ACDelco R45T vs. R45TS spark plugs

[BigRed76]

I'm getting ready for a tune-up on my '70 GMC, and it's got a bone stock 350 in it. The 350 has ACDelco R44T plugs in it now, and from what I've found that's the correct plug. Now I have two questions...
I have a set of new R45TS plugs, they are one heat range hotter, and are the "extended" plug,
Will this heat range work well? And does the "extended" plug have any advantage over the normal plug?
I have no issues with just getting the R44T plugs, but figured if I could use this set of plugs I have laying around then I would.
Thanks in advance for any opinions on this.

[MikeB]

Hard to say on the heat range. What do the 44s look like?

T = tapered seat
S = extended tip

[octanejunkie]

Here is a nice explanation on heat range from our friends at NGK

Generally, low power engines such as lawn mowers don’t produce a large amount of heat, hence use a low heat range (or hot) spark plug such as a 4 heat range. This means the spark plug will heat up easily and reach its optimal operating temperature. High performance engines on the other hand produce a large amount of heat, hence a high heat range (or cold) spark plug such as a 10 heat range needs to be used to resist the heat developed by the engine.

According to the charts posted by MikeB, both plugs you have are the same heat range, the difference is the Extended Tip - which may or may not be an issue (fit) for your application.

In my experience, if you found something that works, stick with it. That being said, I run a colder plug with vortec heads to help resist detonation in So Cal.

[MikeB]

NGK's 10 heat range is the equivalent of an AC Delco 42. Must be for a 12:1 drag race engine. (I know you weren't saying these are for street engines.)

In my last SBC, I used NGK plugs with a 5 heat range -- BKR5ES -- which seems to be somewhere around AC Delco's 44-45 heat range.

Of course, AC Delco has changed it's numbering system to complicate things!

[octanejunkie]

Originally Posted by MikeB

NGK's 10 heat range is the equivalent of an AC Delco 42. Must be for a 12:1 drag race engine. (I know you weren't saying these are for street engines.)

In my last SBC, I used NGK plugs with a 5 heat range -- BKR5ES -- which seems to be somewhere around AC Delco's 44-45 heat range.

Of course, AC Delco has changed it's numbering system to complicate things!

Was all for example, and the explanation of why heat range might be a consideration.

Personally I'm running AutoLite plugs. I based my plug choice on research, local availability and cost - obviously the are also the correct type plug for my application (vortec) and I could find a few options for hot-cold at the local parts store.

[BigRed76]

Well here is a comparison, the left plug is the R44T and the right plug is the R44TS. The length difference in the tip is about 1/8".

[MikeB]

Wow, I didn't the body sizes were different. But they appear to be to scale. If so, the plug on the left would be great for header tube clearance.

[BigRed76]

Originally Posted by MikeB

Wow, I didn't the body sizes were different. But they appear to be to scale. If so, the plug on the left would be great for header tube clearance.

I'm not sure if the body sizes are actually that much different. These are pictures from the internet since I don't have a R44T pulled out of the truck to take a picture of right now.

From researching the Napa catalog I have found that the R44T was the recommended plug for truck 350's until '77, then the catalog lists a R44T for "heavy duty" and a R45TS for "light duty".

[Wrenchbender Ret]

The extended tip plugs work much better in OHV engines. They are not for flatheads.

[67 Burb]

Just go with the R45TS plugs. That's what I'm using in my Burb. That's the plug listed for some of the 350 applications in 1971. They should be OK for a daily driver, but if you're working the truck, then maybe go for a cooler plug like a 44 or 43

[BigRed76]

Originally Posted by 67 Burb

Just go with the R45TS plugs. That's what I'm using in my Burb. That's the plug listed for some of the 350 applications in 1971. They should be OK for a daily driver, but if you're working the truck, then maybe go for a cooler plug like a 44 or 43

Yeah the truck is mostly just a driver, so I believe the heat range will be fine. Im sure that the extended tip plug won't have any clearance issues in the combustion chamber, and you'd think it would cause a better burn too

[67 Burb]

Originally Posted by BigRed76

Yeah the truck is mostly just a driver, so I believe the heat range will be fine. Im sure that the extended tip plug won't have any clearance issues in the combustion chamber, and you'd think it would cause a better burn too

I gave mine a .045 gap and haven't had any problems. It starts and runs just fine.

[BigRed76]

It's settled then, I'll go ahead an run the R45TS plugs. Thanks guys

[t.o.zwei]

This is awesome! I have always been confused why the computers always suggest R45ts and I have R44t or autolite26 in my 350's. Does it matter what head I have on the block? one set is supposedly of a 69 corvette and another set out of a 77 K20.

[James the III]

Originally Posted by t.o.zwei

This is awesome! I have always been confused why the computers always suggest R45ts and I have R44t or autolite26 in my 350's. Does it matter what head I have on the block? one set is supposedly of a 69 corvette and another set out of a 77 K20.

Yes some early sbc have plugs with a metal gasket..
The later ones use the tapered seat type..
I forget when it was changed..

[67 Burb]

Originally Posted by James the III

Yes some early sbc have plugs with a metal gasket..
The later ones use the tapered seat type..
I forget when it was changed..

The info I have is that the R44 plug with the gasket was used in the small block up to 1970, and the R44TS tapered-seat plug came in 1971.

[old blue 86]

I know this is a old thread but wanted to add info to the last post.
The change over from gasketed to tapper seat is not cut and dry.
For instance I have a 1970 441 head on my truck with gasketed
plugs, which follows the above.
What gets funny is a previous experience I had. I had 2 sets of
1968 291 double hump heads, the older ones with no holes on the
ends. One set had gasket plugs and one set had tapper seat.
Figure that one out. Same casting number and year 2 different
plug types.

[67 Burb]

Originally Posted by old blue 86

What gets funny is a previous experience I had. I had 2 sets of 1968 291 double hump heads, the older ones with no holes on the
ends. One set had gasket plugs and one set had tapper seat. Figure that one out. Same casting number and year 2 different plug types.

They must have been made on the day GM changed over to the tapered seats.

[toolboxchev]

Originally Posted by BigRed76

It's settled then, I'll go ahead an run the R45TS plugs. Thanks guys

I have used them, tried the R44TS lost a couple tenths in fuel mileage. Mine is an older motor soon in need of a rebuild. The R45TS is what I have been using for over 10 years. The 87 octane ethanol likes the extra heat stock mostly stock application. 1 step over stock Comp Cam, 76 cc chamber head, Accel Super Coil, and Eddy carb.