My only disclaimer is that you should read all of this before starting, and take your time. The information here applies to various Buick V8 and V6 engines, so make sure you understand the details as they apply to your engine. Your mileage may vary and your car may be different than mine was. The usual "Do this at your own risk" disclaimers apply. This is a pretty long and detailed page, so give it a good read before you start this process. Use common sense and if you mess things up, it's not my fault. I've done this swap twice now, but some of this was written from memory, so let me know if you have any questions before you start unbolting and modifying things. Various readers have written in with questions only to find out that have actually found errors or unclear text in my descriptions and I have updated the page as a result. I realize this page is pretty long, but I wanted to be sure that all of the possible information was available to folks so they could understand this swap before they did it.
225, 231, 252, 300, 340, 350, 400, 430, 455, and Oh My!
It is important to mention up front that many of the Buick V8 and V6 engines are identical in many respects, particularly in the area of the distributor. Any place that I refer to the 455 in a generic sense should be interpreted as applying to the other engines as well, unless specifically noted as otherwise. I did my work on a 455, but with a little extra double checking and head-scratching you should be able to do the same thing to any other engine that shares the same distributor mounting dimensions. Additionally, the concepts here will apply to any make and model of engine. In the interest of full disclosure, my HEI distributor swaps were done on a 455 vehicle using junkyard donor distributor from a 350.
The 400/430 engines are very similar to the 455 engine, and I believe that the swap described here will apply unchanged on those engines. If you have done this swap on a 400 or 430 engine and can confirm exactly how this works on a 400/430, please let me know about any details that differ from the 455 conversion so I can include them here. Likewise, the 300 and 340 engines are also very similar and this swap should work there as well. I have had one reader confirm that the swap does work on the 300 engines, and the differences they provided are noted in the text now. The primary difference is that the 300/340 engines share the same size distributor gear as the 350 engine, so the process about swapping your original distributor gear onto the donor HEI distributor is not needed.
Interestingly, this swap also works with most of the Buick V6 engines produced over the years, but you must be careful about the electronics as up until 1977 the Buick V6 engines were the "odd fire" design where the cylinders were not evenly spaced in the firing order. Also, the pre-1964 V6 engines may not work for this swap - see the notes in the 215 V8 section for details. For the later-model V6 engines, the distributor body in the 231cid/3.8L V6 (used with much fame in the Turbo Regals and GN/GNX cars in the mid '80s) will fit into the earlier V8 engines. That means that any Buick V6 distributor up until they went to DIS in the mid to late '80s is a potential donor for this swap. The earlier 225cid V6 engines are basically the same as the later 231cid/3.8L V6 engines and even the later 252cid/4.1L V6 engines, and many of the pieces the early 225 V6 engine swap with the 300 V8 engine - the basic distributor housing was used in various Buick engines for a very long time. On the odd-fire electronics gotchas, note that HEI was introduced in mid-1975 and the odd-fire V6 went away in mid-1977, you so have 1975, 1976, and some 1977 V6 HEI units to pick from to get the correct odd-fire electronics. As with other swaps, I have not actually tried this and cannot 100% confirm this for sure until someone actually gives this a whirl. If you have, please let me know.
There are also some interesting possibilities here for converting not just to HEI, but a fully computer-controlled HEI distributor. If you want to put fuel injection on your early Buick engine and you want the computer to control the timing, you need a distributor to match that - one with no vacuum advance and no mechanical advance where the computer controls the timing. Distributor housings for computer controlled engines had some important differences, and if you could get a housing that would fit, you should be able to make this work. If this thought intrigues you, go back and read the previous paragraph about the V6 engines and think about the fact that the 3.8L engine was used into the 90's, and survived on as the GM "3800" supercharged engine used in various GM vehicles through 2008. (I'm not sure how far parts swap forward, but that's a topic for another page...) The basic idea is to combine the later model V6 distributor housing/shaft with your existing distributor gear, then add Chevy V8 style electronics from the same year as the donor distributor, and if you do it right you should get a EFI-ready distributor for your early Buick engine made will all GM factory perfect GM parts. I have created a separate page to document this effort.
That's a lot of possible swapping around - but it's not clear to me that any
Buick engine uses the same distributor housing. I have been told that this swap
does not work on the 215 engines because the distributors do not physically
interchange, but I have not been able to confirm this. However, TA Performance
has information posted that
says that all Buick V8 engines (including the 215) distributors will
interchange, with the known exception of the gears being different. The pre-1964
V6 engines may be in the same boat here - the Buick 198cid V6 engines were originally
based on the 215 V8 design but were redesigned in 1964 to match the newer 300/340
V8 engines more closely. Based on this, if the 215 swap does not work, chances
are the same is true of the pre-1964 198cid V6 engines, but if the 215 swap does work,
then the early 198cid V6 swap will likely work as well - stranger things have been
known to happen. Based on what I have learned, I am inclined to believe that
this swap will work on a 215 V8 or pre-1964 198cid V6. If you wish to convert your 215 engine to HEI, you can
also look to
a later model Land Rover for swap ideas (they bought the engine tooling and
produced that 215 engine all the way into the 90's for use in various vehicles)
or that you go aftermarket. I have been informed by one of the folks who wrote
in asking questions about this swap on a 215 that Performance Distributors out
of Memphis, TN makes a HEI-style distributor specifically for the 215 engine. I
also have seen that DUI (Davis Unified Ignition) has them available as well.
I'm not sure where I originally got the idea for this swap. I might have ready about it elsewhere or I might have dreamed it up on my own. In any event, I tried it, and it worked, so I wrote the page and have kept adding details, tidbits, factoids, etc. as people have written in and given them to me and as I have found them out on my own.
Many thanks to:
The Basic Concept
All the preceding and following verbiage aside, it's really a pretty easy swap; the hardest part is getting the distributor into the motor to start with - for my swaps I was working on a Buick 455 where you either have to pay extra for a "real" 455 HEI core distributor to start with, or use in a 350 HEI unit by swapping the gear from your 455 points distributor onto the 350 HEI distributor. If you have a 350 HEI, then it should drop right into your 350 with no mods. Also, Chris Enos has informed me that the 350 HEI unit will bolt into the 300 engine without any mods. There are "later" style HEI units (after '80 or so?) for the Chevy motors that are not discussed here, but I don't think there were any of that "later" style HEI units for the Buick motors. Just make sure you have the '70's style by verifying the year of the donor vehicle. I can recognize 'em on sight, but describing it could be harder if you don't know what to look for already... These instructions assume the old distributor is out of the car already and the old points-style coil is removed from the engine. That's easy enough to do and should be pretty self-explanatory if you have a factory manual for your car handy.
Depending on the condition of your HEI distributor core, you may need to do some work on it before using it. I'd recommend tearing it down, cleaning it, and putting it all back together with all new electronics just to be sure you have exactly what you want. The pickup unit (the star thing that mounts on the distributor housing around the distributor shaft under the advance weights at the same height as the star mounted on the distributor shaft), module, advance weights/springs, cap, rotor, and coil are all standard GM HEI parts. Just tell the guy at the parts store you're buying stuff for a '75 Buick LeSabre with a 350 and HEI and you'll get the right parts. For buying stuff from Jegs, just buy for a standard GM V8 HEI - the only difference I've found is the color of the two small wires that go to the coil - both of my conversions used the red and white coil wire versions, but check yours to be sure. I think it depends on the year of the donor distributor - maybe the other colors are the "later" style? I've also been told that the Buick/Olds/Pontiac/Cadillac HEI is different than the Chevy, and the wire colors at the coil are how you tell the difference. In any event, make sure you get the right stuff for your donor distributor. Also, there is a small wiring harness that connects the module to the capacitor and to the cap - I found a piece in the Classic Industries catalog under part number 66946C that's listed as "HEI and Capacitor" for "All" HEI units for only $19.95, and the picture makes it look like it includes the wiring out to the cap as well as the grommet. If so, this is a great deal to replace the hashed wiring and grommet you usually find on a junkyard distributor.
After you rebuild your HEI unit and get it ready to go, you install it like
any other distributor installation, run new plug wires, and bypass the resistor
wire to get a full +12V to the HEI unit. That's really all there is to this swap
- like I said, it's pretty easy, just the rest of this page contains all of the
gory details you'll want or need to know to complete the swap successfully.
Rebuilding Your "Donor" HEI Distributor
To rebuild the distributor, you'll need to drive out the pin that holds the gear onto the shaft. You can mount it in a vise to do this, but don't scratch or gouge up the gear or the smooth surfaces where the distributor housing touches the "hole" in the engine while installed. (Use small "soft" wood blocks on the vise jaws to make this easier.) If you gouge these surfaces up, you may find it very hard to get it back in and/or adjust the timing later on. Once the pin is out, the gear and a washer will come off the bottom of the shaft. Start making a note of what goes where and in what direction - a quick photo or two works wonders when you go to put it all back together again a few days (weeks) later. (Don't ask why I know that. :-) After the gear and washer are off, the center shaft and mechanical advance mechanism will slide up and out of the housing. You can then remove the vacuum advance, module, external wiring harness, and the pickup. Don't forget to take off the old o-ring on the outside of the housing and replace it with a new one when you put it all back together! (This prevents oil seepage - it's cheap, easy, and the old o-ring is probably hard as a rock and ready to fracture into a million pieces anyway. Mine were.) At this point you can remove the advance springs and weights - the weights are held on by small e-clips. The clips tend to fly off and get lost when removed, so go slow and don't lose 'em! The weights are directional - take note of exactly how they mount to the top of the shaft! They are also a very tight fit on their little pivot shafts. Wiggle 'em off as best you can, you can use a small screwdriver underneath them to help pry them up if you do it carefully. There should be some small plastic or nylon "buttons" underneath the weights - don't pry on these "buttons" or they'll break and you'll have to hunt down replacements. (These allow the weights to rest on something but still slide across it as they swing out to perform their "advance" function.) Assuming you're getting a new advance kit, the old weights and springs are junk, but save 'em for reference on reassembly - the wear and corrosion patterns will help you figure out what goes where if you get confused. (That's a handy tip for any parts disassembly you do on a car - the old parts will be clean/shiny where they rubbed or were bolted together, so you can use that to help reassemble the jigsaw puzzle. :-) At this point, the bottom part of the advance mechanism should be able to slide off the center shaft, but it may need some coaxing. The housing itself should be bare (nothing else to remove), and the center shaft should just have the upper advance weight mounting plate on it.
Clean everything carefully and don't mess up the center shaft. It's precision ground and any nicks or gouges will ruin it. The exterior of the distributor housing should be cleaned up enough to paint it - this helps keep it corrosion free and looking nicer longer. I used gloss black, but your tastes may vary. Make sure to mask off the inside of the housing (especially the pad where the module mounts) and the part of the housing that is "inside" the engine before painting it. A good rule of thumb is to only paint what you can see when it's installed in the engine with a distributor cap on it.
I highly recommend you make some internal improvements to the HEI unit while you rebuild it. Jegs has all of the "hop up" stuff you'll need here. The pickup and possibly the capacitor inside the housing are about the only things you need to get from your local parts store. A key thing is to get an adjustable vacuum advance kit. It takes some time to tune it right, but it's worth it in the end because you can tailor it to your car and your driving habits.
After the housing is painted (and dry) it's time to assemble the unit with your new parts. Put a light coating of moly engine assembly lube on the shaft before putting it all together, but don't overdo it. A thin film is fine. Install everything onto the shaft and then into the housing in reverse order that they came apart, but with your new parts. The advance weight kit and the vacuum advance will have instructions on how to install them. Follow those instructions carefully, and it all (hopefully) makes sense once you look at for a minute or two. The easiest thing to screw up is the advance weights since they look very similar when reversed but they must be installed the right way to function properly. Once you're done assembling the distributor, install a new rotor and cap (Get a clear cap from Jegs. They make it very easy to set the initial timing...), and install your new coil (I run an Accel SuperCoil. Jegs has lots to choose from, though.) into the cap. Make sure you hook up the wires in the cap correctly, and that you hookup the 3-wire connector from the distributor base to the coil correctly - it should only go on one way, so don't force it. There is a groove in one side of the connector that matches a protrusion on the cap. Turn the cap over and look at it carefully to be sure you've gotten it right. Once you line up the little metal connectors in the cap, the connector should push into place fairly easily.
Don't forget to re-install the gear (in the right direction!) with the washer
above it and put the roll pin back in to hold it in place. You really ought to
replace the roll pin to be sure it's not going to sheer off or fall out, but you
can try to re-use the old one if you need to... If you are converting a Buick
350 HEI unit to work in a Buick 455 motor, you will need to use the gear from
your original 455 points distributor, but you will need to drill the cross-ways
hole in the gear that the roll pin goes in to the larger size from the 350 HEI
distributor. It's soft metal and the drill bit is a normal size. Just go slow,
keep the drill straight, and don't "hog out" or elongate the hole by wiggling
the drill around too much. File the edges of the hole smooth if needed to remove
any burrs or "flashing" that may be hanging around. Clean up the metal shavings
on the gear with a good dousing of WD-40 before you put it all back together
At this point you have a completed unit ready to be installed into the motor.
The usual "installing a distributor" instructions apply here. Consult your
manual for the basic procedure and get familiar with it so you can do it right.
Get the motor to TDC on the firing stroke for cylinder #1. Figure out where the
#1 wire will go on the distributor cap; follow the factory specs for a later HEI model if
possible - this makes it easier to work on the car later. I suggest you get a
manual for a '75 Buick with an HEI and use it as a reference. Install the new
HEI distributor into the motor. Note that you may need to use a long screwdriver
to turn the oil pump input shaft a bit to get it to accept the distributor base
properly. If the distributor goes in part way but won't completely seat, check the oil pump
shaft and align as needed. Remember that the gear and the oil pump shaft will
turn approx 1/8 of a turn as the gear on the distributor mates with the gear on the camshaft.
new distributor may be really tight in the front cover (both of mine were very
hard to get in and move around at first...) and it is physically larger than the
points unit was. Temporarily removing the smog pump (if equipped), upper
radiator hose, and fuel line may be helpful here. (You may need to re-bend the
fuel line slightly to clear the larger cap on the HEI distributor...) The clear
cap I told you to get will make exactly lining up the rotor with terminal #1 a
Taming The Wiring Beast
At this point it's down to wiring. You need to get this thing power, and possibly hook up a tach. The wiring itself is fairly trivial - it's taking the time to do it right that makes it more involved. If you want to add a tach wire to hook up a tach with in the car, run that wire in the harness along with the ignition feed wire I describe here and then through the firewall later. I think the factory used green or blue wire - check a manual for a '72 Skylark with the rally gauge option to be sure. Anyway, be sure to leave enough of a loop of tach wire at the firewall end of the harness to hook it up later - about 24 inches extra is a good bet. The original coil setup uses a special resistor wire to drop the voltage at the coil down to approx 7 volts. That's no good for an HEI unit - they want full battery voltage to put out a good, hot, long spark. So you need to run a new wire to power the new HEI distributor properly.
An HEI distributor draws more power than a points ignition, and the power wire should be the same as GM used on factory HEI installations (12 gauge wire) or larger (10 gauge wire). Don't skimp - do it right. Failure to use a large enough power wire will likely result in a weak ignition above 4000RPM and misfire - some would describe this as the engine "falling over" at higher RPM. If you have this symptom, check your wire size to be sure. Also, cheap-o no-name-brand replacement modules can cause similar "over 4000 RPM" issues - stick with known name brands for key parts like the module, coil, cap, rotor, etc. If the parts store offers you a choice of modules, look at the prices and names on each one. It'll be pretty obvious what's going on if you think about it for a second, and if not, take note of the info and then go online and search for the company name and other info. RockAuto.com is a great place to shop for parts online so you can do this form the comfort of your own home.
Trace the existing wire coil feed wire from the positive (+) side of the coil
(it's usually pink at the positive coil terminal) back to the connector on the
firewall to figure out how to replace it. There will be a junction in it
somewhere near the coil and the pink wire from the coil will connect to a yellow
wire that goes down to the starter and a whitish wire with a weird "fabric"
insulation on the wire that goes from that junction back to the firewall. First up is to cut the yellow
wire off, tape it, and leave it in the harness. It's only live when the starter
is spinning and is used to give the points-style coil more voltage while
starting the car. It's not needed or used for HEI - just tape it off to be sure
it doesn't ground out sometime in the future. If you're really adventurous, you
can remove it all the way down to the starter - it connects to the "S" terminal
on the solenoid. The whitish fabric covered wire is the resistor wire that we want to replace.
Once you follow the harness back, it will go into a big connector on the
driver's side of the firewall at the same place the fuse block is on the inside
of the car. You can remove the connector at the firewall by taking out a small
bolt in the center of it and then pulling the connector off. It's actually two
connectors - a U-snapped connector with a smaller square one inside the "U".
They lock together - mess with them a bit once you get them off to figure out
how so you can put it all back together properly later on. Open up the harness
(some have a "split loom", others need to be un-taped) and trace the resistor
wire back to that U-shaped connector and carefully note what slot it goes to in
the connector. You will need to remove the brass connector and attached resistor
wire from the U-shaped connector and replace it with a new brass connector
attached to a normal (non-resistor) piece of wire that will eventually get run
out to your new HEI distributor. To do this, you will need to pinch the small
brass connector for that wire together from the "inside" of the connector
(inside when the connector is fully assembled, that is) and push it out the back
of the plastic housing. (See my article on
Reusing Plastic Wiring Plugs for
more information on doing this.) If you look carefully at the flat "blade"
portion of the brass terminal you will see that it has a angled slot cut into
it. All you do is try and "close" that slot by pinching the blade together
sideways and push it back into the plastic connector at the same time. That
pinching motion lets the brass piece slide out of the plastic housing. Whatever
you do - don't mangle the plastic housing! If you do, you're kind of screwed.
:-( You should get a new brass connector piece from
Ron Francis Wire Works - I think you
want it's item FM-8. (Look at the pictures they have on their site to understand
the "slot" mentioned above.) You'll also want to order an HT-16 (HEI Tach
connector), HE-15 (HEI Ignition connector), and a BM-8 (the brass connectors
that go into the HEI Tach and HEI Ignition connectors). While you're there, get
a roll of new white wire - use the correct 12 gauge or larger wire here! (NOTE:
I previously specified that "16 gauge should work, but 14 gauge is a
better choice" and was caught by several astute readers. GM used 12 gauge for a
reason, and you should make sure you also use a large enough gauge wire!
Apologies for the mix-up, but hey, this is free advice after all, and I have to
go back and fix the power lead on my car too, so don't complain. :-) This is the feed wire for the ignition system and a bit bigger
won't hurt anything. Put one of your new FM-8 brass terminals on the end of your
roll of white white and crimp and possible even solder it together. Slide it
into the proper slot on the firewall connector until it clicks and stays.
Compare the depth and orientation of the other brass connectors in the
"U"-shaped housing to know how to orient it and when it's been pushed in far
enough. Again, don't mangle the plastic housing. Run your new white wire along
the factory harness back to the area of the distributor. If the harness was
taped originally, you can either re-tape it or put a new split loom style cover
on it. Taking the old resistor wire out helps make room for the new one, but
adding a tach wire may make things a tight fit. I found it's easiest to remove
the entire harness from the firewall, transmission and most of whatever else
it's attached to so you can get to it easier. The harness just unplugs from most
things - just take note of where it was plugged in at and don't break/mangle
anything when you take off the harness. Also, don't break any plastic clips that
hold things in place (like the ones holding the harness to the firewall...)
unless you plan on replacing them. Depending on the grime level in your engine
compartment, this may be easier said than done. :-) Now, once you get the new
wire in the harness far enough to be out near where the original pink coil
positive wire exited the harness, you can re-install the harness to the firewall
and engine, and plug the firewall connector back in again. Don't forget that
bolt on the firewall connector, and be sure you don't over-tighten it. Just snug
it up and call it good enough.
Now, you should have one or two new wires running through the harness from the firewall connector all the way out to somewhere near where the old coil was. You should be sure you have enough wire there to hook them up to the distributor - be sure to leave enough slack in them to adjust the timing later - and then trim the wires to a reasonable length. Hook the wires up to the proper terminals on the distributor cap using the BM-8 terminals and the HT-16 and HE-15 connectors from Ron Francis by crimping the brass terminals to the end of the wires and pushing them into the back of the plastic connectors. Make sure you get the right wire to the right terminal on the cap. The plastic connectors only mount in one place each but the little brass terminals inside will go into either connector - you must get the correct wire in the correct connector. The connections on the cap are labeled very clearly on top - so pay attention. I found the easiest thing to do it to plug the connectors onto the cap (they will only go into the right place) and then push the brass terminal and wire assembly into the correct connector while it's still on the cap. Tape the two wires to the distributor together or use a small piece of plastic split loom to keep it all neat and pretty.
At this point you should have the HEI distributor installed, wired, and ready
to hook up the plug wires. The HEI distributor uses a different kind of spark
plug wire terminals - so you need to get new plug wires. (You needed a tune-up
anyway, right? :-) Get wires for an HEI setup - the "you cut to length" setups
from people like Accel let you custom route the wires how you want and typically
come with both HEI and points style distributor plugs for the same price.
(I like Taylor wires because they work well and come in a large variety of
colors so you can match the color scheme on your engine. Yeah, I'm into having a
pretty engine compartment... Deal. :-) Remember, you're going to be putting out a much hotter spark, so you need to pay
more attention to getting quality plug wires and installing them nicely. Crossed
wires and voltage leakage could be a serious performance problem not to mention
a hazard to you. If you've ever gotten shocked by 50,000+ volts from an HEI
coil, you'll know what I mean. I have, and it hurts like hell. It's not going to
be fatal, but it will certainly "encourage" you to use better plug wires and
watch what you grab while the engine is running. :-) Be sure to use wire
dividers to keep the wires routed nicely and away from the exhaust manifolds.
Lastly, you should replace your spark plugs with ones designated for a later
Buick 350 or 455 that came with HEI. (I used a '75 Electra in my case.) The
later plugs come with a much wider plug gap (.050 - .060 is not unheard of.) and
you should set the final gap to the specs for the later HEI motor. The hotter
spark will jump a bigger gap. This longer spark lights off the air/fuel mixture
better and gives you a more complete burn, better mileage, and more power. It
also helps keep the plugs from fouling. Since originally writing this, I've
learned that the mondo .050" and up gaps were only used for a few years, and
that a more reasonable gap around .040" might work better. See below for notes
on tuning your motor to it's best with your new upgrades.
Startup and Tuning
The next step is to double-check everything and then fire up the motor. If you did it right, it should fire up right away. If it doesn't start, follow the usual list of suspects - is there power to the distributor? Did you install the distributor correctly? Is it timed close enough for the motor to start and run? Did you get all of the plug wires on the distributor in the correct firing order? If you've never removed and replaced a distributor before, expect to mess around with it a bit - it's tricky to get it right the first time unless you're just that good or that lucky. Don't despair - it happens to the best of us. Take your time, and troubleshoot it logically. It's usually something small and stupid that gets forgotten. Once the motor is running, let it warm up and then give it a basic tune-up. Expect to need to re-tune the carb a bit - the better spark allows you to run a leaner mixture because more of the fuel you put into the motor is actually being used - this is part of where you get the mileage gains from this conversion. You'll also want to re-set the timing - a bit more initial timing is recommended - and re-set your idle speed to whatever you desire. The car may very well idle very nicely at a lower rpm than it did previously, thus allowing you to drop the idle a bit for better mileage and less noise at idle. I typically use something like 650rpm in drive; you should use what you think is appropriate and makes you happy. You'll also need to make sure the idle mixture is correct. The idle mixture is critical. After you get it set right you should double check the idle settings and the timing settings and go through a couple of rounds of tweaking each one for the final settings that work best for you. Keep careful notes of whatever your final settings are for later use, though - the factory manuals will not be accurate for you anymore. To set the idle mixture you should use a vacuum gauge and adjust them to get the highest vacuum at idle (in gear for automatic equipped cars) on a quality vacuum gauge. (The mixture screws should be turned out roughly the same amount to ensure both sides of the carb are running equally.) Once you get this setting, you should then adjust them to lean out the mixture (usually by turning them in/clockwise) enough to get about a 30-50rpm drop in the idle speed. This is a good estimate of what Edelbrock carb tuning books refer to as "Lean Best Idle" and helps drivability, mileage, and keeps the plugs clean. You can tune the vacuum advance later as you have time and inclination - I think the instructions that came with mine recommended setting it for the slowest possible advance until everything else is sorted out. Then you should set it to a bit more advance and drive the car for a few days to see how it works. Repeat this until you have found the setting that works best for you. As I mentioned already, expect to play with the timing and idle mixture/speed settings a bit to get it all right - you've changed out a major piece of the motor and made it much, much more efficient. After getting most everything else right, you may also want to vary the plug gap up or down to see if it has any net effect on the motor. In addition to subtle changes in power and mileage, this also affects details like length of time between tune-ups. Due to the long-term changes you need to note here, it's best to mess with this once everything else is happy and set reasonably well. Take notes and keep an eye on the plugs over several tune-ups. Basically, if the rest of the motor is working up to par, then everything works that much better and the "optimal" settings can take some time to discover. You may also find that you have other little things in need of a tune-up because of this - perhaps your carb is in need of an overhaul, or you have a vacuum leak that needs to be tracked down and fixed. In the end, this is a good thing. It takes time to find and fix the little stuff, but a much better running car will be the result. It's much more fun to drive a car that works right - not to mention that it costs less to drive it. That means more cash to cruise more, or to sink into more parts for your car. Either way, you win. :-)
The net increase should be a few more mpg (depends on your driving habits
:-), easier starting, smoother idling, and a generally better running engine.
That, and you'll never have to worry about changing points ever again and your
plugs should last longer. Your ignition system should be all set for at least
50,000 trouble free miles - I've heard of people going 70,000+ miles without
touching anything once an HEI system is set up right - without any decrease in
performance or mileage during that time. Compare that with a points system that
needs fiddling with every 8000-10,000 miles or so - in short, HEI rocks. Yeah,
your mileage (literally) may vary, but once you get it set up right, your car
will be better than before you made this change.
Below is a simple set of pictures I shot during the conversion process on the 455 engine in my 1970 Buick Electra. I got a little too anxious to finish and didn't take as many pictures as I wanted to originally, but this should be enough to help you though this process.
Close-up of the old shaft - the roll pin holding the gear on got sheared off while the engine was running! This caused the distributor not to rotate and the engine to not run, thus kicking off this upgrade process...
Comparison photo of the two distributor housings. Notice that from the o-ring down they are identical, but that the HEI unit is much larger in diameter. The angle of the photo makes the HEI unit look a lot taller, but it's really about the same height overall.
Close-up of the advance weights on the HEI unit as I received it. No wonder this motor ended up in a junkyard! These things are rusted in one place. Lots of WD-40 and some gentle persuasion was needed here. Take careful note of how the center plate mounts and how the weights mount for when you put it all back together again. The e-clips go around the two shafts near the ends of the center plate.
The new HEI unit partially assembled. You can see the new Accel module (with the yellow sticker on it), the new pickup (the thing the white and green wires are connected to), the new adjustable vacuum advance unit (the adjuster is a tiny allen key inside the vacuum connection), and the new center plate for the re-curve kit already installed. The housing has been painted, except the inside and the part that goes inside the engine.
Another shot of the same. You can see how I broke one of the little nylon rubbing blocks under one of the advance weights. There was still enough there to work (I think), so I used it as-is. You can clearly see the e-clips on the new center plate for the mechanical advance mechanism.
The advance weights and springs are installed, the new Accel coil is mounted in the clear distributor cap, and the new rotor is waiting to be installed. The 3-wire distributor to cap connector is also hooked up in this photo.
Close-up of the new advance weights and springs. You can also see the capacitor (which I clearly re-used) and how the incoming wiring harness hooks up to the module, the capacitor, and to the ground screw inside the housing.
Here is the new HEI unit, fully assembled and ready to be installed. You will have to partially remove the coil to get the new wires installed (it helps hold them on), but you'll want it installed to check clearances as you install the new HEI unit into the motor.
Here's the new unit installed with new plug wires on it. I needed to remove the radiator hose while I was installing it (clearance), bend the fuel from the pump to the carb slightly to make room, and splice into the wiring to get it all working. Notice that the old coil is gone and that the new plug wires are neatly routed to where they need to go.
Here you can see the new spark plug wires running through the wire dividers on the driver's side of the engine, along with a good view of the distributor itself - note how close the fuel line and radiator hose are to the new unit. A nice set of color-coordinated wires that are installed properly really does a lot to make the engine look a lot better.
Same idea for the passenger's side. Again, the plug wires are nice and neat - not only does it look nice, it also helps eliminate crossfire between the plug wires. If you look closely you can see the small black plastic clips holding the wires in line as they go over the radiator hose. If your new plug wires didn't come with any of these - go buy some. They're easy to use, cheap, and do wonders for the appearance of your engine compartment.
Buick 300 Specific Details
The information and pictures in this section was provided by Greg Hardy. He had done the HEI conversion on his 1965 Skylark with a Buick 300 engine (it's shown in the last picture below), and ran into a few issues that he asked me about. With his help and permission, I've documented those issues here.
The main issue is that the 300 is narrower than the 400/430/455 engines, which means the clearance between the distributor and the heads is much less. The second and third pictures below show this most clearly - the HEI cap comes very close to the front of the intake manifold and the front mounting bolt on the intake manifold. Greg ended up using a button head style bolt in this location to get the required clearance. He also had to rotate the distributor base for clearance - both at the vacuum advance unit and on the protrusions on the side of the distributor cap where the mounting points are at.
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Page last updated 12/27/2011 10:23:21 AM