my engine was running super lean for a while (plug tips white). the car would run fine on normal driving but would backfire out of the exhaust whenver I got on it.

I fixed the running lean issue (didnt change the plugs though) and it started running prefectly. I changed the coil at the same time also. I checked the plugs after a day of driving aroung and part of the plug was a nice brownish color and the rest of the plug was still white. I left them in since it was running so good.

Anyway, the car was running perfeclty for the last week or so then tonight it started surging a little bit while I was on the freeway and when I got on it it started popping out of the exhaust again.

I can find no vacuum leaks, the plugs wires are in good shape and in the correct locations...I am just hoping the plugs got jacked up when it was running super lean, cause I am sick of this issue!!! I am going to pick up some new plugs tomorrow.

here are the specs:
383 10 to 1 cr
lunati 60302 cam
edelbrock heads
TTI 1 7/8 headers
rpm performer intake
670 street avenger
MSD ready to distributor
Denso alternator swap
stock coil on there now
using champion RC12YC gapped at 35

THanks for any help or ideas.
initial timing at 18 total at 38 in by 2500

Running too lean increases exhaust gas temperatures, and can melt the ground straps on spark plugs, especially with Nitrous Oxide. An excessively lean carburetor will have a tendency to surge at idle.

added a pic of plug from number 5. The other side of the plug is brownish...this side is white...

Looking at the picture, it looks like the spark plug is the wrong heat range. The RC12YC is a fairly hot plug. You really need a cooler heat range, like a C63YC. I think the NGK R5672A-8 is the equivlent to the C63YC, but usually is less expensive.

Can running too hot of a plug cause the issue I'm having? New plugs and the carveuns great for about a week... Then the problem comes back....

The more you advance the timing the more it affects your fuel mixture, 38 degrees is at least 3 degrees more than i've ever been able to run in a 383. Check your dizzy and make sure the advance is working correctly. You corrected the lean condition, hope you re-jetted it. Wheres your LM1 or 02 sensor? I'd run those plugs, they look fine to me. If it was too lean the electrode would show heat damage, none is aparant from the pic.

That white is just a leaner idle curcuit most likely, i'd fatten it up a bit or jet it up, the street avangers are on the lean side from the factory. And if you look closely at the ground strap, you'll see the blue heat mark, it should be right in the middle of the strap between the tip & base, Its closer too the base, that meens it has too much total timing, i'd lower it to 35*, most every BB i've built run the best at 35* & no more.

Hello franken, your fuel air mixture burns at a constant time whether your engine is running at 1000 rpm or 6000 rpm. Thats why you advance the timing to start the burn earlier at high rpm so the F/A mixture hits optimum burn around TDC. If you start the burn to early the mixture has already achieved optimum burn befor TDC and acts lean on the cylinder. Richening up the mixture overich conceals the problem but you're not making optimum power just burning more gas. Class dismissed.

I have not used the street avenger carb, but I do have a 670 truck avenger carb and the transition circuit was lean. I think the idle restrictions were 0.025" or smaller. I drilled them to 0.028" and it really helped fix the off-idle stumble, and I was also able to get more adjustment from the idle mixture screws. Before, I had the mixture screws about 3-turns out and the mixture screws has very little effect. After drilling the restriction, I was able to set the idle mixture screws at 1-1/2 turns.
I think the colder plugs would make it easier to read the plugs. I have been using the NGK V-Power R5672A-8 spark plugs in my Brodix B1-B/S heads for years with no problems. I am also running them in the new engine with the Edelbrock Victor heads, but I have not looked at the plugs in that engine yet. I am not sure why replacing your plugs helps? If the plug gets too hot it can cause pre-ignition. I mean really, if you have to replace the spark plugs anyhow, why not try a colder heat range?

The stock Jets on a 670 Street Avenger are 65 primary and 68 secondary , I would try the 68 secondaries Jets in the Primary side (since you have them already) they might be a touch to Big , may be 66 / 67 will work better , and the secondaries try some 71 / 72 and see what happens , on the Street Avenger the Gaskets should be re-usable.

I would say for a street driven car those Champion 12's should be OK. The plugs look nice and clean but I think a 670 carb is just not enough. Also I agree with earlier posts, many times the surge you feel can simply be too much timing.

Ideally I would say go to a 750, if not, try 35 total timing and maybe 2 jets up in the primarys.

I run NGK 6's in a 11:1 440, equal to Champion 10's. I would recommend NGK V-power XR5's for you.

I actually was running a 750 holley and it was leaking a bit of gas..and I already had a 670 street aveneger sitting in my garage...so instead of fixing the 750, I just threw the 670 on it.

I am going to lower the overall timing to 35...but I am not comformtable with recurving a distributor other than changing the springs...the springs I have in there now give me 18 degress advance by 2500 so I would have to set the initial to 17 for now...

I have also never changed jets...I am pretty much self taught with all this stuff...so there is a lot that I am unsure of...

Well my friend no better time than now to learn. With that set-up you are going to start sometime.

Changing jets is easy. Four bolts hold the front carb bowl to the main body/metering block. Remove bolts (drain gas from bowl) and there are your 2 jets sitting there waiting to be changed. Check size and go up 2 sizes and see if that makes a difference.

to check plugs properly you should be taking a blast down the highway, pull over and shut the motor off clean and look at the plugs.

Ok, well doing what I can right now...the problem has gone away.

I turned down the timing to 17 initial and 35 total. (18 mechnical advance) and I pulled the coil to test the resistance and it was out of spec with what it should be so I picked up a MSD blaster 2.

Left the plugs that were in it and took it for a drive. Ran great with no popping out of the exhaust and the surging went away also.

So it looks like a big part of problem was a bad coil!

I will be ordering a jet kit to see if I can fine tune it more...but the main issue seems to be fixed now. (bad coil!)

THe coil was pretty new (only in the car for a week)....just an auto part store stock replacement. Other than it just being a piece of junk out of the box, what could cause the coil to go bad? I checked and with the car running I have 6.8 volts at the coil..so it doesnt seem to be getting too many volts.

I am pretty sure that the MSD blaster doesn't even need a ballast when using the ready to run distributor...? (I already 12 volts directly to the distributor) Would piping the a full 12 volts to the coil give me better spark?

THanks all!

The voltage on a stock coil is reduced through the ballast resistor to about half of the avaiable voltage so 6.8 sounds about right. Read the papers that came with your new coil. Normally you have 12 volts to the MSD box and it supplys the voltage to coil. If you are not using an MSD box putting to much voltage to the coil will cause it to overheat and shorten its life.

Does it say "Made In China" on the bottom of the bad coil? That's where I'd start. (No offense to you Chinese mopar fans...)