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Post Info TOPIC: Spark plug help


Etobicoke On Rod-side Member

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Spark plug help
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I was getting ready to install my plugs but the thread on the AC Delco R45S are to short.

The plug bottoms out well before the threads can get a good bite. 

I don'r recall the SBC head number, but the plugs screw in straight.

I bought new R45S but now that I recall the old plugs I had were from the previous heads on the engine. 

 

Anyone know what would be a decent plug to use?

 

IMG_20171105_1335165.jpg 



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Brockville On, Old Autos Star

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R45 's are about 5/8" shorter than the 45S, the S version is an extended tip.

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Etobicoke On Rod-side Member

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So I took a bit of a break to clear my head.

Tried again and I think the plug seat is the issue.

Take a look at the plug and you can see where it is rubbing and will not thread in.

The threads are fine as I have no issue running my plug thread chaser 

IMG_20171105_1419419.jpgIMG_20171105_1423450.jpg

 

 



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Etobicoke On Rod-side Member

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So it turns out that the body of the plug is a few mm's too big in diameter.
Will not let the plug fully sit.

I took a flap disk to one plug to see and ground down to the same diameter of the crush washer and had no issue threading the plug all the way in to the seat.

Question is, are there plugs out there with a slimmer body?

IMG_20171105_1501343.jpg

 

IMG_20171105_1501539.jpg



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London On, ELTA Member

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Frank,
I have NEVER seen such a thing with A/C 45's. I wonder if they're the new Chinese sizing??? Are you sure they are the right plug for the head. Some of the newer heads take the 5/8ths head plug and not the 13/16ths.



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Etobicoke On Rod-side Member

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Stamped made in USA

I am going to pick up a different plug tomorrow and see. After all that, pulling what little hair I've got, I remember changing the heads but don't recall what they were.

Might be a conical seat, which is a thinner plug from my searches.

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Niagara Falls Member

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rochie wrote:

Frank,
I have NEVER seen such a thing with A/C 45's. I wonder if they're the new Chinese sizing??? Are you sure they are the right plug for the head. Some of the newer heads take the 5/8ths head plug and not the 13/16ths.


   Thats my thoughts to. The 5/8 plugs are probably what you need.



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Toronto On Member

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Try an R45TS AC spark plug. It's a tapered seat plug that's used on later cylinder heads and the socket size is 5/8".

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Etobicoke On Rod-side Member

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Bruce Rossiter wrote:

Try an R45TS AC spark plug. It's a tapered seat plug that's used on later cylinder heads and the socket size is 5/8".


 ThanX Bruce, 

These are the heads that I had got from you and completely forgot that I had put them on my block.

Purchased plugs that were the same as the ones I had in my parts bin that came off the old heads with out thinking.

 

Hitting the local jobber in the morning.



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Courtice On Rod-Side Member Pin Striper

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I'm using what Bruce recommended on 993 heads.

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Etobicoke On Rod-side Member

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Picked up a set of AC Delco R45TS, they are in and now to get the plug wires on and looking neat.

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Hamilton On Rod-side Member Amsoil Dealer

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The larger plug (R45S) has a flat seat in the head and uses the gasket and the smaller plug (R45TS) is a tapered head and uses no gasket so check the head and you will tell which plug it uses.

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Toronto On Member

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58chev wrote:

Picked up a set of AC Delco R45TS, they are in and now to get the plug wires on and looking neat.


 It's good to hear the R45TS plugs did the job for you and they are the right plugs for that cylinder head. I wasn't sure which heads you were using until I looked at the washers on the plugs in your picture. The washer compressed into a taper indicated that you had a tapered seat head.



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