Thread: need help finding plugs for my sbc....

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i'm trying to figure what plugs to run in my car.....i work at a parts store and can get pretty good deals...i have a 350 running about 10.3:1 compression with cam headers double bump heads milled to 60cc with dished pistons and the works and am having trouble finding plugs to use...i found normal ac's burn out quickly(cr43ts), i ran NGK's before but cant remember the number and they ran good UR4 seems to ring a bell i think u looked plugs for a 350 outta a vette...i tried the acdelco rapid fires they were a little pricey so i thought what the hey...nothing but problems!!! will work great for a while then all the sudden miss miss miss...spray the headers and find which one is missing clean it and its good again for a while...now i read people saying run projected and some say non projected tip any reasons why...pros & cons? whats a stock sbc plug non projected?? not sure.....i have a msd coil and module as well so good spark...so if anyone has any recomendations or part numbers it would help alot...i was looking a NGK iridiums but thats $80 plug change at my price...

hey, ive been using ac delco R45TS gapped at .045... 350sbc... im at about 10.7:1 CR bored .060 over... have to run 94 octane or better or it runs like TRASH. They seem to last a decent bit but i like to change them about once every 2-3 months... I've also learned if you let the car warm up properly *living in a cooler climate anyhow* then the plugs should last a bit longer.... but myabe its all in my head

r45ts or rc8 are taper seat if old humper they would not be. look up number for the year of heads and go to the stock hp out put for that engine and cross it to what you want you may want to drop to a colder plug if you have a good ingnition like msd or stock hei you do not need them hi rent plugs i like autolites deneso or bosch

You want to avoid precious metal fine wire plugs such as platinum and iridium in high performance engines because the fine wire has a tendancy to heat up and cause preignition. From what I have heard, AC Delco plugs are the most resistant to burning up in high compression engines. I've run all kinds of plugs and the only one that every gave me trouble was an NGK because of a cracked insulator. I don't associate this with the manufacturer, though. Someone probably dropped the plug while it was in the store.
Maybe you should consider a colder plug? You should also run non-projected tip plugs in high performance engines. Projected tip lugs give slightly better fuel efficiency, but the delicate ceramic insulator is stuck way out in the combustion chamber where it is subject to damage. You say you have to clean your plugs, though. Are they fouling or are they burning up? Fouled plugs could be an indication of too cold a plug, too rich a mixture, or oil consumption.

or all the above yes it sound like you may have some tune up work to do .the plugs in a good in tune engine will last alot longer that .

where all double bumps heads(no accesorie holes) non tapered plugs i can remember the casting numbers

they did not come out with tapered plugs late 69 or70 look it up if you work at a parts store

well i'm gonna try some r43s plugs and see how it runs or some ngk XR5 i might run ngk i've always had good luck with them...i'm running a acdelco rapid fire #1 right now i think its tappered so oops....i switched heads last summer and never thaught about it....which is dumb cause i shoulda know that....