plugging, and facing the plugs towards the Cylinder walls, amkes no use of all that work and spent money.

Indexing plugs is something anyone can do, but there is a BIG catch. You must buy LOTS of plugs in the hope that you get 6 or 12 that face the right direction. You can buy indexing washers, but the correct depth into the chamber must always be held. You lose here as much as you do facing the wrong way. On race engines, each plug hole is measured for thread start with 1 constant measuring plug. Each hole is measured for difference and recorded. This is all done before the Head is assembled. The with the aid of a Plug Indexer, every plug is measured for thread start. A plug is choosen that will index in at the required position. Got love the work. Just to install Spark plugs. Then all the spare sets have to be done.

dgz924s

Good stuff m42racer! The issue on getting the plugs to stop at proper index was my next question. Thanks!

Bill L Seifert

I have heard of indexing for years, and there are as many people that say it doesn't work, as those who say it works. One other, a lot of modern plugs, (some Bosch Platnums for instance) have four electrodes on the tip, which I would think would automatically index them.

I am sure no expert, and every thing that I have done that was suppose to give me a couple of HP, didn't seem to improve proformance. But, that's just me.

Bill Seifert

1987 944S Race Car

dgz924s

Go figure Bill! As most little "tweeks" end up....50/50.

Joe Weinstein

I bet the gain is the placebo effect. My car handles a little better right after I check tire pressures,
even when I didn't need to change anything.
Joe

Bill L Seifert

Joe,

Boy, ain't that the truth.

Bill

m42racer

Doing this to the average Porsche engine is a stretch. Its done by those who have done everything else and just want everything perfect. There is probably way more obvious faults that should be fixed on most engines before this is done.