Just fired up my 250 for the break in. Runs great, but the spark plugs on 1 & 2 and 5& 6 are mostly black. 3&4 are nice and tan. I have a clifford intake with a holley 390 cfm carb. Like I said the engine runs great. Does the added length of the outer intake runners cause this?
Thanks, Herb

Install another set of plugs & check again. Or glass bead your plugs & reuse & reinstall.

Checking the plugs while idleing is not the way to check plug readings IMO.
Especially if if has a rough idleing camshaft.

With the Clifford intake, it sends a poor/weak signal to the carb, the intake runners are huge.

MBHD

Is the intake heated

Change the heat range on those plugs may need a hotter Or colder plug.If that clifford is one of the Older(first kind) It may have ribs in it under the carb. If so remove at 3 of them.You can reach in the intake runner and grind them do smooth to the floor. The runners worked to well and would lean out 3&4.

doggone it learn somethin new every day.
I have an older Clifford, think it has the ribs but not sure, I will look. Unheated too.

Larry,
I checked and my Clifford has those ribs.
Are you saying that will lean out 3-4 at IDLE or at FULL THROTTLE (or both?)

My understanding it would pretty much do it to both. The intakes i have done for guys and Guys that have done it themselfs Say It made a difference in over all readings and Idle issues (plugs Loading up) And Racers used to use 3 difference Heat range Plugs The end two (1&6) (2&5) (3&4)is how they paired the Plugs. This was done more by many Racers & mainly for the single carb set-up because of the UnEqual runners. I personaly never ran one of those older intakes.( with the runners)

Sorry for the late response Been outta town the intake is new

I would not worry about it too much.
Just get a wideband O2 reader/gauge so you can get it dialed in just right.

MBHD

The intake is heated. I'm not sure what a wideband o2 sensor is.
The truck has not been driven as of yet.

I use the LM1 wide band reader to tune my Syclone.
http://www.ebay.com/itm/Innovate-LM-1-Di...b2fd06a&vxp=mtr

I have this for my inline 6 http://www.innovatemotorsports.com/xcart/product.php?productid=16290&cat=262&page=1

Using a wideband O2 reader takes out the guess work on what yoyr engines A/F ratio actually is.

No real need to pull out your spark plugs to try & read if the engine is lean, rich or who knows what.

It will allow you to see your engines A/F ratios from the drivers seat. From idle to part throttle, the full throttle.
It is an accurate way to see if your carb is jetted correctly.

I would never tune w/out one, makes tuning so-much easier.

MBHD

I assume I'd have to have a port in one of the exhaust pipes. It has dual exhaust.

You can have a O2 bung welded in both exhaust pipes.
http://www.ebay.com/itm/O2-BUNG-for-OXYG...1b3f3b0&vxp=mtr

So you can read 3 cylinders @ a time, swap back & forth.


MBHD