Mike B Smith

Can anyone advise the best plugs for my small block, the engine has Jegs (Profiler) aluminium heads a compression ratio of around 9.25, mild comp cam with .477 / .480 lift, headers, Moroso recurved HEI distributor and Holley 670 Street avenger,at the moment I have a set of Champion RC12YC plugs and are not sure that these are the best, I am in the UK so European equivalents would be appreciated as we struggle to get US brands,

MelWff

Pro-filer makes multiple types of heads so the best thing for you to do is go to their site, find the head you have, and look at the recommended plug. Purely as an example the head below has a recommended plug of NGK R5671A-7 or colder.

https://www.profilerperformance.com/...ree-heads.html

cv67

x2 they would know best, Id use a stock heat range, sometimes going colder loses you power.

HeadsU.P.

Its like recommending best beer, pizza, burgers and toppings. Dozens of opinions. None of which would help you, sorry.

But I can tell you or warn you that the Heat Range Chart is different between brands. One company range could be 1-9 (which is the last digit on the plug number) with nine being the hottest plug. Another company a 9 could be the coldest plug.

gg521

Here is a conversion chart: http://www.sparkplug-crossreference....HAMP_PN/RC12YC

Sigforty

NGK FR5 (7373) should work decently for you.

resdoggie

I use those same plugs in my AFR 195's and they work well for the heat range.

There is no 'best' but there is 'recommended' so go from there.

REELAV8R

It's what I use as well. You go too cold and they will carbon up, too hot and you get detonation or pre-ignition. Heat range 5 in the NGK is just right for the street. You could go to up to 6 or down to 4 but I have found 5 to be the sweet spot.

naramlee

best thing for champion plugs is a garbage can... that's my .02 cents and im sticking with it... anything but them...

Accel u-groove shorty plugs are my fave, but mildly pricy... but shorter than most plugs so that can pay for itself.