Question: Spark plug R45TS issue

[Stage Left]

I think I'm going nut's

First it was the oil filter deal PF25 Vs the new PF454 not having the same rubber seal size as the PF25. So I'm using a Purolator oil filter PL20049

Now I just pulled a spark plug, and went to buy a new set. Same AC R45TS number, but the plug is not the same dimension as the old one. I only own the car for a short time, this plug could be close to the original set??? 1975

The original plug ground electrode is longer/deeper into the engine head with a shorter outside ceramic wire connection.

So the new plug groung electrode is shorter / into the engine head with a longer outside ceramic wire connection.

Did AC Delco make a change in the early years and stayed with the same spark plug number???

I did go back to the auto store and pulled one more set, same deal...
Anybody know....

[DarkShark]

Originally Posted by Stage Left

I think I'm going nut's

First it was the oil filter deal PF25 Vs the new PF454 not having the same rubber seal size as the PF25. So I'm using a Purolator oil filter PL20049

Now I just pulled a spark plug, and went to buy a new set. Same AC R45TS number, but the plug is not the same dimension as the old one. I only own the car for a short time, this plug could be close to the original set??? 1975

The original plug ground electrode is longer/deeper into the engine head with a shorter outside ceramic wire connection.

So the new plug ground electrode is shorter / into the engine head with a longer outside ceramic wire connection.

Did AC Delco make a change in the early years and stayed with the same spark plug number???

I did go back to the auto store and pulled one more set, same deal...
Anybody know....

Is the engine original? How about the heads?

FYI- the PF454 oil filter is for a big block Chevy. The Purolator that you purchased is for a small block Chevy- and fits a 1975 Corvette small block motor. So, if it fits- I assume you have a small block.

The R45TS means that the plug has a tapered seat with an longer extended tip. Assuming both plugs are 45 series... the threads are the same. 4 in 45 means that the plugs are 14mm and the 5 is a heat rating.

You may be looking at the difference between a 45T and a 45TS.

[Stage Left]

The engine is original, and yes it's a small block L48 matching numbers.

As far as the spark plugs go.... old and new plugs state R45TS on them. And yes the threads are the same just the dimension of the plug changed as stated before. Note:this old plug could be an original...looks like it anyway. But why a change in dimension.
I think I might go to the auto store and pick up one more R45TS and take a photo next to the old R45TS plug and then post to see for yourself. It's making me nut's.
Maybe possbile that AC Delco printed and S on the old plug in error back in the day.
Is that the difference between a 45T and 45TS short Vs long plug? if so, what difference would it make to the engine performance when using a short or long plug with the same number R45.

Thanks for your reply.
Tom.

[DarkShark]

Originally Posted by Stage Left

...Is that the difference between a 45T and 45TS short Vs long plug? if so, what difference would it make to the engine performance when using a short or long plug with the same number R45...

Tom-

It is my understanding that sometime in the '90s, the industry attempted to standardize designations on spark plugs. Therefore, I'm not surprised that the old plugs look different from the new plugs- especially since the old plugs may be pre-standardization. I don't think there will be a large performance gap between the designs. In many cases, when designs change- it is usually for the better!

Congrats on the new Vette!

[Stage Left]

I did send an e-mail to AC Delco earler in the week, here is their response:
Thank you for writing ACDelco,
>
> We appreciate your e-mail regarding spark plug R45TS. We did redesign the
> plug back around May 2006. It is longer and has a different rib
> configuration.
>
> It will still work for any vehicle we catalog it for.
>
> To see the recommended spark plug for your vehicle please visit our
> website

Thanks DarkShark, Also I was speaking to them by phone a they stated their data only go's back up to 15 years, could have been even more changes thru the years!

Thanks again.
Tom