I read a previous thread where people were talking about using AC R45S plugs for an L46. Think the specs were originally AC R44S. Going to change plugs this week and wanted to hear some thoughts. Also gap .035"? Thanks
http://www.69corvette.com/69specs.html

 

R44S at .035 is correct.

 

Thanks

 

The newer catalogues will show a R43 as the correct plug not the 44 because the '44 is obslele....this is not correct...also its not the end of the world....the best alternstive is a 45 as a good all around plug and yes, a gap of .035

 

45s are a good choice for street use.

 

Use R45


The AC R-44 spark plug, also known as GM #5569993, was discontinued in April of 1990 and replaced by the R-43. So, the R-44 has been gone for a long time.
In the AC system "R" means the plug is the RFI resistor type; "4" means it's a 14 mm thread, and "5" is the heat range - suffixes as previously noted, which decode to other plug geometry features. Some manufacturers also use prefixes to the numerical heat range to denote geometric features. The higher the heat range number, the "hotter" the plug meaning that it runs hotter for a given load than lower number heat ranges. Most other manufacturers follow this convention, except Denso, where a higher number is colder.

For normal street and highway driving AC heat range "5" works best in all SBs, regardless of horsepower rating. It's driving conditions that determine plug heat range, not engine horsepower.
Heat range "5" AC plugs usually are the best selection for normal road operation, regardless of HP rating. Engines with TI or HEI ignitions can tolerate a lower heat range since they have double the per spark ignition energy of the point type systems so they will tolerate considerable fouling before misfire occurs

 

Thanks for the explanation

 

If your ignition is stock points, then .035" gap is fine. If you have changed over to an electronic ignition, set gap according to specs for that ignition system (this assumes that you have a coil which is recommended by the ignition mfg). The coil really determines the spark potential; the gap can be wider, if the spark potential is high enough to 'jump' it. But, .035" will work OK with any system.

 

When the 44,(correct for 70), seemed harder and harder to find, I tried the 43's,(LT1) plug. No good fouled . Went to the 45's and never looked back.
!970 11-1 msd ignition. Think 40 or 45 on the gap.

 

Thanks- going w/the 45s

 

I'm digging this up because at the autoparts store their system tells them the correct plug for a '69 L46 is an R43S. I balked at purchasing them, but has anyone else run R43S?

For my application, I would think this would be too cool of a plug. I run pretty rich, and typically just cruising.

 

You are correct the R43S is too cold. If the R44S is no longer available go for the R45S.

 

I have a 76 l-82 with mild cam.
It had some accel 276s in, and the shop recommended to us champion rv17yc
are either correct? or what should i use?

 

Last weekend I checked my spark plugs to order some to be prepared to change them. Built in is still R43S, normally darker than on pic. But at last drive before checking them I had some fun so they are a little more grey now. Pic makes it a little more white but its grey so no problem

For the moment I just adjusted them to 0,9mm and now I am looking for new ones - R43S isnt available so I will look for R44S or R45S - what would you think would be better ?

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NAPA, Autozone, and Amazon all list R43S, why do you think it is not available?

 

This has been specifically answered at least a few times directly above.

 

I thought to have read that above - as English isnt my mothers language and I live in Austria please excuse me.

I contacted AC Delco, they seem to have a dealer in UK, maybe they can send some ....

Napa / Autozone isnt existing here in Europe, european Amazon doesnt have it also


So, if R43S and R45S would be available what is the advantage of the 45s especially when R43S was the original one ?

 

Again, it's all explained in detail above (?)

 

Stocki, the R44S is the original plug, which is no longer available. The R43S is what the autoparts store list for the L46, but it is too cold of a plug. You need to run a hotter plug; therefore, the best choice is the R45S.

 

Thank you very much, you helped me to understand why