Thread: Lucas vacuum advance DIY repair

Well here it is the homemade diaphram!

I got my hands on a sheet of 1.5mm nitrile cost 10 clams for about 200x400 he had it laying out the back of course lol. I was hoping for 1mm but the spring has so much resistance I don't think the .5mm is going to help it.

Firstly get your vac advance apart as per above. Get the inner section of your VA or your old diaphram and trace around it, I used the VA as a guide for the knife. DON'T slice through the kitchen table or the wife will never let you bring parts inside again. Clean up any rough edges with your knife it dosnt have to be 100% but at least 98% lol.
Get your old diaphram and arm and line it up with new one, firmly press down on the arm to find your centre of the diaphram. I simply used a ball point pen to piece the rubber slightly.
Assemble the arm as the post above simply line all your washers up and whack the screw in.
And there you have it a brand new diaphram for your vac advance!
The key to getting it all back together is to really tap the fold down tight! I went over and over it, on top and on the sides. Then with a cold chisel to really seal it up!
Suck on the vac port and stick your tounge on the hole.... VACUUM!!
I checked it with a timing gun and it advances perfectly!
There you go no need to buy a new vac advance anymore!
Cheers Jim

James,

I realise this is Diaphragm Mk2 & not the Plastidip Mk1, but did you use any sealant on the surfaces where the sheet & metal contact or are you just relying on a good tight fit only?

Originally Posted by 4bee

James,

I realise this is Diaphragm Mk2 & not the Plastidip Mk1, but did you use any sealant on the surfaces where the sheet & metal contact or are you just relying on a good tight fit only?

I did consider using a sealant but originally it didn't have any so I didn't. Being nitrile I don't think it will stick but it would probably help seal it still. Looking at the plasti dip diaphram I can see in 1 or 2 small spots it where didn't seal perfectly, I'm assuming because it was an uneven coat and the 2nd time around I really hammered it shut way more than the 1st.
It relys on a tight seal really the original unit would have been pressed, but like I said some sealant can't hurt either. I was thinking a tyre tube would work just as well as a diaphram.
Cheers Jim

Thanks James.

I note from the Reglin Rubber website that their material seems to be a far cry from what Lucas used waaaaaaaaaaaay back then, so anything with an internal reinforcing should be great..

is reinforced with a tear and flex resistant Nylon fabric. It has excellent mechanical strength and is flexible and

Originally Posted by 4bee

Thanks James.

I note from the Reglin Rubber website that their material seems to be a far cry from what Lucas used waaaaaaaaaaaay back then, so anything with an internal reinforcing should be great..

Sounds perfect for the job, the original is a material probably nylon coated in some sort of rubber. The original dosnt have a lot of flex but it dosnt need it as it's moulded to move forward and back. Anything cut flat should definetly have some flex to make up for the original shape if you understand what I'm trying to say haha
I'm hoping over time the rubber will concave slightly to help it flex more but that spring is so strong if the vac can pull that it will definitely flex the flat rubber.
Cheers Jim

This is the link to the old boy fixing his, don't blink though he's done in about 20 secs
YouTube

Old Boy????


Cripes, I hope I have skin like that when I'm olde. Mid 20s I would have said.

From your description the "cloth" is very similar then?

Originally Posted by 4bee

Old Boy????


Cripes, I hope I have skin like that when I'm olde. Mid 20s I would have said.

From your description the "cloth" is very similar then?

Bahaha yeah maybe it's just the gramaphone and his level of skill that makes me say that hahaha.
Yes it's definetly a cloth type product originally. So far with mk2 the nitrile rubber I've had a good outcome. Can definitely feel the difference in performance and checked over with a timing gun, the timing clearly advances like it should. I need to put a 2nd mark on my HB at around 26° (need to check degrees exactly) to make sure it's advancing as far as it should but honestly by looking at my 12° mark it's advancing up to where it should.
Pretty happy with my frugal self save near $100 and my vac advance is still the original Lucas one on the outside, dosnt look like a cheap knock off.
Cheers Jim