Tiny Holes in Dist Cap...Why?

Just want to confirm something. I'm changing caps from dealer to aftermarket. The stock one his 4 tiny holes drilled in it.. about 1/16".

 

The aftermarket does not have the holes. I'm thinking heat/condensation?

 

A member on another site said his points went "green" without the holes due to condensation... drilled holes and all is fine now. But Diablo does not have points to begin with... but the school of thought may be correct.

 

Anybody have any comments or ideas on these little holes...should I drill?

As I recall from my NGK days, those holes were to allow ionized particles to escape. If they were to accumulate, they can cause arcing and loss of voltage to the rest of the system...V8 engines were more prevalent to this phenomenon, given there was a great frequency/abundance of "firings" and voltage. I can only imagine the amount of voltage circulating in a high compression TWELVE cylinder engine.

Hi, i replaced my cap by the aftermarket part 1 week ago. I left it like it was without the holes that my original cap had, thinking that this way it will keep dry inside when driving in rain.

 

BIG MISTAKE!!!

 

Within 200 km the car lost power and started to misfire over 4000 rpm.

When the engine was cold, it was better, but the hotter it got, the more misfire i got.

After removing the cap again, i saw it was full of green slime- the result of oxidation and obviously there was still a lot of condensed water in it.

The cap cannot be used anymore, the contacts are nearly gone.

 

I installed another one and drilled in the holes like in the original (6 of it, 1 left and 1 reght from each screw) and now its running fine.

 

So the holes semm to be important, although i now ask the question why Jaguars do not have this problem.

 

Hope this expierence can prevent some of you from having the same problems

 

 

Regards

 

 

Steffen

i also ordered a cap and rotor from the napa #rs,so has anyone else installed aftermarket cap and rotor.also digatec how many miles was on your car when you changed the cap and how did the old one look ?

The first one had 40000 km, was not lookig bad but in rain the car did not run good anymore. i got also new ignition wires so i decided to change it all.

mine has 44km on it,only changed the plugs,i do have the aftermarket dist cap,rotor,just havnt had a chance to change them yet.

I was really surprised what a difference new cables, cap and rotor make.

The engne sound some way dirrferent and has definetly more power, especially at higher revs. Problem is the contacts in the cap fade away very slow, you do not feel it. When the new is in, you suddenly recognzie how big the difference is.

thnaks for the feed back

when an electrical arc occurs active ozone is created. as the rotor turns fresh air is passed through diminishing corosion and displacement of metal which causes spark discharge to areas in the cap other than correct timed plug wire terminal. The jaguar draws manifold vac through the dist base via two lines sealed by the cork or paper gasket between the cap and aluminum base. yes the holes are needed and very functional. Jeff mccormick

thanks rocket man

Just pulled my cap because I was having a problem with the car stuttering, and this is what I found.

 

Not sure if my cap is OEM or not. It's a Magnetti Marelli but there are no holes drilled in it. The contacts look like they're in good shape still after I cleaned them up.

 

Where and how many holes should I drill? L Diablo says his cap had 4 holes, digatec said 6 holes.

 

Thanks guys...!

Hang on Jay, I kept the stock one and will take a pix for you...let me dig it out.

Here it is next to a regular ink pen to give you an idea.... I have 6 holes.... between ever other wire contact

it seems like drilling holes in a cap is not good for it,it seems its best to go with an oem cap,i have a dist cap from napa havnt had a chance to install,how much is the factory cap?

Thanks Frank! :prayer: 6 holes coming up...

 

Adam: With all that's in this thread why do you think the holes are a bad idea?

real marelli caps with holes O.E. use rotor as fan to cycle air in and out of cap.Real marelli caps with no holes are jaguar marelli which passes manifold vac through the aluminum base below cap mounting surface. Proper installation of less expensive jag cap to lambo requires modification or the result is what the above photo reveals.In addition excessive oil and or grease inside the dist. housing will compound this issue as will poor conductivity of plugs and wires. Jeff McCormick P.S. see previous post

Ok, so somebody along the way put a Jag cap on the car

I cleaned it up and drilled the 6 holes. You can just see them in the pic.

Getting late so I'm going to put it all back together tomorrow.

great pics of the cap lamb jay keep us posted

No Problem Jay...

Rocketman and Craig are 100% correct...

Many miles on mine.. runs perfect.

 

See sticky above, I think I paid 65 dollars for the cap...OEM is 900-1200, I think.

just drilled 6 holes in my napa cap,will install soon,will let you know how it goes,thats crazy 900 for a factory cap.

Got mine all put back together and the car seems to be running great. But for some reason I have a check engine light. See here http://www.lambo-power.com/phpBB2/viewtopic.php?t=8174

 

Not sure what to think as it's running fine, no stuttering.

have you cleared the ck eng light?what year diablo do you have?

Cleared it via the jumper on the LIE? No I have not done that. It's a 95 VT.

i had codes when i installed my exhaust system,cleared it with the lambo tool that plugs right on the side of the pcm,no codes returned.

What Diameter are the holes?

 

I was told by a very good Mech. that the holes cause more trouble when you drive in the rain. Water get in for sure and we all know what happens with water in the cap.

 

I had the same thing happen as JAY with a cap that didn't have holes. I bought it direct from the factory. I changed it and regulated the climate in my garage, (I had 78% humidity before installing a dehumidifier and air conditioner) and the problem went away without putting in the holes.

 

I've also talked to several Lambo parts departments. Two had caps with holes and two had caps without. All said that they came directly from the factory.

 

I'm really confused about this one!

 

I do want to mention that the NAPA cap is an poor quality may cause problems. You could burn out the core pack. However, if the 70,000 volts it produces back feeds into the two computers that run on 12 volts, your up the river. Replacing these are not cheap!