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From: Lorn H Olsen <lorn@dynacomm.us>
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Subject: Re: Tempest spark plugs
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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
>=20
> Colyn,  let me respond.
>=20
> a) So far,  only the Champion fine wire plugs are showing a =
significant problem with cracking of porcelain on the central electrode.
>=20
> 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.
>=20
> b) TAT has no evidence that the Tempest plugs have any issues of any =
kind.  Fine wire or massive.
>=20
> 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.=20=

>=20
> d) I think this is covered above - - -=20
>=20
> 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