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Spark Plugs 38 Century


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While going over the vehicle, I removed what seems to be original equipment; a set of AC 45 Acniter spark plugs... They're bit worn, may be usable, but I decided to replace them with a new set... I sourced a new set of AC Delco R45's which appear to have a much narrower electrode than the originals and also have fewer threads per inch... Did not like that at all.. On top of that and to my surprise, yes! to my surprise, they are made in China!  AC Delco Made in China.;(   Sorry but, aside from looking a little scrawny, I don't want them in my car, I rather put the old ones back.. Am I splitting too many hairs here?

 

Do you guys know of anything better than the new Delco R45? I found a set of period correct Blue Crown-Husky M5 (made in the USA) that are listed as an interchange to the old R45 Acniter plug. Anyone ever used them? As far as newer interchanges, Autolite 3076 might work but have not confirmed...

Thank you.

Edited by philipj (see edit history)
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3 hours ago, philipj said:

have fewer threads per inch

 

?? AFAIK, all 14 MM spark plugs have the same thread pitch. Therefore the same number of threads per inch.

 

Can you post a picture of both plugs?

 

Here is the AC spark plug chart I posted in another thread.

 

 

Spark_Plug, AC chart.jpg

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So Bob is selling the reproduction AC R45 plugs? I have seen photos of the reproductions with the number 45, but without the words acniter. Please let me correct my statement about the fewer threads... The older plug is cut all the way up, but the new one has a  blank area near the top that is uncut... In other words, I can count the number of rows/threads on both and the original has 2 more because it is cut all the way up. I have photos, but I am having trouble with my phone.. As soon as I can resolve the problem I will post them. Thank you.

 

This is a photo of the new AC Delco Green Stripe #45...

 

AC DELCO Spark Plugs Green Spripe #45

 

21530-2_zpse0fb94a0__20793.1463179130.jpg?c=2&imbypass=on

Edited by philipj (see edit history)
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ACDelco has not offered a non-resistor 45 type plug in years. The plug you show might be a licensed reproduction product if it is new, was there any info to that effect on the box or sales info? If not licensed I would be careful. The ACDelco R45 plugs are available at your local parts stores and Bob's. Those I have  that are of recent manufacture are all made in Mexico and don't have the exact look of the AC Spark plugs manufactured in Flint.

 

Dave

Edited by Dave39MD (see edit history)
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9 hours ago, philipj said:

So Bob is selling the reproduction AC R45 plugs? I have seen photos of the reproductions with the number 45, but without the words acniter. Please let me correct my statement about the fewer threads... The older plug is cut all the way up, but the new one has a  blank area near the top that is uncut... In other words, I can count the number of rows/threads on both and the original has 2 more because it is cut all the way up. I have photos, but I am having trouble with my phone.. As soon as I can resolve the problem I will post them. Thank you.

 

This is a photo of the new AC Delco Green Stripe #45...

 

AC DELCO Spark Plugs Green Spripe #45

 

21530-2_zpse0fb94a0__20793.1463179130.jpg?c=2&imbypass=on

 

Acniter not required on the plug. A 45 sparkplug may or may not have acniter, may or may not have the green rings, and still have been made by AC Spark Plug in Flint. All plugs made in Flint had them identified just above the area where the gasket is and they did not have the dots on the shell.  It usually said AC Spark Plug  Flint, Michigan.  That identifier was "stamped" really rolled into the shell.

Edited by Larry Schramm (see edit history)
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Larry,  The pictured plug is newly manufactured and not by AC in Flint. If you google it you will find they are being sold by a Corvette supplier as new ACDelco green stripes.  Currently 45 is not a good number in the ACDelco system. The source I googled does not mention it to be a licensed product so who knows about the engineering , actual heat range, or anything else. If I was the OP I would stick with new ACDelco R45s or NOS AC's from ebay or other sources.

 

Dave

Edited by Dave39MD (see edit history)
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1 hour ago, Dave39MD said:

Larry,  The pictured plug is newly manufactured and not by AC in Flint. If you google it you will find they are being sold by a Corvette supplier as new ACDelco green stripes.  Currently 45 is not a good number in the ACDelco system. The source I googled does not mention it to be a licensed product so who knows about the engineering , actual heat range, or anything else. If I was the OP I would stick with new ACDelco R45s or NOS AC's from ebay or other sources.

 

Dave

 

Dave,

 

I know that because it is not identified as from AC Flint.  The place that they made sparkplugs was torn down about 10 years ago and it is now nothing but a large concrete parking lot with trees growing out of it.  Just present the information to let others know when they are looking at plugs.

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philipj,

 

In reading some posts on Autolite plugs it looks like they moved production from Mexico to China sometime ago. The older application ACDelco plugs, like R45, were made by Autolite. So your China plugs maybe current production. It could  have taken years to run out of the Mexican inventory at ACDelco. Pictures of the box and plugs would help if it matters to you.

 

Dave

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  • 2 weeks later...

The new plug has the missing first thread. This may be to help start it in the hole, or it may be a cheaper way to build it. :D 

 

In the Corvair world, we have the same difference between the original FF suffix plug and the replacement F suffix plug (44FF vs 44F). AC Delco discontinued the FF and says the F (with the missing thread) is a fine replacement. The F and FF suffix are 1/2" reach plugs, I am not suggesting them as a solution, just an example of AC Delco dropping the first thread on another series of plugs with only one consequence.

 

And that consequence is: If you use the missing thread style plugs, all will be fine. Unless you then find some plugs later that have all the threads. Carbon may build up in the head in that missing thread area, and that carbon will be cut out when the full threaded plug is screwed in. Of course, you have a cast iron head, and the carbon will blow out the exhaust, so chances of this ever being an issue for Buicks is SLIM. We Corvair owners have aluminum heads, so we use a thread chaser to make sure the carbon is removed if ever we find fully threaded plugs.

 

Now, your R45 new does look like it has a more extended tip than the removed plug. What is the distance from the surface the gasket hits to the tip of the shell electrode? Larry, see any problem trying to run these plugs?

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On ‎3‎/‎12‎/‎2018 at 6:30 PM, philipj said:

As far as newer interchanges, Autolite 3076 might work but have not confirmed...

Quote is from POST #1.  3076 is a 7/8" plug, not 14mm, and thus is not an option.

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Hello Frank,

I noticed all the same things you mention... The missing extra thread as well as the slimmer electrode and what appears to be an extended tip... I was pretty disgusted thinking, AC Delco made in China, sold as a replacement, and they don't even look like the original ones-who knows how really good they are!. Unfortunately, I did not measure them and they're in the car. I still may buy the NOS Blue Crown and use those instead...

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Why don't you try running the R45 ACDelco plugs and see how they do since you already own them.  Many times the plug companies have had to consolidate part numbers, heat ranges, and extended tips designs to keep an offering available.  After running them you can always pull one to see how they are doing and most old spark plug catalogs explain how to diagnose the color and condition.

 

I have used the newer R45's in many different vehicles and have found they are just fine.

 

Dave

 

 

 

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On ‎3‎/‎25‎/‎2018 at 10:39 AM, philipj said:

New plugs compared to old and alternate NOS cross over to AC 45....

 

IMG_3987.JPG

 

 

 

Actually the plug on the left should be identified as a R45S plug because it has the "skirt"  or extended tip area below the thread area. Without seeing the number on the right plug, assuming it is a R45 spark plug.

 

The plug on the left is not labeled correctly and/or assembled correctly.  It is definitely a extended tip or skirted sparkplug shell.

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In that case, I have the wrong plug in the car right now..@#$!  Am I risking any damage here by having the longer plug? They're new out of the box labeled R45-direct replacement. The original plug on the right is an R45.

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14 hours ago, philipj said:

In that case, I have the wrong plug in the car right now..@#$!  Am I risking any damage here by having the longer plug? They're new out of the box labeled R45-direct replacement. The original plug on the right is an R45.

 

As long as they are not hitting the piston, they should be fine. You are only talking maybe 3-5mm longer tip of the plug.  It will put the spark further into the center of the combustion.

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AC 46 is no longer made, however, they are available on Ebay.  46 is one step hotter than 45.  How do your current plugs look?  If the 45s run clean (not fouling) then you're OK.  Constant city stop-and-go driving with lots of idling might warrant the 46, otherwise get up to speed on some back roads and burn-off that residue the fun way!  ;)

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The R46S (or R45S, for that matter) is an extended electrode.  The '46' denotes the heat range, so 46 and 46S are the same in that regard.  The 'S' plug has a longer reach into the combustion chamber.

 

R46:

s-l640.jpg

 

R46S:

s-l300.jpg

Edited by EmTee (see edit history)
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To answer your specific question AC 48 is the cataloged plug for a 47. I will attach Buick information below but AC info confirms the application. It is a very hot plug which suggests to me some fouling tendencies which may or may not be present in your engine. Selecting a "correct" plug for your engine is more art than science as suggested in the many responses above and in other threads. When I started selling plugs for AC we were trained to train the techs of the time to read the plugs and select the right heat range based on the customers driving style. Usually up or down a heat range from the manufactures spec was reasonable. A little old lady taking her Roadmaster out once a week and not getting it hot would need a different plug than a salesman traveling from LA to Phoenix.

 

As stated by many the non resistor plugs and most resistor heat ranges are not being manufactured so if you want a 48 , you will need to search ebay and other nos sources.

 

How will you be driving your car?

 

Dave

Straight 8 plugs.jpg

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Hello Dave,

 

Thank you very much for posting the additional information... It is good to have a correct place to start for that year engine, and I also understand your point regarding driving style.. So now I know that an R45 spark plug is too cold and the R48 would be the most appropriate since I don't drive my vehicles hard or for long distances.  It will also only be driven about once a week minimum... If I wanted to be on the safe side I could try to find some R47's but I think it may be impossible...

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Phillip, 

 

How is the car running with the plugs that are in it? As long as it is running well, I suggest you drive it and enjoy it. You also need to remember that what was original equipment might not be any more appropriate for today's gasoline than the plugs you have in it. Today's gas is higher octane than what was available in 1938. 

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All the plugs were pretty dirty and could not get the car to run right, but I think it was more of a carburetor, choke,  manifold heat control valve issue than anything else... Still, with the new gas and repairs, can I ignore the initial factory recommendation to use the R48 plug on the 1947 engine?

In my case and to play it very safe, I was going to opt for the R46 instead to be in the middle ground..

Edited by philipj (see edit history)
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Phillip, It has been asked and answered many times. Start with what you have and put some miles on it and see how it does. If you have carb problems changing plugs won't help. If everything else is right and you feel the R45's are too cold and fouling out go one higher to R46 or 46 if you can find them and see how they do. You can post some pictures of the plugs after some road trips and let us have a look.

 

The 48 plugs will be difficult to find and I would not run them today.

 

Dave

Edited by Dave39MD (see edit history)
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On thing for sure, you wont HURT it with too cold of a plug. The worst that could happen is that they will dirty up too fast. Even if that happens, I would double check carburetion/choke before assuming the plugs are the issue.

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Thank you for the advice... For the time being, I will leave the new R45's in the car and see how it runs with the tune-up and carb rebuild... I have found (Very expensive) a set of R46's that I will keep as spare and back up in case the R45 foul up... Even if I found the R48's I don't think I 'd dare to run them with today's fuels...

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On ‎4‎/‎1‎/‎2018 at 9:13 PM, philipj said:

You're correct, the R46's can be found on Ebay... On the other hand, are the R46S a hotter plug?

 

No, they are the same heat range.  Just a longer reach of the electrodes for the "S".  Both plugs are resistor plugs.

Edited by Larry Schramm (see edit history)
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