Autolit 295 ?

[50farmtruck]

I know I should have searched here first, but I bought some Autolite plugs from NAPA today & they sold me 295's. It seams like most folks here run 306's. Should I exchange them? 295 = resistor & 306 = non resistor correct? What does this mean to the engine? My engine # is T310-30244 & I'm pretty sure it's a 230.

Thanks,

Bryan

[Don Coatney]

Resistor plugs cut down on radio interference. Is the heat range of the plugs in question the same? Heat range is the distance from the water jacket to the electrode.

[50farmtruck]

I was reading another post that listed the heat range of a 295 as A7 & a 306 as B7. I don't know what that means though. I read somewhere else though to run a hotter plug for long periods of low RPM & a colder plug for long periods of high RPM. The more I read on the subject, the more confused I get.

Bryan

[Alshere59]

Heat range is basically just how hot the center electrode is which you probably found in your research. Since they do have a optimal temperature it is a good idea to look at to keep it from fouling if to cold etc. To see if it is correct for your engine look at this link (while for racing) as it gives some good information on what to look for. I normally like to do some highway driving maybe 5 miles and then read them. Just the way I was shown and really don't have the why on that.

As a general rule of thumb yes a hotter plug for slow speeds etc but on our flatheads I am not sure this is really needed if your showing a band roughly in the center of your ground strap you should be good. Factory recommendation should get you where you need to be on heat range assuming a stock engine. Higher compression dual carbs require a closer look. IMHO

Hope it helps.

http://www.max-boost.co.uk/max-boost/internet_articles/Spark%20Plug%20Reading.htm

Edited May 21, 2011 by Alshere59

[50farmtruck]

Thanks Alshere59, that link is very good. I've read a number of articles on the subject but none with such clear pictures. Very helpful. I haven't got the truck to run yet, but it seems like these plugs will be fine for getting her started. I have Mystery Oil in the cylinders & all so I'll be changing them shortly after getting it fired any way. Then maybe I'll go to 306's just to ease my mind.

Thanks for the help,

Bryan