Need help with rotor phasing

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downsr

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Have 340 stroker engine and been having trouble with it kicking back occasionally when I go to start it. I took the distributor cap off and saw where the rotor fires on the pins for each cylinder only goes about half way across. It is a new msd 8388 vacuum distributor. How can I check to see if it is out of phase and how can I fix it ? Have read that msd had a problem with this on some of there distributors anyone know anything about this
 
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Right now it is 24 initial with 10 degrees mech. It was 18 initial with 18 mechanical still did same thing. I put a mark on the distributor in align with rotor button. I took the cap off and ran the #1 piston till it started up on compression stroke at 44 degrees on the crank the rotor and the mark I made was aligned but the reluctor was not aligned I continued to turn the crank till the reluctor was aligned. The crank read 31 degrees.The rotor was well past the # 1 post on the cap. This is a vacuum advance dist.
 
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Have you checked it with a timing light? vacuum line plugged.
 
The timing is correct.I drilled a hole in top of the cap on #1 . Started the car looked down the hole I drilled with timing light looks like it is firing between # 1 terminal and #8. The vacuum advance is plugged off
 
Can the pickup plate be re positioned? Or have a pic of it, same here not familiar with it.
 
Kicking back on startup isn't going to be caused by phasing.

Remember that the spark happens when the pickup tells it to fire and has nothing to do with rotor position.
Now if it was so far off as to fire number 8 or 2 when it should be firing number 1 then that would be a problem with phasing.
 
Msd does make a adjustable rotor cap but not sure if they make one for a mopar distributor.I cut a square hole in the cap so I could see the post for #1 and the rotor button as I turn the engine. While rotating the engine by hand on compression stroke when it reached 40 degrees btdc rotor button is aligned with the post on # 1. But the reluctor was not aligned with magnetic pick up. I continued to rotate the engine till the reluctor aligned with the pick up. The balancer reads 30 degrees when they are aligned. I put the timing light on it and the initial is 22 btdc. The 8388 is the same as the mech dist but it has a vac advance on it. Uses the same cap
 
Agreed. kickback is a seperate issue usually from too much initial/dcr. Phasing: drill a 1/2" hole in the top flat of the cap 2/3 of the way between the center terminal and the #1 terminal & shine your timing light straight down on the rotor while idleing & above idle (ported I am assuming) & see if the rotor is pointing close to the #1 cap terminal. vac adv will shift it CCW on a SB & a 11 deg can will shift it .270", a weak 9/32". to change it you can try the other roll pin hole in the reluctor if this aftermarket dist has one or redrill a new roll pin hole in the reluctor or widen the rotor mounting notch in the top rotor shaft to shift the rotor clocking over then JB weld the other side of the notch to restore its original width. On the kickback you might need to reduce your initial or wire in a momentary NC contact switch to the ign & push it then get it cranking then let go while cranking. First make sure the battery/cables/starter are up to snuff. wouldn't hurt to check turning torque when hot with a torque wrench/1&1/4 socket on the front crank pulley. first ground the coil wire & see if it now cranks over fine which will eliminate friction. on the RP you can get a "close" guesstimation by turning the crank till the reluctor is dead even with the magnet then make a mark on the side of the dist with your sharpie at the top metal rim directly plumb down from the rotor clocking location (confirm springs are retraced which they should be) then replace the cap & see if the mark is in line with or close to the center of the cap terminal outside "bulge" keeping in mind which way the can will shift it. The rotor blade width is .244" and the cap terminal width is .214" on an OE dist. holler how it goes
 
downsr said:
Have 340 stroker engine and been having trouble with it kicking back occasionally when I go to start it. I took the distributor cap off and saw where the rotor fires on the pins for each cylinder only goes about half way across. It is a new msd 8388 vacuum distributor. How can I check to see if it is out of phase and how can I fix it ? Have read that msd had a problem with this on some of there distributors anyone know anything about this
Click to expand...

If you google rotor phasing you'll get lots of info, including a movie by........MSD

Not familiar with this dist.......is the electronics internal or are you triggering an external box. If the latter the trigger wires might be reversed if it's a magnetic trigger As said above, MSD does have adjustable rotors for some of their stuff
 
Remember spark will take the path of least resistance, wet spark plug = least resistance.
With the cap off line up the reluctor and pick up and look at the crank degree, this will be the starting point of the timing, once the engine is running you can't check it because the advance weights are swinging out advancing the timing which should be around 18* at or just above Idle.

18* is just a good starting point and not carved in stone
 
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Also keep in mind that you are not doing this check at RPM, meaning the rotor is going to advance more as RPM's go up.

Brian was typing while I was. :D
 
Do you know what springs, or what rpm the mechanical advance starts moving?
 
Do you have a thread where you posted the specs on your engine?
 
For brian6pac the springs are 1 heavy and one light silver and the mechanical starts at 1200 rpm ..To answer revhendo it is a 340 stroked to 416 .570 lift solid roller camshaft 235- 245 duration pump gas motor. When I checked it running I had it below 1000 rpms so the mechanical weights should not be a factor. With the engine not running, when I line up my reluctor with the pick up my crank is at 30 degrees btdc and my rotor button is just going past the #1 post on distributor cap.With the car running at idle below 1000 rpm my initial timing is 22 degrees before btdc. I would think if I shut the engine off and turned the crank by hand to 21 degrees btdc that the reluctor an the pick up would be all lined up because the vacuum adv is plugged off
 
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30* to start is to high that's why it's kicking back, not sure why it's less at an idle unless it's retarding it electronically. When I set up a motor to do a break in run I set the crank at 10* btdc
line up the rotor and pickup and lock it down, when it starts it never more than a couple degrees off or right on in many cases. I always use a mopar electronic dist because they never fail me.
Every body knows a failure during a break in run is the worst.
 
To answer the parts question yes MSD does make an adjustable rotor , 2 of them actually because they make 2 different diameter distributors . That said as everyone is saying you have too much initial
 
I have tried 18 initial and it sometimes still kicks back. What initial would you suggest. I really never had this problem until I put this distributor in .
 
My 1970 book says the factory spec is 5* BTDC, hot, vacuum disconnected, 900 RPM
 
May not be your problem, but I've known a few big block Chevies that would knock the nose right off the starter at 20° initial.
 
Hang on
The kick-back on cranking may in fact be firing to the wrong cylinder.
But check out what OP says; He set the balancer to 44*BTDC for some reason.
That is not right.
Set the balancer to whatever your initial is set to. Then check the positions of the reluctor and rotor.
The reluctor should be just leaving the Magnetic pick up in the normal direction of rotation, and the rotor should be very close to right under the tower that fires #1 plug. It can be up to nearly 22.5* either way away from *1 tower, before it will fire the wrong tower, at below about 1000 rpm, or before whenever the flyweights begin moving.
Your job is to ensure that when the flyweights start advancing the timing cam, that the rotor is marching towards the #1 tower, to ensure the spark is traveling a shorter and shorter path, as the rpm increases.
Some engines may in fact march the rotor past the tower with increasing rpm and that is ok too. It can continue for quite a ways on a teener for instance.
So again, you have to make sure that as the rpm increases, that the rotor does not march too far. This would be highly unusual. This is why the rotor tip is about 1/4 inch wide, so the coil won't kill itself trying to fire these sometimes wide gaps
 
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