Correct Spark Plugs

[Leo B]

Hi, Correct Spark Plug for R2 seems to be for example Champion J12YC. But I have dished pistons and Golden Hawk head and Paxton. Should I choose Champion like RH10C which is recommered to Golden Hawk? These pistons and head means also that my R2 has lower compression that factory Avanti R2.
Edit: I have R2 Carburetor 3507S

Edited March 28, 2022 by Leo B

[brad]

J series plugs are the reach, or more correctly, the length of the threads that screw into the head. H series would be too long for an Avanti engine as there would be sharp threads protruding into the combustion chamber. That is a recipe for hotspots and damaging pre-ignition. Avanti engines have the pockets that the spark plug seats machined deeper for the shorter plugs. I like platinum plugs like Autolite AP85. Bosch made one but they are now discontinued. Thier number was WR9FP. If you indeed have older heads, then you want the longer H series plugs. A 10 heat range is too cold. you might go the H14y used on later non Avanti cars.

 

Edited March 28, 2022 by brad

[64studeavanti]

Are you absolutely sure about the depth of the spark plug sockets being different? I have several sets of 570 heads from various Avanti engines as well as older 294, 555 etc heads. As near as I can tell, the spark plug sockets are the same. Additionally, the part number for Avanti 570 heads is the same as for non-Avanti 570 heads. How could you order,  or the parts guy get you the correct head, using the same part number?

[Leo B]

OK. Rockauto.com suggest H14Y for Golden Hawk. I have understood that Golden Hawk has 535976 Head and Dished Pistons.
I thought that Golden Hawk Head difference the to R2 Head is that 535976 combustion chamber is smaller (more to piston area) and there for the spark plug threads can be longer. I dont have R2 head to compare.

[Gunslinger]

5 hours ago, 64studeavanti said:

Are you absolutely sure about the depth of the spark plug sockets being different? I have several sets of 570 heads from various Avanti engines as well as older 294, 555 etc heads. As near as I can tell, the spark plug sockets are the same. Additionally, the part number for Avanti 570 heads is the same as for non-Avanti 570 heads. How could you order,  or the parts guy get you the correct head, using the same part number?

It's not the sockets that are different...it's the length of the threaded portion of the plug and how far into the combustion chamber the electrode protrudes.  They each use the same socket to install and remove the plugs.  

[64studeavanti]

Perhaps terminology issues. I realize that the J and H plugs have different reach.  There are some noted Studebaker folks who insist that the Avanti heads are machined differently for the shorter plug. I am obviously not one of them. All 570 heads have the same part number. If the machining was different, there would be a separate part number so they could be ordered correctly. Additionally, it has been my observation that all the heads I have, regardless of casting number, are machined the same for spark plugs.

[Leo B]

Hi, Thanks. I Understand. Heads are different (combustion chamber) https://www.studebaker-info.org/Tech/Heads/Headcasting.html
There for Head 535976 is thicker in the plug area and has more threads. I will use H14Y 1/2 reach instead of J-series 3/8 reach.

 

[64studeavanti]

I don't have any 582 heads for comparison, however the studebaker part number is the same for the 582 casting for trucks as well as R2. It is logical that the heads are the same as well. The heat range is likely more significant than the reach. Studebaker originally recommended J9Y for Avanti and JT engines. A hotter plug J12Y was specified in a service letter with J10Y being one step cold for sustained high speed driving. I believe they also specified a hotter plug H18Y instead of H14Y for non Avanti/JT engines.

I believe the H series plugs have a 7/16" reach. I do not believe H14Y are available. However many have been successfully using  Autolite 437.

[Leo B]

52 minutes ago, 64studeavanti said:

I believe the H series plugs have a 7/16" reach. I do not believe H14Y are available. However many have been successfully using  Autolite 437.

Yes.

Champion H14Y 7/14" 11,2mm reach and J12Y 3/12" 9,5mm reach.
https://fi.gsparkplug.com/1x-champion-spark-plug-h14y.html
 

Autolite 437 = Champ H14Y
https://www.sparkplug-crossreference.com/convert/AUTOLITE/437

[64studeavanti]

J series plugs have 3/8" reach. H series plugs are 7/16". The thread on both is 1.25mm which is roughly 20 tpi for us non-metric folks. The difference in reach is  1/16". That is approx 1.25 threads. The 1.25 thread difference is likely not significant. 

 

Since your motor was not a combination engineered by Studebaker, I would start with Autolite 437 or equivalent and check the plugs after a couple thousand miles to determine if you need to go hotter or colder.

[mfg]

Champion J12Y's have always worked great for me!

[Leo B]

26 minutes ago, 64studeavanti said:

J series plugs have 3/8" reach. H series plugs are 7/16". The thread on both is 1.25mm which is roughly 20 tpi for us non-metric folks. The difference in reach is  1/16". That is approx 1.25 threads. The 1.25 thread difference is likely not significant. 

 

Since your motor was not a combination engineered by Studebaker, I would start with Autolite 437 or equivalent and check the plugs after a couple thousand miles to determine if you need to go hotter or colder.

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