Shep69 149 Report post Posted January 15, 2015 Hi my MSD 8578 has a slight movement when the engine is running. The motor seems to run fine. I can only assume that the shaft is bent . You can see the dizzy cap move in an oval direction. Is this a big concern? I have put a timing light on it and I am still getting good advance. The dizzy was in the car when I purchased it . Cheers Shep 1 Shep69 reacted to this Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 15, 2015 IS it bolted down good? Pop the cap and be sure its correctly located in the notches, and be sure the rotor is the correct one. Quote Share this post Link to post Share on other sites
buening 63 Report post Posted January 15, 2015 Make sure the rotor is on all the way. They have a notch that fits in a slot in the distributor shaft, so make sure it is in the slot and fully pushed onto the shaft. Quote Share this post Link to post Share on other sites
Shep69 149 Report post Posted January 15, 2015 Thanks for the replies. Yes checked everything. I'm going to change out the manifold with a edelbrock rpm so when I remove the dizzy I will place it in a vice and dial it up to see if the shaft has any runout . The motor seems to run fine. I just wanted to know if anyone else has come across this before. Could the drive gear be damaged? Cam? Quote Share this post Link to post Share on other sites
sportsroof69 13 Report post Posted January 15, 2015 Yeah, I wouldn't run that until you figure it out. It "could" damage the cam. MSD sells replacements shafts. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted January 16, 2015 I run the same distributor, MSD 8578, and never had any issues like you are experiencing. I've replaced the shaft when installing a steel dist. gear so I can honestly say the material is fairly soft below the surface treatment. So your shaft can be bent. Fortunately, the shafts are relatively inexpensive, about $30 from MSD. But you will need a press to replace it with ease. Quote Share this post Link to post Share on other sites
Shep69 149 Report post Posted January 16, 2015 One thing that I have noticed is that the previous owner has put a 302 cam in the 351 Windsor changing the firing order . Would the 351 distributor gear be the same for a 302 cam. Just wondering if they are interchangeable? Or could this be causing some issues bending the shaft. Quote Share this post Link to post Share on other sites
Wycked69 20 Report post Posted January 16, 2015 260/289/302/351W dizzy gears are the same size and pitch. Quote Share this post Link to post Share on other sites
buening 63 Report post Posted January 16, 2015 Have you tried cranking the motor over with the cap off to see if the shaft looks bent? If the rotor wobbles, remove it and still crank it over to see if the top of the shaft moves in oval fashion. A dial indicator would help immensely due to the slow cranking speed/rotation of the distributor shaft. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted January 16, 2015 260/289/302/351W dizzy gears are the same size and pitch. That's correct, the only difference is the 351W has a larger diameter distributor shaft. One thing that I have noticed is that the previous owner has put a 302 cam in the 351 Windsor changing the firing order . Would the 351 distributor gear be the same for a 302 cam. Just wondering if they are interchangeable? Or could this be causing some issues bending the shaft. There is no difference in the distributor gears. One thing I would check is make certain the gear is installed at the correct depth on the distributor shaft. As far as the 302 firing order cam in a 351W. I have seen long term negative side affects of the 302 firing order in a 351W. The 302 firing order in a 351W tends to ruin the front crankshaft main bearing. I understand that is why, or partly why, the firing order was changed for 351W and later 302 HO motors. Quote Share this post Link to post Share on other sites
