1979 308 GT4

Difficulty is encountered with the USA 1978 - 1980 308 GT4s because the timing specs are found in the 1978 GTB owner's manual. The 308 GT4 shop manual does not provide the right specifications and the GT4 owner's manual does not provide the correct specifications either.

The 308 GT4 shop manual covers twin distributor models with total mechanical advance of 13 [distributor] degrees and a set of retarded points that are timed to 6 [engine] degrees BTDC. The 'advanced' set of points is timed to 16 [engine] degrees at idle. The flywheel marks on these cars are:
A5 34
AF 16
+6
PM1-4 (5-8)

With respect to the 1978 USA model (GT4, GTS, and GTB), the mechanical advance provides 16.5 [distributor] degrees of advance and the retarded points are timed to 3 [engine] degrees AFTER top dead center. The timing marks on these cars are:
A5 I 34 (timing line between the numbers)
AF7 I (timing line after the number)
PM14 I (58) (line after the numbers)
I -3 (timing line before the number)

The manuals were not clear to me but the PM1-4 is for the cylinder closest to the REAR distributor.

When defeating or removing the 'retarded' points, the 'advanced' points can be statically set to the AF7 mark and have a mathematical chance to allow the A5 34 (34 degrees advance at 5000 rpm) mark line up at speed.

The 1978 USA distributor advance curve (shown in the 308 gtb user's manual) indicates a total mechanical advance of 16 and a half degrees (at about 6800 engine RPM). At 5000 engine RPM (2500 distributor RPM) the advance curve shows 14 degrees of distributor advance. Multiply 14 by 2 gives 28 degrees of engine advance. Subtract 28 from 34 and you get 6 degrees before TDC. Since there is a mark on the flywheel at 7 degrees (AF7 I) this can be used for static timing and is close enough.

To static time at 7 degrees the inspection cover needs to be removed. Mine had 2 8mm locking nuts. There was a rubber gasket under the plate.

 

Removing the plate revealed extremely hard to make out letters and numbers as indicated above. The stationary indicator mark obscures all but a fraction of the marking making things somewhat difficult. I used 3.5 power magnification and a flash light to see the marks.

To align the marks I put the car in 5th gear and rolled it along with the left rear wheel, while observing the marks through the peephole. I then fine-tuned the rotation with the car in neutral, using a screwdriver on the starter gear teeth. I got within a millimeter of exact alignment.
The photograph shows exact alignment with the line following the AF7 mark. Of course you cannot see anything because the stationary marker obscures all but a small portion of the line.
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Then the bolt and 2 nuts for the rear bank distributor were loosened and the ignition was turned on. The distributor was rotated anti-clockwise until the little red light illuminated on the Crane xr3000 unit. (see photo)
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After aligning the distributor, one needs to check that the rotor is in close alignment with the nib on the underside of the distributor cap. The Crane manual suggests cutting a hole in a distributor cap and using a timing light to observe the location of the rotor when spark fires to see that it is close to the nib. If it is not aligned correctly then the sensor has to be moved in the distributor to get it to align.

Anyway, I used some 'cleaning putty' to make an indentation of the rotor on the underside of the cap and things seemed to align reasonably well. (see photo)
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In its USA configuration for meeting emissions, these carbs were leaned out quite a bit at idle and my crazy notion is that the idle circut is designed with this in mind. Therefore it was designed so the idle speed of 900-1000 can be achieved with the thing running way lean and timed at 3 degrees AFTER top dead center. Then, years later, when the cats are removed, the timing is set to 7 degrees BEFORE top dead center, and the idle is made more rich (I have #60 idle jets), it will idle faster and there is not enough adjustment range with the idle SPEED screws to slow it down.

My car currently idles around 1800 with the idle SPEED screw backed out almost all the way (but just in far enough so the levers don't loose contact and allow the plates to bind in the throttle body).

I know that leaning out my carb's idle MIXTURE screws certainly will slow the idle down. Currently they are backed out just beyond where they start to slow the idle (which is just one of a hundred ways to set these jets).

My plan tomorrow is to crank in all the MIXTURE screws in a tad at at time to lean it out and bring the idle speed down. My impression is that this will bring the idle down, give me better CITY fuel economy and still not be so lean that it pops and coughs.

I have searched f-chat on this subject and I think that the people that do not have a fast idle problem have the idle MIXTURE screws in farther than you or I.

Again my thought is that there is something in the design of these USA carbs (DCNF 72,73,74,75) that won't allow enough adjustment of the idle speed when the idle is richened up from the USA smog settings and the idle timing is advanced from 3 deg. ATDC.

 

Guys, if you take a GT4 that was badged as a Ferrari down to the metal, is there the indention where the Dino badge would have gone? ...filled with body filler? The Ferrari badges on GT4s sit on the surface and are not sunken in.... On the early GT4s that were badged as Dinos, the Dino badge sat in a depression like the nose badges on era Ferraris do... Also, were the GT4s sold in Europe always badged as Dinos? Even on later GT4s that came badged as Ferraris from the factory, is there a Dino badge depression under the paint and body filler? I had heard that the GT4s that were badged as Ferraris were only those in America. Is this true? Ferrari opened up a exhibition in the factory museum to "all Ferrari 2+2s" but it does not include the GT4. Why did Ferrari exclude the GT4? Don't get me wrong I love GT4s (even see on my profile that I want one) I just think their history is interesting...

 

Ed. GT4's sold in the UK (and I guess Europe too), were badged Dinos from launch to circa 1976/7 when the Series 2 cars were introduced. These later cars were badged Ferrari (portrait) rather than Dino (landscape). Mine is a S2 car and therefore surface mounted.... can't answer question about indentation though.
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My car is a late series 1. It has a surface mount Ferrari badge on the front. If I look at just the right angle I can see the filled mounting post holes for (I'm assuming) the Dino badge through the paint right under the Ferrari badge. So in 1975 it looks like the Dino badge wasn't sunk. The dealer instructions on how to change the early Dinos into Ferraris seems to show that the Dino emblem is on the surface as well. It also seems to instruct to put on the Ferrari badge and leave the Dino badge in place. This would look funny as is, would look even worse IMHO if one was sunk and one was surface.

 

All series 1 US Dino cars had a recessed Dino badge on the front.
I've seen series 1 cars with:

the recess filled in and a Ferrari badge surface mounted,
and
a recessed Dino badge and a surface mount Ferrari badge,

 

If Ferrari badged a GT4 as a Ferrari thus considering it a Ferrari, I wonder why it was excluded from the 2+2 exhibit??

 

Time to start re-doing the vacuum lines and finalizing carb setup. The plan is to defeat the vacuum system and to defeat the vapor pump, but continue to use the vapor charcoal cannister with it's intake manifold injection. All the lines and hoses and devices will simulate the original engine compartment look.

Here are some pictures before starting.
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The small fabric covered hoses I found were somewhat gray so I used some flexible black spray paint to darken them.
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This is a picture of the vacuum lines. They control the diverter valve for the air pump and the flapper on the airbox intake. Although the flapper seems like a good idea, even when it was working it only stayed closed a few hours (according to the owner's manual). It would be a disaster if the flapper failed in the closed mode.
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A simple plug on the vacuum line nipples will defeat the system, however, I want to keep the original apperance with the original hose configuration. Therefore I made a custom 'T' union that is plugged. I used one from the auto parts store so as not to damage any original parts. The part is marked with red to indicate to me (years from now when I can't figure out why the flapper is not working) that this is a modified part.
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The vapor pump was the source of carbon particles entering the carbs, causing the car to run poorly and presumably allowing me to get a good deal on the car. The label on the pump is on the back side that is not visible. Since the label was in poor condition, it was removed and preserved. The pump lines are plugged from the inside with one of those rubber vacuum line plugs.
That little hose clamp is one of the car's original SIMPLEX French clamps.
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Vacuum lines in place and now ready to finalize carb adjustment now that the timing is set and there are no vacuum leaks evident.
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Can't adjust the carbs with these plugs. Too many short trips around the block in the cold winter weather. (No snow on the ground!)

I was having trouble with irregular idle speed and it was most likely due to these plugs. New plugs made it run like a new car.

I have a good idle now, but my progression system is probably too rich with 62 idle jets. Need to order some 55s.

Too bad I can't get NGKs locally.
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Here is the image from the tech. revisions. I hope everyone has a copy of this file, it is interesting reading for all GT4 owners.
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These photos show the coolant tank before and after revision. There was a mouse nest under the tank! I had wondered why the antenna coaxial cable was severed just before entering the trunk. The mice chewed through it.
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Here is a picture of the mouse nest that was under the expansion tank.
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I finally bought the Facet pump. I got it from International Autoparts. It looks more original without the decal.

The mounting ears of the Facet pump need to be bent a little so that the fittings clear the fittings on the fuel filter.
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Pictures of the Corona pump in place prior to removal.
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I am usually not good about inspecting 'new' parts, I guess I always expect them to be perfect. Well, it is a good thing I checked inside this new gas filter element. There was a piece of paper in there.

The new filter came with a gasket which fits in the upper part of the filter holder.

I tired to preserve the silkscreen words on the fuel filter bowl, however, they came off with the masking tape. I wound up painting the whole thing Krylon semigloss black. I turned it around and mounted it so the raised letters were showing.
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I has some of the 'Cad. Plating' paint left over so I thought I would practice a little on the diverter valve for the air pump.

The pictures show the diverter's home before it was cleaned up.
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This picture shows the new Facet pump in place with the correct hoses and hose clamps. The little black thing connected to the fuel pump mount is a capacitor for radio interference supression.

Not shown is the little jumper wire from the pump mounting bolt to ground (this is needed because the pump's body is the ground, but the pump is rubber mounted)
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