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I'm fouling the # 2 spark plug.

I changed the plug wires, changed the cap and rotor, I took a compression test I have 120 psi in every cylinder ... cant figure it out. The car has a slight backfire when at 3000 rpm on the high way cruzin and backfires a lot on deacceleration ?? Is it the infamous 2 piece valves playing games with me. I think I have a burnt valve. Need some suggestions.

Thanks Ron
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Nah. It's not the valve. Don't worry about them.
They just suddenly come apart and the internal noise of the valve crashing into the piston and being compressed into the cylinder head is unmistakeable.

There won't be any doubt when it happens.

High probabilaty of one of two things. #2 has a vacuum leak unique to itself or The plugs are fouling and showing mostly on #2, or both.

Are you sure that you have the right plugs?

The stock iron head should take an AF-32. On a low compression C you should also be able to run an AF-42 which is hotter.

I have found that as of recent the cross over substitution charts are wrong.

What has happened is the following. The Motorcraft BF-32, which is the 18mm plug has been discontinued.
Motorcraft has substituted the BF-42.

Companies like AC have crossed that over as the 45. The 45 is the BF-42 not the BF-32.

Now the computer geeks that just know data, came to the conclusion that the 32 is a 42 and heck we can do that with an AF too right?

You have to see what some of these jerks have done! Someone crossed over the F11y, F9y, and the F7y as all being the same, depending on whos charts you look at.

The 17 year old NAPA kid who thinks he's an expert on everything, is likely to give you whateva' jabonga plug he can get and tell you you're an a-h if you don't agree.

Bottom line, run a Motorcraft AF-32. That's the correct plug for the car.

If they wanna' argue, like the quote says, just tell them "if I had the time, I'd join a club, and then beat you with it".
If he keeps it up, just tell him that you heard that his girl friend is late. See what a smart ass he is then.
Yes its only on #2 the rest are buring perfect. I was running BF32's and then this year switched back to BF42's.

#2 is oil fouled ?? it has to be a worn giude and or a faulty valve seal .. I would say ?

Doug . I hear ya on the auto parts stores... they gave me the wrong filter for my AUDI and now it sits with a burn'd up motor.

I have a set of BF32's I;m gonna put back in ..could it be a bad SPARKPLUG ??

Thanks Guys.
Plug quality? Sure. Consideer how the things are made.
Do you buy any electrical componenets?
Quality control on them is like a 50/50 proposition.
The problem is that they actually need to employ people to check quality on the components. They just don't want to do that. They might have to pay health care costs you know?

Incidentally Trane says that the quality went out the window when they went non-union. Good workers are too expensive. Screw them and the customers.

I find that the 42 heat range for me causes more problems then it helps. I like the 32's, and the Motorcrafts at that. Let AC stick their plugs in a 'vette where they belong.

Champions are you next best bet and that's a frightening thought!

One thing that I like to do with ALL FORD v-8s is to remove the PCV hose from the intake manifold and run it to the bottom of the air cleaner.

You can be blaming a lot of serious internal issues on a crappy PCV design. The location on the Ford intake manifold is too low and it siphons oil into the intake.

Maybe #2 just gets more crap from it then the others? Just like Grandpa has his favorites and his black sheep.
...just an added note: I had ONE plug that was not fireing properly, fouling. I happened to check the 'OHMs' resistance of the plug wire itself; it was way off from the other Seven. Must have been some broken carbon core somewhere along it's length. I replaced the entire set, No more problems...
I thought about it and it may have started when I chanegd from 32's to 42's ... ??

The PCV hose is into the rear of the intake .. and maybe the aircleaner is a better place for it we dont really need a full 15 lbs of vacumun for the crankcase ??

I changed the plug wires and it made no difference.

Monday I will chaneg the plugs back to 32's and we will see.

Thanks for the help.
I hate these little gremlins. I start blaming it on stupid things like I put my left sock on instead of the right.

I'm not blaming the carb but you can clean it up a little with 68 main jets. You can get the 32's nearly white with brown/grey tips which will help oncarbon build up and thus fouling the plug.

It's better to go leaner and use an earlier power valve like an 85. An 1850 idle is a lean carb while a 3310 is noticably richer at idle.

The 3000 rpm that you mentioned is right around the idle to main circuit switch over.

Anyway, good luck!
Look to see if you have a leaky valve cover gasket near the inlet for number 2 cylinder.

I have read of oil leaking from the valve cover then getting sucked into the inlet port.

I think the guy replaced the engine before he discovered this... and he could have fixed it with just a couple of new gaskets if had spotted it.
Ok changed the plugs to ASF 32 P's ..problem still there.

The carb is a new Holley AVENGER ..I have not ruled that out yet .. it seemed to have started right at that point I put a new carb on a tuned the car up.

Two things came to mind .. the carb and a broken valve spring which is easy to over look. The carb is a possibilty since I had to check the power valve and found a pinched gasket .. so tomorrow eve we pull the valve covers and carb.

I think I fixed it ... it was the carb .. power valve was a 65 .. I dropped it down to a 45 and bummped up the jets to 68's and wa the popping stopped and its smooth as glass.

Not usre about the one plug fouling .. I will check that in a couple days ... I never seen a lean condition ..sound like a miss and popping on acceleration .... boy if Only I richened her up before POCONO ..160 mph could have looked a little better.

Richened it up to 68's? Wow, they are on the lean side.
On my Holley 4779, 750DP I run 71 primary, 75 secondary, 7.0 power valve.

The hot ticket would be to run an 8.5 and 67 or 68 mains.

One thing that you need to look at is the idle restriction.

If it is smaller ther .028" then the idle is going to have flat spots or stumble off of idle. LEAN stumble.

The DP's idle rich because this retriction has been enlarged to cover the scavenging leaning effect from a good set of race headers.

I think at this point an exhaust analizer might be in order. It won't hurt. Itis hard to tune in the dark.

The Holley 670 cfm Avenger comes with 65's I drove her tonight .. 72's are in order.

Ok here the the problem .. on the vacumn guage she has 0 at idle .. the second I touch the throttle jumps to 5 , 10 & 15 .. seems to drastic ... I cant pinpoint the vac to pick a power valve.

Idle restriction ?? You mean ???

This is not a double pumper .. I put on a Hollet Street Avenger ... dont forget this is a 79 351C smog motor ..

Only thing that puzzles me is the AVENGERS reaction to my case a lean condition ... never had a HOLLEY BARK at me ... maybe I have always been TEARY EYED with a rich condition .. thinking I needed a BIG carberator. YOU KNOW when your young the bigger the better ... AM I GEETTING OLDER AND WISER picking the right carb and then fine tuning it ??? I think thats the case here.

I haven't used that series.

I have looked at the carb and the specs.

You have to fix the idle vacuum problem first.
You should have 15-20 inches at idle. Are you sure that your gauge is ok and that you are reading manifold vacuum and not port vacuum at idle?

You can't possibly have 0 inches at idle. The engine wouldn't run. You would have more then that even if the big vacuum port for the power brakes is wide open.

Incidentally, is the power brake assist working? Maybe you blew the booster can out?

The idle restriction is essentially the fuel jet for the idle circuit. It is located in the main metering block. Almost all Holleys, including the emission varieties come with a .028" diameter restriction.

On the leaner emissions carbs the factory leans the system by increasing the diameter of the idle air bleed in the main body.
What this does is lean the air/fuel ratio on the idle circuit.

All the idle screws do is change the volume of mixture the engine gets, not the A/F ratio.

On your stock engine, that should be ok. Leave it alone unless you find that you have a stumble off of idle that you can't find. If your exhaust analizer shows lean in the 2000-3000rpm area, and then good thereafter, it is the idle restriction is too small.

Since you initially indicated a lean misfire, I just suggested for you to look at that. That was the point of the suggestion.

I did notice that you have a huge pump squirter at .031". I don't know what that is about on a carb like this. I would have expected a .025 or .028". This is a street carb. Hum? Interesting.
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