Its running a little rough...

[mrandig]

Figured I'd start out with something simple as my first post.

My new-to-me '68 Charger R/T is running pretty rough, and definitely has a backfire (afterfire).

I'm going to go through the motions here, and post whatever I find; let's see if we can get this figured out.

Any thoughts as I go along are appreciated.

 

[fine69]

Welcome!
You could put a vacuum gauge on your carb and play with the idle mixture screws to squeeze an extra inch or 2 out of it.
Is there crappy old gas in it perhaps? Maybe some fresh premium with a can of Seafoam could help.
Would love to see more of your charger. Mine was originally Y2 with black top.

 

[mrandig]

First off, the carb. Turns out this has a 4150 Brawler, which I didn't have on my bingo card, but it's all good.

Floats are low but OK, idle mixture screws set at 1-1/2 turns out. Should be OK for a minute or two...

NOPE. This still runs like crap.

 

[mrandig]

Next up, let's try the vacuum gage.

LOL

Apparently, the PO decided to plug this line. Hard to see in the picture, but there's a piece of plastic in there.

Now that's fixed. This car will have vacuum advance like the good Lord intended. Vacuum is now right around 14HG.

Yes, I am running manifold vacuum vs. ported. Both idle and vacuum are not terribly steady, and we're still after-firing.

 

[mrandig]

Just at a glance, the distributor looks incredibly advanced, but I'm not there yet. Let's pull some plugs first.

These are AC-Delco Platinum 7 plugs. Fancy! Somebody was a big spender.

They actually don't seem to have spent much time in service...

I'm going to put some Autolite 85s on anyways, just because I like them.

Did I mention these old plugs couldn't have seen much use?

Look closely...

DAMN. I think I just found my problem. Cylinders #2 & #4 aren't firing.

 

[super-bee_ski]

Great post and great tech/Investigative work and certainly shows you sort of know what your doing...Very refreshing!
Thanks for posting...watching for updates...nice car by the way!

 

[mrandig]

I need to figure out what would cause two adjacent cylinders not to fire.

A carb problem wouldn't cause this.
A coil problem wouldn't cause this.
Bad timing wouldn't cause this.
Odds are against two Mfg. defective plugs installed side-by-side.

I'm not going to worry about valvetrain issues until I run out of other ideas.

Maybe switched plug wires or a vacuum leak? Let me check and I'll report next post.

 

[RemCharger]

The switched plug wires wouldn't be unbelievable.

 

[pnora]

If that intake is an open plenum and for sure 2 and 4 are not firing I would suspect a vacuum leak. Either at the intake to head area or possibly a gasket on that carb. spacer.

 

[mrandig]

Somewhere a village has lost their idiot.

Plug wires #2 & #4 were switched.

Running much better, however that's not saying much. At least the backfire (afterfire) issue is resolved.

Once I make a victory lap and get done patting myself on the back, I'll see what I can do to get this running better. I need to take a break for a little while.

Stay tuned...

 

[pnora]

Two other items of concern. 1 take a look at the reluctor and make sure it is not a 6 cylinder reluctor. If it is an 8 cylinder reluctor verify the correct gap at all 8 points.2- there are bolts on the carb holding it down. Make sure that they are not to long and bottoming out. If they are that could be a leak. I prefer studs for that reason.

 

[rickseeman]

Now that you're running on all 8 cylinders I think you should do the vacuum tuning on the carb again.

 

[mrandig]

Woo Hoo

That's what I'm talking about. Nice and steady...

 

[mrandig]

So, are midget hands a prerequisite for working on these cars?

I can barely move my hands now; they are so beaten and abused. I think they're actually swollen.

 

[mrandig]

I think I'm also going to need some new spark plug wires.

 

[mrandig]

Anybody notice anything here?

Look closely...

For some reason, there's two different sets of wires here.

Everything needs to hit the trash.

 

[dadsbee]

Typical set. 1/2 90's and half straight boots.

 

[rickseeman]

The 90's go to the drivers side bank.

 

[moparedtn]

While you're at it, if that engine is anywhere in the neighborhood of a stock build, hook that
distributor advance to ported vacuum - as Ma intended.

 

[4mulas]

I noticed the fuel line going over top the distributor and advance unit. Not ideal
Glad you got it figured out as for the backfiring issues