Need advice, plugs fouled, backfiring thru carb UPDATE

Basic combo info - 340/W2; .557 cam, Proform 750 DP, Victor W2, MSD 6AL, MP distributor with Firecore cap/wires, RC9YC plugs. Cam 2 100 octane.

Car will hardly run, very hard to start. It ran briefly the other day when it was real warm out but then not again today when it was colder. Most of the time it turns over but will not fire/run.

Verified spark with inline spark tester, seems to be OK. Actually shocked me pretty good at one point. Verified proper MSD operation by breaking pickup circuit, nice blue spark. Fuel is pumping for sure, it's fouling plugs.

Distributor was out at one point so I have not been able to verify correct timing after I put it back in but it's close. I made a reference mark before I took it out, it's probably around 15-20 advanced but I can't say for sure. # on distributor plate is 13.

Carb has been apart a couple times after backfiring. Checked all gaskets to see if they're covering any holes, all appear OK; blew out all the orifices, cleaned all the carbon, checked the power valve (front only) works, holds vacuum. Did the floats on the bench but not while the car was running. 6.5 PV in it but last time I checked vacuum at idle it was under 7.

Verified engine/distributor timing like 8 times. Checked firing order/wires good.

So mostly it turns over but won't fire. I suspect some of the problem has to do with insufficient spark. I had a battery go down and replaced it but all the start attempts have drained the new one too.

Did a compression check, all except #t5 were 175-180 psi. #5 was low at 120, squirted some oil in it and it went up to 150. I understand the #5 might not sound so great but it should run on 7 even if #5 was totally dead.

I have gotten it running a few times but it won't stay lit without keeping the throttle pretty far open and it won't idle. The plugs keep fouling then it won't start again. It also pops through the carb when cranking and when the throttle blades close. Gas in the body caught fire a few times when attempting to get it running.

I feel like I'm killing the thing trying to get it running. The starter is gonna be toast soon too.

I know I may be chasing multiple things here but I can't really isolate anything until it runs.

Hope someone has a suggestion on how to keep this thing running. It sounds OK when it's going.

Thanks for any suggestions.

Here's a pic of the #1 plug.

Attached picture 8079856-IMG_0115.JPG

Posted By: RMCHRGR

Re: Need advice, plugs fouled, backfiring thru carb - 03/21/14 03:56 AM

OK, I guess I can say I made some progress since I got it running and 'idling'. Can't say where it was idling at, my tach is not hooked up but it was over 1,000 rpm for sure.

I did what Mr. P said with the timing and it seemed to help get it started. While it was running, it was @ 14 on the damper.

Got a new set of Champion RC9YCs because I didn't think they were fouling because of heat range.

So once it was running, I realized that it was REALLY lean, like piston melting lean. My A/F gauge was reading 13 and when I snapped the throttle it went to 15-16. Temp never got too high and I shut it off after a little while. I could feel it running hot.

In addition, I am still having a hard time getting it to start consistently though and when it doesn't fire, it fouls the plugs.

I went and got 3.5 PV. That was in it while it was running. I thought it might have been contributing to the lean condition so I put a 4.5 afterwards but I didn't get it running again due to plug fouling.

Seems like adjusting the throttle plates had the most affect on starting the car and getting it running. I was still popping a little but not as bad as the other day. Probably cause it's lean when running?

Man, I am lost with this, shouldn't be this hard.
Hope you guys can provide a little more guidance.

Here's a pic of the plug after it ran.

Attached picture 8082239-IMG_0122(2).JPG

Attached picture 8082239-IMG_0122(2).JPG

Posted By: RMCHRGR

Re: Need advice, plugs fouled, backfiring thru carb - 03/29/14 03:13 AM

Well, still having problems. Been through about 5 sets of plugs at this point. I can get it to run a little now and I actually had it running OK today for a bit. However...

I was watching the A/F fuel gauge and it was in the ballpark - whack the throttle and after the initial lean spike it went down to the rich side but it was idling around 13. I goosed the throttle at one point and it suddenly went way lean so I shut it off. Could not restart it after that.

Checked the plugs, still fouled. I can't keep buying plugs! Plus, this has to be killing my rings. Oil pressure is still OK I guess, was 60 psi or so at a high idle. 20W-50 VR1. I need to change it though, it's getting black and and looks thin.

Here's some things I've done in no particular order - changed coil, cap, rotor and wires. Changed plugs to a hotter Autolite 3824. Rebuilt carb for the 10th time. Replaced accel. pump diaphragms. Replaced primary needle and seat. Adjusted throttle blades again to verify transfer slot opening. Idle screws out 3/4 turn. Set idle stop screw. Checked clearance at accel pump lever, can fit a .015" in at WOT, slides in and out, can pull the bottom of the spring a little.

Seems like the only way it will start is to crank it for long time while pumping the throttle. It will spit back out the carb but if the plugs are dry enough it will fire. Mostly it won't idle unless the throttle is open kind of wide. I'm not sure why it runs and idles sometimes and not others.

Looking for more suggestions. Why is thing so rich and hard to start? Do I need a different carb? I have a TQ on the shelf...

Posted By: MR_P_BODY

Re: Need advice, plugs fouled, backfiring thru carb - 03/29/14 03:34 AM

How far out are the mixture screws... put in a set
of 12s.. dont worry about lean at idle yet.. your
in the park at 13 afr.. whats the base timing now

Posted By: RMCHRGR

Re: Need advice, plugs fouled, backfiring thru carb - 03/29/14 05:10 PM

Just to be clear, the car will run and actually seems to run OK, just intermittently. I believe the hard starting issue is what's causing the plug fouling.

Maybe I'm incorrect but I am not overly concerned about mechanical problems like a bad valve. When it does run, I don't really hear much in the way of any ticks or a miss or anything like that. The valves probably need to be lashed but I'd rather get it running consistently before I do that. Still could be hanging up but I've seen cars run sort of OK where a valve isn't even touching the seat.

I could be wrong but I would think that from the fact that it is capable of running that the pickup wires are correct. I also double and triple checked the coil wires from the MSD according to their wiring diagram - orange to +, black to ground. If I take the coil wire off the cap and crank it to fill the bowls or something, I get a good, blue spark.

The main issue I am having is getting it started consistently, having it stay running and not foul plugs.

I'm in NY, it's still pretty cold out, I'm thinking this may have something to do with it but not too much. Regardless, it's still way too rich to the point of plug fouling. I believe the carb is spitting because it's flooded, not backfiring because of timing.

I would like to switch out the carb for a known good one, I might try to make that happen. I don't have another one that would work at the moment, only a TQ and no adapter.

Float level seems correct. According to Quick Fuel who makes the Proform carbs, fuel should be halfway up the sight glass @ 6.5 psi. That's what I got. Have the pink pump cam on #2 to delay the shot a little. Power valve is a 4.5. Only in front, blocked in back. The throttle blades are closed to where the transfer slot is a little square. They're the same front and back.

I went to the parts store and got another set of plugs (#6) but I went hotter to an RC12YC. Gonna gap them to .050". Battery is charged up. Temp is about 50 degrees and drizzling rain.

Sorry for the long response. Thanks for the replies.

Posted By: DodgeCharger

Re: Need advice, plugs fouled, backfiring thru carb - 03/29/14 05:56 PM

I had a bad carb once. On a new motor. I couldn't get the car to run right. It was very rich and the car wouldn't idle. The plugs were black. I pulled the intake and resealed it. Still nothing. Then I got a known good carb. Bolted it on and the car ran perfect. I would get a known good carb and try it. If that carb runs the same it is not the carb. Then I would get another MSD box. If that doesn't correct the problem I would look elsewhere but most likely one of the two should do it.

Posted By: RobX4406

Re: Need advice, plugs fouled, backfiring thru carb - 03/29/14 06:50 PM

557 and only able to run 18* of initial, that really weak. It's only got 170 cranking pressure. Not earth shattering

I'd take a jumper cable, hook it to the neg battery and straight to the engine block. See if it starts easier. If so you found a grounding issue.

If it's not some crazy compression, doesn't appear to be, that should be above 20* timing and easily spin over.

Lots fo times those bigger cams never give you a really clean idle profile, but, you can get it better than fouling plugs. I have a 340 with stock compression and a 508 camshaft with it locked out at 36*. Starts fine even when warm out here in the desert.

Posted By: RMCHRGR

Re: Need advice, plugs fouled, backfiring thru carb - 03/30/14 12:07 AM

OK, got it running pretty well. I was even able to hot start it without too much trouble. It was running long enough that eventually I ran out of gas.

Once I got it running, initial timing was 26 degrees. Plate in the distributor is 13 so x 2 = 26. I remember now when I got it a few years ago I checked the timing and being surprised where it was at. Looked like almost 30 on the OE damper. Makes sense now.

As stated, I went to a hotter plug and it seemed to help a little. They were still getting a little carboned while fiddling with the idle but nowhere near as bad. I checked them at one point, no carbon at all. At least it was running and I was able to restart it.

A/F ratio was between 12.5-13 at idle. Seems like the A/F ratio is really sensitive to the idle mixture screws/throttle blades. Seems like a 1/4 turn can move the meter almost one point either way. With no load seems like the best throttle response is around 12.5. I'd like it to be leaner but I have not actually driven it yet.

Thanks for all the suggestions and tips. Took some doing to get to this basic point but I've learned some things for sure. I admit, I'm kind of a rookie at tuning. I was a tech for a while but I never dealt with carbs or distributors when I was working. I know it ain't rocket science but it can get confusing when you're chasing multiple issues.

Probably be back asking about bogs and hesitations soon.

Posted By: MR_P_BODY

Re: Need advice, plugs fouled, backfiring thru carb - 03/30/14 01:22 AM

Quote:

OK, got it running pretty well. I was even able to hot start it without too much trouble. It was running long enough that eventually I ran out of gas.

Once I got it running, initial timing was 26 degrees. Plate in the distributor is 13 so x 2 = 26. I remember now when I got it a few years ago I checked the timing and being surprised where it was at. Looked like almost 30 on the OE damper. Makes sense now.

As stated, I went to a hotter plug and it seemed to help a little. They were still getting a little carboned while fiddling with the idle but nowhere near as bad. I checked them at one point, no carbon at all. At least it was running and I was able to restart it.

A/F ratio was between 12.5-13 at idle. Seems like the A/F ratio is really sensitive to the idle mixture screws/throttle blades. Seems like a 1/4 turn can move the meter almost one point either way. With no load seems like the best throttle response is around 12.5. I'd like it to be leaner but I have not actually driven it yet.

Thanks for all the suggestions and tips. Took some doing to get to this basic point but I've learned some things for sure. I admit, I'm kind of a rookie at tuning. I was a tech for a while but I never dealt with carbs or distributors when I was working. I know it ain't rocket science but it can get confusing when you're chasing multiple issues.

Probably be back asking about bogs and hesitations soon.

Cool.. your getting there... I never worry about the
AFR at idle... I set it so it idles the best it can
and set the WOT to the best MPH... I only use my AFR
to set the cruise... but once I get all the points
dialed in(idle, wot and cruise) I take a reading so
I can get back to it fairly easy.... and yes the mixture
screws can be touchy with how much you move them..
what I do is once its warmed up.. slowly turn in
one at a time till the rpm starts to drop then back
them out 1/4 turn... go around the carb a couple of
time to get it right... you might be lowering the
curb idle(the idle screw) during this process but
do it all a few times and it'll come right in... but
the base timing is what you have to set FIRST.. thats
a MUST

Posted By: RMCHRGR

Re: Need advice, plugs fouled, backfiring thru carb - 03/30/14 03:01 AM

Quote:

Cool.. your getting there... I never worry about the
AFR at idle... I set it so it idles the best it can
and set the WOT to the best MPH... I only use my AFR
to set the cruise... but once I get all the points
dialed in(idle, wot and cruise) I take a reading so
I can get back to it fairly easy.... and yes the mixture
screws can be touchy with how much you move them..
what I do is once its warmed up.. slowly turn in
one at a time till the rpm starts to drop then back
them out 1/4 turn... go around the carb a couple of
time to get it right... you might be lowering the
curb idle(the idle screw) during this process but
do it all a few times and it'll come right in... but
the base timing is what you have to set FIRST.. thats
a MUST

I think I understand not using the gauge for idle because the A/F ratio did not necessarily give the best throttle response. (at least at idle)

Felt like I was kind of chasing my tail a little, in and out with the idle screws, up and down with the throttle blades always coming back to the point where it was around 12.5 on the gauge.

Hope I can get it running good without getting too much more involved. I gotta drive it to see how it responds under load. Hopefully in the next couple days.

Posted By: sunroofgtx

Re: Need advice, plugs fouled, backfiring thru carb - 04/02/14 08:30 PM

Crazy question, but what kind of fuel are you running?

Posted By: racingblues1426

Re: Need advice, plugs fouled, backfiring thru carb - 04/02/14 08:48 PM

Why do you feel you need to gap the plugs at.050. That is a red flag for me. I've run msd 7al boxes for years and never had one work as good as when the plugs were gapped at .030. Try me suggestion and see if it doesn't work immediately. Forget msds' suggestion about plug gap.

Posted By: B G Racing

Re: Need advice, plugs fouled, backfiring thru carb - 04/02/14 09:02 PM

Most multispark systems like a wide plug gap.Start with a standard gap of .035 and if it bucks or sputters open the gap it up to .040 and if it still doesn't smooth out go to .045 or .050.
Another thought is the valve setting correct?A valve not closing will cause similar issues.

Posted By: RMCHRGR

Re: Need advice, plugs fouled, backfiring thru carb - 04/03/14 04:02 AM

Man, I tried to reply like three times here and I keep losing my text.

Anyway, the car is running. I took it out for a ride today for the first time in over a year. Seems to run OK, gets up and goes. Surprised myself!

Fuel is a mix of pump 93/Cam 2 100 unleaded. It will run on 93 but I can get the Cam 2 at the pump down the road from my house so I try to keep at least 5 gallons of it in there.

Plugs are at .050" cause I thought it would help to promote more spark energy. Dunno, I guess I could try .035" on my next set of plugs. Almost everything I've read over the years about plug gaps says .045-.060" is what you want. I think advancing the timing and going to a hotter plug is really what helped.

When I did the compression test, I thought I might have a roasted valve in the #5 cylinder but I'm not really sure. I don't have a leak down tester. (on my list) Could be bad but seems to run OK anyway.

I changed the oil which I think helped with compression. The old oil was thin and black. I'll probably be rebuilding this engine sooner than later.

Thanks again for the tips, this has been helpful.

Posted By: RMCHRGR

Re: Need advice, plugs fouled, backfiring thru carb - 04/21/14 08:56 PM

Quote:

Check the MSD distributer wires,may be backwards.

This was my problem.

I'll admit, I have been messing with this hard starting issue for the better part of two months and it was driving me nucking futs.

Even though the car would run, it was very hard to start in all situations and no adjustments were having any effect - timing or carb. It would eventually fire after multiple attempts though it never stayed running without holding the throttle open. Once it got warmed up it would stay running which is part of why this was confusing.

I figured I needed to try something different. Something was telling me it had to be ignition/timing related since the plugs were still black no matter what I did to the carb.

I read back through the thread here to see if I missed something. I read BG's reply and started looking into the issue some more. Turns out it is a somewhat common problem with magnetic pickup (Mopar) distributors. You kind of really have to read through some of the replies on the MSD forums and decide for yourself to switch the wires.

The thing is, the MSD instructions don't really make any mention of this particular issue and I wired it like they said. I kept re-checking believing it to be correct and since it kind of ran, there was no real reason to think I had it wired wrong. Plus, I did all the MSD troubleshooting procedures with no apparent issues.

So just for kicks, this AM I went out and switched the wires. Two pumps on the throttle, turned the key and the car fired instantly and easily and stayed running. I was relieved but completely annoyed at the same time.

Need to start from scratch on tuning now but at least its starting and running right now so I have a proper baseline. Live and learn I guess. Thanks again for all the replies.

Need advice, plugs fouled, backfiring thru carb UPDATE