Spark Plug Length

[my69]

Just bought a new set of ACDELCO plugs #R45TS. When I removed my old AC plugs (same numbers) they are about 3/16 of an inch shorter. Whats up with that? Is this going to make any difference? Are there two types of ACDELCO plugs with the same number? Any help would be appreciated.

Thanks

Mike

 

[brusso]

Not sure about differrent lengths for same part number, but the longer the porcilan the hotter the plug. On shorter porcilan plugs, the heat has less distance to travel to the cars cooling system, so they run "cooler".

 

[Jack]

I can't tell you why there may be difference in lengths ... but if sp is even a little too long it can hit top of piston (bad). A 69 probably has small combustion chamber heads ... the spark plug location may be lower & closer to piston than in later models ... 69 may also have higher comp pistons (higher tops/domes) ... placing them closer to plugs. If, over the course of time, the heads may've been milled and/or block decked ... the plugs' location will be even closer to pistons. Before going any further, suggest check close for interference ... be cautious.

Somebody set me straight here ... is a R45TS a "tapered seat" gasketless plug? ... and did a 69 come with gasketed plugs???
JACK:gap

 

[Tweek]

http://www.acdelco.com/html/pi_plugs_ident.htm
Jack, this should help in your plug ID, I didn't want to type all that info, but yes it is a tapered seat (R45TS). As for the 69 being gasketed plugs, my book says and all the cross references I can find on original motors from the Vette (350, 427) that they are.

Ron

1969 motors listed for corvette with spark plugs my book calls for
350 ACR44... 0.035 gap
427 (390hp) AC43N...0.035 gap
427 (435hp) AC43N or AC43XL...0.035 gap
427 (430hp) AC43XL...0.035 gap

 

[my69]

My motor is not original. I believe it was replaced in the 90s.

Mike

 

[Tweek]

Mike, a head casting number would help in your search, but as Jack said, if someone changed pistions, machined heads or decked the block you could be flirting with trouble! Are you sure there isn't a "X" at the end of the plugs, because they could have the same number, but be longer with the suffix "TSX" instead of "TS"

 

[my69]

Thanks everyone. I appreciate the help.


Mike