360 Plug help

[Skrawny]

Working on the new to me Dart with a 360, what I have for receipts amounts to a 4876907 short block.
Edelbrock RPM air gap manifold, Performer RPM aluminum heads, TTI headers, and a demon 750 vacuum secondary carb.

Looking at the plugs they appear to be either too cold of a plug or running to rich.

The carb is apart working on rebuilding, and has # 70 main jets and #78 on the secondaries.

What are your thought on the looks of these plugs???

 

[ch1ll]

You need to know your compression ratio before you can choose the right heat range plug. Those plugs look rich to me.

 

[Skrawny]

Looking thru the books its looking like 9 to 9.5 to 1. The short block is the lower compression one but I am not positive what all has been done thru the years also.

 

[Bewy]

Those plugs are equivalent to a NGK 5 heat range, which is correct. I would use NGK 4s, one step hotter.

 

[RustyRatRod]

The plugs do show rich, although not what I'd call pig rich, but they are reading rich. What does the carburetor have for PVRs and IFRs? Also for primary and secondary idle and high speed bleeds?

 

[TT5.9mag]

I wouldn’t change the heat range just yet. It looks close. Those plugs are pig rich everywhere. Idle, cruise and wot. You’ve got some carb work to do. Then get a new set of plugs and retest. What’s the timing set at?

 

[Skrawny]

The carb doesn't appear to have adjustable air bleeds, and the power valve in it looks like a 56 or 65 depending on how you read the numbers. The 65 power valve is the replacement in the kit.


Would i be better off with a different carb??

 

[Bewy]

For about 3 decades or more, Holley carbs did NOT have replaceable air bleeds. Carter & Rochester 4bbls NEVER had them them.

And they worked just fine.....