Benefit or danger of hotter plugs

[charge69]

 My Charger has a tendency to foul plugs.  Right now it is running R12YC or something like that Champion plugs. Would it be acceptable to go a heat range or two hotter (13 or 14 Champions) to remedy this problem? I do not know about these things so, maybe I should go a range or two colder! Another brand?

Any suggestions on a better plug?  I am running 11 to 1 compression JE forged pistons with a CompCams hydraulic roller. Also have original, but rebuilt AFB carbs that are supposedly right as far as A/F ratio for my engine. Headers now so no heat to the intake manifold and it is a little cold blooded but idles in neutral just fine when warmed up.

[cdr]

unless you are starting the car a lot without driving it,the plugs should not be fouling.

[charge69]

Well, I do occasionally start it without driving it but I usually bring it up to temp before shutting it off. More often than not, I do drive it for a short while. It does seem to "load up" in gear at idle even after it warms up. I am thinking it might be more of my carb-tune at fault here but, .... I don't know.

[cdr]

i sounds like a carb issue.

[BSB67]

If you have 11:1 CR and running a Champion R12YC, you are already too hot in my opinion.  I suspect your problem is elsewhere too.

[firefighter3931]

Agreed with the above ; plugs are too hot allready and the problem lies with fuel delivery.  

Just out of curiosity : where is the base timing set ? A combo like that with a big cam and lots of compression is going to want lots of spark lead.


Ron

[c00nhunterjoe]

On top of timing, arent you running 2 4's? Big cam and 2 4's can be a challenge to tune for low rpm idle and cruising without loading up if you are not patient

[charge69]

Sorry, been out of touch for a while.  I am suspecting fuel delivery also as it runs like a top at higher rpm's and tends to load up in gear at idle! The carbs (original 2-4bbl. AFB's) were supposedly completely rebuilt and tuned on a test mule engine but, I think I have either a needle and seat problem overwhelming the bowls or a bad accelerator pump (not sealing properly) on the primary or rear AFB.

I have a digital-6 MSD ignition that starts at 0* and moves up to 20* BTDC @ 900rpm. It idles at about 1000 to 1100rpms when warmed up.  Not sure exactly when it is all in but I think we set it at 3000rpm with a total of 35* advance.  No pinging or pre-ignition or, at least, I cannot hear any and it runs great at higher RPMs.

simple question, when setting the idle on these 2 4-bbl cars, do you adjust only the rear carb?  The front carb, although the holes are blocked off does have a screw that will adjust the idle speed up or down. I have left it alone after making sure it did not touch the linkage and just adjusted the idle speed with the rear carb.

Guess I will look at carbs and accelerator pumps again, readjust the float height and put some colder plugs in and see what happens!

P.S. A vacuum gauge shows about 12 to 13 inches of vacuum at idle!  I am running a stock Hemi convertor (supposed to be about 2500rpm stall). Could that be the problem that it is pulling the engine too far down letting the timing drop back to 0 as it falls below 900rpms?

[charge69]

I did look at the MSD ignition booklet and it says the ignition retard goes away at 800 rpms and will not come back until the engine is at 500 rpms. I do not think my engine drops to below 500 rpms when I put it in gear but... if it does, the ignition retard to 0* might be fouling my plugs.

[BSB67]

I did look at the MSD ignition booklet and it says the ignition retard goes away at 800 rpms and will not come back until the engine is at 500 rpms. I do not think my engine drops to below 500 rpms when I put it in gear but... if it does, the ignition retard to 0* might be fouling my plugs.

I'm not familiar with your ignition system.  Are you saying that is continues to drop timing to 800 rpm?  Ideally, you don't want to pull any timing at all below your normal idle.  If your normal in neutral idle speed is 1000 rpm and has 20° of initial, you do not want it to drop below 20° when you pull it into gear and your rpm drops a lower rpm.  If you have a large cam, it might like even more initial timing.

[charge69]

My Charger starts at 0* timing to help the starter and puts in 20* timing above 800 rpms when it starts. I like to idle the car at about 1100 rpms in neutral/park and when I put it in gear, the idle drops significantly.  I do not think it drops to 500rpms or less but the MSD box will revert to 0* timing if the engine drops below 500rpms.  My total timing is 35* at about 3000rpms and it runs great at 3000rpms or above. No detonation issues that I can detect.

I have come to think it is a carb issue but the MSD could actually be exacerbating the problem if the engine drops below 500  rpms.  My tach does not work on my Charger and I do not know if this is happening for sure but .... Maybe I will turn off the "auto-retard" and see how it performs.

[BSB67]

I like to idle the car at about 1100 rpms in neutral/park and when I put it in gear, the idle drops significantly. 

Let me ask it this way.  What is the timing at 1100rpm, and what is the timing in gear?  If your timing in gear is less than your timing in neutral, you need to fix that, for starters.

[firefighter3931]

I like to idle the car at about 1100 rpms in neutral/park and when I put it in gear, the idle drops significantly. 

Let me ask it this way.  What is the timing at 1100rpm, and what is the timing in gear?  If your timing in gear is less than your timing in neutral, you need to fix that, for starters.

The Engine is getting pulled down by the converter making carb adjustments more difficult. The converter is too tight for the current engine combination. When the converter is "right" your idle speed should only drop 200rpm going from neutral to drive. 


Ron

[c00nhunterjoe]

Sounds like you need a partner behind the wheel so you can check your timing while its in gear. Start there. ASSUMING the msd is not retarding the timing at idle, you might want to try bumping your initial up to 22 or 23°. You might be surprised.

[charge69]

My timing light seems to have "disappeared" from around here and my friend says he doesn't have it so ....... Another timing light is in order. Think I'll get one that shows RPMs also.   I am suspecting the torque converter is too tight for my combination and that will be a real headache to change out! Just might be easiest to pull the engine and tranny with the TTi headers and x-pipe system installed!

First, I'll check timing and get the numbers and check out carb floats and other things carburation

[Kern Dog]

If you have 11:1 CR and running a Champion R12YC, you are already too hot in my opinion.  I suspect your problem is elsewhere too.

For years I ran the RC12YC plugs in my 493. I also had a problem with "dieseling" after shutdown. I switched to the colder  RC9YC and the problem stopped.

[charge69]

I do have a set of "10's or 9's" around here and it might be worth a try!  Easy to change on a HEMI. The Charger runs great from 2000rpms up but, sometimes, not all the time, it will load up and need to be revved up to clean it out! After it gets up to operating temp, it idles just fine in neutral pulling about 13 in. of vacuum.

Meanwhile, a new nice timing light that shows timing in degrees and RPM is in order.