My old truck had one of these old Sun Tach boxes (didn’t work) and I thought it was cool and I wanted to keep it - and NOW I have a use for it. For those that remember my Homemade HEI distributor - this will be a nice way to hide the ugly “modern” electronics if you can call a HEI module modern.
@HemiRambler I also like it...….one question though, NOT a criticism, just a technical question.....in OEM installation, is the module inside the HEI cap or on top.....and does that affect cooling (longevity) of the module? Ray
Here is info posted by HemiRambler on the distributor build. https://www.jalopyjournal.com/forum/index.php?threads/1072803/ Phil
@Hnstray, That's a great question. In a factory application the HEI module is mounted well under the cap - it bolts directly to the aluminum distributor housing where points normally would be - and for good reason. Between the module and the aluminum there is Heat Transfer compound to help dissipate the heat from the module. If you notice my adapter plate is made from aluminum for this very same reason. The question I have yet to answer is - how much heat exactly are we dealing with? I plan on setting this up on my distributor machine and running it for several hours to see if there's any heat rise within the module. Just gotta find my thermal probed and a couple other parts. It ought to be interesting.
This is very similar to another conversion shown on the HAMB using a voltage regulator housing. Done by Zibo I think? Like this, he used the terminals for connecting to the distributor. Just as an aside, new electronic boards are available for the Sun tach.
I had a GM four pin module tested at AutoZone. A couple minutes wired to the test equipment and it was too hot to hold in your hand. It was a bad module. Don't know if a good module would get as hot. Phil
I ran it for an hour and a half and the last 30 minutes it rose 1 deg or less every 5 minutes. Using a "K" type thermocouple inserted into a hole in the aluminum heat sink the final temp I measured was at 186F. Admittedly the test was a tad bogus since I couldn't find any heat sink compound - I hilbillied it up using some silver antiseize. I'm gonna rerun it soon, just need fresh batteries for my hand held temp gun which I was using for case temps. Somewhere I have a HEI - I may run that was well to get a baseline.
HR could you ventilate to cover with small holes, perhaps around the perimeter, to allow for venting?
Shouldn't need vent holes if the piece of metal works as planned for a heat sink. Figuring what the temp is inside the distributor on some of the engines that the module was on originally.
Jim (Bubba) did a similar conversion for a friend of mine for his Studebaker. The HEI module was in a fairly thick and finned Aluminum box, that we tucked up under the dash. After running it for awhile I recall it was fairly warm to the touch. Probably not any help there, I mean the box we had could have been dissipating the heat, or retaining it I guess.
If you are mounting this on the firewall, it can mounted on some stand-offs, and install a small 12volt cooling fan. The type they mount on top of microprocessor chips. They are around 1.5" square, 3/8" thick. I have done this with 12-6volt converters, I just use the 12 volt input to supply it. A couple of small holes drilled in the case to let air in, and you're set.
So that's the question really. I am kinda breakin' the rule's here as I have no ventilation thus far. I've run these modules on a finned aluminum block in the past but they were always exposed to air. The question here is can it live inside the sun box. Right after I ran this test my distributor machine got UNHAPPY. It's kinda buried next to a car in the garage so I have to move a couple cars to get to it. BUT! I have to move my truck tomove those and wouldn't you know my truck takes a dump!!! It's a 12V cummins and I am a newbie to diesels - I tracked it down to a bad grid heater relay set. Parts came TODAY - so the truck's running but its raining so not pulling the hot rods out - dang I really wanna run some more tests!!! To Be Continued!!!!
I'm thinking there's vent holes in the base of my distributor on my '89 Chevy, I have one I pulled out of it and will let you know tomorrow.
Heat is one of the killers of solid state semiconductors (transistors, IC's, etc). Most industrial stuff is rated to around 60Celcius. Some military spec stuff will go to 80. Get rid of the heat, keep the insides happy. You could cut the back of the box out, so that the backside of the aluminium heatsink plate hangs out and mount it directly onto the firewall, etc, (with heatsink compound), or even attach a finned heatsink to the back plate (with the fins on the outside of course).
I've read several somewhat conflicting numbers on that. Commercial 0-70C, Industrial -40-85C, even saw some military listed at 120C! I'll have to talk with some of my "wirebender" friends and see what we used to use at work. In any event - yes agreed - Heat Bad! The idea here is conservation of effort that still yields maximum results. I've run this test now a multitude of ways and have seen relatively decent drops in temp with minor changes. I'll update with real numbers once I repeat a couple tests to ensure I'm not talkng out my a......
I used a heat sink from the late 90's Vortec engines. It was part of the coil/module bracket bolted to the intake. Had to cut one fin off, and drilled relief holes for the nubs on the back side of the module. Used a steel bracket to bolt it to intake for now. It's in the wind by the SBF distributor.
Yep, those are available dirt cheap. I want to HIDE the module in plain sight so that IF I ever have to work on it it's "easy" to get to - otherwise I'd stick it under the dash. Getting old and lazy means under the hood for me.
I'm just running mine for now out in open, as I had a few other modifications going on at same time, and wanted it back up and running. One could use that heat sink, inside an enclosure just for the extra "sink" capacity.
At the moment I am doing the same except I have two mounted on a plate of aluminum - a buily in spare. For this I wanna hide it. Extra fins are good, but you gotta get the heat out of the box too. I ran a few tests on seeing what effect each method I came up with has. Lots of ways to skin a cat.
I found out the hard way that you could not put them under the dash with an aluminum plate with the proper grease and make them live! It requires a good heat sink and a small fan. Good luck on yours, Gary
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