NGK Plug recomendation

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roccodart440

roccodart440

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NGK seems to have two heat ranges for the 440, a (4) and a (5).

They are the XR4 and the XR5.

Anyone have any experience with these or any recommendations?

Engine is a 440, 602hp 10.5:1, 260@.050, .650, 112LSA, eddy RPm heads
 
Assuming the lesser number is the colder, I would try the 4.
 
I run BKR6E in my 10.2/1 340 and my bone stock 360 magnum… not so sure on 440’s but I would try the 3 between 6 and 4 to see how she runs..
 
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Edelbrock Perf RPM head requires a 14mm x 3/4" reach plug. XR4 & 5 are short reach plugs. 4 is hotter than 5. 10.5 compression with 600 hp should probably be in a 5 or 6 heat range depending on fuel type and quality. Maybe colder yet? Some NGK numbers to look at would be FR, or GR series, R5671A-_, or R5672A-_ series. 5/8" hex would be recommended for headers. Not all of the race series plugs are available in -6 heat range. What plugs were used to dyno at 602hp? May want to follow with the same.
 
Picture is a BKR6E posted

10.5 - 1 383/432 Eddy E Street Heads 75cc

I called NGK and asked what plug

Anyways

I tried the 5 at one point and the threads on the plug showed color four/five threads down , to hot
8BF727C0-D79D-4422-9B53-7F91AF3E19E0.jpeg
 
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Not too hot. Look at the grd strap. Colour change is half way through the bend, perfect.
 
Sorry guys

That picture I posted is a BKR6E

I reworded my original post

Thanx Scott
 
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