C3Paul

I have been searching CF and internet to find out the correct spark plug heat range for my engine, but not having much luck.

My engine is 383ci with 10:1CR and aluminium heads and almost stock HEI with upgraded high voltage chip.http://www.ecklerscorvette.com/corve...1975-1980.html

I have bought these spark plugs but am not sure if the heat range 4 is little too hot?
http://www.ngk.com/more_info.asp?AAIA=&pid=2656

NGK heat range goes from 10(cold) to 1 (hot)

What heat range would you recommend for the initial starting point?

I would like to stay with NGK product as it is easily accessible in the UK

capevettes

I have been using NGK UR4 plugs in my 383 in my 61 for many years. Runs great. It is 10.25:1 compression, 202/160 iron heads.

Ironcross

The same heat range used before the change

MotorHead

I have been using the same spark plug for years with aluminum heads that is NGK V-Power BKR6E it is medium cold and I never had a problem with them on a 550HP and now 600HP small block, they are 3 bucks each
V-Power Resistor Spark Plug
14mm x 3/4" Reach
5/8" Hex
ISO projected
Gasket seat

http://www.ngk.com/results_cross.asp...on.y=12&mfid=1

C3 Stroker

On my previous 383 with AFR 195 heads, and also with Trick Flows, I used AC Delco FR3LS's which were recommended by both companies. The current number for these is AC #41-629. These worked out perfectly for me.

For NGK and other brands, cross refence with this link:
http://www.sparkplug-crossreference....DELCO/FR3LS%20

MotorHead

Pretty much the same as I run, as the cross-reference calls for NGK BKR6ES and says:

"A cheaper alternative are NGK BKR6E plugs, but they won't last as long."

So maybe you will only get 50,000 miles on them

MotorHead

That is a tapered seat plug, he might be looking for gasket seat plug, you have to be careful in this regard