The Stovebolt Site Forums The Shop Area The Electrical Bay Brand new HEI for Stovebolt <$100...see how

You've seen these distributors on eBay and I mentioned them recently in a previous post. A fellow asked me what all was involved in adapting them to the Stovebolt engine so here it is in case anyone else is interested. One nice thing is you won't need any special tools. Nothing more complex than a dial indicator and a bench grinder. Yes, these are ugly (image below). A lot of things in life are. At least the Stovebolt engines seem to like these.

First, buy the 230/250/292 HEI distributor. This will cost you something like $70 or less including tax and shipping (which in many cases is included in the price). I see some for $65~67 or so. These days that's about the cost of 3 pizzas and a tip to put it in perspective.

Next, you will notice the end part (which engages the oil pump) is installed with a pin and works sort of like a little U-Joint...image below. Carefully drive the pin out, set it aside and remove that piece. Note which side faced where on the gear (I scratched a little mark on both for reassembly).

Mark a line about .16" back from the original radius end as you see below and identify it by wrapping a piece of masking tape around the shaft. Now with a bench grinder carefully and slowly re-create that radius cut at this new location (move it backwards on the shaft, basically). You can see this below also. I used the bench grinder to roughly make the cut and a common round file and some 180 sandpaper to dress it up a bit. You will notice the tip looks too long now. We'll fix that next.

Check your measurements...we're creating a shaft that mimics the OEM distributor dimensionally and that is important as it lines the gear up correctly with the gear on the camshaft...but as I said check your measurements, please. It helps if you have a points distributor to compare. Once you have the radius cut made, remove about .16" from the tip end with a hacksaw and file to remove any sharp edges. You can leave it a bit long if you want. Maybe remove .14" and adjust later with a file. Easy to remove material. Difficult to add it. You can see my finished piece below. Place this back on the shaft as it was originally installed and replace the retaining pin. You've finished the hardest work so enjoy a cup of tea now.

The diameter of the part which enters the engine is correct for the Stovebolt (and it includes a sealing O-ring), but you'll need to remove the flange and file that area of the shaft down carefully to match the other (larger) part of the shaft because the flange for the 230/250/292 is incorrect for the 216/235/261. More about that in the next post...

First please remove the O-ring and apply tape where any metal dust/shavings might enter the distributor. You'll see there are two diameters to the shaft. One is roughly 1 inch and the other is more like 15/16". Essentially what I do (lacking a lathe) to remove the flange is to just carefully make several hacksaw cuts (removing little crescent shaped pieces all around the flange) and then slowly use a common file to make it the same diameter of the larger part. You can see me doing that in the images below. You can also see a reason to be careful with your hacksaw.

You'll be surprised (I think) how easily this work goes. Just work carefully and slowly and please don't obsess over perfection. With aluminum it is common to get a stray nick or two. Those won't matter. Now replace your O-ring. Then as you see in the image below a clamp-on collar will be used to establish a new flange matching the same measurement of the OEM distributor (or the Langdon distributor which also mimicked the OEM dimensions). The bottom of the flange will be 2.76" from the bottom edge of the driven gear or 2.143" from the top edge of the driven gear.

Once that is done, you'll be ready to install, connect new plug wires and set timing. When you install, the rotor will rotate counter-clockwise as it goes in by about 1.5 inches (on the circumference of the distributor body) and you can wiggle it a bit if you didn't guess the location of the oil pump just right...I use a light to look down the hole and estimate where the tang will be after it rotates. Make certain you connect with the oil pump driven slot. Hope this is helpful. Please contact me via PM or at [email protected]

I am a big fan of HEI distributors in general. I don't have one on my '50 daily driver because it doesn't look like it belongs there.
This truck has numerous upgrades including '53 full pressure 235, 12 volt conversion, T-5 transmission, limited slip rear axle, but you really have to know what you are looking at and crawl under the truck to see that it isn't bone stock. But that is just me, and I am all for everyone else to be just themselves.

You can isolate the coil (maybe even make it round like Tom Langdon did if you wish) and use a common GM rotor and distributor cap to lessen the ugly part...

What application is that alternative cap and rotor, Jon?

I think it was for a 1978 Chevy 250. For $10 you can find those distributor caps all over eBay. I think the rotor was less...maybe $7.

Looks like maybe that is a 75-78 version of the distributor cap. The dizzy is a unique part number for those as well.

Any reason it wouldn’t clamp down and wire up on the later style housing? I don’t think the wiring would be a big deal. Not sure about the fit up.

Well, there may be some confusion, but let's try to put that to sleep with this post. The distributor cap which contains the coil and the rotor is a matched set. You can't swap or mix-match those. You will see the interior views show this. And the GM rotor screws right on to the imported distributor...either style, but they must match their intended cap. And you will also see the cap has a square peg built in (1) which can be fit into either of two square notches built into the distributor body. This gives you some freedom of location and it is important to note either style cap only has one square peg...to eradicate any idea that one cap fits this distributor only.

And the cap with the 4 attaching screws fits right on the distributor body and will work with an externally mounted coil (you'll see it requires an old-style coil wire).

But there may be a question about wiring since it will be slightly different...but not really if you sit and think about it all. With coil in cap you have a plug-in connector supplying 12v+ from the ignition and a green wire which feeds a tachometer if used. Then there is a 3 wire rear connector. Red wire is + to coil, yellow wire is negative to coil and black is ground. The red wire leading in to the distributor will be + from the relay or ignition switch. The black wire will be ground and the brown wire will be connected to the - side of the coil. So you will have a one-wire connection using the coil-in-cap model. The power wire (12v+). That's it. Having the coil in the cap handles almost all of the wiring path.

With the separate coil type, 12v+ connects to the positive side of the coil and also the red wire coming out of the distributor. The negative side of the coil connects the brown wire coming out of the distributor. And the black wire coming out of the distributor goes to a known good ground.

Okey dokey...Let's try a separate posting.

Ok, one more thing...a question remembered from an email conversation several months ago. Why are the contact pieces different size in the red cap? Well, for one thing the coil-in-cap rotor has a slightly wider tip. And for the other thing, the contact pieces in the non-coil-in-cap model sit closer to the center. The diameter of the travel circle on the non-coil-in-cap model is roughly 3.2" and the diameter of the travel circle in the coil-in-cap model is roughly 4.2". Different geometry.

And an image of the connector for the coil in cap. You will see there is one harness sending 3 wires into the distributor. Red, black, brown as I mentioned earlier. And there is a separate harness with two connectors. One will be the connector from your relay (hopefully you use one) or your ignition switch (if you feel lucky or if you just enjoy replacing these) and it will be the heavy gauge positive 12v wire. The connector you purchase will have a red wire and a green wire. The green one is output for your tachometer. Hope this is helpful.

Helpful indeed. Thanks, Jon.

The short cap/rotor with a separate coil does knock a fair bit of the “ugly” out of the equation. Although, no one is going to accidentally mistake it for a stock dizzy.

I do kinda wonder about GMs reasons for making the change to the coil in cap setup. Maybe it was just cheaper to build or assemble. Or maybe there were issues with the earlier short cap/ rotor design? Would be curious if anyone knows anything about that.

Actually Tom Langdon and I talked about that some years ago. He said there were a couple of reasons aside from the cost savings. One, having the coil right at the distributor simplified production, installation and servicing in one swoop. And also as important to those, it made the distributor measurably more efficient.

My suggestion would be this:
person looking at your engine "duh, is that a stock distributor?"
Your answer "yes, you bet it is." And stop at that point so you don't have to explain it isn't a stock distributor for the 235.

Again, here are a few good points: everything in it is brand new (including the vacuum advance biscuit), GM replacement parts are available essentially everywhere (try to find a Pertronix module in Monahans, Texas). And they last. The one I'm using has been in use off/on since 1997 (over 25 years) and nothing has broken on it and nothing needs to be replaced. I bought a new connector device...actually I think they were 4 for $10 on Amazon, but that was only because I had been using a single + plug and I wanted an output for a tachometer. And...if you're one who likes to tinker, the advance curve can be adjusted by monkeying with the springs.

Auto mechanics instructors back in the 1960s-1980s got to attend "new products" training sessions at GM training centers during the summer break. The closest one to my school was Memphis Tennessee. The reason we were given for switching to the "coil in cap" setup was to minimize the tendency for high voltage to "flash over" from the cap to the distributor housing in case a plug wire came loose or got open circuited. They over-engineered those early HEI systems because of the 50 KV+ capacity of the coils. They also had to make a thicker rotor center after a couple of years of production- - - -the spark from the coil in cap system would drill a hole in the early rotors and fire straight to the centrifugal advance in case of an open circuited plug wire.
Jerry

1975 was the first year for HEI, had black rotor which would burn thru and leave you walking.

Didn't the early HEI vehicles say to set the spark plug gap at .060? Then they change to .045 because of burn through on the rotor.

The .060 (and .080) plug gaps were there in the vain hope that there just might be something flammable between the spark plug electrodes when the plug fired. Once catalytic converters came into general use, the fuel mixture could be richened up enough to get a more consistent cylinder burn without a plug gap the mechanic could throw his hat through. I owned a shop in California during the bad old days when the manufacturers were jumping through all the hoops that Uncle Sam and CARB were dreaming up- - - - -and trying to meet impossible fuel economy standards at the same time!

Afternoon, can this process be duplicated on a distributor for a GMC 270? I'm guessing so. Thanks

Anything distributor that will work with a 50s Chevy six cylinder engine will work with your 270 (and 228, 236, 248, 256 and 302) GMC. I have a Chevy tall cap 6 cylinder distributor (from 1954) in my '52 GMC 228.

I bought a brand new 1974 GMC k1500, 350, 4bbl, 4 speed off the lot in my senior year in high school. It had HEI and .060" plug gap, leaded gas.

I would think with the HEI you should eliminate the ballast resister, is the existing wiring enough or should the gauge be increased?

GM used 12 gauge wire to HEI, this will require at least that same size wire feeding the key switch.

On a side note, the separate mounted coil and low cap versions had extra long wires coming out of the distributor to reach the coils. The coils were mounted between cylinders 3 and 4 on a special made bracket, I suspect this why the early versions have a different part number.

Other than the obvious (coil location) Is there a difference between these “in cap”coil dizzys and the Langdon s10 HEI for which Tom spec’d 10 ga wire feed?

Chuck

I installed a Tom Langdon S10 HEI with 10 gauge wire, but I used a Bosch style relay, so high voltage did not go to the ignition switch.

It would be difficult to get a wire "too large" when powering a HEI system. The resistance of the primary winding on a HEI coil is about 1/2 Ohm, which means that the momentary current flow in the power feed wire can approach 30 amps, before the inductive reactance of the primary windings begins to limit the current flow. At 2K RPM, the current flow in that wire starts and stops 66 times a second. A 10 ga. wire might be "overkill", but it's certainly not "too big" when carrying intermittent current pulses of that amount of amperage.
Jerry

Good idea on the relay feeding the distributor, you could keep the whole harness in stock form, plus pulling the relay would make a pretty good no start security feature.

The smaller HEI's are a modified unit from late model S10's, I'am not familiar with them. I like the older big cap four pin module versions. Both are the same principle and do the same thing, but don't interchange parts.