72 C3 small block - what plugs?

[GreigM]

Ok, so every time I touch my car I break something. Hot on the heels of my oil pressure gauge issue (fixed after a blow out of the line with some compressed air) I was taking the plugs out to clean them after it got flooded and managed to break one (think it may have been old and brittle).

It was a NGK BPR6FS
However, on the other side of the block I have
NGK YR5GP

Its an unmolested '72 small block 350.

What is the correct plug to use? And does anyone know the plug gap?

So that I'm not just taking from the forum, let me give back a couple of pics - it really is a thing of beauty.

 

[62 C1]

I have a 383 stroker in my C1 which was built by Peter Knight, a very good engine builder and he recommended NGK BR6EF

 

[teamzr1]

Look at the face of the head where sparkplug mounts
if the face is tapered then must use Tapered Seated plugs and not flat ones

Here is a website that shows for 1972 350 CI sparkplug types

spark plug cross reference

www.sparkplug-crossreference.com

Use this website to enter any sparkplug model number, and it shows other makes and brands
I think 45TS is one step hotter

If I recall, Denso bought up NGK as to plugs

 

[GreigM]

Yes, both are tapered. With a bit of digging I got the specs from the ngk site and both look the same physical dimensions. I think the YR5GP is an older US plug, so will go for the BPR6FS and fingers crossed (given it is more available in the UK). BPR6FS on left here, YR5GP on right. The one 44TS above is pretty much the same, slightly shallower reach (by 0.4mm) but it can't be a problem or I'd know by now

 

[teamzr1]

Yes, both are tapered. With a bit of digging I got the specs from the ngk site and both look the same physical dimensions. I think the YR5GP is an older US plug, so will go for the BPR6FS and fingers crossed (given it is more available in the UK). BPR6FS on left here, YR5GP on right. The one 44TS above is pretty much the same, slightly shallower reach (by 0.4mm) but it can't be a problem or I'd know by now

The YR5GP is Platinum, so think they would be a bit more costly than the nickel ones
Gap is a bit different, depends on how engine idles if one is better gap than the other

 

[Mad4slalom]

Ok, so every time I touch my car I break something. Hot on the heels of my oil pressure gauge issue (fixed after a blow out of the line with some compressed air) I was taking the plugs out to clean them after it got flooded and managed to break one (think it may have been old and brittle).

It was a NGK BPR6FS
However, on the other side of the block I have
NGK YR5GP

Its an unmolested '72 small block 350.

What is the correct plug to use? And does anyone know the plug gap?

So that I'm not just taking from the forum, let me give back a couple of pics - it really is a thing of beauty.
View attachment 26104
View attachment 26106
View attachment 26107

You are not wrong , that looks gorgeous in that colour

 

[Roscobbc]

Ignoring the other manufacturers spark plugs and concentrating on NGK's number system - the number in the centre of the plug part number indicates its heat range. So as shown above with numbers 5, 6 and 7, with 5 being 'hot', 6 'mid range' and 7 being a little colder.
The other numerals like R relate to it being a resistor plug (to minimise radio interference) and E relates to electrodes (if I recall correctly)
Cold range NGK plugs extend to 8 and 9. These will generally used for extended high speed operation, perhaps racing use.
If your engine is 'old school', so with a carb (especially if oversized and/or a 'double-pumper' with secondary 'squirter's) perhaps modified with a larger carb, headers and a 'hot' cam its quite possible that your engine requires a richer idle mixture and larger 'squirter' settings or jets to overcome the cams poor vacuum signal.
This in turn can create potential spark plug fouling when/if the car is used for extended low speed urban driving. Typically a hotter range plug would be specified to 'burn-off' any carbon deposits that could potentially foul the spark plug.
However correct spark plug selection is not just about heat range selection, other factors are equally important.