engine missing at idle question

[SteveC]

Ok as some of you know i recently rebuilt my 352 FE in my 67 It has been running fine up untill about a week ago i have a slight miss.

Not real bad but it idles smooth then the idle drops for a sec maybe 100 or so rpm then idles fine...every 3-5 secs maybe less.
when i turned the engine over with remote start and the coil wire off i can hear like a woosh sound on closer investigation i found the sound to be coming from #4,5,6 spark plug holes. I pulled the sparkplugs and checked them they look almost new i put them back in and made sure they are tight...turned it over again and the woosh sound is gone, i also check to make sure the wires were on good...havent tried to start the truck since it was cold and i was outside with out a coat.

Ill start it probally tomorrow and see if that helps,,
The question is can a spark plug not sealing the hole well cause a miss?? I probally should check the timing as well i have to go get a light when time allows.

[saidyene]

It absolutely can cause a miss. You have to have 3 things to have a running engine: fuel spark and compression. With a bad seal at the plugs your not getting enough compression. Check it out now that the plugs are tight. You should see an improvement.

[69rangerman]

Ditto. I was surprised at the change snugging the plugs had on my compression tests.

Hope that's it.

[willowbilly3]

Ditto. I was surprised at the change snugging the plugs had on my compression tests.

Hope that's it.

How do you do a compression test with the plugs in?
Another thing that can cause a fluctuation like that is float level.

[SteveC]

well taking the plugs that were wooshing and tightening them helped.. alot. It idles smoother now the rpms dont drop anymore, the vacuum gauge nolonger moves up and down with every miss. And the truck starts a lot better warm( It would act like the engine is dragging).

Thanks for the help guys