Possible MSD 6al Problems

[AMiller]

So, Im stumped. Have a MSD 6AL on a 351 Windsor motor and MSD Blaster Coil.

Car runs good, starts well, and idles fine. Been noticing a pop sound at lower rpms in the passenger side exhaust.

Thought it might be an air leak. Changed exhaust manifold gasket and tightened the header to exhaust pipe connection and nothing changed.

Checked plugs , looked ok but changed anyway. No change. Changed plug wires, no change.

Noticed that the header tube next to firewall was not as hot to touch as other 3. Headers are wrapped so you can touch briefly without getting burned but cant leave your finger on the tube. The other tube was very warm but not so much that I couldnt leave a finger on for a time. Checked that plug again. Looks pretty good. It is firing. Maybe not quite as gray brown as the other 7 but close.

Also noticed that idle has dropped lately. Not much but enough to notice. Still idles fine but a little lower. The last thing I have noticed is the motor is not reving out quite as high as usual. Maybe only 200 to 300 rpm difference but its noticable.

Anyway, Im now thinking that the MSD box is the issue,just wondering about other thoughts and ideas???

Thanks Guys,

Aaron

[Karl Bebout]

Aaron, I'm pretty sure that the MSD box would not adversely affect only one of your cylinders. If its bad, wouldn't it be bad for all of them, since it has no idea which plug its firing?

BTW, you can find testing procedures on the MSD web site, for both the box and the coil.

[jhv48]

Definitely sounds like an air leak. Possible intake manifold or carb base. Spray some carb cleaner around while the engine is running. Especially on the rear corner of the intake manifold by the suspect cylinder.

[AMiller]

I only wonder about the MSD Box do to a friend of mine who circle track races. His car started to feel off and noticed a popping noise in the exhaust while on throttle. Turned out the MSD Box was missing on one cylinder randomly.

I will give the carb spray a shot though.

Thanks,

Aaron

[Gaz64]

Compression and leak down test.

Engine specs please, compression ratio and cam timing.

Possibly intake manifold vacuum leak.

Unlikely to be ignition.

[Clois Harlan]

I would look at the carb first, possibly something in the idle circuit or look at the accelerator pump. Check jetting (pull each jet and idle screw out and clean with carb cleaner). Also, check your plug wires.

[Mike I]

Aaron,
What plugs are you running? I can tell you from experience that MSD and platinum tipped plugs such as Bosch Platinums are not a good mix. MSD should only be run with copper core plugs IMO. Just a thought.

Mike...

[Jaydee]

Maybe even a sticky valve or lifter?
JD

[STEVE-O]

Replaced your distributor cap and rotor lately?

[Clois Harlan]

A good point Steve. I know my MSD cap gets quite a bit of build up and I just replace the cap. All fixed.

[AMiller]

Wanted to thank you folks for lending your thoughts. Things are looking up.

Almost tore the top end off but gave one last go at the obvious. Turns out I had a few small problems that lead to a dead cylinder. Still not sure the exact circumstances but the end result was clear.

At some point the e-clip that holds the vacuum advance arm in the distributor came off and let the arm lose. This seemed to lead to very weak spark on #4 cylinder, Why? I dont know. Plug would fire when you removed it to test but was not making good fire in the cylinder.

Last but not least it seems there was a slight vacuum problem.

Anyway, she no longer has a rough idle, no popping in the passenger side exhaust, pulls clean to 6 grand and 8 out of 8 cylinders produce hot gases now.

Aaron

[zrayr]

Originally Posted by AMiller

".......I will give the carb spray a shot though....."

just a FYI, you can use plain water in a spray bottle instead of carb cleaner if desired. The effect is identical, the RPM will change if a leak is present, and the water won't catch on fire like carb cleaner can....

Z.

[Cobrafan1]

MSD filed for chapter 11 bankruptcy reorganization last Friday.