My 66 is running a slightly modified 350 (mild street cam, headers,Quadrajet, and Performer intake). I started out using AC R45TS plugs gapped at .045 which worked great for awhile until they started fouling. Today I decided to go with a hotter plug and installed a set of R45TSX plugs factory gapped at .050.I'm not a plug guru but feel that I'm going the right way. The R45TS's worked okay but all 8 of them I took out were black with carbon, not chunks of carbon surrounding the tip, but just a carbon hue on the entire end. What should I expect from the the TSX plugs and is the .050 gap good to keep?

I'd gap them back down to 0.035-0.040
0.050 seems quite large

AC R45TS is a pretty good plug, actually a nice warm plug. Find out why its carboning or fouling the plugs.
Is the carb running rich?

Dave

What ignition do you run? it could be going bad too. It may not be the plugs.

Ron

What ignition do you run? it could be going bad too. It may not be the plugs.

Ron

I'm running an HEI with no upgrades. Maybe a Blaster coil would help me out. I do think I made some progress with the TSX's because I checked one of them after yesterday's drive and It looked almost pefect.

I don't have my plug book handy--isn't the TSX designed for a .060--.080 gap? (Isn't that what the X signifies--an eXtended gap?) Closing it up to .050 probably has the side electrode not aligned properly with the center electrode.

My first thought is that your old plugs were probably the correct heat range; but you've got an over-rich mixture leaving all that carbon on the plugs. Might be rich at idle; cruise, or heavy throttle--but I bet the fuel curve is the problem not the plugs.

Both plugs your running are the same basic heat range ,just different gap/tip type.

Higher # in AC plug = hotter plug and lower # = cooler plug

That being said how long was it running the with r45ts plugs before they fouled?

1wk 6months or 100 miles 3k miles?

And i also aggree the 45''s are a good heat range for a street perf sbc,maybe even 44's in some cases that are setup to run very clean/dialed in very well.

Anyway,if the plugs fuel fouled fairly quickly and you verified the float is ok,float lvl is ok,no dirt is in needle & seat,chock blade isnt stuck and is opening fully,fuel pressure isnt over 6-7 psi max ,then i you need to go in this direction.

Since your running a perf cam what base timing are you running?

If its less then 16-18 deg its retarded and the motr retarted the worse things when it comes to intake vacuum/carb signal goes.

In that case you to have to adj the prim throttle plates so far to get a decent idle they can be paretially or fully out of the idle circut causing the motor to be idling more in main circut then idle circut which is too rich.

And with a q-jet if it has a strong power piston spring for a stock motor that has higher idle vacuum its even worse. That's because in that case the stronger power piston spring will prematiruely pull the prim meter rods partially or fully out of main jets at idle too . Then if the prim throttle blades are adj past /out oi idle circut/position the motor will run very rich .

I see this issue time and time again when people run perf cam in street motors,its a veyr common issue,most perf cam neeed at least 3x-4x more base timing then a stock GM cam needs.

So check the base timing with idle low(6000-650rpms) and vac adv unhooked/plugged and tell us what its at.

Set base timing to 16-18 deg and look for approx 36-38 total and things should be be better.

But if that results in a better/stronger running motor but still has rich issues then you have to take an idle vacuum reading with auto trans in gear .

Then after you get that info choose a power piston spring that approx 1/2 the idle vacuum in gear and try that.

Summit still sells eledbrock q-jet power piston spring kits in case you need them.

Scott

Yep, Scott is correct, for AC plugs the # represents the heat range...the higher, the hotter...

The TSX's came pre-gapped at .050. I checked them all before installing and they were all real close. I think I'll leave them in and try a different power piston spring because the base timing is already at 16 and total is 36. The engine runs strong with everything set like it is. As far as how much time I put on the TS plugs...no more than a couple hours which included everything from tuning, idling in the garage, and 3 or 4 test drives of about a mile each. I am also running 4.5 PSI to the carb. I found this to be the sweet spot on my regulator.

your plugs are expected to look that with the usage you mention. Get that thing out on the freeway for 50 miles, let it clean out. The old plugs are probably fine if allowed to burn off the carbon built up during the idling. 3 or 4 test drives of a mile each = carboned up plugs.

No, an aftermarket coil won't help.

bigger plug gaps are better, those TSX plugs are cool.

Like Tom said try to get the car out for a decent ride to see of the plugs clean up.

If yes great but if not then i would chk out the carb related items i suggested further up in this thread to see if that gets it squared away & running cleaner.

BTW,your timing is close enough/ok where it's at even though you could try 18/38 to see if the motor responds well to it & doesn't detonate with the additional 2 deg timing on both ends.

The fuel pressure @ 4.5 psi sure isnt over driving anything either so your good to go in both those areas ,that's for sure.

Scott

My 66 has a stock rebuilt 350 with stock heads, a Performer intake, an Edelbrock 1406 four barrel carb, headers, and an unknown too big cam. Even with 60 psi compression in one cylinder before the rebuild. all the plugs burned pretty clean and alike. Since the rebuild they seem fine, although I have only checked once at about 300 miles. I have the RT45s, new and apparently a 75 HEI dist. From what you are saying, I would try leaning the carb some, I don't think ignition would be the prob.

Thanks for the replies. I guess it's time for a road trip!