I just installed a complete MSD System, Pro-billet tach drive distributor, 6AL box, blaster 2 coil, new super conductor 8.5 wires, new plugs.  I used the R44TX ac delco.  I am having a miss/hesitation on accelleration and it runs like crap at the top end.  I have the bushing that allows for a total of 25 degrees of centrifical advance and the spring set up that allows full advance around 3500-4000 rpm.  My idle is a little rough, but it starts ok.  My initial advance is 12 degrees.  What am I doing wrong?  Also, can I install an adjustable vacume advance on this distributor?

Help please, anyone...

Well, lets first have some faith in the MSD equipment that it's all ok and something is not defective from the factory, unlikely with MSD. Consider how you have the wires routed. One of the things the engineers at Mallory, (my old job) was how the wires are routed. If you have two wires runing with each other in close proximity, a voltage can be induced from one to the other. Magnetic pickup wires that run along side of each other should be twisted. My cd box is mounted in the compartment where the jack goes and the wires from the distributor to the box go down one side of the console and the wires to the coil from the box go down the other. I'm assuming that yours in mounted in the engine compartment, but check for the above. Also, check the battery and ground wire for the box, and the voltage when you are runing. CD boxes don't work if the voltage gets too low. The system sounds like it's adjusted good enough to run ok. The MSD is a mag type pickup and no ballast resistor is needed. I'd back the total advance down and see if there was any differance. Did you check the resistance of the plug wires after you cut and assembled them? In my set up the coil is grounded to each head, it's mounted on the firewall. Take it out and flog it, then shut if off, coast to the shoulder and pull out a plug. See if its got some color. To my knowlage MSD's don't have a adjustable vacume advance, I looked on the MSD web site and couldn't find one. Some one correct me if I'm wrong on that one. One other thing, if the pickup wires from the distributor are reversed, it can make a differance in the timing and performance.

whats the spark plug gap, should be somewhere around 45-50, also I think your adv. curve is a little slow, from my expereance total should all be in by 2800-3000 RPM with a total of 34-36, it seems your total of 37 degs is a little high, try giving it 10 degs. initial = 35 total might help the rough idle, one reason I don't fool around with springs, weights, and bushing is that I'am never sure its right, thats why I have a pro spin the dist. on a dist. machine, another thing to consider is that you don't have a vac. adv.its important to have one on a street machine, its job is to pickup the adv. at low RPM for a smooth transision until your mech. adv. comes in, you'll also get better gas mileage with one than without, with the slow curve and no vac. adv. that might be the reason for the hesitation on accel, if you have the dist. spun have the Tech give you a before and after to see if you made a mistake or if MSD gave you the right info. anips38594.5778703704

My plugs are gapped at 60 thousands, I will change that to 45.  It has a vacume advance, but my overall advance is too high, I guess, so I will take out 5 degrees of centrifical advance by changing the limeter bushing.  I think 10 - 12 on initial with 20 centrifical is where I will start looking.  I do have some parallel wires, I will fix that.  A lighter set of springs will let the advance come in faster and with less total advance, hopefully the top end will straighten out.  I checked the voltage and connections when I installed the equipment, I will give it a second look.  Thanks for the advice, I will let you know how it comes out.

I think the 25 total bushing is OK, just adjust you total by how much initial you put in, 10 initial + 25 built in to the dist.= 35 total, now the 45-50 spark plug gap is a starting point, if MSD recommended a gap go with what they recommended,if it was 60 stay with that for starters,like I said, I think the adv. is too slow, shoot for the 2800-3000 all in, change only ONE THING at a time, it gets confusing if you change everything at once, it might just be the slow adv. now, when you time your motor have the vac adv. disconnected and the vac. line plugged.     anips38594.771712963

Good point, thanks!

Sorry about the confusion on the vacume advance, it has a pre-set vacume advance.  I was wondering about an adjustable vacume advance that would allow me to control my total advance at lower rpm.  Crane sells them, so does mallory, but not MSD. 

I try not to take to much for granted, MSD makes a good product, you would think because they make millions of these things mostley for the street that they would probably would install a Vac. adv. that was pretty much middle of the road and work with just about anything, because these things are mass produced by the millions I'am sure there are bad ones out there, hopefulley not in your case, just take your time, work on one thing at a time, if everything was OK before you made the change, then you'll track it down, good luck   

Your 68 has resistor wire that runs to the positive side of the coil.  If your using this wire to supply voltage to the red 12volt switched wire on the ignition box then you will only have roughly 9 volts which is not enough to run an MSD system.

Their instructions are pretty clear about this.  To by pass the resistor wire you must find the wire at the firewall where it enters the fuse panel and run a non resistor wire up to the box to get a full 12 volts.  The other option is to run a 12volt wire off the bat terminal on the altenator to the 12v switch wire on the box.  However you decide to do this the wire must have 12v before and after cranking.

Because of what I wanted to do, I went directly to the fuse box, there are three spades on the fuse box
marked Batt, Acc, IGN, I made sure they were switched on and off by the key switch, took a volt meter and checked for 12 volts when on and during cranking, when cranking volts will drop a little not much, its been a while and I can't remember if it was Batt or Ign,
ANYway I piggy backed off the the spade to a circuit breaker with a 12 ga. wire, out of the breaker with 12 ga to a hidden disconnect switch, out of the disconnect with 12 ga wire, through the firewall grommet, to the HEI, you can do the same with the MSD box with or without the disconnect switch I believe.   

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