Fouled Plugs?? [Archive] - Chevelle Tech

: Fouled Plugs??

Chevy 70 SS vert
Aug 4th, 07, 11:38 PM
On BB's I have heard that in the past that they are known to foul spark plugs. Today my car while driving it it started acting funny as if it was missing on acceleration (so I suspect a plug is fouled). I haven't had a chance to pull the plugs yet. Spec's are below

454 bored over .060 to a 468
Quadrajet 750cfm recently rebuilt, been running real strong.
10.5:1 Compression-Pump 92 gasoline
Ac delco 44 plugs ( don't remember the letters of the plugs)
Timing set @ 10-12 degress before.
Newer ignition wires.
Pointless ignition.
New coil-last summer.
New Dizzy dist cap-Last summer.

Car has been running great till this afternoon.

Anybody else foul plugs on their BB's? Is this something common?

Aug 6th, 07, 12:15 PM
It depends on the state of tune your car is in, if it's running rich any engien can foul plugs. Id go ahead and try new plugs and wires as well unless they are real new. They can look fine on the outside but still be bad.

Aug 6th, 07, 1:09 PM
CHAS,its the state of tune and cond of motor that fouls plugs,its not being a bbc or sbc that determins that.

With that said AC 44's are a fairly cool plug, not real cold but many sbc & bbc run better with 45's on the street esp if the motor see's a lot of stop/go traffic and not a lot of open road higher speed cruising that tends to keep the plug cleaner.

I dont know what your heads are so i dont know if your runing std reach r44's or the longer reach r44n. If your running the longer reach r44n try r45XLs which has a slightly extended center porcelin.

What this does is help the plug resist fouling in traffic by having the porcelin deeper into the heat of the combusion area which helps to burn off depostis at idle or slower engine speeds.

But when your cruising at higher speeds or getting on it the opposite happens because the higher flow rate of air & fuel can now cool off the porcelin keeping the plug from overheating.

I run the extended tip R44XLs type plugs in my 396 with speedpro forged 9:7 comp mildomed pistions with my strock 063 heads and block/heads were miled for rbld and still not plug clearacne issues of any kind if your running the extended tips.

Also make sure your plugwires are in good cond,if in doubt get a good quality set of spiral core wires that have a lot less resistance per ft then cheap std duty carbon core wires,the additional current flow to plugs can help them to fire if they are getting dirty untill you hit the open road to clean them off at higher cruise speed.

Run a copper or brass terminal dist cap & rotor to lower resistance vs the AL contacts which allows even more current to the plugs & run a little hotter stock size/looking coil like a pertronics 40k volt.

Running all these higher quality lower resistance ign parts along with a little hotter stock looking/size coil (pertronics 40k volt) will help a plug fouling or misfire situation. But it wont fix a way over rich & or oil use issue,it will just extend time breween plugs fouling in that situation.

But also make sure to chk the motors idle vacuum (auto in gear) to ensure you have the correct power piston spring in your q-jet. This is to ensure the power piston spring isnt lifting the perimary meter rods out of the mains too ealry like partially up at idle or when just off idle at slow speed/s which will end up with an over rich mixtutre. This can eventually fuel foul plugs esp if they are colder plugs along with low grade ign parts like cheap high resistance carbon core wires and cap/rotor with AL contacts,all junk Iign parts in MHO.

Lastly,you stated running only 10-12 deg initial,that approx 6-8 deg retarded which is substantial. The retarded initial timing can causee lower idle vacuum enough so to cause a low speed idle or off ilde rich mix from carb due to the 8 deg retarded initial timing casing lthe ower intake vacuum.

So since your running an aftermarket perf cam adv the initial to approx 16-18 deg along with possibly beefing up your ign system parts along the way too.

But check the total timing to ensure its aprox 36-38 . If its over 38 at 3k rpm or when reved over 3k rpm to like over 4k rpm then you will have to get the mech adv in the dist recurved for approx 20 deg mech all in by 3k rpm.

But dont retard the total to get it back down to 38 total if its over tha. Thisis because the initial will also be retarded deg for deg what you retartd the total to get it back to 38 which os what some people do beacuse its easier but its the wrong thing to do for a proper street perf ign curve.

But running the initial like 8 deg retarded gets you lost power,wasted fuel,soggy feeling motor,hotter running motor,etc which is just not a good thing.

Then 20 deg mech + 16-18 deg initial = 36-38 total.

Have a vac adv installed with approx 14 deg additonal adv for better part throtle resp & fuel economy on the street.

As always listen for ping after these changes and if you hear some back off the initial a couple get to hopefully get rid of it assuming your running 93 oct fuel in your perf bbc like you should be with the comp your running.


Chevy 70 SS vert
Aug 16th, 07, 9:36 PM

I will try you suggestions Scott.

Last I checked it was running 38 degrees total advance on the timing.

781 heads ported polished bowl blended and cc'd.

No sign's of running rich (Fat).

Aug 17th, 07, 11:29 PM
Chas,even though your running 38 total which is fine you still need to chk the initial timing which should be approx 16-18 deg.


Chevy 70 SS vert
Aug 20th, 07, 9:12 PM
I pulled the plugs over the weekend all were lite gray and clean except for one which was oil fouled as that spark plug wire was disconnected at the Dist cap. Pplugged it back it and problem is solved. :-) But I now own a set of R45XLS's so next time they need changing I will switch them over to the 45's.

Runs awesome!

Thanks for the responses guys!