HEI DUI vs MSD

[RCJ]

I'm not using the module or coil its just a gutted hei dist.

[POS Dakota]

I'm not using the module or coil its just a gutted hei dist.

Why? Are you using some kind of ignition with additional features or something?
I could see the rev limiter thing, but I have an internal module with one built in.

Just curious.

[RCJ]

I've used the HEI alot and the external coil and msd box is more reliable.

[POS Dakota]

I've used the HEI alot and the external coil and msd box is more reliable.

Really? I've never had a problem with HEI. I love it.

I have been recently eyeballing one of those msd programmables though...just because it's something for me to play with.

[7racecar7]

So first Run at it, I have a 2BBL on it as limited by our class, have an issue up around 6500 RPMs almost near the end of the straight away where it fades off (not sure if its distributor related or a carb issue) I have the DUI in, i think this is more on the side of the Carb. The 2BBL is set for 6.5 of pressure.

Question, is it possible in any way for pressure to be less that 6.5 at higher RMPs under load, I didnt notice the guage but next time I will.

[donc]

So first Run at it, I have a 2BBL on it as limited by our class, have an issue up around 6500 RPMs almost near the end of the straight away where it fades off (not sure if its distributor related or a carb issue) I have the DUI in, i think this is more on the side of the Carb. The 2BBL is set for 6.5 of pressure.

Question, is it possible in any way for pressure to be less that 6.5 at higher RMPs under load, I didnt notice the guage but next time I will.

Seeing as though you posted about fuel pressure, If you dont have, you may want to try an anti-pullover discharge nozzle for the accelerator nozzle. Some of the carb. guys have done something in circuits to cure fuel pulling out of nozzles @ high rpm. but i know this works.

[7racecar7]

So first Run at it, I have a 2BBL on it as limited by our class, have an issue up around 6500 RPMs almost near the end of the straight away where it fades off (not sure if its distributor related or a carb issue) I have the DUI in, i think this is more on the side of the Carb. The 2BBL is set for 6.5 of pressure.

Question, is it possible in any way for pressure to be less that 6.5 at higher RMPs under load, I didnt notice the guage but next time I will.

Well there is defiantly an issue, the car is poping and bogging in going into the turns under load and starts near the end of the straight away, the only thing i can think of is the fuel pressure as I thought maybe it was running out of fuel but i bumped that back up to 7 same deal.

Any ideas? From a distributor prerspective anyone have any issues with wire crossing with the cable, i have the livewires they look durable enough not to transfer a spark to somewhere. Next guess is to take the fuel pressure regulator off, floats are set, timing is confirmed 35degrees and gaps are at .35 scratching my head on this one. I also picked up a hard start on one attempt not sure if that is related

[7racecar7]

Update: Back to the DUI vs MSD

The issues I posted were not related to the DUI, after I fixed them the DUI ran flawlessly for about a year and a half. Call it 25-30 races. There was nothing done to the DUI in the off season. About 2 weeks ago I noticed the timing was advancing past the setting. This DUI has an advance in it comes in at 3500, so where I would normally set the timing total at 4,000 and the timing would not move past even if you put it up to 5K.

I adjusted the timing down last week and now this week I saw it jumped up even further at 4500 past my total timing setting of 35 up to almost 40+. So the theory of if its not broke dont fix it prolonged the DUI vs MSD test, id say the DUI is broke now or at least worn.

This brings us to the MSD going in (a year and a half later). The MSD has the timing locked out so when it went in its locked in all the way through the RPM, checked and is steady, it did start a little harder (high compression), so you can just spin the starter then hit the distributor switch after a few revolutions to easy up the start.

So far in the garage the MSD sounds a bit more snappy. Ill post back if I see anything new on lap times or anything I can notice vs the DUI. Nice little plus about the MSD is it has a rev limiter built in you can adjust up to 10K, DUI has the same option but I believe its an added cost and is external (they may have built in one by now). I also can run the scott spark plug wires on the MSD that I favor a bit event know the Live Wires are just as good. (the scott wires would not click on properly to the DUI and you had to buy the Live Wires)

On another though, I assume the springs are starting to wear on the DUI could that be the case why the timing is moving ahead at higher RMP, i know when I chose to use the timing curve keeping an eye on the timing/springs were important?

[dirtracr5]

good idea to go with locked out timing. one less thing to break. no need for an advance curve on a circle track engine.

[540Hotrod]

A year or so ago I did an article for Auto Enthusiast magazine where we back to backed a D.U.I. setup against an MSD in a 9 second 572/720 Malibu. Overall it did very well for something you plug one wire into and I'm sure with a little more track time it could have done even better!

http://www.amosauto.com/Articles/Gm/Tec ... butor-ills


JIM

[barnym17]

It is more likely bushing wear on the weights than the springs.

[metriccar]

How does the MSD hold steady timing through all RPM with no advance? I've found that for reasons I can't remember (if IgnitionMan is still on here he'd know), that due to the nature of these things, if you're running an HEI or inductive discharge ignition system, the distributor will retard as you increase RPM. At least with mechanical advace, it will offset that some, which is why I run it. Otherwise if you set timing at 3,000 RPM say at 36 degrees BTDC it will be for example 28 degrees BTDC at 6000 RPM, even if no mechanical/vacuum advance.

[F-BIRD'88]

If your timing is self retarding that much at 6000rpm, its not the distributor.
Look at your timing chain and cam/distributor gear and cam walk.

The electronic's switching time lag latency high speed retard effect (on a good HEI module) should not be more than 1° per 1000 rpm when reving past 5000 rpm.

@ 6000 rpm thats only 1degree lost. so set it at 37° BTDC. (If you want 36° at high rpm)

[7racecar7]

update dui started acting up with the advance amount 12 races into the season the timing was advancing to far usually set at 35 and one race day checked and it was up to 40+ at 4000 rpm sent back to dui the said no issue however i put my msd in same day and timing held at 35 so there was no engine issue.

had dui lock out timing and they sent back.

on the msd i replaced the coil once as it was dead one morning and would not start, the msd was crisp but that may be because timing was locked, i started this year with msd same distributor with replaced coil. first 2 races of season car would buck at end of night almost like the distributor was turning on and off. turned out to be a break in the module where it connects to the heat sink.

so now im back to the dui, the msd im rebuilding so over 2 years say 40 races the msd ran about 22 and the coil and module went bad during that time.

dui the advance did not hold, locked out now running locked. in short so far ive had more issues with msd their coils and modules but ive used their products longer

more updates on progress of dui to come, got my eyes on trying a mallory next

one difference the msd had less slop from factory than the dui

[rally]

The HEI is a good piece. I used one on my drag car years back, still on the shelve and for sale if anyone is looking for a nice setup. DUI parts were added to mine. DUI hi-po coil and module with rotor, good Accel cap and rotor with brass terminals and speical nylon screws to prevent arching inside cap terminals. Its also locked out for total timing. MSD is now in my engine. Nice unit. Anyhow HEI Distributors are good. Wouldnt be afraid to go back to one.