[michaelj]

Hello all,

I'm currently in the middle of a full-on HEI rebuild with the goal in mind to maximize timing performance to achieve the best possible fuel economy. We're not talking your basic cap and rotor type rebuild, but a full disassembly and cleaning, checking the advance mechanism, re-curving of advance weights and an adjustable vacuum advance. I will document everything here visually for those that are interested, but first I have a question:

What is an ideal shimmed clearance between the distributor housing and the gear? I have a Moroso shim kit for such an adjustment, but there is no indication as to what I'm shooting for. Currently, I have about .058" (via feeler gauges) endplay. You can physically lift the rotor shaft up when installed, which has a distinct effect on the timing, retarding it quite a bit.


Shaft endplay - shaft at its bottom of travel

Shaft endplay - when the shaft lifts, as it would under acceleration, timing retard significantly

Anyone have a spec to I should try to achieve for clearance? Thanks!

 

[michaelj]

After some further Googling, I found my answer. Endplay should be shimmed to .015".

 

[michaelj]

Okay, I've gotten a little ahead of myself so please let me take a moment to properly introduce this thread, and my reasons for starting this project.

I purchased my 229 V6 powered El Camino with the plan of having fuel economy over horsepower, because I knew this would be a day to day work vehichle. It has been a constant effort since the Camino came home to me, that first started with cleaning/tuning the carb, completely replacing all vacuum hoses under the hood and the replacement of a couple thermo-vacuum switches to get my city fuel economy up from 7 (SEVEN!!!!) to the 10-12 range. Better, but not impressive at all. I was pleased to see my highway economy eventually in the 20-23 range. I've already well documented my continuing efforts at preparing a 200-4R overdrive transmission for better highway fuel economy (project still ongoing, need to button that up), but I don't do as much long-haul as I do short hops, so getting a better handle on city consumption is a priority.

I had also eventually replaced the HEI cap, & rotor as part of my new-to-me vehicle mainentance, and as part of my economy quest also got a higher output coil and a new module from Summit. I was sad to see that these had little effect. Fast forward in time... I'm not convinced that I've done everything I can do to my stock HEI and I KNOW that I should have better economy. Research has shown that a stock HEI can be an excellent performer standing up to a lot of the aftermarket ($$$) unit$. Articles here (see CoyoteOn2's excellent ignition articles in the Tech section) and elsewhere all indicate that there are other things to do and check to breathe new life into an old distributor and find hidden horsepower or economy that was waiting to be released, so I began this project.

My research has shown, that a properly functioning advance system is essential to realizing some huge results. Sometimes the mechanical advance can be frozen in place by rust or sludge on the shaft. Sometimes the weights aren't moving properly. The stock centrifugal advance springs were pretty stiff and make for a late acting advance system. Changing them with a recurve kit should show some definite results. I have already shown that my existing, installed distributor has excessive end play, which has the direct effect of retarding the spark and counter-acting the advance system. So why spend big money on new dizzie when a little time, effort and 1/3 the cost can yield big gains?

Starting Off

First, some light reading:

HEI rebuild article on the web

vettemod.com forum thread

I removed the cap and marked the position of the rotor in relation to both the distributor housing and the firewall. The two yellow marks seen below line up with the rotor and are used for installation and getting initial timing close. You can also see the new module I had previously replaced. Also note the tang on the rotor mounting plate, which ensures that the rotor can not be installed 180° out of phase.

 

[michaelj]

Disassembly:

After the distributor is pulled, knock out the roll pin on the gear and then pull the gear off. A toothed washer and steel washer will come with the gear.

Some distributor gears can be extremely worn, this one looks great.

The advance mechanism can now be pulled out the top of the housing. It can be difficult to pull if the shaft is very dirty or rusty. This one is quite varnished with oil and sludge, but once you pull it past the internal bushings you should be fine.

 

[michaelj]

I forgot to mention, if you are finding it difficult to pull the shaft free of the housing, you can spray or soak in some solvent like WD-40 or lacquer thinner to soften the varnish for an easier pull. Be careful to observe any marring of the shaft from the gear, and this can damage the housing's internal bushings. Smooth sharp edges of any marring with light touch of emory cloth.

 

[80v6]

HEI Rebuild.

I see a dial back timing light and some road time in your future for maximum advance curve. I put a Rebuilt Cardone in mine but havent had the time to tweek it yet. Still need to find out if the adjustable vac advance cans will work with the v6 distributor. If you havent tried a MSD unit, they sure can help make the most from your gas. Good luck.

 

[fixitman1]

Just my 2 cents, and its great to learn how to do the rebuild,but you can buy a new ready to install hei for about 40 bucks .:texas:

http://www.skipwhiteperformance.com/detail.aspx?Item=PE-350-R

 

[Lindsay]

Agreed on the Skip White unit: $48 to the door as purchased within the past 2 months for a 350 CI. It's probably one of the best values for any replacement/upgrade on our vehicles.

 

[michaelj]

Thanks for the reply guys. Some of my reasons this thread was
a) to learn something new
b) to illustrate the process
c) help others with a super cheap, and relatively easy option to help bring new life/performance/economy.

Ideally, you could refurbish your dizzie for around $15. For that price you could shim the shaft end-play to help maintain proper advance at fluctuating RPMs, and get the springs only curve kit. Both items would have a noticeable impact, without the cost of new module or adjustable vac advance.

That Skip White unit looks like an incredible deal, though, and should be promoted more for guys that aren't as "tear it apart and put it back together" as I am.

I'm hoping to finish the installation today. Stay tuned.

 

[80v6]

HEI Distributor.

Sorry, I was under the impression you where working on a v6 distributor :dontknow:

 

[Otterfox]

Look forward to seeing you finish off the project : ) :You_Rock:

 

[michaelj]

@80v6, I am. The Skip White dizzies are still an excellent choice for others with more cylinders.

@Otterfox, thanks man!

Spoiler alert! I got everything back together late this afternoon and I was able to take a quick couple laps around the block. HOLY CRAP!!! Throttle response is quite improved. Acceleration, too. It feels like I have a two more cylinders!

We'll see what the numbers say once I run through a couple of tanks and can get an idea of what my new economy is.

 

[michaelj]

Also @80v6...

The adjustable vacuum advance I got from Moroso is physically identical (as far as I can tell) to my V6 can. The only thing I can think of that could possible change is the amount of movement the can effects (i.e. total amount of vacuum advance.)

 

[80v6]

Dizzy Rebuild.

Sounds like you did ok. learned about the weight/spring trick with a 74 impala. What a differance! :nanawrench: Got a part # on the can? :You_Rock:

 

[michaelj]

@80v6,

Ordered from Summitracing.com:
MOR-72315 ADJ VACUUM ADVANCE KIT

 

[michaelj]

Build continued:

Furthering the cleanup:

A small cir clip holds the pickup in place. Once the circlip is removed, the pickup assembly lefts right out. DO NOT disassemble the pickup, leave those three bolts along.

Underneath the pickup is a grease well. The grease inside is probably very dried out by now.

First, pry off the plastic cover

Scoop out the old, dry grease

Remove all attachments, wires, etc. and clean distributor body and shaft

Repack grease wells with axle grease

Install vacuum can and pick up. Don't forget to reinstall circlip to hold pickup in place.

 

[80v6]

Vac can

Thank you.

 

[michaelj]

Assembly - new advance springs

The best articles I've read about doing this job all indicate that when trying to recurve your distributor it is better to only change the springs. I trust that advice, simply because it minimizes the variables in the equation. A lot of kits have new weights and center plates that are visually very different from what I have inside my HEI. I've read that the quality of a lot of kit weights is questionable (no personal experience with that.) And besides, I'm not changing my engine in any other way; same cam, same compression, same carb. I just want my mechanical advance to open a bit soon than before, so I'll reuse my GM weights and center plate. Also, a springs only kit is the cheapest way to go. Here is what you get:

Mr. Gasket (MRG 928G) ADVANCE CURVE KIT-DELCO HEI
Visual comparison of the three springs in kit

From what I've read, the GOLD spring is the best bet for improving street driven performance and economy. For the street, the BLACK spring is way to weak, as the weights will not return as readily. I may try the SILVER in the future, but for now I'm going GOLD.


Visual comparison of OEM spring and GOLD

The GOLD spring is described as closest to OEM, but you can see here the difference. It's wire diameter is considerably thinner than stock. Even though it has more turns of wire it is still much easier to install/remove than OEM.


Mechanical Advance: cleaned, assembled and ready to install

When assembling, be sure to install the weights and center plate correctly. For me everything had numbers up, but I'm not sure that ALL HEIs are that way. Be sure to check your BEFORE you rip it apart. I should say that I did not add any sort of lube or grease underneath the weights because I do not want them to attract dirt or become sticky as the lube dries out, causing the weights to stick or bind.

 

[bonos40]

Michaelj:
tell us about the motor:
I have a 229 V-6 that at 66,000 miles ate itself. that year had a soft cam and totally destroyed the motor.
We have since rebuilt it .40 over 10-1/2 pistons ,comp valve job , crane cam , edelbrock intake and 5oo cfm carb. Never played with the distributor , but sounds like a good area to look for more power. great article thanks

 

[michaelj]

Assembly - Module

If you're doing this job for the first time you may consider a new module for your dizzie. I had previously purchased a higher output module, so it wasn't on the to-do list. I do, however, still need to give the module some attention. After cleanup and during reassembly you should coat the module's mounting pad with heat sink compound, to help wick away heat and help with the module's longevity. Di-electric grease is not the same thing! It certainly doesn't do the same job. This is what you need:

Coat the mounting pad with a nice film of compound, then install module and screw it down.