Plug gap?

[Charlie Chops 1940]

Was doing a little light reading - the plugs in the track roadster after supper tonight. They look a little lean which seems right based on how the car runs. I have an MSD 6A box and matching coil. The gap was set at .040". Should I open that up a little? .050? .055?

Whadaya think?

Charlie

[phat46]

You'll have to explain that one to me Charlie.  How does opening up the gap make it run richer? Not being a smart * I just don't understand.

[Charlie Chops 1940]

It won't make it run richer. I'm just wondering if the gap needs to be a bit bigger given the stronger ignition system.

Charlie

[Learpilot]

This is from www.msdigntion.com
Plug Gap is based on Compression.
Up to 10.5  Gap  0.050 - 0.060
10.5 to 13.0 Gap 0.040 - 0.050
Above 13.0 Gap 0.035 - 0.045

This for the MSD 6A or 6AL

Rick

[GPster]

The author's name escapes me but I once read a book written by a guy about car wiring. He had explanations about things like vapor lock and other information on why and how to make an older car survive in conditions now-a-days. He had re-furbished a late 40s Cadillac that had been used by the Queen of England to tour Canada for a return visit by Royalty years later. His common sense explanation about plug gap is that it centers around detroit new ignition systems and the buyers' concern over cost of parts and labor. When they start telling you that spark plugs will last 100,000 miles the're not saying anything about erosion on the terminals or the gap widening with age. They are saying that new plugs should be gapped at .040" knowing that the new ignition systems will jump a gap of .075" when the plugs get older. With that in mind compression and plug reading might be a more reliable source of information than manufacturers specs. That and I know it's a fun car but I don't think it will go 100,000 Miles before you have the plugs out again. GPster

[Charlie Chops 1940]

Thanks Rick and Joe.  I knew I had read about the wider gap somewhere - it must have been on he MSD site, but I forgot. Aounds like .055 would be a better starting point for 10:1.

Charlie

[UGLY OLDS]

Not to steal Charlies thread BUT....What is everybodys opinion of CD ignition like MSD , Mallory, & others supply :?:  Not the particular brands,but the whole CD ignition "theory" . I understand the "longer-multiple" spark discharge process, but wonder why if something this simple can be this beneficial why the OE's would not have jumped on it years ago to help with emissions & driveability issues. I think at their level of engineering & production, it would be quite economical to include this system in ALL vehicles .... :?   Thought's anybody  :?:



Bob....