Ok needing some input on Distributors. I am probably biased and sold by the marketing propaganda on the DUI dizzys. Those of you that have these are they really good or can you even tell the difference between the new one or the stock one. I currently have the stock one with some of the parts already updated. Like the cap, rotor, module and coil. Will I notice a difference by upgrading my 45 year old dizzy. Oh yeah one other thing I upgraded the lower dizzy gear to a melonized one because of my roller cam also.


Thanks in advance,


RR

 

If it delivers a spark at the right voltage when you want it, it really can’t get better from there. DUI distributors are great and the way to go if you’re having issues, but a well set up and running HEI is about as good as you can get for ignition without going to coil on plug.

 

I'll say this about that. I once thought the same as the fellow above. And after several attempts to repair my original distributor I threw in the towel and purchased a middle of the road HEI Distributor from Summit. Then, in my spare time, on and off as it were. I spent the next 2 years trying to get the curve just right. Mind you, I'm likely far pickier than the average guy. But I just couldn't get it right. Yes, all in by 3K RPM. But, the way it advances up to 3K RPM makes all the difference. I would have a studder between 2,500 -3K. I would recurve and then that was fine, now it stumbled at 1,500 -2,300 . And on and on it went. I now own about 20 sets of distributor weight arms. And God only knows how many springs.
I contacted DUI. I didn't purchase a off the shelf unit. But rather had them make me up a custom curved distributor, (yes it's a HEI) specifically for my engine in my car. They asked me a lot questions. I answered them all. Then they said give us 3 months.
2 months later they shipped me a custom curved distributor. I dropped it in. Set the base timing. Then went ahead and checked everything, spot on everywhere. Vacuum advance timing perfect right on the 2 inch rule.
Anyway, I live in Australia, so with the currency exchange, the high cost of shipping, etc. This was NOT an inexpensive option. But I was that sick of trying to get a cheap HEI dialed in perfect.
Bottom line.
Although extremely expensive. I plugged that baby in. And my car never ran better, never!
just bloody spot F, ing on. Purrs like a kitten, pulls like a train. Problem solved!

 

Sounds like the difference was in the capability of who was working on the distributors and also possibly the choosing of a questionable aftermarket distributor to start with ?

 

That's a bit nasty. The sub standard distributor mentioned above is a unit sold as a gen. GM restoration replacement part. Made in Taiwan if I remember correctly.
Most of us don't own a distributor machine. Thus why having a professional that actually has one set up your distributor makes a lot of sense.
Setting up a ignition timing curve for drag racing is one thing, street driving is considerably more complex. And we are limited by the weights, shape of weights, shape of footballs. Etc. that are available to us. And custom grinding without a distributor machine is a heak of a lot of guessing.
So yes, go ahead and insult all you want. But. The OP likely isn't wanting to custom curve a mid range HEI either. So, spending a couple bucks on a top quality part that gets the job done. Well, .. whatever.

 

I wasn't being nasty - just pointing out to you bashing the HEI over the other system distributor you bought custom built by someone with a proper distributor tuning equipment that knows what they are doing is hardly a fair comparison of ignition system types.
You simply DO NOT have the capability (equipment) to fine tune a distributor.
Most likely if done in a similar manner your original dizzy would produce equivalent result.
I actually DO have my own distributor machine and a self built (very simple) vacuum advance testing rig.
I have NEVER had to 'Richard" around grinding anything - NOBODY that I'm aware of actually changes the shape of the weights or "football" - that is beyond most "shops" ability
I "built" my own STREET DRIVING distributor with "special "vacuum advance unit selected to address "kick back" due to lightened flywheel.
Took a bunch of searching OEM vac can specs and bench testing to "find" suitable vac can.
The issues you were having sounded like just a bad combination of mechanical and vacuum advance "tuning" not a fault of actual ignition system type.
AMEN

 

My car runs ok with the original dizzy, but it does stumble a little when going into first gear. The problem I had originally was trying to find some bushings to fit in between the football weights. My original bushings had or were nearly worn out. Every set of curve kits that I ordered (bushings) were not compatible with my original weights. They were usually too big. So I had my son make me some bushings on his 3d printer and they seem to be working okay, with the exception of a stumble every now and then when going into first gear. Not sure how long they will last since it does get pretty hot in the dizzy.
I might just bite the bullet and order a custom dizzy for my car. However, they are going to ask what compression ratio my car has. I know originally these cars came with about 8.0 to 8.5 cr. My L48 has 64cc heads now and xr276hr camshaft, so how do I go about figuring compression ratio now?
L48
xr276hr camshaft
64 cc heads with 2.02 valves and 185cc intake runners
2101 Eddy intake
750 Eddy Carb
Holley long tube headers

I am guessing in the vicinity of 8.5 to 9.2 cr???

 

LOL - sounds like you are a bit disenchanted with the results of what you have changed on your distributor.
The stock GM HEI module is probably as good as anything out there - GM spent millions developing that system and has way more engineering capability then anyone.
Where things can be improved is with the actual tuning of the distributor - mechanical and vacuum advance curves as the stock system is "tuned" with entirely different parameters in mind.

 

The HEI that came on my C4 is a nice unit and it makes a good spark. Being original to the car I am hoping that they have it curved properly. IF I had to have anybody look at my distributor it would likely be the guys at DUI. They have a reputation that was hard earned by good old fashioned work and making customers happy.

The MSD Billet Tach-Drive distributor I bought was ridiculed by a local speeds shop owner who said that they were all over the place in their settings. He was convinced that the MSD distributors were "okay" but needed to be set up by someone who knows what they were doing. He put my brand new MSD distributor after I put the springs and bushings in it in the distributor machine and the curve was already there and it was near/perfectly adjusted. It functioned like the factory distributor and the factory curve had closely copied what was original. My other distributor is part of the K66 Transistorized Ignition System and it was rebuilt and calibrated by Dave Fiedler who did an incredible job on my T.I. system parts. I am using all MSD equipment in my ignition system versus the factory K66.

The only negative side of this is that the HEI ignitions are so popular that there are a lot of bogus/junk parts being made for them today. Many of us who use an HEI distributor have a habit of storing spare parts for the HEI system. I keep a new coil, pickup, cap, rotor and controller for the HEI system on the shelf. I would not say that they are the "most reliable" any more due to the influx of questionable parts used in the original HEI distributors.

I "trust" the HEI but still take spares on long trips just in case...

 

My L48 with stock pistons, 64cc heads, and .016” compressed thickness head gaskets has 9.48:1 compression. There are calculators online if you need to change any variables.

 

The distributor on my 79 is now $400- new, and still needed another $100- in parts and some tuning to really dial-in (adjustable vac can, shims, Moroso spring kit).

Before spending that much on a boutique distributor, read this thread.

https://www.corvetteforum.com/forums...s-for-sbc.html

You're probably still better off with an LS swap, but an app-programmable distributor sounds pretty cool.