hi there, have got a 82 shovelhead which isnt running too well at the moment.
i seem to think the plugs ive got are for an earlier engine.
the heads have a cast #66 on them ? if this helps?
im curious to know if the plugs are meant to be long reach or short reach ?? if anyone knows what actual plugs are needed this would help!
thanks steve
I think my mates is an 82 will call him tomorrow unless someone posts before me. cheers burnzi
If the 66 is above the plug hole and the fins between the rocker cover are all the same height you have the early heads 66-74, they are a short reach plug Champion RJ12YC. 75 on they went to long reach , below is something i stole from another site.Hope it helps.
"TAKE THIS FWIW. It is not gospel, the absolute truth, or the American Way. It is based on my experience and those I trust. Corrections are encouraged. Head castings were changed significantly during the life-span of the Shovelhead motor. The castings have the date cast into them. Basically there were three major revisions of the head casting. The first appeared on the generator case Shovel and lasted into the early seventies. It is distinguished by a row of equal height fins in the center, between the rocker box areas. These are decent heads, but since they're old, many aren't in good shape. Valve seats were much improved over the Panhead, madeof a hardened steel alloy. However, if you find a set of these heads, be prepared to replace the seats, as most of the used ones you'll see at theswaps have been cut several times and may exhibit significant valve seat recession. The next revision came in the mid seventies, around 1974 or so and lasted until 1977 or 1978. These heads, known as 'crown' heads, had a row of fins in the center that formed an arc, or crown. The ports were opened up significantly, yet they had a lot of extra meat in the casting. This is why they make a good base casting. There's a lot of potential in them. The last revision was in 1978 or 1979. These had no "separate" fins in between the rocker boxes, just a flat area with recesses similar to fins and are known as 'late' heads. The late heads had very little extra meat in them to remove for porting work. In 1981, they changed the spring deck so that adding even a mild aftermarket cam meant you had to cut the spring seat to gain enough clearance, or fit high lift spring collars. The dates are approximate because AMF, in their infinite wisdom, used whatever castings were available at the time to assemble motors. It is not unusual to find a bone stock Shovelhead with one crown head and one early head on it. The next time you're at a swap meet and find two different types of Shovelhead castings, compare them. Look into the ports. It's pretty easy to see which ones are the better heads. Crown heads are in demand by HD drag racers and command a premium. You won't see too many at swaps
Hi Guys, It's interesting that Harley plugs list the same plug for all the late Shovels, 5R6A from '80 up. And the only difference is that the alternative recommended by other manufacturers is 1 grade hotter for 82 and later. Making them last longer before fowling?? I can only guess. Remember at the same time (82-84) Harley was playing around with other ideas, such as the extra top end drain lines and valve guide seals introduced on 82. This was to correct a supposed problem with too much oil pooling on the rocker covers and entering the combustion chamber. The drain lines only affected the 82 model year, the valve guides remained. Compression had already been lowered to 7.4 to 1, and they may have been using stop gap measures to comply with EPA regulations until the release of the Evo. Restrictions created by the new noise and pollution regs were the reason for the demise of the Shovelhead. The Evo carried the torch from then till 99. As much as I loved my Shovel, and swore I'd never ride an Evo, I now own an 89. I have grown accustomed to its face and I can still tinker. Don't think I'll go Twinny though. Another Shovel as well as my Evo would be the ticket. A man can dream. ( Or maybe not, just ask Dave.) Cheers, Cris
HI, just look down the plug hole with a torch , & measure the depth early heads are short reach spark plugs 1/2 " deep thread , later 1977/79 & up is 3/4 " deep , cheers
