articfriends

iTrader: (1)

The majority of stuff I build, tune and dyno uses mefi and mercruiser/gm "tbi" style distributor. I have used that syle distributor and revved as high as 7000 rpms. Ive found on various dynos and now on my own that somewhere around 5600/5800 that the stock original mercruiser 7 pin distributor modules will overheat and cause motor to misfire. Cheaper autoparts store ones will overheat and break up around 5200 to 5500 and even burn out.
i normally switch EVERYTHING automatically to the davis unified ignition module and i can turn these things anywhere i want. So i dynoed a project motor last week, 454 w modded mag mpi intake, ran good, had stock ign module. Added the whipple sodemount supercharger and all stuff goes with it , my dui modules for both.motors showed up. Start pulling yesterday, cant get past 4000 to 4600 without motor breaking up. Chasing it, plugs, timing, plug gap etc, makes ZERO difference. Swap stock.module back in, bang , pulls to rev limiter.
has anyone else had a bad D.U.I. module? This is second one to cause.me problems in past 2 years, normally there stuff is top notch, Smitty

sutphen 30

I'd look at the dwell tables in the ignition section of the mefi programming.plus,theres a rotor that has fins on the bottom,that helps keep things cool.

articfriends

iTrader: (1)

ive had to lower dwell before to get them to go to 7000 and not overheat the module, just surprised the dui module acts so bad vs stocker, ive had opposite results before. I have the 2nd new dui module im going to try today

F-2 Speedy

iTrader: (6)

Are you running the stock OE Merc coil.........reason Im asking, I bought new after market coils for some builds and they wouldn't play nice with the Merc distributor, they would double fire @ 10* and 270* and over heat the ignition module, changed them out to the stock coils and the problem went away.

Edit: you're running the efi coils so not the same

SB

iTrader: (1)

What are you using for heat transfer paste ? Hope it's not clear. I use Arctic Silver CPU paste. Very thin, and then use razor blade to make thinner. Make sure to remove traces of old stuff from dist.

S30 may definitely have your fix - definitely look at dwell on the programming. Ran into this on a coil on plug (I know, not the same) engine and if you can believe it, the coils where burning thru the silicone/rubber and plastic. Basically, most of the coil assembly's would burn. What a mess and stink. This was my lesson on dwell.

On a few carb'd app's I bypassed the modules and installed the Crane HI-6M (now Dayton Sensor's). Needed different advance curves on those anyway, so easy decision there.

SB

iTrader: (1)

On the EST (GM HEi with External Coil) distributor ? I don't get it. (i don't get much.) Who's coil ?

F-2 Speedy

iTrader: (6)

I'll see if I can find the packing slip

Edit: Universal Ignition Coil High Output 12V MSD Ignition Systems 60K Coil Black

I know may Soon Die......LOL they didn't but kilt my chit

articfriends

iTrader: (1)

Stock merc coil, i did back to back testing previously w a msd coil, stock merc coil, dui coil on dyno and made zero, zip difference.
i slso tested crane box and msd box and aside from being able to lower dwell alot to more to keep module happy (takes load off) and turn 7000, at sub 6000 ranges made zero difference in hp, may have idled better when multi sparking under 3000 or what ever, Smitty

articfriends

iTrader: (1)

i used the clear stiff that came w the dui module, again, broke up somewhere between 4200 and 4800 inder boost, free revs to 6000 though no load and when you swap back to merc module w same paste easily pulled to tev liniter at 5600. I havent lowered dwell yet, have in the past when i had these things break up w stocl module at 5600 and dui.module at 5900. I think the.module is junk. Btw, this 454 is breaking 700 hp and ft lbs tq, real surprised w this tiny blower!

F-2 Speedy

iTrader: (6)

that's a good number............are those 2.3 whipp's