Problem isnt timing...faulty ignition or distributor...PLEASE HELP SOON!!!

Well I have been setting timing until I am blue in the face and have concluded that the timing cannot be the problem. I have set it everywhere from 34 to 45 total and have come up with the same thing....crap. I noticed that when I was trying to find the total timing the timing light would speed up and right as it got to 2500rpm or so the timing light would slow down to a slow flicker, slower than at idle. I thought the light would only get faster as the revs got higher. Someone told me there is a problem with either my distributor, ignition or both. I have a mallory magnetic breakerless distributor with mechanical advance and a MSD6a ignition. The box is many years old.
Upon dropping this new engine in there was no bogging off idle and it would peel out at ease from any rpm in first gear. With no change the truck stumbles below 1500 rpm, bogs when floored and struggles to rev to 5500 when my combo should be good to 6500. It has lost over 1 second in 1/4 mile times.
What could be the problem? I have replaced plugs, wires, cap and rotor, bushings and springs in the dist., coil. I have replaced all fuel lines, fuel pump and fuel filters. The only thing I havent replaced was the MSD6a ignition which is many years old. Please help. I need to have the problem solved.
Should I just break down and buy an HEI distributor and scrap the MSD6a? Thanks in advance for the help.

Are you running the right plugs and gap for the MSD6a? I was having somewhat of the same problem in my '74 Nova. I replaced the plugs and set the gap to .035 timing was right but it didn't run right. Then I noticed I had a HEI distributor, which didn't come on the '74's, so I changed plugs and set gap at .065 now it runs great. If your distributor isn't OME run plugs and gap meant for it not the truck.

Be aware that some dial-back timing lights will show a considerable difference from what the timing really is if there's an ignition amplifier box in use.

I have an MSD 6AL in my roadster along with a Mallory Uni-Lite.

The 462" engine was initially timed statically, then started and the timing shot with a Sears Penske non-dial-back timing light.
It was on the money so I did the 20 minute cam break-in from there.

Couple years down the line - and having re-adjusted the timing with the old timing light I bought a new Sears Penske dial-back timing light.
The timing showed 20 degrees off from what it really was.
(This was with the dial set at zero.)

I forget which side of zero on the timing marks the dial-back showed, but it didn't make any difference.
I set the timing with the old timing light and took the dial-back light back to Sears.

Forgive my ignorance but I dont know what a dial back timing light is. This is the basic timing light that you hook up and push the button and it flickers. when revving past 2500 the light barely flickers at all. The truck wont rev past 5500 without struggling and it barely pulls to that. Whenever the engine was first put in it would peel out at part throttle and only reving to 2000...now it stumbles below 1500 and just doesnt pull through the rpms. The only thing that hasnt been replaced is the distributor or the MSD box. Thanks for the time and help

A dial-back timing light is one that has an adjustable dial on the back - on the back at least on the ones I've seen.

You can set the dial for 36 degrees BTDC and when you spin the engine past the "all-in" point the timing light will show zero on the timing marks.

A nice feature for those who don't have a degreed dampener or timing tape installed.

Set the dial at zero and use like a regular timing light.


Looking from here, it looks like your timing light could be bad.

Keep in mind that at higher rpm levels the light will look like a solid beam of light, but it will show the timing marks at a standstill or floating around for a degree or two due to play in the timing chain.

Is there someone you could borrow a light from and see what happens?


One further thing, older timing lights are polarity conscious.

Little brother loaned some guys his old, but in nice shape timing light at the dragstrip.
They came back whining that the light didn't work.
They'd put the battery leads on backwards and burned it up.
It did flash, but not well and that was pretty much the end of that light.

First think I would do is to check the timing statically, and verify if my timing light is working properly.

Before I would scrap the MSD or shell out the money for an HEI, I just take it out of the loop and wire the ignition without it. If everything ran well, I'd either replace the box, or consider HEI.

IF YOU ARE WORRIED ABOUT THE DISTRIBUTOR TAKE IT OUT AND HAVE IT (SPIN TESTED).MSD CAN ALSO CHECK YOUR BOX.

Not to ask a stupid question here but,are you running a vacuum or mechanical distributor and if it is a Mallory Vacuum advance are you running full or ported vacuum?I had the same problem with a Mallory on my SBC and it turned out to be a vacuum problem.Mallory distributors are set up for full vacuum,set your initial timing high and your full to normal.When its on ported every little vacuum pulse screws with your timing.Hope that helps.

Sorry,didn't see it is a mechancal advance.

Well My timing light is brand new. I bought it because my old one was doing the same thing. There is nothing close to a constant beam of light at high rpms. Past 2500 or so the rate of the pulse is cut in half. I am installing a Mallory HEI saturday in hopes that it will solve the problem. If not what else could it be...timing chain jumped?

Some times big problems can be caused by easily overlooked basics. Is the MSD a new add on? if so, make sure it is grounded directly to the block & the power lead connected directly to the starter or + battery terminal. BTW, do you have a rev limiter?

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Originally posted by DynoDon
Some times big problems can be caused by easily overlooked basics. Is the MSD a new add on? if so, make sure it is grounded directly to the block & the power lead connected directly to the starter or + battery terminal. BTW, do you have a rev limiter?

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That's a very good point.

My MSD 6AL came with the 3000 rpm chip installed.
There were a couple of extra chips with it.
6000 and 7000 rpm I think.

Different rpm chips area available at Summit and similar.

The rev limiter aspect cannot apply because I have used this box in the past. I used it with the previous engine and it ran fine to 5500rpm. I used it with this new engine and at first it ran beautifully but it suddently lost power and a great deal of it. It decided it didnt want to have any power below 1500rpm or rev past 5500rpm and struggle the entire time getting there. The Mallory HEI is going on tomorrow to see if that was the problem...if it isnt the problem I have no idea what else to change. Thanks for the help.

been reading your problem and i think that maybe you should ck your exhaust to see if it is blocked in any way.had an inner pipe colasp on me awhile back,gave me the save problem.good luck