Hi,

Ok, so I pulled off one of the spark plugs today off my 77 transmode. It looked in decent shape, I cleaned it. The gap was huge...not sure how large since I didn't have a large enough gauge to measure it with.

Bought the RV back in July and not sure when the plugs were replaced but I did notice the acceleration (when I drove the RV home) was bad.

Is the bad acceleration caused by the large spark plug gaps ?

Should I re gap the plugs to .040 ?

And would replacing the plugs improve the gas mileage by any noticeable amount ?

Should I stick with the AC Delco plugs or are the plugs made by Bosch, NGK, Autolite, Or Nipendenso a better choice (performance and gas mileage wise) ?

Thank you for the help.
AJ

A '77 would have HEI, so larger gaps are generally accepted. Higher coil energy will jump a larger gap. Large gaps and high ignition energy tend to provide stronger more consistant flame initiation. The original gap of R46SX was .060 and of the R46SZ was .080". I run my HEI plugs at .060 and have acceptable performance.
When you say the "acceleration is bad" it is not clear what you mean. A little clarity such as its sluggish, hesitated on tip-in etc would be helpful. These things run 0-60 in something like 16-18 seconds so they are not hot rods. If the performance is really poor it could be caused by any number of things including ignition.
As far as brands go "AC" stopped making plugs 10 or so years ago. Current "ACDelco" plugs are supplied by NGK, I believe. I'd recommend them or Bosch or Autolite. High dollar iridium or multi electrode are a waste of money in my opinion.

mrgmc3 wrote on Mon, 10 November 2014 20:26

A '77 would have HEI, so larger gaps are generally accepted. Higher coil energy will jump a larger gap. Large gaps and high ignition energy tend to provide stronger more consistant flame initiation. The original gap of R46SX was .060 and of the R46SZ was .080". I run my HEI plugs at .060 and have acceptable performance.
When you say the "acceleration is bad" it is not clear what you mean. A little clarity such as its sluggish, hesitated on tip-in etc would be helpful. These things run 0-60 in something like 16-18 seconds so they are not hot rods. If the performance is really poor it could be caused by any number of things including ignition.
As far as brands go "AC" stopped making plugs 10 or so years ago. Current "ACDelco" plugs are supplied by NGK, I believe. I'd recommend them or Bosch or Autolite. High dollar iridium or multi electrode are a waste of money in my opinion.

Thanks for the info but now I am more confused: People here say gap it at .040 but you are saying to gap it at .080 ??

The plugs on it are the SZ ones. I am thinking I am just going to clean and re use them.

Would there be a difference btwn the gap at .040 and .080 as far as how it runs and mileage ?

Thanks.