Gap increase for better MPG?

Here's my theory. If it were really that simple they would do it at the factory. Most likely this story got started by someone who took their old gunky plugs out and put in a new set of plugs, and oh by the way, gapped the new ones wider, and concluded that it was the wider gap that made the mileage go up.

If the truck runs fine with no missing or stumbling you are probably already getting close to optimum fuel mileage.

On 15 May 2007 14:51:40 -0700, 86GMC wrote: I was reading through some earlier posts on this list, and noticed that increasing the plug gaps could lead to an increase in MPG. With the price of gas, I'm wondering if this would work on my truck? Here's how it's currently set up: 86 GMC 1500; 5.7L V8; R44TS @ .045 gap; HEI; Delco cap, wires, & coil, NAPA roter; Rochester Q-jet. The truck runs fine, so I don't want to mess with the ignition system too much, but for better MPG I'm willing to give it a try if there's no real down side. Anyone tried this? What plugs? What gap? What, if any modifications? What downside? Thanks in advance for any replies.

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Group: alt.trucks.chevy Date: Tue, May 15, 2007, 10:07pm (EDT-3) From: snipped-for-privacy@moore.net (Ashton=A0Crusher) Here's my theory. If it were really that simple they would do it at the factory. Most likely this story got started by someone who took their old gunky plugs out and put in a new set of plugs, and oh by the way, gapped the new ones wider, and concluded that it was the wider gap that made the mileage go up.

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I've Been doing this for years and it works. First time I ever heard about it was when I read about it in a Chevy performance magazine. Gapping .010 inch to .015 inch over stock will give you a slight improvement in fuel mileage but If you go beyond that, you could experience hard starting and even misfires at speed. You must make sure that the entire ignition system is in good working order and you need to check the gap on a regular basis (I check mine in the fall and spring). Low resistance ignition wires are a help also as is a high output coil (both give a stronger spark).

The Q-jet can be made to give you respectable gas mileage by being very meticulous about setting it up. I paid a mechanic to do mine and ended up doing it a few weeks later because the guy screwed it up. Helms used to have a great field repair manual for the Q-jet but I don't know if the still offer it. If you really want good fuel mieage, just do the basics like front end alignment, tire pressure, driving techniques, etc.

/?/?/?/?/?/?/?/?/?/?@@@@@@@@@@?/?/?/?/?/?/?/?/ You should never confuse the issue by injecting the truth. ~ unknown ~

Plug gap will have nothing to do with mileage. The only reason the gaps were widened over the years was to fire the leaner mixtures. If you're not experiencing misfire, then you'll not increase mileage.

Any of these Magical fixes, if they really worked the Auto Manufactures would be doing it as it's in their best Interest.

On Wed, 16 May 2007 21:49:16 -0700, JBDragon felt we'd all be better off knowing the following:

You know - if you increase the gap a lot, you will kill the spark. Kill the spark the engine doesn't run. You get out and push.

Hence perfect gas mileage!

Well be smart about it and do it on top of a large hill so you'll still be able to go someplace and not have to push.

On Wed, 16 May 2007 22:20:37 -0700, JBDragon rebooted the Etch-A-Sketch and scribbled:

ROTFL!

Sounds like I'll just stick with the set-up I've got. The slightly wider gap = fatter spark = more complete combustion logic makes sense though. Anyway, thanks to all for posting their experience.