1979 308 GT4

Now that it is snowing I am going to dig into the ignition system. A previous owner had converted to Crane XR3000 units. One had failed a few years ago and a newer unit was placed on one bank. The 'electric eye' in the distributor on that bank was not replaced and the wires were spliced together with electrician's tape.

The Crane units were mounted to a piece of scrap galvanized steel.

The coils are Lucas non-resistor. The hardware was a combination of SAE and sheet metal screws.
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Here is the distributor ready for cleaning. I'm going to have to get my hands on a gear or bearing puller to get that top bearing off if I want to take apart the advance mechanism. I can see some old grease on the advance mechanism, but it does seem to move smoothly. I'm going to replace the three-wire Molex type connector with this fancy one (http://www.ferrarichat.com/forum/showpost.php?p=136111088&postcount=132) and add in some faux condensers to the outside of the distributors.

My plans for the coils are to switch to those Blaster coils (http://www.shopatron.com/product/product_id=MSD8202/424.0) and I am going to use the Eastwood (http://www.eastwoodco.com/jump.jsp?itemID=728&itemType=PRODUCT&path=1%2C2%2C389%2C390%2C397&KickerID=126&KICKER) cadmium spray paint for the body. This will simulate the look of a Marelli coil.
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I just LOVE this attention to detail! This is exactly the way I restore my toys. -rick

 

After some poking at the advance mechanism through the 'inspection hole' it looks like one of the pins won't compress and is getting held up on something. The little collar around the pin will compress, but the pin-head won't press in all the way.

 

Based on my preliminary review of the distributor I need to take the advance mechanism out and clean it up.

There are a number posts on testing the advance mechanism and there are some unique contraptions that people have devised to check the advance mechanism. I also need to check that both of my distributors advance together. Rather than build a spinning contraption or restore an old vacuum tube powered unit (though I love vacuum tube electronics) I am going to try something a little different.

We know what the 'factory' advance curve is supposed to look like. It has 'advance' on the 'y' axis and 'rpm' on the 'x' axis.

We DO NOT know that at any given engine rpm what the optimum timing is. That is to say, I don't think they had the engine on the dyno and at every 100 RPM interval from 1000 to 7000 the checked for optimum timing duration. I may be wrong, but I suspect they used emperic formulas or 'experience' to either match a pre-existing Marelli advance mechanism or to specify to Marelli what the specs should be. The 'factory' advance 'curve' (not really a curve, mostly a line) is like many things, a compromise that was found to work fine with the stock 308 engine.

Having mentioned the above, one can see that a distributor machine can let you try and match the factory curve, but you really need a dyno to check that the curve is right for your engine (which is probably no longer stock). Alternatively 'seat of pants' or onboard GPS-gadget testing would help optimize the timing (or at least the maximum advance setting).

So the question that I want to answer is simply: DO BOTH DISTRIBUTORS ADVANCE THE SAME; ie SIMILAR 'CURVES' AND SIMILAR MAXIMUM ADVANCE.


We know that the force of the spinning weights increased as RPM increases and the more the weights move outward the more the distributor cam advances so I imagine a device that is constructed from a TIMING wheel and a DIGITAL TORQUE wrench...

 

With a torque wrench and a degree wheel I could make plots of Torque on the 'x' axis and degrees advance on the 'y' axis.

The 'x' axis torque is a surrogate for RPM because torque = force and this force is the same as the force of the fly weights against the springs when it is spinning. This force is proportional to RPM.

My advance 'curves' will look just like those made with a distributor machine, the only difference is that the 'x' axis is force and not RPM. I will not even suggest or imagine that any usefull equation would allow a conversion from my measured force to RPM and I will say I don't care that I don't have RPM information. (The only reason to have the RPM info is to superimpose over the factory spec. curve. This would be nice to have but not neccessary as final maximum advance will be set by testing)

All I need to do is see that the 'curves' from each distributor can be superimposed over EACH OTHER and they both peak out at the SAME maximum advance. Once I have this information I can fine tune the maximum advance once the car is running. I would do this by first setting static advance to the recommended spot on the flywheel then, either by using some millimeter marks on the distributors or using a different reference spot on the flywheel I will progressivly advance the timing and test drive the car. When performance falls off or if detonation is detected then back off a little and it is set.

Final thoughts, this method is not suggested to be better than a spinning advance machine, but it is better than nothing and if the curves 'look' OK then I can live with a little imperfection in the mid portion of the curve as long as the maximum advance is set to optimum.

Setting the maximum advance is not rocket science. Just rotate the distributor one way and test it then the next way and test it and see which is better. If your afraid of detonation, back off a little or check a plug cut for black specs on the insulator.

The Ford Model A had a spark advance lever on the steering wheel to fine tune the spark advance to the quality of fuel available. Many old outboard engines and vintage Indians and Harleys had a similar 'manual advance' of the timing. This is a lot easier than getting out of the car and loosening 4 nuts and 2 bolts and carefully rotating two distributors the same amount.
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The first picture shows the bearing puller in action. The advance mechanism consists of two fly weights. One side is marked with an orange dot which I exaggerated with a red dot.

Disassembly of the mechanism shows a washer between the cam and the advance mechanism.

I photographed the parts as they came apart to ensure correct reassembly.

Everything was cleaned then measured. The dissasembly sheet is shown. With this sheet the mechanism can be put back together even if all the parts are mixed up.

The mechanism should probably have two longer pins as on one side the pin is held so far out it just misses the hole for it in the back of the flyweight and was catching on the edge of the little washer. This was not allowing the pin to compress and was limiting maximum advance on that distributor. There was also a large groove or wear mark where this pin makes contact with the outer assembly.
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Sorry for these posts being a little sloppy, but I was kind of dreaming about this technique when I woke up this morning and when I got home from work I wanted to quickly try this to see if it would work.

On my way home from work I stopped by Sears and picked up an 'inch-lb.' torque wrench that was on sale. It turns out it is still too coarse for this measurement.

I wound up going back to my old style torque wrench and using it in reverse to take the readings. So instead of holding the handle and letting the indicator needle point straight, I held the indicator needle and let the large rod point straight. The indicator needle is a hefty 1/4inch and seems to be made of the same flexible steel as the main rod. Anyway I was able to make this graph.

The indicator degree marks on the advance mechanism were printed out from my computer. The circumference of the advance mechanism yielded 0.61mm per degree. I printed out 100 hatchmaks and they measured just about 61 mm (just to check that the printer really prints to scale).

There is black electrician's tape around the point cam to protect it from the 19mm 'crow's foot' wrench.

The orange clamp is just to help me hold it in place, the vice just keeps it from tipping over.
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I am in ABSOLUTE AWE with what you're doing!!!!!!

AUGURI!!!!

 

Does anyone know if Euro GT4s came with boxer paint jobs? I heard that only USA cars were painted this way - does anyone know if that is true?

 

Good question, here are some from Peter's registry (http://www.dino-gt4-registry.com)

Location is not exactly the car's original market, though. Some could have been re-painted also. Most with boxer paint are listed as USA.

08548 308 - - - Red-Boxer/ - Japan
08600 308 - - - Red-Boxer/Tan NY, U.S.A. Euro. car
12102 208 - - - Light met. Blue-Boxer/Creme Italy
13402 308 - - - Red-Boxer/Black England
13446 308 - - - Silver-Boxer/Dark Blue Netherlands
14042 308 - - - Silver-Boxer/Black Monaco
14612 308 - - - Red-Boxer/Black cloth Belgium

The photo is euro 13446 by Erik van den Eijnden.
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With a little better grip on the technique (and better GRIP on the distributor housing) I was able to exert more torque and get the mechanism all the way advanced until the flyweights hit the housing. Now my curves look better. Without having ever done this before I did not know how much torque was needed to get the flyweights all the way out.

I will have to do some more research on this but my owner's manual (the 1975 yellow and red) says 13 degrees advance.

Obviously here I have about 17.5 to 18 degrees advance.

The curves of front bank and rear bank are close enough for me. I will put things back the way they came and lubricate the mechanism with Moly lube.

One bank distributor had some large gouges from the pins digging in, but this does not seem to cause a major problem based on the curves I obtained. (good thing because I don't think one can fix those gouges).
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Just as a comparison, here are 'home made' advance curves made with a spinning distributor machine. These are from the on-line distributor alignment document by Mike Florio (avilable on www.dino308gt4.com). (It is required reading but does not show where all the parts go if you forgot how it came apart, so I hope I have provided some additional info.)

I am real pleased with my own curves, especially since they were produced with common tools in the shop without a distributor machine.
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I replaced these o-rings with new ones from the hardware store. The originals were hard and crunchy.
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I picked up two wheels today from Transwheel. These are my thoughts:

1) Since up to this moment I have spent zero dollars on labor, I was prepared for an 'blank signed check' experience in getting the wheels done correctly

2) The wheels are better than I imagined, based on the rough initial apperance.

3) The tires were mounted with no signs of damage to the wheels finish and no evidence they had to 'touch up' the rim edge after the tire mounting

4) The raised letters are a little diminished, but I expected this and it is very acceptable.

5) The finish on these wheels is better than original. I compared these wheels to very well preserved 1977 308 Campagnolo and the original wheels have what seems to be a much thinner clear coat with a lot of orange peel in some areas. I posted some poignant remarks regarding over restoration on another thread and to be honest these wheels have been over-restored. (They shure do look good though!)
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Prototype for mounting the Crane ignition modules. With the wires exiting the back of the module the installation will be a lot cleaner. The wires will be shortened appropriatly (except the wires to the light sensor, there have been some posts on other threads indicating those wires should not be shortened)
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This distributor is cleaned and ready to be installed. Notice the fake condensers and fake terminal and the mini-bayonet connector for the rx3000.
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This is the best source I have so far as a representation of the original components of the 1978/1979 engine compartment. This is off the internet and is a scan of the small photo in the R&T 1979 article on the GT4. I wish I had the original article so I had a clearer picture.
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http://www.amazon.co.uk/Original-Ferrari-V8-Keith-Bluemel/dp/1870979788

 

I have that book, however, the good engine shots for 308gt4 are of what looks like a series I eurpoean version which is quite different from a series II USA version. Also, the car with the good engine detail looks like it has been restored, therefore, one does not know how close they were in matching parts with what was originally on the car.

 

Hi Mark, great job of documenting your project. i have an interest in the Marelli, as you can tell from my thread, thanks for posting.
i would like a close up of the tag on the Marelli to see numbers and all stampings if this is possible.
This is not a good time to ask, any chance you have wire diameter and coil count on the distributor springs, may be able to satisfy this request by looking at the photos more carefully.

At what distributor speed do the flyweights theoretically max out against the drum? I know you wig wagged the cam with a torque wrench and got some good data for others to compare. Will you be puting this Marelli on a Sun machine to generate an advance curve as well?

My pins on my Marelli are too short and wallowed oval holes in my old weights, i need longer pins, do you have a lead on longer pins?
thank you
Craig
i bet i have got 10-20 more questions on this subject.
please see - http://www.huskyclub.com/tavspinterogeni.html

 

oops, i did more reading and find the curve at website you link, looks like 16.5 degrees at 3000 rpm at dist. This is a Marelli S159 ?? Do all GT4 have exact same Marelli? what is the static advance on this engine? ending up with what total advance at 6000+ at engine?
The kink (or step change)in the curve is created by double spring set, i always wondered why the two spring weight sets, when many Marelli have just one spring per weight, it makes sense.

 

1) I will post some good pictures of the Marelli plate.
2) I still have one distributor disassembled waiting for a new optical module. I can check and post spring diameter and coil number
3) Not shure the RPM at which the flyweights are maxed out on my car
4) Don't know where to get longer pins

Great web site I think I remember surfing through Miura restoration photos on the huskyclub web site some time ago but can't seem to get to them from a link on the main page.

 

Not shure of the model number at this point, the GT4s came with either 1 or 2 distributors. The ones with 2 distributors came with either 2 or 4 sets of points. The 2 distributor, 4 point model was the 'smog' version that is on my 1978 USA legal car.

I am still researching the static advance and total advance for my car. I have a lot of specs but they cover european and USA cars with 2 and 4 distributors and with and without catalyst. So far I know my distributors are about 17-18 degrees maximum, whereas the USA cars are supposed to be 13 degrees. My car does not have the original engine so it may no longer have the 'smog' distributors. The exhaust is european but the carbs are USA. Still sorting it all out.

 

Plate from Marelli distributor currently on my car.
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