No top end power, need help

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67Dart273 said:
I'd be backin' up a step or two.

Use a piston stop to verify timing marks are accurate.

Do some checks for sloppy timing chain.

Use a delay timing light, "crackedbacks" idea of temporary "timing tape" from masking tape, or just sit down and scribe some degree marks on the balancer, so you KNOW where and what the timing is doing.

Regardless of "what the engine likes" it should run pretty fair "on top end" at 34-36* total timing, no vacuum, until you get this sorted out.

And take the trouble to "map" out what the mechanical advance is up to, IE too slow, sticky, rusted shut, and check the dist. for wear.

THEN after you know what the timing and spark is doing, go after the fuel.
Click to expand...

Sounds like a lot of work, but I gotta KNOW what the timing is doing rather than just assuming. It may take some time until I can map out the mechanical advance, ill start some more reading.

Not sure how to check for a sloppy timing chain, Ill look around for that too.

Truthfully this is seeming like it will take a while especially since I am opening up a business next month and about to start working 60+ hours a week!
Its a good thing I love my Mopar! :burnout:
Thanks everyone for the ideas
 
EmersonC said:
Double checked all 8 and they are definitely getting spark
Click to expand...

Spark is good. But not end all for miss. Had a intake rocker come loose on magnum engine. Ran like crap, wouldn't idle. Had spark so pulled valve covers prepared to pull heads off and was happy to find the rocker.

Wiped lobe, broken rocker could do this. Not saying it is your problem but before tossing money at it you could pull covers to check valve are opening and closing.
 
A sloppy timing chain would make it stumble at low rpms and pull better on top...
Checking it its still a good idea if you have more then 16 crank degrees of slop in the chain. Its time to replace it before it leaves you stranded some day.

Reading back thru you thread you state that the snap on timing light has a tach that its idling at 3000 Rpm Are you sure about that? sound way high.
 
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UPDATE

Took a while but I have an update. So I checked the timing chain slack and it seems rather tight. Only about 3-5* of slack, not much. BUT I did notice something new.... The dist cap is not looking so good (see pictures) The top of the "rotor" had lots of black carbon buildup and grey specks all around the inside of the housing. All of the points on the cap looked seriously worn. They looked partially blackish/blueish and had serious divits on the points. Maybe about half of the thickness of the metal! I sanded the rotor and cleaned it up. I can replace the cap rather easily, but replacing a part does not solve the problem. What could have caused this? It is a new Mallory dist (only about 6 months old).
 
Cudafever said:
Reading back thru you thread you state that the snap on timing light has a tach that its idling at 3000 Rpm Are you sure about that? sound way high.
Click to expand...

No, I have serious doubts about it idleing at 3, it doesnt sound like it and i am guessing it is because I have the MSD ignition box
 
I would check rotor phasing. Google it.

What is the exact run-down on your ignition system? Mallory ?? what model?? dist? driving a what?? model box if any, etc
 
67Dart273 said:
What is the exact run-down on your ignition system? Mallory ?? what model?? dist? driving a what?? model box if any, etc
Click to expand...

Edelbrock Performer intake manifold
Edelbrock 4 bbl carb #1406 w/ electronic choke
MSD Digital 6A #PN 6201
MSD Street Fire Spark Plugs wires
0.6 Ohm Flame Thrower Coil
Mallory Ignitions Distributor w/ Vacuum advance. (Not sure the exact model, I know it was a rather simple one)
Resistor is bypassed
Amp gauge is bypassed as well

Any ideas what might cause the pitting on the dist cap?
 
I'm not familiar with your distributor, but it might be possible that the trigger interface between the distributor and MSD is reversed which changes the ignition trigger point in time. This changes "when the spark happens" in relation to rotor position. As I said above, Google "rotor phasing." What might be happening, is that with the trigger leads possibly reversed, the spark is firing when the rotor is not lined up with the cap contacts.

https://www.google.com/search?um=1&...1398.9j4.13.0...0.0...1c.1.18.img.zxpz0buVuuM
 
the dist move about 3 degree or the crank? i have never seen a time chain that tight. new, you have around 5 degrees of play. when looking at the crank.
 
I 2nd 67Dart273 diagnosis, as soon as I saw that cap I was thinking the same thing phasing is out 180. Changing the trigger wire will bring the timing right in where it's golden. and your idle is 3k that is way high you sure it's not 300.
 
UPDATE:

I looked into and checked the rotor phasing and it does seem to be late, that is it appeared to be clockwise from where is should be.

HOW I CHECKED:
Drilled a hole in the plastic dist. cap at the terminal for the #1 cylinder. Fired the car up, hooked up the timing light to the #1 spark plug and looked at what I had.

So now I gotta look into correcting this. And as I am typing this I just realized that I checked it with the vacuum advance hooked up, hold one minute..

Ok so like I thought disconnecting the vacuum from the carb made no difference. I did also check it as I revved the engine and as there was more vacuum the rotor moved counterclockwise and matched up to where it should be at idle, directly in front of the contact point on the cap.

Clearly I need to do more research on how to correct this, any links to good threads?
 
Oh ya and...

I have a Mallory Magnetic Breakerless dist.

And I checked for vacuum leaks and the intake manifold does have a leak so I will have to fix that soon
 
First thing to try is to switch the pickup leads. Vacuum advance WILL change phasing. What needs to happen is that with "no" advance, the rotor must be approaching "corner to corner" with the cap contact, and as you add more vacuum, and finally "full" vacuum advance, the rotor must be on the "leaving" side of the cap contact with no less than "corner to corner" contact.

In other words as the vacuum advance goes from no to full advance, you need to "split the difference" so that the rotor centers on the cap contact.

This could be from pickup leads switched. Wrong parts or wrong assembly, worn parts or even a defect in manufacture. Without seeing how this thing comes apart, I'm not familiar with these distributors. If there is any sort of "sliding" adjustment on the pickup mount or the breaker plate, that might be "somethin"
 
Look to see if you have a vacuum leak also. But the timing issue would be a huge problem on its own. Mike
 
UPDATE

To those that are still subscribed here is the most recent update (and thank you).



Reason for thread:
  • Very rough idle
  • When throttle is ever so slightly opened it runs very rough and shakes all over the place
  • Horrible mileage
  • Every once in a while she dies on me when I come to a stop, but fires up quickly after the engine has died
I have rebuilt the carb because it probably need it. And she does seem to run better at from 1/4 - WOT which is good but Im still having idle problems and she still dies on me at stops sometimes.

As suggested I switched the dist. pick up leads that connect to the MSD box. And I could not even get the engine to fire. Though I was not adjusting the timing as I was try to get the engine started (no one around to help with that).
Is this not what everyone meant?

I checked for a fuel leak along the line and did not see anything leaking with the engine running

Checked the firing order and it all the spark plugs are attached to the correct cylinder.

Fixed the vacuum leak


Now I am thinking there it might be a fuel issue. I saw air bubbles coming up through the fuel filter the other day. Just drove about 15 miles stopped at the hardware shop (15 min) came back started the car and looked at the fuel filter. It was 3/4 empty when I saw bubble come up for about a minute. This does not sound good or normal.
Some days my fuel filter looks almost completely empty (2%) and other days it is mostly full (90%). Im thinking I should check the fuel pressure somehow?

A fuel pump issue seems to make sense, it would be more noticeable when the engine is at idle because the pump arm is moving slower. Where as at high RPM the pump arm is flying.

What are the thoughts from the community?
 
Did you ever change the cap/ rotor? Just all that junk may be causing a misfire.

So far as correcting it, you might have to get ahold of Mallory. I'm not familiar with the specific mechanics of that dist.

How far off is the rotor? If "worst" the rotor is "corner to corner" with a plug contact, that would be OK. I doubt that it is.

So far as the filter, that will happen--fuel gets hot
 
67Dart273;1970085348 How far off is the rotor? If "worst" the rotor is "corner to corner" with a plug contact said:
Ohhhh. It should be that close eh? I rechecked the rotor phasing and it is not even close to the corner. At around 1/3 throttle or so it is close to dead center (with vacuum advance hooked up). At idle its well past the cap contact point, somewhere around a full contact points worth clockwise.
Click to expand...
 
THAT needs to be fixed, and explains all the "junk" in the cap. What you have there is a miniature welder, 'er maybe a miniature plazma cutter
 
EmersonC said:
Ohhhh. It should be that close eh? I rechecked the rotor phasing and it is not even close to the corner. At around 1/3 throttle or so it is close to dead center (with vacuum advance hooked up). At idle its well past the cap contact point, somewhere around a full contact points worth clockwise.
Click to expand...

Tell me again? Is your ignition "all in the distributor?" Or does the distributor trigger an external box?

What specific distributor is this?
 
EmersonC said:
I have a Mallory Magnetic Breakerless dist.
And a MSD Digital 6a
Click to expand...

Can you post the exact model?

Very first thing I'd try is to switch the distributor wires and recheck rotor phasing
 
I did switch the wires and the engine would not start. I was not messing with the timing as I was cranking it. No one here today to help.

The timing is currently set to around 15*
 
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