So I've got a blank slate for the ignition system for the carbed 347 in my '82 f150, and I'm wondering what direction I should go in. Is the stock distributor and stuff good enough for this motor, or would it be wise to upgrade? I don't really know if it matters, but I'll be running a Edelbrock 1406 carb and performer intake manifold, along with Trick flow TW heads. This is really the last aspect of the truck that I havn't bought the parts for, so I should probably get on this at some point soon. I've seen stuff about DS I and DSII distributors I believe, but don't really know the drawbacks to either or.

 

The stock systems are good for stock engines. They are not that great for modified engines. The stock engines are smog controlled, and that makes the timing curve different. Your hopped up engine, to run it's best, is going to require some experimentation with the timing and the timing curve, and the vacuum advance also. The stock dist is not very user friendly in this aspect, you have to take the whole dist apart to change the weights and or the springs underneath. A aftermarket dist will be easier to adjust and play with to get the most out of your engine.

I can't recommend a certain brand, but I would look them over carefully and see how easy it would be to tune them, get parts for, etc.

 

ok, that is all good to know. Now is there a particular style of distributor I should search for? I've read vacuum advance is better for my application that mechanical, correct? It seams like the HEI ones are a very common replacement

 

The DUI (Davis Unified Ignition) is a good setup. They take the GM HEI setup and put it on any distributor. And the module they use is better than a standard GM module. One wire hookup to run, and one for the tach.

Almost all distributors have mechanical advance, but in a vacuum advance distributor, they have both. The vacuum advance really affects when the motor is under load.

I have a Mallory Unilite distributor in the 82. Very easy hookup (3 wires, and 2 of those go to the coil), and all the adjustability you could want. Got it off ebay for $100.

I think Summit was having a deal where if you buy an MSD distributor, they will give you a free 6A capacitive discharge ignition module. With that setup, you get 2-3 or more sparks per combustion cycle up to 3k rpm instead of just one spark.

 

so it sounds like if I want to do everything I can to help low end power that MSD deal would be a good setup then huh? I was thinking of just going with a plain jane summit distributor with vacuum advance, but if there is a good tangible benifit to the MSD, I would most likely spend the extra money

So after looking at Summit, no more MSD sales. So with that being said, $400 is probably more than I feel like spending on a distributor and box at the moment. It looks like the $125 summit one with decent adjustability will most likely be the ticket

 

The vacuum advance on the dist helps with fuel mileage, that's it.

Racing engines don't run it because they run pretty much wide open all the time, and they do not have any vacuum to speak of to even run the advance. Their situation is more of a special purpose type, so they don't run it.

Street engines run it for efficiency. You can read about how the initial timing is set with a timing light, and then the mechanical advance is adjusted for the rest of the timing curve, and it all adds up to around 38 degrees or so. If the engine is not under load, it can take a lot more advance than this, usually up to 50 degrees total. So when the load on the engine is low, the vacuum is high, and the vacuum advance adds on the extra advance for fuel mileage. When a load is presented to the engine, the carb opens up, the vacuum drops, and the vacuum advance relaxes, taking away the extra advance.

 

If you are talking about Summit Racing SUM-850021 - Summit Racing® Blueprinted HEI Distributors - Overview - SummitRacing.com, it should work fine.

 

Thats the one I was thinking about. Aside from plugs and wires, what else will I need for the ignition system? I remember having to replace those ignition modules on the passenger fire wall like every other month.

 

Franklin is right about the stock ignition having a slow timing curve for the stock smog engines. However, the Duraspark II ignition system itself is a very reliable, high-energy ignition. and you already have it.

You could keep your stock Duraspark II ignition, but have the timing curve changed for the modified engine. Performance Distributors (the same company that makes the D.U.I. Distributors) sells rebuilt Duraspark II distributors and they will custom curve it to suit your new vehicle specs. They will ask you what size engine you have, transmission type, weight of vehicle, carb cfm, cam size, etc. and if you are running emissions equipment and curve the distributor accordingly. I run one these myself and with the custom "performance" curve, I noticed a big difference when I used it on my own modified engine.

http://www.performancedistributors.c...dduraspark.htm

Although this is more expensive than the Summit distributor, the advantage of going this route over aftermarket ignitions is that replacement parts will be available and in stock in every parts store across America, should you ever need it. Again, the Duraspark ignition is a reliable, high energy ignition and if you get the timing curve right, you will not see any performance gain going with an aftermarket ignition, unless you are going to actively drag race your truck or spend lots of time above 5,000 RPMs.

Another problem with the aftermarket "HEI" style distributors is the sheer size of it. This is a GM design, and unlike a GM vehicle, it is going to sit right in front of your engine for everyone to see. If that doesn't bother you, that large cap with everything piled on top of it is not going to clear the stock thermostatic air cleaner, so you can plan on buying an open-element air cleaner to go with the new distributor. That may cause you driveability issues in cold or humid weather.

Its hard to beat MOTORCRAFT parts for plugs and wires. Replacing the ignition module every month is not normal. Either you have a problem somewhere or you are buying inferior ignition modules. The cheapo $25 ignition modules from AutoZone are notoriously UNRELIABLE.

 

Could also just take it to an engine builder/machine shop and ask them to recurve it for ya - easiest done in a Distributor Machine:

 

Lariat, that is a very informative post. I never really considered how much bigger the HEI would be than the stock setup. I will have to take that into consideration since I'm not sure what I'm doing about an air filter quite yet.

On the note of plugs and wires, I was planning on running motorcraft plugs and ford racing wires (not sure if they are made by motorcraft or someone different though). If there is no difference but price, I'll stick to motorcraft. Back in the day when I was having all these ignition module problems, they were cheap-o autozone ones. I even kept 2 spares in the glove box. would a napa one be better than autozone, or is there a reputable supplier for these things?

 

I thought Packard made most of the quality wires being sold, even OEM, but I am not sure about that.

 

I have a slightly used Autozone Duralast DSII and a good original I'll let go, I no longer need them. I personally prefer the DSII to Gm HEI systems. DSII doesn't have the rotor burn through problems that plague HEI systems. As for curving the DSII distributor, under the electronics is a pretty basic Ford distributor like was used from somewhere around 1959 on. It has a slotted stop on the advance cam, and may be two sided one with more advance. Ford small blocks run good with 38-40 degrees total centrifugal advance if you are running some compression, if real low, like less than 9:1 you can push it to 42-44. Vacuum advance as was pointed out, is for fuel economy, You do not want vacuum on top of a real aggressive centrifugal curve.

On a side note, Chris, what are you doing with my antique distributor machine?

 

This is the second time you've said something like this.

I got that image from Google, it looks like the one in my machinist's shop that's why I use it.

 

Ok, because it looks just like mine, it's an Allen and good to 9000 engine rpm.