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NEED HELP WITH MSD ISSUES
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jeep_406
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Joined: 12 Sep 2002
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Location: Tewksbury, Mass 01876
53123.48 points


1972 Chevrolet Nova

PostPosted: Sat Jun 19, 2010 1:43 pm    Post subject: NEED HELP WITH MSD ISSUES Reply with quote

I've always had a problem timing my engine since I switched to an MSD setup years ago. Always thought it was the 6AL box. On the engine dyno with my distributor but the shops box and coil my 408 ran best with 38 degrees total. When I installed the engine back in the car with the distributor in the same location but with my box and coil the car would hardly run. I had to run it up at least 10 degrees more. Sorry I'm getting long winded here.
I've run it up as much as 58 degrees total without vacuum advance and haven't got it to ping or detonate.
I'm going to install a box in a friends 41 Ford with a ZZ4 so I put his new 6AL box in my car and got the same readings as I did with my box. I've checked phase, tried reversing the wires to the distributor, check grounds, checked wiring schematic a number of times. Cam is straight up, timing mark on balancer is dead nutz. What am I missing.
The car preforms very well for what it is. It just blows me away that the numbers are so far off and I wonder if I'm leaving more on the table.
By the way, when I reversed the wires I got an additional 20 degrees timing. Engine didn't like 78 degrees Shocked
I also run an MSD Adjustable timing control PN 8680 and an MSD Launch Control PN 8735 but I had the timing issues before I installed these.
It's an obsolete Distributor PN 8461 with a mag pickup and the 6AL box has a PN of 6420. I sent the box back to MSD a few years ago and they said there was nothing wrong with it. Hope I didn't put anyone to sleep with this post.

On another note I've only run the car one day with the cam change and was a little disappointed. It only went 11.32 but it was hot out and although I don't have weather info it wasn't good. The DA was over 2600 feet but i don't know exact. I know some of you guys would love DA that low but in New England especially in the fall the DA can go 3-400 feet below sea level.
I'd like to make an effort to get into the elusive 10's and then probably change back to the old cam for street manners. Right now I have to kick it into Neutral when stopped to maintain any vacuum. I'd rather have the AC and run low 11's than sweat my balls off for a tenth or so. Any help would be appreciated.

Jeep
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MufflerBearings69
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1968 Ford Galaxy

PostPosted: Sat Jun 19, 2010 2:34 pm    Post subject: Reply with quote

I see you swapped boxes but never tried another coil?

I would have tried that out. Maybe just a shot in the dark, but sometimes I get lucky like that.

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jeep_406
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1972 Chevrolet Nova

PostPosted: Sat Jun 19, 2010 3:39 pm    Post subject: Reply with quote

I didn't think a coil would cause the problem but I'll locate another coil and give it a try. I'll let you know if it works.
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Big Dave
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PostPosted: Sat Jun 19, 2010 5:02 pm    Post subject: Reply with quote

MSD boxes are notoriously fussy about coils being matched to the impedance of the ignition box. You will not MSD sells twenty or more coils but only suggests one or two of them for each box. There is a reason.

http://en.wikipedia.org/wiki/Impedance_matching

Big Dave
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jeep_406
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1972 Chevrolet Nova

PostPosted: Sun Jun 20, 2010 3:31 am    Post subject: Reply with quote

Big Dave,
I'll have to check that out. When I got the dizzy & the 6AL box it had only been used for about a dozen pulls on a dyno. I didn't get the coil so I bought one of the Vibration resistant units from MSD. This was a long time ago and the coil has been repainted so I don't know the number. Misplaced the invoice. One thing I do know is that I could never run the engine without an abnormal amount of timing. Possibility of it being coil resistance never occurred to me. Kept thinking it was in the box. Never had a problem with the unit. Through trial and error we found the engine likes 58 degrees total not including vacuum advance. That was before we made a cam change and added 500 RPM to the torque converter stall speed.
My best bet is to most likely contact MSD and see what coil they suggest or find out from them what the 6AL specs are and how to test it. I'd love to find the problem.
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bill jones
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PostPosted: Sun Jun 20, 2010 8:21 pm    Post subject: Reply with quote

-I'm curious if you are using the same timing light when you were on the dyno and again when you are setting the timing away from the dyno?
------------------------------------------
-You stated you run a timing control and a launch control.

-I haven't tested any of those "controls" on my ignition testing machine lately--but from testing experience I can say that it's easy to end up with issues with those "controls".

-and you also said this timing related problem was there before the "controls"----so I'm wondering again about if the timing light has ever been verified as to it's accuracy in more than one comparison test to another known good timing light----and tested on more than one application.
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Big Dave
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PostPosted: Sun Jun 20, 2010 8:51 pm    Post subject: Reply with quote

Timing light would only be a issue if it is a dial back timing light. I do not use them on my engines as I have a degreed damper with a pointer set at TDC with a dial indicator. A straight timing is always going to trip at the correct time, and MSD would have you believe that only their dial back timing light will work with their ignition modual (a claim I rather doubt, but I have not tested).

Big Dave
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MufflerBearings69
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PostPosted: Sun Jun 20, 2010 10:53 pm    Post subject: Reply with quote

jeep_406 wrote:
I didn't think a coil would cause the problem but I'll locate another coil and give it a try. I'll let you know if it works.


For what its worth I have always used a plain old Blaster 2 with my 6AL and never had an issue. I'm still on my first 6AL (11 years old) and never an issue. I was told by a guy at the speed shop in Daytona to use the Blaster 2- coincidence or recommended I dont know.

I have a MSD tech book here somewhere, been looking for it to see if it says anything good about impedence.

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jeep_406
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1972 Chevrolet Nova

PostPosted: Mon Jun 21, 2010 1:00 am    Post subject: Reply with quote

I used the same light to check timing on the dyno. I also checked it against the light they normally use at the dyno shop. They both read the same. I also have a dial back Snap-on light that won't work with my setup. A friend's dial back light seems to work fine but it also reads very high.

I picked up a Blaster 2. PN 8202. It ohmed out identically with the coil I have been using. Haven't put it on the car yet. I'm pretty sure the coil I've been using is PN 8222. That's the High Vibration version of the Blaster Coil. Don't expect it to make any difference.

I've had the improper timing reading ever since I put the MSD setup in the car sometime around 2002. I added the Launch Control and Adjustable Timing Control later. They did what they were intended to do.
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Knarley Darley
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PostPosted: Mon Jun 21, 2010 5:30 am    Post subject: Reply with quote

Check the coil wire, and for that matter ohm check all of the plug wires. I have had weird similar problems. I dont know if it is the primary wiring of the box, or the secondary resistance of the coil and or plug wires that hits some kind of threshold causing the box to get a mind of its own. I have had them timed while cranking the engine , and then we put fuel to it so it would start, and poof it had 15 degrees less timing running at over 3000 rpm, or when the multi spark function turns back to a single spark per cycle the timing would drastically change. Make sure that thing is grounded good to the engine and the chassis, also ground the distributor (very important even though it seems impossible for it not to be grounded) I have had them shut off on me on street cars and the only thing I did was add a seperate ground to the distributor housing to get it running again. Keep us posted
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jeep_406
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1972 Chevrolet Nova

PostPosted: Mon Jun 21, 2010 10:35 am    Post subject: Reply with quote

Thanks for the help guys,
I hope to get back to the Nova in the next day or so. It has always performed very well for what it is but you wonder how much more there might be in the package.
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clay
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1972 Chevrolet Nova

PostPosted: Mon Jun 21, 2010 11:43 pm    Post subject: Reply with quote

Really odd thing there. I haven't dealt with that one yet. I don't see how a timing light could make timing appear more advanced than it really is. If that was the case, it would have to fire some amount before it received input from the inductive pickup. Now I have heard of some timing lights showing timing being more retarded than actual due to delay in the internal circuitry and I'm thinking maybe due to the light itself. I run your same basic combo - 6AL, Blaster 2, and multistep retard with a Pertronix pickup in the distributor. My most recent problem was when I installed the turbo's for some reason I started picking up interference on the wires from the distributor to the MSD unit. It showed up as the tach having a slight bounce every once in a while usually around 2000 - 3000 rpm. It also developed a miss when I tried to go above about 10 lbs. boost which I had run around 20 with the Procharger. I installed shielded cable from distributor to the MSD and added grounds from the heads to the chassis and no more tach bounce or miss. Never saw any of this affect timing however. I wish I had something else more specific to tell you. Coil is something different from dyno to car. Might also try unplugging the alternator - shouldn't affect it but it's something different. I might even go as far as sitting a battery on the ground and just hooking up the MSD unit to it. This should absolutely isolate any effect the car should have and see if anything changes. Maybe excessive electrical noise on the supply side? I'm stabbing here - but it's all I have. Clay
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Tue Jun 22, 2010 3:06 pm    Post subject: Reply with quote

Jeep,
I would check to make sure you have a good #10 gauge minimum feeding the box. Measure what it is getting for voltage when the car is running at the power input wire. Grounds should be good too. I think it might be power related.
Paul

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jeep_406
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1972 Chevrolet Nova

PostPosted: Wed Jun 23, 2010 2:59 am    Post subject: Reply with quote

I changed coils today. That didn't make a difference. I also used #1 wire battery cable from the battery to supply power to the box with no change but I didn't try changing the ground. If I get a chance I'll do that tomorrow.
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af2
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PostPosted: Wed Jun 23, 2010 9:21 pm    Post subject: Reply with quote

Did the balancer move?
I have killed myself to find it 10+ retarded.
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