427 down on power

[Excaliber]

"Reluctant to rev", that description just doesn't sound like a carb issue to me.
Verbal or typed descriptions/symptoms are particularly difficult to get a handle on, by the way...

Of course if the secondaries aren't working that will reduce the horse power, but it should not make it reluctant to rev. THAT description does sound more like:
Plugged exhaust (not likely).
Retarded mechanical camshaft timing.
Retarded ignition timing, base or advance curve incorrect or sticking mechanical advance.
Along with plugged exhaust factor in valves sticking in the guides or grossly misadjusted, which could give the same symptoms as plugged/restricted exhaust.
Weak spark, can't fire the fuel properly.

[patrickt]

Originally Posted by Excaliber

"Reluctant to rev", that description just doesn't sound like a carb issue to me.
Verbal or typed descriptions/symptoms are particularly difficult to get a handle on, by the way...

But if we give Southern the benefit of the doubt that the engine was running right when they put it in the big wooden box, then the problem was in the installation. If that's the case, then what jumps to mind is: 1) Carb linkage, 2) Ignition Box & Spark, and 3) Exhaust (yeah, there could be an obstruction). Ignition timing shouldn't change, valve timing shouldn't change, plugs shouldn't be fouled, etc. on 2 hours worth of running.

[PatBuckley]

...and inadequate fuel supply.

[FatBoy]

Thanks guys for all your input.

The exhausts are fine i.e. not plugged.
The ignition is an MSD 6AL with an MSD billet distributor.
It starts up and ticks over just fine after a few seconds of warming up.
I'm inclined to think it is fuel starvation. The plugs are very clean (possibly too clean). I'm going to pull the carb today to make sure there isn't any dirt in it.
With regard to "reluctant to rev", by that I mean it lacks power and starts to miss above 3,000rpm.

Thanks again.
Paul

[patrickt]

Originally Posted by FatBoy

With regard to "reluctant to rev", by that I mean it lacks power and starts to miss above 3,000rpm.

3000 is when most of our FEs are just starting to wake up -- and throw in the dieseling and you've got some real clues. How 'bout bad fuel? Water, alcohol, crap in the fuel? Put a timing gun on it and double check your timing at idle; anything between 10 and 15 BTDC will pass for now. But I don't think it's a timing issue, I'm betting on fuel (that means condition of the fuel, carb. adjustment, and linkage) or the spark.

[Excaliber]

Starts to miss above 3000, whoa, big clue there, the mystery deepens, what does it all mean...

Any hint of a backfire condition (popping sound in the air cleaner/carb in particular), which is sometimes associated with a lean condition (among other things)?

[FatBoy]

Originally Posted by Excaliber

Starts to miss above 3000, whoa, big clue there, the mystery deepens, what does it all mean...

Any hint of a backfire condition (popping sound in the air cleaner/carb in particular), which is sometimes associated with a lean condition (among other things)?

There is another clue, is also runs on occasionally when it is turned off and then spits back through the carb.

Another suggestion of lean mixture ?

Paul

[Ron61]

What is the water temp. of the engine after you drive it for a short time? The miss and other things are starting to sound more like maybe a timing or fuel issue.

Ron

[Jac Mac]

1. They wouldnt have left some 'soft' valve springs in for the run in period would they?
2. Some wally hasnt stuck a 3k check chip in you MSD by chance?
3. Has your MSD been rewired for a waterproof plug & the wires crossed in error?

[Silverback51]

What you are describing is exactly what mine was doing. After swapping out every piece in the ignition system except the the ignition switch, I found that it was the voltage regulator. It was spiking and causing the MSD box to go crazy.

Disconnect your alternator and see if the mis disappears.

[My427stang]

If its missing above 3000, something is wrong, you are right to be concerned.

- Check your firing order closely
- Look under the cap for a burned rotor or rotor button in the cap
- Make sure you have the right MSD rev limiter in it if you run one
- If you run vac advance, disconnect it and try it, sometimes a partially broken wire on the module can intermittently break contact when vac advance pulls in
- Make sure all plug wires are separated so they cant cross fire
- Check for gross vacuum leaks
- Check all plug wire resistance
- Check valve train adjustment and/or bent pushrod

[My427stang]

3 doesnt look too good to me, may want to check that wire and plug, especially with an MSD. May even want to check compression on that hole

[Ron61]

427 Stang is right about #3 looking bad. Looks as if it isn't getting any spark at all of a very weak one. As for the leads to #7 & #8, yes, separate them as much as possible. I use the good wire also and after dark with them just separated by the plastic spacer I have seen them cross over once in a while, so I put them two spaces apart. Remember the high ignition voltages are more prone to do this than a stock one was.

Ron

[patrickt]

By any chance can you put your finger on the #3 header without burning your skin (or without burning it as bad as you do on the other header tubes...)?

[FatBoy]

I haven't run it today, I've been checking everything else.
I've pulled the rocker covers off to make sure the valves are opening and closing properly, which they are.
I think I'll give SA a call tomorrow to see what Bill says.

Thanks,
Paul

[TButtrick]

I'd be focusing on #3 plug. Try swapping #2 and #3 wires and take it for spin. Now see if #2 is fouled as #3 was. If not, you might try checking exhaust and intake lift per cam specs on #3. Take a REALLY close look at the rockers and valve springs on #3. Broken springs/bent valves/worn lobes can still give a positive compression check (at this stage) as your problem manifests iself at higher RPMs. Even with a completely broken valve spring, you can still have a positive compression check. A leak-down test on #3 might reveal a problem.

Your problem is most likely isolated to #3 and behind the dizzy (but not excluding the cap/rotor) BUT I've had a nightmare of problems with a 6AL. MSD quality does not parallel their marketing. The voltage source to your MSD has to be clean and at full potential. You can easily check with a DVM to see if there is a voltage drop across the source. Hook up one lead to the originating source to the 6AL and the other at the input to the 6AL. There should be no voltage drop across the source (zero resistance). I tossed the 6AL and stuck with good ol' Petronix after the box disintegrated. BTW, there IS a way to bypass the MSD 6AL. Do a search. It's out there.

[CHANMADD]

I have just had a similar problem manifest itself and I am about 99% sure its a cam lobe that has gone flat(SH**T) Check for a loose rocker as a telltale sign

[Excaliber]

I wouldn't worry to much about the 'run on' condition when you shut the engine off. Thats generally caused by one or two things.
1. Idle speed to high.
2. Octane rating of the fuel to low.

As the engine continues to push the pistons up and down AFTER you turn the key off (which is ignition only) the pistons continue to draw a fuel/air through the carb. Just enough for the compression stroke to 'self ignite'. A small piece of carbon glowing red hot perhaps, acting like a 'glow plug' ignites the mixture. Or it might simply be the 'heat of compression', like a diesel engine with no spark plugs. Higher octane fuel is harder to ignite so it takes a 'real' spark to set it off, thats why higher octane fuel works to eliminate 'run on' or 'dieseling' as some call it. By closing down the carb butteflies, and thus lowering the idle speed, it's more difficult for the pistons to pull in a fresh charge of fuel/air, thus starving the motor to death.

Run on can be a VERY serious problem, until you get that resolved use the clutch with the car in gear to stop the engine at the same time you turn off the key. Run on can cause a timing chain to jump, break pistons and wreck havoc in general if it's pronounced and allowed to continue. In some cases the engine will actually run BACKWARDS, very bad when this happens.

[Dwight]

Is your fuel pressure gauge near the carb.? What size fuel line do you have from the tank to the carb.? Do you have an electric fuel pump? Where is it mounted? Below the tank or above the tank? Did you use silicone sealant in your gas tank, maybe to seal around your sending unit? Silicone and gas do not mix! Ask me how I know.
Dwight

[Rick Parker]

Paul:

Is it a matter that the engine does not (1.) gain RPM quickly or (2.) Does it go "Flat" and "Nose over" when it reaches a certain RPM or (3.) Does it begin to miss, stumble and refuse to gain RPM.???

While it is running, drop a few drops of water on the individual pipes relatively close to the heads.
Do the drops all skittle and dance like they are on a "Hot" surface"???