Spark Plug Gap Revisited

[festyfanatic]

I recently bought a 1988 LX 5 speed with 75,000 miles on it. To me it appears that the car was used very infrequently over the last 20 years. The interior and exterior are in great shape. But the engine compartment has some parts that were coated with rust which they tried to clean up, which leads me to believe that the car sat outside quite a bit. I'm surprised that the undercarriage isn't rusted more. The car actually runs pretty good but it doesn't seem to run as smoothly as my previous 88 LX which I ran until it had 293,000 miles on it. Or maybe I'm just not used to driving a carbureted vehicle anymore. Just for my satisfaction, I'd like to change the plugs, wires, cap and rotor. I've searched the forums several times concerning the proper spark plug gap. The plug manufacturers state .044 for the gap. But the sticker on the inside of the hood states .039 - .043. In the past, it seems to me that I set the plugs at .041. What do most of you who change your own plugs set them at? Does replacing the plugs and wires do anything to the timing? Thanks in advance for your help.

[fastivaB6TG25MR]

As far as i know wires will not effect timing ... I gap my b6t at .44 cause thats what the capri manual says to do... If someone knows of a better or different spec let me know...

[TominMO]

The proper size of the gap relates to the robustness of the ignition system. The difference between .041 and .044 is not that much. I would be inclined to the larger gap, for a larger spark, which will burn fuel more effficiently.

I am using a gap of .048 - .050, because I have a 45,000-volt coil installed, which can handle the larger spark. This has consistently proven to give better mileage.

Also a good idea is to index the plug itself. This involves putting a small mark on the porcelein of the plug to use as a reference, so that as you are screwing it in you can check that the open gap on the electrodes is more or less facing the intake manifold/intake valve. Basically what you don't want is the bottom electrode to be in the way of the spark, as fuel comes in thru the intake valve.

[WmWatt]

I use .040 because it's what is available in that range on my spark plug gap feeler tool.

[festyfanatic]

Alright, got the plugs and wires changed. Set the plugs at .041 and what a difference! No more hesitation and jerkiness.......just clean acceleration! I used Denso Standard #W16EXRU11 plugs and Denso #671-4211 spark plug wires that I bought from Rockauto. Hopefully, this will bring the mpg up. It was ranging at 39-42 mpg before the new plugs and wires. My other 88 LX was a consistent 46-47 mpg.

[sanjeet]

festyfanatic: good one its great to have a smooth running engine and its really worth the effort, TominMo good point about indexing and its not the most common subject, you are obviously very knowledgeable on more technical side, I enjoyed reading your input and that's comming from a KIWI.

Hei kona ra from Aotearoa (land of the long white cloud)

[TominMO]

festyfanatic: good one its great to have a smooth running engine and its really worth the effort, TominMo good point about indexing and its not the most common subject, you are obviously very knowledgeable on more technical side, I enjoyed reading your input and that's comming from a KIWI.

Hei kona ra from Aotearoa (land of the long white cloud)

Naw I'm not all that technically knowledgable; just a little trick I picked up somewhere.