George,

I have been using REM38S plugs for about 1,000 hours. My engine is an O-320-D1F 8.5 compression, 160HP Lycoming. I run as lean as possible for a carbed engine. As far as I know, the 38 has been the standard recommended plug for this engine. Should I be considering cooler plugs?

Lorn

> From: George Braly <gwbraly@gami.com>
> Date: February 14, 2012 7:51:26 AM EST
>
> Colyn,  let me respond.
>
> a) So far,  only the Champion fine wire plugs are showing a significant problem with cracking of porcelain on the central electrode.
>
> However,  since the scrutiny started - - an unrelated collateral issue has arisen from observation of the frequently encountered high resistance of the internal RFI  resistor.  THAT issue is identical for both massive plugs and fine wire plugs.   That problem is not nearly as significant as the cracking insulator problem.
>
> b) TAT has no evidence that the Tempest plugs have any issues of any kind.  Fine wire or massive.
>
> c) We do prefer the 29 heat range plugs.   If they were available we would recommend 27 heat range plugs.  The reality is that the only people that need high heat range plugs are people who operate with rich mixtures - -  to keep down plug deposits.  With routine lean mixture operation there is so far no discernable plug deposits on colder heat range plugs.    I have personally operated a set of experimental  -27 heat range plugs for several hundred hours.  The plugs remained clean.   In general,  everyone should attempt to identify and operate with the coldest heat range plugs that do not create deposits or accumulate oil.
>
> d) I think this is covered above - - -
>
> Regards,  George

--
Lorn H. 'Feathers' Olsen, MAA, ASMEL, ASES, Comm, Inst
DynaComm, Corp., 248-345-0500, mailto:lorn@dynacomm.us
LNC2, FB90/92, O-320-D1F, 1,800 hrs, N31161, Y47, SE Michigan