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Spark Plug Suggestions for 56 D500 315 hemi
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56D500boy
Posted 2017-05-15 5:25 PM (#540089)
Subject: Spark Plug Suggestions for 56 D500 315 hemi



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In preparation for removing and painting the valve cover(s), I investigated what was needed yesterday. "Discovered" that the spark plugs have to be removed because they go through holes in the tubes (which then work like washers for the spark plugs) and the tubes and their rubber gaskets overlap the holes in the hemi valve covers. No biggy. Just interesting for a hemi noobie like myself to discover.

In doing so, I discovered that the shop I had try to get the engine started back in Sept.(2016) had installed AC Delco R43S spark plugs.

Doing a cross-reference on AC Delco R43S shows up a few options including:

Autolite 175
Autolite 4275
Autolite 84
Autolite 85

I checked to see what Dave Homstad recommended (http://webpages.charter.net/dhomstad/D500EngineFrame1Source1.htm ):

"Spark plugs:

Original plugs were Autolite 4S-250.

Champion RJ12YC
AC R44S
Autolite 85
AC Rapid Fire #7

So, the Autolite 85 was common to both lists.

The mention of the Autolite 4S-250 as the original plugs led me to check out the Mopar 55-58 parts pdf. See below. Didn't really help. I can't find a specific D63-500 listing for the plugs.

I did find the 4S-250 listed in the 56 Dodge AMA pages for the D500.

Then I searched on 4S-250 and found a link back to this forum and long discussion about long reach and short reach plugs for the D500 hemis. It just made my head hurt:

http://www.forwardlook.net/forums/forums/thread-view.asp?tid=16105

I think the plug that I removed was a relatively short reach plug, certainly not 3/4" of thread.

HELP!!??











(EarlyMoparHemiCrossSection.jpg)



(EarlyMoparHemiSparkPlugListings.jpg)



(EarlyMoparHemiD500SparkPlugListing.jpg)



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Attachments EarlyMoparHemiSparkPlugListings.jpg (228KB - 30 downloads)
Attachments EarlyMoparHemiD500SparkPlugListing.jpg (233KB - 34 downloads)
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56D500boy
Posted 2017-05-15 8:13 PM (#540098 - in reply to #540089)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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Location: Lower Mainland BC
I think this settles the long reach vs short reach question. D500 hemis want the short reach:

http://www.forwardlook.eu/Dodge/TSB/Dodge_TSB_October_18,_1957.pdf





(57_D500_ShortvsLongReachPlugsTSB.jpg)



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60 dart
Posted 2017-05-16 12:03 AM (#540121 - in reply to #540089)
Subject: Re: Spark Plug Suggestions for 56 D500 315 hemi



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unless you find/use the earlier plugs , autolite 85's is about all you're gonna find in the right heat range ------------------------------------------------------later

Edited by 60 dart 2017-05-16 12:04 AM
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udoittwo
Posted 2017-05-18 9:07 AM (#540317 - in reply to #540089)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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R43S is a colder plug used in most Hi-Po MOPARs and GM small blocks of that era until the GM 350s came out. It will foul faster with lower grade fuel of that era. Good for HARD driving. Not practical for normal street use.
R44S was used in performance and regular driving. Best all around plug with the fuel of THAT time.
R45S or R46S is used in most of these older cars today because it is hotter and less chance of fouling on todays fuel especially if you do a lot of around town driving. The R45S will give you the performance with todays fuel. R46S is good for "normal" driving.

None of those plugs you have listed will harm your motor. Mostly it depends upon how you drive and what type of gas you use.

RJ12Y was Champion's overall performance/driver plug of that era. Similar to the R44S or Autolite 85.

The RJ10Y is about the same as the R43S or 84. A cold hi-po plug with a short life span and prone to carboning up. These plugs aren't used in much today with todays fuels.

Bottom line in currently available sparkplugs, you should use the same as the R45S or by manufactorer -

AC R45S,
Autolite 86, AP86, AP4275
Bosch WR10FC
Champion RJ14YC
Motorcraft A42C, AS42C
NGK XR4, XR4VX
Nippondenso W16PR-U


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udoittwo
Posted 2017-05-18 10:17 AM (#540319 - in reply to #540089)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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P.S., if you have any interest in trying the MOTORCRAFT 84[same as R43S, the AC plug reccomended for HI-PO MOPARs of this era], I still have some NOS sets I think they are from the 60s or 70s. They have slight surface rust but only around the area where the socket grabs and not on the top terminal or threaded area. Maybe it can be seen in my pict. but I will guarrentee it will not affect how the plugs work. I have used them in my 67 GTO and they work fine.

IF anyone is interested, I have have 34 NOS plugs, enough for 4 + plug changes. $40 TOTAL and I will ship them. A little over $1 a plug is a very good price.

Later,
Karl.



(DSCN6458.JPG)



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56D500boy
Posted 2017-05-18 10:34 AM (#540321 - in reply to #540317)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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udoittwo - 2017-05-18 9:07 AM R43S is a colder plug used in most Hi-Po MOPARs and GM small blocks of that era until the GM 350s came out. It will foul faster with lower grade fuel of that era. Good for HARD driving. Not practical for normal street use.


Thank very much Karl for the detailed answer. Very informative. I will look for the R45S plugs locally.

PS: I am running Chevron 94 in the old dear. This is the best fuel available (other than race gas) available to me. I run it in my 93 Audi 9.3:1 20valve five cylinder 350 hp turbo engine as well. Very little pinging even under 26 psig boost.

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Powerflite
Posted 2017-05-18 2:08 PM (#540342 - in reply to #540098)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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56D500boy - 2017-05-15 5:13 PM

I think this settles the long reach vs short reach question. D500 hemis want the short reach:

http://www.forwardlook.eu/Dodge/TSB/Dodge_TSB_October_18,_1957.pdf



No. All hemi's and hemi-based poly motors should use long reach plugs. This bulletin doesn't address hemi motors at all. It basically says 2 things:

1. 1957 325 poly motors used to specify short reach plugs. Now in '58 they changed them to use long reach plugs because it worked better for them.

2. 1958 big block motors (D500) use the short reach plugs.

It doesn't discuss hemis at all. But all hemis use long reach plugs. By the way, there is a typo in the memo. In the second paragraph, they say LD-3 1957. This is an oxymoron because LD-3 is 1958. It is clear that they meant to say 1958 instead.

Edited by Powerflite 2017-05-18 2:34 PM
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56D500boy
Posted 2017-05-18 4:03 PM (#540353 - in reply to #540342)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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Powerflite - 2017-05-18 2:08 PM
56D500boy - 2017-05-15 5:13 PM
I think this settles the long reach vs short reach question. D500 hemis want the short reach:
http://www.forwardlook.eu/Dodge/TSB/Dodge_TSB_October_18,_1957.pdf


No. All hemi's and hemi-based poly motors should use long reach plugs.


Okay that hurt my head. I *just* bought a set of new R45S and then came home and read the above.

So I phoned our local early hemi expert Norm Frey (actually his son Mike) and his answer was short reach including the R45S. He suggested that I count the threads in the head to confirm when I remove the valve cover to paint it this weekend. That will solve the problem of conflicting suggestions.



Edited by 56D500boy 2017-05-18 4:04 PM
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udoittwo
Posted 2017-05-19 7:54 AM (#540397 - in reply to #540089)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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I'm sorry, I guess I messed up? I can't find any other listing then the AC R45S for the 1956 D500. Incase you don't know the term, "reach" is the length of the threaded area. A R45S has 3/8" of thread that goes into the head where a "long Reach" has 3/4" of thread. In 1957-58 they DO call for a long reach 3/4" reach plug [AC R45XLS] for the D500. Same heat temp but a 3/4" reach instead of the 3/8" reach.

Long reach plugs were usually used in aluminum and or super high compression heads because the short reach had a tendency of blowing out and stripping the threads out of the head. The longer reach gives a lot more thread surface against the soft aluminum.

IF your motor DOES call for a long reach, the R45S short reach plug should not hurt but won't burn the fuel as well BUT putting a long reach in where it calls for standard 3/8" short reach may cause damage by putting the plug further into the combustion chamber where it could hit the piston or valves.

Again, I did not know it called for a long reach but do not install a long reach unless you are totally sure it calls for them.
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Powerflite
Posted 2017-05-19 10:40 AM (#540403 - in reply to #540397)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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I stand corrected. It looks like the Dodge hemi's do use a short plug - at least for the 270 motor. I have a loose set of 270 hemi heads and I installed a short reach plug from a big block into it. It looks like the right amount of extension into the combustion chamber. Just be sure to remove the washer from the plug first. The '55-up Chrysler hemis do use the long reach.

Edited by Powerflite 2017-05-19 10:51 AM




(Short Reach Dodge.jpg)



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56D500boy
Posted 2017-05-19 10:57 AM (#540404 - in reply to #540403)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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Powerflite - 2017-05-19 10:40 AM I stand corrected. It looks like the Dodge hemi's do use a short plug - at least for the 270 motor. I have a loose set of 270 hemi heads and I installed a short reach plug from a big block into it. It looks like the right amount of extension into the combustion chamber. Just be sure to remove the washer from the plug first. The '55-up Chrysler hemis do use the long reach.


Sorry but you "experts" are making my head hurt. Lesson learned.

I will confirm the thread situation when I remove the right bank valve cover this weekend to strip and paint it.

BTW, I've had conflicting opinions on the sparkplug gasket. Some say the "tube" is the gasket/crush washer. Others say you still need the crush washer with the tube because the "crush" provides tension that keeps the plug tight.

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56D500boy
Posted 2017-05-19 8:17 PM (#540426 - in reply to #540404)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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In the interim, I found a spark plug conversion chart.

The AMA 56 Dodge document suggests that the OE 56 315 D500 hemi spark plug was an Autolite 4S-250.



Searching for 4S-250 turned up a conversion chart that lists the AC Delco R43 as the equivalent 3/8" reach plug with R44 and R45 progressively hotter.



Edited by 56D500boy 2017-05-19 9:08 PM




(SparkplugConversionChart_Annotated.jpg)



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56D500boy
Posted 2017-05-19 9:27 PM (#540432 - in reply to #540426)
Subject: Early Hemi Spark Plug Installation Procedures



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Found this stuff from the Imperial Club's website:

Bottomline = no spark plug gaskets.







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udoittwo
Posted 2017-05-20 7:34 AM (#540446 - in reply to #540404)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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I'm guessing that is supposed to be a shot at us when you said "you 'experts' are making my head hurt. Lesson learned". Sorry for your headache but I am not an "expert" in anything and don't claim to be. I simply answered your question. Unless you have some exotic motor or not original to the car, ALL 1956 Dodges/V8s used the same as an AC R45S. I was trying to explain why the R45S as issued in 1956 may not always be the best application with todays fuels and driving habits.
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56D500boy
Posted 2017-05-20 9:37 AM (#540449 - in reply to #540446)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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udoittwo - 2017-05-20 7:34 AM
I'm guessing that is supposed to be a shot at us when you said "you 'experts' are making my head hurt. Lesson learned". Sorry for your headache but I am not an "expert" in anything and don't claim to be. I simply answered your question. .


I liked your first answer Karl. It was Powerflite's first (adamantly long reach) and second (oops, short reach) answers that did my head in (sorry Powerflite but...). Your second answer was reacting to Powerflite's first (long reach) answer.

My "lesson learned" is I need to do more of my own due diligence on these matters and not necessarily rely on the opinions of Forum Members, especially when they are as conflicting as I got. It's settled now. Short reach. (Thanks for that photo Powerflite in your second answer).

Now my issue is gasket or no gasket. The original tech info said no gasket, just use the tube, but that was for a R43, not and extended nose R43S (or R45S). I also found some comments on that (which I will consider):

https://www.jalopyjournal.com/forum/threads/331-hemi-oil-leak-throug...



Edited by 56D500boy 2017-05-20 9:38 AM
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Powerflite
Posted 2017-05-21 7:36 PM (#540546 - in reply to #540449)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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Yeah, after I wrote that I realized that I may have stuck my foot in my mouth so I decided to offer the best answer in terms of a trial fit to make up for it.
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56D500boy
Posted 2017-05-21 8:00 PM (#540547 - in reply to #540546)
Subject: RE: Spark Plug Suggestions for 56 D500 315 hemi



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Powerflite - 2017-05-21 7:36 PM Yeah, after I wrote that I realized that I may have stuck my foot in my mouth so I decided to offer the best answer in terms of a trial fit to make up for it. :)


You're forgiven. I have BTDT on another forum where I am not a Noobie but one of the self-proclaimed "experts". Back peddling hurts but if you make a mistake, it is always better to correct it than to ignore it.

Someone once said, "It's not the mistakes that you make, it's the solutions that you find to correct that mistake and the number of innocents that have to be silenced to maintain your air of infallibility"



Edited by 56D500boy 2017-05-21 8:01 PM
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