[ihc] RE: Plugging Rob

["Jim Grammer" <jgrammer@xxxxxxxxxx>]

Hi Rob -

I take it the book was an Autolite application guide? Where IH published
spark plug info it was invariably Champion IIRC. The late '70's light truck
operators manuals called out J10YC's, which is an obsolete # AFAIK. Champion
guides steer you to a J12YC, which according to the Champion heat range
chart I have is the projected nose equivalent of the J6C. That prolly makes
Greg's recommended J8C something like a J14YC in projected nose(not on my
chart, Greg?).

On the Autolite chart, the 85 is 1 step hotter than the 303. Autolite has
more heat range steps than Champion, so the steps may be closer together.
Lots of anecdotal reports over the years suggest fewer fouling problems with
projected nose plugs of either brand. There does seem to be some 'Ford vs.
Chevy' mentality around plug brand selection, but in general folks seem to
prefer the Autolites' durability. There has been the occasional report that
going from an 85 to a 303 cured a ping problem, this goes to Greg's point
about the effect on apparent timing and overall engine tune. The ping could
have been cured by changing the timing curve, but the plug swap was an
expedient. I think I prefer to run projected nose plugs for the variable
heat range effect and fouling resistance, and tune around them. I still need
to reduce the overall timing in my Travelall for just this reason. Running
premium gas does the trick for towing the way it's currently set up, but
ouch!$$$$

Jim

Date: Tue, 20 Apr 2004 21:14:12 -0700
From: "Robert  Marks" <scoutmarks@domain.elided>
Subject: [ihc] spark plugs

Long time lurking, as I have been too busy with work.

Some time ago, discussion about spark plugs said to use the Autolite
85's and not the 303's.     The 303's were used in the 74 and later 304.
345. 392's according to the book.  I take it the 303 are a hotter plug
for emissions reasons?  Any ideas?


Rob Marks
NW Binders