I would like to make the big switch from points distributor to HEI.The distributor shield has to go on the '74.Can I use another year model shield for the HEI distributor?does anyone know the difference in size??to sum it all up I have to have a chrome shield on the distributor.and I dont want to add one of those ignitor units to my existing unit. ..THANKS

 

I'm told a 75 box will fit ... haven't tried it.

 

There is no chrome shielding that will fit an HEI. The HEI shield was a big black plastic cover with a metalized inner liner.

 

If you want to retain the small size etc, google for Daves small Hei in Arizona ?? or NM??

He converts your present dist to hei mounting the module on bottom and using an external coil. He bead blast, new bearings etc and curves for your needs. Never heard a negative.

You can do this yourself with a gm hei module and MSD magnetic trigger setup.

 

One option you might consider is replacing the points with internal solid state, magnetic or option designed points. You'll keep everything except the points including your coil. Jegs and Summit have the conversion kits. However, an HEI is hard to beat.

 

Go to summit racing and type in this part number. (PNX-1181) This unit replaces your points with a hei unit and you can still using your stock distributor. I swear by pertronix stuff......... I run this stuff every saturday night at the local short track (stock car) and it is very reliable. I am a engine builder and my motors regularly see 7200 rpm's and I tell all people whom run my motors to go with pertronix stuff for race classes that require you to have a stock looking distributor.... For street use they are flawless !!!! If $$ is no object or you race class allowes you to use aftermarket looking ignition I tell all my customers to go with MSD. Take care... Butchford

 

Take a closer look at 75 thru 77 distributor top shield for HEI dist ... not 78 thru 82; plated steel
http://www.madvet.com/opener.htm?609405+609405

 

Just out of curiosity, why do you want to do that? A properly set up and curved points-style stock distributor will out-run anything on the market, especially if teamed up with a basic MSD system... and the points will last forever with no adjustment needed. There is no reason to yank the stock distributor.

 

There is no need to remove the stock distributor... this pertronix unit fits under the stock dist. cap and it just replaces the stock points and condenser.... Are you saying that the point system with a msd coil is superior to a aftermarket HEI unit such as pertronix with a 50,000 coil ??? please explain lars ????

 

My 76 top shield is chrome plated steel, not plastic.

 

I wouldn't use a PerTronix - I'd stay with a good set of points and add an MSD system. You can even retain the stock coil, but an aftermarket coil will perform better. Yes, the MSD on a stock points distributor, with a good curve, will outperform an HEI, and there is no peformance gain from a PerTronix conversion. I did dyno testing at Westech with Matt King from Hot Rod Magazine where we demonstrated this to be true on a 302 Ford that we ran all day with various ignition system configurations.

 

I've heard of quite a few pertronix failures. HEI is reliable.

 

I've had petronix on before,but it left me stranded and had to go back to points system on the side of the road just to get home.I just believe that a HEI distributor is far superior and reliable.

 

I've had petronix on before,but it left me stranded and had to go back to points system on the side of the road just to get home.I just believe that a HEI distributor is far superior and reliable.

 

It is, save for the junker epoxy coils in the caps, even the aftermarket "50,000 volt" ones

A points system will give, on the very first spark on new points, about 6,500 volts to the plugs. The drop-in systems, PerTronix Ignitor, Mallory Unilite and magnetic, Breakerless, Comp-U-Fire, Crane XRi and others, work the same way, give no more voltage than a points set, they just do it consistantly. These systems have no dwell extension and/or drivers to make more spark energy within the coil, no matter the voltage feed into them, no matter the coil used, plain and simple. These systems have been refered to as "HEI" by others and overhype advertizing by their manufacturers and misguided and misleading magazine test editors, when in fact, they are not even close to producing HEI type spark levels and performance.

A large cap HEI will give 18,000 volts with a stock coil, and aftermarket coils will give 22,000 volts, period. Reason: the coil temps go nuclear from tgwo reasons, epoxy filling, as these filllings do not allow heat leaching out of the core. So, what heat is made in the core, stays in the core. And, they are placed under a cover, which holds even more heat into the coil, which increases coil resistance, which lowers the output voltage, and on, and on.

Remote mounted oil filled coils work well with the HEI, using cap adapter MSD 8401, a section of magnetic suppression, spiral or "magna" core coil wirte gets the better coil to the adapter and better overall spark. I have seen a lot of large cap HEI's deliver upwards of 32,000 HONEST volts when this coil change is made. Oil filled coils leach heat from the core much the same way a thermo-siphon cooling system does, so...core heat is trqansferred to the outer jacket, and both the core and coolant are constgantly and consistantly cooled, over and over again.

Contrary to what some know it all's have tried to put over on the unsuspecting user public, the modules in HEI's are NOT the main problem with rev limiting some are saying is the cause. Unless they are damaged by a coil that is layer shorting, they aren't the problem at all. The coil is. Best rev limiter GM ever developed. Get that epoxy coil out of the cap, better distributor overall, that large cap HEI. Recent magazine and other testing of HEI modules has proven that even the "cheapie" offshore modules perform within one percent of the big name modules.

HEI myths:

Module is the cause of rpm limiting, nope, in cap coils are the real cause.

Mechanical advance curves can be limited by altering the slots on the mainshaft. Well, maybe, but why do that, when the start/stop and curve points are done with the weight and center curvature profiles? Use the right three parts, spring them correctly, correct curve is then in place. 375 center plate, 41 weights are good for 21/22 crankshaft degrees of mechanical advance, same parts used in ZZ distributors, from ZZZ to carburetted ZZ572, and every small and big block Suburban from the late 70's to early 80's and most medium to heavy duty trucks.

Any old set of weights and center will do, I've got these, but the timing isn't right. Yup, as there are only 437 different curve combinations from factory weights and centers, try 'em all, or use the two numbers above, your choice. Nope, new weights and centers are NOT available separately from GM. Nope, current curve kits abvailable don't work.

The magnetic pickups never give trouble. Another misnomer. In reality, HEI magnetifc pickups are right down there with Mopar pickups as far as low pereformance, and the4y suffer frm wire breakage, and other problems. Best in the industry are the Ford/MSD pickups.

HEI was designed as a performance distributor. Far from it, it was designed for two reasons, 1, emissions compliance. The EPA requires new vehicles to have ignition systems that don't require maintenance for 50,000 miles, and no tampering is allowed within the mileage frame. So, GM and others had to develope no tamper systems, and we got the HEI. 2, as emissions regs required leaner air/fuel ratios, less and less fuel molecules were induced into the chamber to burn, and these molecules were placed farther apart than from richer mixtur4e strengths, so...a higher voltage system had to be developed to light the further away from each other fuel molecules off. this was done by increasing spark voltage oputput and larger spark plug gaps to get a better spark kernal as less fuel molecules pass through the spark plug gap.

HEI caps were designed to stop crossfire and scatter sparking. NOT, they were designed to get the coil into the cap, and all the components inside the cap, nothing more. A correctly phased small diameter distributor, even as small as a Mallory, won't have cross and/or scatter fire issues.

HEI's are no maintenance. Nothing could be farther from the truth. HEI's require the same amount of maintenance as any other distributor, save for points adjustment. Don't lube those weights at their pivot, expect the pins and weights to try to auger their way apart, wearing both out, to the point of breaking the pins right off the reluctor plate.

Now, this is NOT an advertisment, it is fact...so...nobody go get crazy over it, advertizing it ain't. The Corvette distributors are expensive, and shouldn't be permanently altered, but, there are ways to do a real live HEI or MSD trigger only conversion to them using parts from low cost regular points distributors. If the points plate and points cam assemblies are used/altered from a junker regular points distributor, the stock Corvette parts are set aside, so... if the owner wants to return it to stock points at a later date , he can do so, and the distributor isn't permanently altered. This requires a remote mounted HEI or MSD module, but that isn't an issue. How do I know this? I am the Dave that is the guy at DAVE's small-body HEI's. and now, I am also doing feedback HEI conversions, for EFI useage. In fact, I have a Corvette tach drive dist here to do as a feedback HEI for a noted MASCAR racer for his personal 1966 427/390 he is Commander 950'ing. Anoother will be here next week to do the same. Please understand, these HEI conversions use real HEi mmodules, not aftermarket stuff like PerTronix, etc.

If anyone tells you a cast iron tach drive or FI dist can't be converted to a real, live HEI, or MSD trigger only, or feedback HEI, smile, and walk away. You already know better.

Just why was the above NOT an advertizenment? Well. I have a policy, I do not do conversions for board members from the sites I visit, no exceptions. So...even if I get an enquiry from someone here, I won't respond, nor do a conversion for them. This frees me up to answer questions honestly, and not get flamed for, and/or accused of "advertizing on the site" by some accusrer types. Decliining work from board members, no ad. This includes anyone responding from the above link to my web site, from this site. I'm here to answer questions, not advertize.

BTW, I own 9 Corvettes, all pre-1970 models.

 

 

I have been a professional wrench since the mid 70's. I've been under the hoods of everything from 50's vintage Nash (Nash-i, Nash-e-seez??) to the latest Audi... NOTHING and I DO MEAN NOTHING has affected automotive reliability and performance more than HEI type systems.

After being schooled 'above', one thing is painfully evident... The author never had to lay in a half frozen drainage ditch hooking 'J' chains onto some cheap bas***ds Dart because he just had to push those points another month. Points set ups begin to degrade from the very first spark, regardless of quality or brand, it's the nature of the beast. Degraded points = bad spark; bad spark = foul plugs. Soon, "Hey, lets all get out and push".

Sure, nothing is perfect, and the first generation HEI set ups were lacking. But I have seen them go 80,000+ miles before quitting time. Points? Maybe 30K at best. I'd say thats trump.

GM pickup coils with vacuum advance did indeed snap wires as they aged. I've dragged plenty of them into the shop, but the tech. got better and the vac advance headed for the burn barrel, problem solved. No twistee, no breakee.

Heat soak has plagued electrical 'everything' since Ben Frankln melted his first kite. Hot copper? You bet, drive that sputtering old points fired Falcon around the block on a hot day and grab that bottle coil: OUCH!

Spark curve: Ideas about spark curves are like vacuum cleaners; every one has one and they all suck. The factorys have always done a GREAT deal of research on stuff like this. They have paid a lot of money to a lot of people to work these things out. The best timing and advance is the one provided. If you plan on keeping all the bolts and gears under the hood, let it be. Keep it lightly oiled and working as provided and you will have nothing but sucess. Sure, you can pick up a little power, maybe, but it's just not worth the trouble it can cause. OK, so Johnny law only gets to write you a ticket for 110 insted of 112 in that school zone... oh well you can always add the two miles per hour to the story at the bar.

I have seen cowboys slap a new bumpstick and lifters along with rockers and a chrome air cleaner onto that SS, then put bus springs on the weights and crank the distributer to the left three or four ticks... the next 30 miles get real expencive real fast. The guys that make your cam will tell you what to do... don't just make it up, you'll be wrong.

Golden rule of timing and curve: The cam decides, not you.

To follow the above line of logic, we should all still be riding horses. Let me tell you, I have never had to get up and hour early and feed my C3's HEI some hay.

I mean no disrespect, but really, I perfer Levis over Buffalo pelts.