Re: Spark Plugs

Posted by su8overdrive On 2013/3/11 17:38:08

Amen. Have been using AC M-8s for decades. First in my '40 120, now my '47 Super Clipper and they give good service, the heat range seems to be spot on. Friends with '41 Cadillac-ack-ack-ack-ack-ack-acks report the same,
and they have at 7.25:1, slightly higher compression than 1940-47 Packard 8s and Su-8s' 6.41 and 6.85:1 tho' my '47's running a '48 327 head for 7.5:1 my auld mechanic having worked in postwar Packard and Hudson garages, knew about this in the day per an obscure Packard Service Counsellor bulletin.
A friend's run a 288 head in his '42 One-Sixty drophead for decades using M-8s without a hitch. Someone told me long ago that as old stovebolt Chevy 216-ci ohv sixes also use the small 10mm plugs, AC continues to produce these for the South American, etc. markets. I hope they and others continue to do so or we're sunk.

BTW, have oft wondered why Packard didn't go higher, 1942-47, than 6.85 compression from the factory given Clark Street's 7.25 since an inline eight is inherently smoother than a V-8 and would allow a slightly hotter cam in the win-win bargain. Any engineering insight? I know the horsepower race wasn't on 'til the '50s, but Buick got a lot of PR out of the power from their compound carbed 1941-42 320, and Packard did increase 356 compression from 1940-41's 6.41 to 6.85:1 from 1942-47 to match Buick's advertised 165 hp---and not as far from the truth as most makes' claims, Packard's among them, according to Flint engineeers tests of all makes at the GM Proving Grounds.

Cadillac complained about Buick's corporate oneupmanship, tho' part of that was Flint's cheek in marketing a few Brunn catalogue customs for 1941.

NO interest in what ifs, coulda, woulda, shoulda Monday morning quarterbacking. And please don't tell me Packard didn't care about such, because i've got a '47 Super Clipper ad crowing about "....the most powerful eight-cylinder engine ever cradled in a production car." The extremely limited production Duesenberg J and blown '37 Cord 812s notwithstanding, that was true regarding torque, but the compound carbed 1941-42 Buick did trump Packard 356's hp and yes we know a 356 with twin carbs would be 190 or so blah, blah, blah.

The point is, Packard cared, so why didn't they boost compression a wee more? The flathead Cadillacs didn't ping
at 7.25, my '47 doesn't at 7.5, nor does my friend's 42 160 ragtop at 8:1, and you know Packard engineering ran all manner of tests, war work or not.


? Anyone?