I have found the factory timing curve is lousy for a modified engine. They do not run much initial advance and tons of vacuum advance. If you try to advance the static initial timing a little bit, it rattles like crazy.

What I have found that works best for me without getting too complicated, is to just disconnect the vacuum advance, and run the initial timing up as far as you can, I have run it up to about 14-16 degrees. You cannot hook up the vacuum advance with it set this high, but even with it disconnected you would not believe the throttle response and fuel mileage you will get running it this way.

If you wanted to buy an adjustable vacuum advance kit, you could probably bring it in slowly, add a little bit during cruise, but you cannot have no where near what the factory was adding with their setup.

 

Disconnecting the vac advance is not the answer.


Yes factory set ups run lots vac and not a lot of mech advance or total ,advance.

The Vac advance is there to improve fuel economy and emissions at part throttle. Many performance distributors do not have vac advance for the simple reason that race cars do not spend much time at part throttle. On most engines including the SBF you want total advance in by 2500 RPM for maximum performance.
The factory set up usually does not see full total advance till 4500 RPM.
Total advance is done with the vac advance disconnected and is the initial and mech combined.

SBF's between 9:1 and 9.5:1 make peak HP with 38-42° total advance by 2500 RPM. 9.5:1 - 10.5:1 35-38° total, and above 11:1, should not go higher than 35 deg, total. Factory engines at 8:1 to 9:1 compression 42-48° total.

Your base timing is set by your total timing for example if you have 30° of mech advance available with the 15L reluctor and if your engine is happiest at 40° total your base timing will be 10° BTDC. Ideally on the SBF you do not want to exceed 12° base timing and I like to shoot for no more than 8°.

Every 0.026" increase in the reluctor slot equals 2° of increased timing.
Every 0.026" reduction in the reluctor slot equals 2° of decreased timing.

The number stamped on the reluctor arm is half the total advance of that reluctor arm. For example a 15L has 30° of advance with a slot width of 0.540"
Increase the slot width to 0.566" would yeild 32° of advance and be a 16L arm. Conversely weld up the arm and reduce the slot to 0.514" would yield 28° advance and be a 14L.

Typically larger displacement engines have a higher number reluctor arm and smaller engines a smaller number. All the arms are swapable between V6 and V8 engines. Basically anything that uses the Duraspark cap.


Once the total advance is set you can adjust the vac advance.
The vac advance must be done with a road test. Any time you swap carbs intakes rear gears you must reset the vac advance. Basically anything that affects the manifold vac at a given RPM/throttle position.

Setting the vac advance is not difficult.

Most all after market vac advance units are adjustable as are good portion of the factory ones, they in most all cases use a 3/32" allen wrench to adjust them.
With a good timing light accurate tach and some patience you can curve the dist your self.
The mystery of setting your dist curve is not the mechanics behind it but the settings you need.

The best way to set vacuum advance is with a road test.
On a steep, long grade, with the vehicle in high gear and with the kick down disabled in an auto at between 30-40mph (50-65 KPH) road speed,occasionally mash the go pedal to the floor, and listen for pinging or a loss of power. If you get either back of. This means you are getting to much vac advance and you need to tighten up (delay) the vac advance,
and keep adjusting and testing till the pinging or power loss is gone.


It can also be done with vac gauge, vac pump and timing light. Do the above road test and note the manifold vac you get pinging at.

The with the engine running, hook the vac pump to the vac pot and, note your base/inital timing. Apply vac with the pump to the advance pot equal to when you were getting pinging. Note the amount of advance, remove the the pump tighten down the spring, hook up the vac pump pull the noted vacuum and look at the change in timing. Then you will know how exactly how much vac advance you pulled out at that manifold vacuum. You can then adjust incrementally and accurately pulling out just enough vac advance to stop the pinging.

 

Franklin, Matt,

Thank you for the replies, and thank you for your patience. I have played around with ignition timing before, but only with a laptop through OBDII.
This SBF stuff is brand new to me.

It all makes perfect sense to me now. The springs in the SBF Crane Cams kit do not change the amount of timing, they just change the "when" of the timing, correct? The Crane Cams kit instructions say "We recommend using the shortest slot of the two available in your Governor for the best economy and street performance". Below that, it says to use two yellow springs to get a start advance of 800 RPM and full advance by 2600 RPM.

What I'm getting at is that I need to buy a new distributor, and I was wanting to get as much done ahead of time as possible. I'm not going to kill myself trying to get every last bit of HP out of this thing, but if there's a significant improvement over stock that's available for a few bucks, then I'd like to take advantage of that.

 

A little trick I read about on this forum and did myself.
Your distributor hold down bolt.
Get rid of the bolt and put a stud in.
When you get your engine finished and installed and need to R&R your distributor for whatever reason,... it makes it a LOT easier!

 

Cool, thanks for the tip Timehunter!

 

Correct the springs just adjust what RPM the total timing comes in by.
The reluctor slot size determines the amount of mechanical advance you get.


With the low miles on your engine your stock distributor should be in good shape I would stick with it and tune that personally. I would be inclined
to install an MSD box before I swapped the distributor.

Check you current distributor and see what reluctor arm is in it. This will tell you what amount of advance it will give you. Make sure to note it before you re-assemble the distributor.

I personally like to try to be around 8° base just for easier starting in a street application and will change the reluctor to achieve this while maintaining the same total advance number. In my opinion to 12° base is acceptable once you get over that slow crank can be an issue if the battery is marginal in cold weather or with starter heat soak starts.

After market distributors only offer an advantage in tuning or if you are going to be spinning high RPM. Other wise they are just dollars spent and do not add HP.
For 90% of street driven vehicles they offer no advantage over the base Duraspark distributor other than ease of tuning the curve. But once that is done it is usually never touched again, unless things like heads are changed, so even then the advantage is questionable.

You're better off putting the money in to a MSD box, or quality ignition wires, plugs, cap and rotor IMHO.

If you are not looking for every last HP don't be looking for every last degree of total advance

I'am assuming the heads you got are the F1Z's GT40 heads as they are the most common.

The total advance your engine will like is affected by the fuel composition, fuel air mix,cam,compression ratio, and combustion chamber design/ volume (fast burn chambers like the GT40P and the E6AE high swirl head like less total advance). The E6 head gets bit of a bum rap. it is a great head for low RPM applications and can return excellent fuel economy, so if you are looking fuel economy and not power in a grocery getter this is the head to use.


Your total timing can be checked with a road test with the vac advance disconnected. Any pinging back it off any power loss advance it. With the variation in fuels today what may be be fine from one pump or in one region may not work from another

If you are going to set the total timing yourself start at 32° total this a very safe no risk point with GT 40 heads and road test (again no vac advance) if you are not running hot have no pinging or are getting a power loss advance to 34° and test and keep doing so till you get pinging or are running hot then back off a few degrees this will give you a bit of a cushion for fuel variations. If you end up at a spot that you like the power it is making but it is running hot you can richen up the mix, but this will effect fuel economy.

If you choose to have the engine dyno'd it would be worth while spending the extra dollars and have them tune it by setting the curve both total and fuel air. Unless of course you wanna do it your self. Be sure to tell the guys tuning it what fuel you will be using reg/ mid/ premium etc.
The vac advance will still have to be done in vehicle.

 

The distributor is all rusted and corroded to pieces, so I am just going to replace it. It's cheap compared to all the other stuff I'm buying, and it would be a sin to stick this thing back in a nice freshly painted engine. The engine does have very low miles, but at the same time it sat within view of the ocean for 30+ years, so the salt air has taken it's toll on it.





18L, so 36 degrees max for stock eh?

The nickels and dimes I don't mind...it's the thousand dollar bills that give me heartburn...lol. It's my Scottish blood. Deep pockets and short arms.

The GT40 heads are supposed to be F3ZE-AA castings. At least that is what was sent to me. I'll advise further as soon as they arrive. I'll CC them to see what size the chambers are.

If the stock distributor is OK for my engine, that's all I need to know. I can leave it at that for now. I'm just trying to get everything gathered up and taken care of before I take it all to the shop. The fee for the dyno buys me a whole day, less set-up time, which they tell me is quick. They said they have a couple different carbs there that we can try if I'm in the mood, and if I want to make other changes, there will be lots of time for it.

The Crane Cams advance spring kit caught my eye, that's all. I already have a new cap, rotor, and wires, so a distributor and cap adapter will finish that part off and clean it all up.

 

You have an 18L/13L reluctor in the stock distributor. There is a small wire retaining clip under the felt in the center of the shaft, once removed and the advance springs are removed the reluctor will just lift off and you can turn it around to use the 13L side.

Using the 13L side that is 26° of advance and figure no more than 34°-32° total with the F3Z GT40 heads that puts your base timing at either 8° or 6° BTDC so pretty much perfect.

You could clean up your stock dist it would not be hard.

You will replace the the pick up coil of course and the vac pot for an adjustable one. The rest can be cleaned with minimal fuss.

I'm not one for manual labour when cleaning stuff if I can get chemistry to do thew work for me I will. 2 chemicals/cleaners will allow you clean your dist to brand new condition with nothing more than soaking.

Strip the distributor to component parts. (You're half way there now) all that is left to do it pull the reluctor and dist gear.

Pick up some phosphoric acid from the local concrete supply (it is used for cleaning concrete and efflorescence from grout) it must be phosphoric acid not muriatic/hydrochloric acid.
Phosphoric acid is non toxic unlike muriatic/hydrochloric and requires no real special handling precautions in the concentrations used for concrete cleaning (typically 20-25% strength) . It is used as a food additive and as a dental etch for fillings so no real worry's about handling unlike muriatic/hydrochloric acid.

Soak the steel parts in the phosphoric acid it will remove the rust and corrosion and leave them looking brand new and it deposits a protective phosphoric coating where the rust was removed, just rinse the phosphoric acid off with water. A quick coat of you favorite rust preventative (WD40 even works) will stop any chance of future corrosion.


For the aluminum dist body you want to use an aluminum acid wash.
Something like FPPF trailer brightener or Lloyd's Aluminium Magic. Either should be available from any industrial supply. Acklands Canada has the small bottles of Lloyd's (see link below) the FPPF Trailer Brightener works way better and does come in 1 gallon jugs but Acklands only has 20L pails listed it is more costly but this a concentrate and gets mixed to like a 1:60 ratio.
I have found nothing better for alum and stainless steel than the FPPF trailer brightener and it leaves Aluminum spotlessly clean and brand new looking.

https://www.acklandsgrainger.com/en/...0ML/p/LYL77816

Amazon link showing the FPPF trailer brightener.

You can use the remainder to clean up any other under hood bits you want to freshen up.

 

Thanks for the info Matt,

That's great. This distributor stuff is pretty straight forward. I may try to clean this one up, we'll see. I appreciate the info on the products to use.

The 13L/18L reluctor using the 18L slot I assume is pretty standard fare for smog era 84 302 w/8.3:1 compression?

Is there supposed to be an E-clip or something similar on top of the pin on the pickup coil where the vacuum advance arm connects? Whatever was on mine was rusted away.

I guess next step is to CC the heads when they arrive and see if I can figure out approximately where the compression is going to be.

 

18L is pretty standard even through the 70's in the 302. I have even seen the 21L used on occasion. And just cause the reluctor says 18L does not mean you are going to get the full 36° of advance. I have seen distributors with springs so stiff the full advance would never come in even at 6000 RPM.


Yes there is supposed to be a an E clip holding the vac advance arm on to the coil pick up plate. If you opt to clean yours up a new coil pick up will come with the plate it sits on.
http://www.rockauto.com/en/catalog/f...ckup+coil,7176


Distributors are pretty straight forward there is no big mystery behind them. But the knowledge about how to tune and settings has not always been freely shared. Even today search the internet on how to recurve one and there is really is very little in depth on the matter considering how prolific their use still is. I think some of this is due the fact that people have always charged fairly decent money to recurve them so they were reluctant to share the information that would allow the DIY'r to do it themselves. Tuning the distributor was a real money maker for shops back in the day. Even now most places charge a couple hundred bucks to recurve one.

By the time we had affordable accurate timing lights and tach's that the DIY'r could afford and take the place of a distributor curving machine mechanical distributors were on their way out.

This one of those things that costs very little to do but time, and can yield significant gains in terms of power and economy.

 

It won't take too much effort to go on the wild side and turn the initial timing up. I think you will be impressed with how it runs if you try it. No harm done if you want to put it back.

 

Franklin2,

It's all good man, and I appreciate the advice. I will definitely give it a try. You guys have all been very helpful with this. I'm learning all kinds of new stuff and having dun doing so.

Now that I see how the distributor works, getting the timing dialed won't take much effort. I just want to get this old 302 working the best that it can, so that's why I've been asking about this stuff. The ignition timing was the last piece of the puzzle.

 

Picked up some stuff at CarQuest today. Oil pan was not only in-stock, it had a Made in Canada sticker...don't see those much anymore. Shouldn't surprise me that it was in stock I guess...they are a common replacement item here.



That's it really. Other than spark plugs and a few other little odds and ends like fittings, etc, I have just about everything (Cyl heads will be here next week). I should be hauling it all off to the engine shop in 2-3 weeks.

I ordered a Fel-Pro rubber 1pc oil pan gasket that was 4x the price of the original 4pc style. I hope it's four times as good. Ordered the rear main seal from Ford instead of an aftermarket. I'm going to spring for new head bolts and intake manifold bolts.

Going to work on rehabbing my stock distributor. I have to drill and tap one of the 8-32 screws for the vac advance. It snapped off flush. No big deal. Going to re-curve it and if it needs to be adjusted on dyno day it won't be a big hassle.

Came across the article below in my ignition timing studying. Thought it was neat and to the point.

FORDMUSCLE webmagazine: Timing is Everything - Distributor Curving for Maximum Power

TGIF.
Cory

 

I read the article in your link above. Everything looks good except I don't like their description of how the vacuum advance works. The have a sentence in there where they say "climbing a hill" or "cruising at light throttle" are both situations when the vacuum would be high, thus giving more vacuum advance. They are right about light throttle cruising, they are wrong about climbing a hill. A large load on the engine like climbing a hill is a low vacuum situation because you have the carb is near wide open. So the vacuum advance drops back and is not in the picture as much.

You will notice in their article, they are suggesting running the initial between 10 and 20 degrees instead of the factory 6 or 8. I agree with that, but like I said your vacuum advance unit becomes troublesome with the initial set that high and will need some adjustment.

 

The climbing a hill bit can sort of go both ways. In an auto you are likely to have lower manifold vacuum. In a standard where you have geared down and reduced speed you may have high intake vacuum, high engine RPM's with not very much throttle input but still high load.

But generally the higher the load on the engine the lower the intake manifold vacuum will be.

I think maybe they were thinking while descending a hill intake vacuum is high and had a brain fart when typing the article out.

So for keeping the intial high i disagree with this for several reasons on street car. It puts unnecessary load in the starting system which can be problematic if your battery is weak or you are seeing sub freezing starts with already slow cranking speeds or high under hood temps or starter hot soaking it could mean the difference between a start and a no start. If you keep the over heat spark advance that speeds up engine RPM when the engine gets hot you could push the advance in to detonation. It offers no real appreciable gains on a street car to be honest and only negatives.. On drag or race car where acceleration tenths or hundredths of second count it's a different story..
But for street applications reliability and driveabilty is the name of the game.