Electronic ignition distributor question

The forum for all of your technical questions on your classic FIAT autos
User avatar
QuebecFiatSpider
Posts: 18
Joined: Wed Feb 21, 2018 7:05 am
Last Name: Lachance
First Name: Christian

Electronic ignition distributor question

Post by QuebecFiatSpider » Sat Feb 02, 2019 4:03 pm

Hello everyone,

Recently I bought a new electronic ignition distributor for my Fiat spider 2000 FI.

When I opened the box to look at what I got, there is one detail that got to my attention. I noticed two small holes under the base of the distributor, which wou can see in both pictures I've taken.

What those two holes are there for?

I'm asking that question because I read somewhere that if some oïl fumes/mist enters the distributor, it may damage the wires or other mechanism Inside. I know that I need to change the seals for new ones in order to make sure oïl fumes does not escape the cam tower….but..in my own opinion, maybe it would be better if there was no holes beneath at the first place!!!

What do you guys think?

Image

Image
User avatar
cgranju
duemila club
Posts: 2075
Joined: Sun Jan 24, 2016 12:08 am
Last Name:

Re: Electronic ignition distributor question

Post by cgranju » Sat Feb 02, 2019 5:14 pm

I don’t have one in my hand to compare to but off the top of my head I would think those are the bosses where the vacuum advance module is bolted to the body.

The drawing up of oil from the internal seal is a truly evil problem when it happens in our cars but it is from the oil at the camshaft not external.
Chris Granju
sunny East TN
owner of a number of Fiats built prior to 1986
User avatar
jseabolt
seimila club
Posts: 6270
Joined: Sun Jan 24, 2016 7:27 pm
Last Name:

Re: Electronic ignition distributor question

Post by jseabolt » Sun Feb 03, 2019 1:00 am

cgranju wrote:
Sat Feb 02, 2019 5:14 pm
I don’t have one in my hand to compare to but off the top of my head I would think those are the bosses where the vacuum advance module is bolted to the body.

The drawing up of oil from the internal seal is a truly evil problem when it happens in our cars but it is from the oil at the camshaft not external.
I'm not real sure about the holes. I agree with Chris. I guess what your asking is, if the internal distributor seal was to leak, oil would run out of these holes and onto the exhaust manifold? Instead of filling the distributor with oil. Kind of like a weep hole on a mechanical fuel pump. So the crankcase doesn't get filled with gasoline.

I've always wondered about this. So far I've been lucky to never experience a leaking (internal) distributor seal but seems to me this would have more to do with excessive crankcase pressure than a bad seal. Like a stopped up oil separator or that plugged elbow hose or the hose going to the throttle body or air cleaner. Or if the oil drain galleries inside the cam boxes/engine block were to become restricted.

This maybe apples to oranges but I was driving my 68 Ford Fairlane down the interstate going faster than I should have been (like 90 mph). I started noticing smoke coming from the back end of the car. I slowed down to 65 and the smoke stopped.

I pulled over and noticed oil on the rear bumper. The smoke was coming from oil being forced out the pinion seal and onto my dual exhaust. I thought I had blown a pinion seal.

When I got home I decided to check the vent on the axle. This axle has a 5/16" nipple with a hose that is suppose to vent into the trunk. The hose had rotted and when I stuck a screwdriver into the nipple, I heard this loud "swoosh" and felt pressure from the axle escaping. I topped the differential off and have not have any issues since. Although I can't say I have ever driven this car near 100 mph since then!
User avatar
QuebecFiatSpider
Posts: 18
Joined: Wed Feb 21, 2018 7:05 am
Last Name: Lachance
First Name: Christian

Re: Electronic ignition distributor question

Post by QuebecFiatSpider » Sun Feb 03, 2019 5:33 am

I thank you both for your "try" on answering... :|

I just hope someone will jump in and tell me what is the real design purpose of those two holes.

I'm really not conviced that the Reason is to let the Inside building pressure of the distributor to escape...does not make sense to me…

Anyway, let see if someone knows the exact answer...
User avatar
bnam2
Posts: 142
Joined: Sat Jan 20, 2018 4:34 am
Last Name: Nambisan
First Name: Byas

Re: Electronic ignition distributor question

Post by bnam2 » Sun Feb 03, 2019 8:41 am

It's a drain/weep hole. I've "used" that function before.
Byas
1965 Fiat 1500 Cabriolet with 1600twin-cam
!971 VW 1302LS Convertible in original condition
1965 KG - under restoration
User avatar
cgranju
duemila club
Posts: 2075
Joined: Sun Jan 24, 2016 12:08 am
Last Name:

Re: Electronic ignition distributor question

Post by cgranju » Sun Feb 03, 2019 10:08 am

dude, there is no "try" :)
Chris Granju
sunny East TN
owner of a number of Fiats built prior to 1986
spider2081
Posts: 480
Joined: Sun Jan 24, 2016 9:36 pm
Last Name: Laborde
First Name: Dave

Re: Electronic ignition distributor question

Post by spider2081 » Sun Feb 03, 2019 11:43 am

I just hope someone will jump in and tell me what is the real design purpose of those two holes.
I really don't know the purpose of those 2 holes. They have no threads in the original Magneti Marelli castings and from your photo it appears the new distributor has no threads either. This distributor casting was probably used on a number of distributors for various car manufacturers over the years. The design is so old I doubt anyone could supply design documentation for their purpose. Could be as simple as alignment dowels for the casting molds. Maybe as other stated weep or drain holes for condensation.

Case in point, I purchased a 1961 Austin Healey 3000 in 1975 for $150 because no one could get the car to run correctly. Problem turned out Lucas published a 4 cylinder rotor part number for a 6 cylinder car. The car would start but would not run over 35 miles/hr. The 4 cylinder distributor casting was identical to the 6. The difference was the distributor cap, rotor and the center shaft with the point lobes.

My feeling is the holes may have no design purpose for the Fiat twin cam engines. My other thought is "how important is it" They are there and we don't use them.
User avatar
QuebecFiatSpider
Posts: 18
Joined: Wed Feb 21, 2018 7:05 am
Last Name: Lachance
First Name: Christian

Re: Electronic ignition distributor question

Post by QuebecFiatSpider » Sun Feb 03, 2019 2:27 pm

I thank you all very much for your answers. I begin to understand what are those holes for...most probably, on other cars using the same castings, maybe those holes get threaded and used to fix Something.

Or maybe they are drain holes...but to drain what???

I've asked that question at the beginning because I am tempted to close them with high temp silicone. to prevent any oïl mist or oïl fumes to enter the distributor. Because those two holes are just above the holes where this distributor is inserted into the cam tower. I'll probably take my decision when I'll remove and inspect the existing one in place on my engine.

I'll see...
User avatar
engineerted
Posts: 415
Joined: Sun Jan 24, 2016 11:22 am
Last Name: Ted
First Name: Russell

Re: Electronic ignition distributor question

Post by engineerted » Sun Feb 03, 2019 4:06 pm

The Holes are for ventilation, there will alwasys be a small amout of electrical arcing from the rotor to the spark plug terminal posts inside. This arcing will generate ozone, the holes are there to vent this ozone. Too much ozone gas, and the air will ionize and the arc will start to jump around the inside of the cap and forming carbon tracks. Not good!

On the race car, I run a high energy MSD multi spark ignition and MSD recomends that you should add 1 or 2 additional holes to the cap. I don't recommend adding holes for a street car that maybe subjected to running in the rain or parked out side.
1978 124 steet car
1974 124 EProd race car
Farmington Hills, MI
spider2081
Posts: 480
Joined: Sun Jan 24, 2016 9:36 pm
Last Name: Laborde
First Name: Dave

Re: Electronic ignition distributor question

Post by spider2081 » Sun Feb 03, 2019 4:31 pm

The Holes are for ventilation, there will alwasys be a small amout of electrical arcing from the rotor to the spark plug terminal posts inside. This arcing will generate ozone, the holes are there to vent this ozone.
I think you are correct here is part of an MSD installation Instruction:

"IMPORTANT:
Due to the number of applications and years that the LT-1 Cap and Rotor are used on, it
is highly recommended to have the Service Manual for your vehicle during this installation.
This Cap and Rotor Kit is supplied with a vacuum line assembly to vent the cap. This helps prevent
ozone and moisture build-up within the distributor cap".

I'm still learning something new everyday.
Post Reply

Who is online

Users browsing this forum: Bing [Bot], rridge and 49 guests