Jeremiah's 73 412 restoration project

[Jeremiah Berger]

[Jeremiah Berger]

Here are some pics of the rear air ride setup

I took this idea from other air ride setups that used an air strut basically a coilover with an airbag instead of a spring.what I didn't like about that is it put all the weight on that eye on the bottom of strut in the middle of the bolt.I used this contraption to achieve a similar objective of getting the pivot of the whole thing inline with the travel of the shock.The spring had the ability to flex with a curve to it where the bag has to stay straight so cannot mount above like spring...

The bottom has bronze fittings pressed in. And the top of the airbag bolts up to the spring seat from the inside.I also added extra support to the bottom where all the weight now sits .

This is all very custom and made by fit and at this point still considering it a mockup of what I will continue to make better.Just thought it may help others with ideas they may have.

have.

[hulken]

[raygreenwood]

It appears that Jeremiah welded a square flat pad across the opening where the original shock normally went up through the trailing arm from below.

That's a pretty good method of strengthening that area which will also allow you to use any shock whose eye is maybe not exactly the same as the stock shock. It also allows using higher torque on the cross bolt without bending the structural tube. It's also easily reversible with five minutes from an angle grinder.

Thank you for posting the detailed pictures of the Bilstein strut inserts. Those are very ....odd.

So, for those who do not know, the reason those Bilstein struts have what looks like a strut rod that is like 3X normal diameter, it's because that is not the strut rod you are looking at.

These are an example of Bilstein "upside down" strut technology. I had heard of it but never really looked into what it was because I was not buying any of them for what I drive and up until recently....these....Bilstein offers nothing to fit the 411/412.

What these are are literally what it says. Instead of the outer body of the strut insert tube being just the lower reservoir with a piston attached to the end of the rod moving up and down inside.....you instead have the piston still at the end of the rod, but with a large machined cover tube, welded to the actual strut rod with its open end facing downward and inside of the strut outer tube.

So, on a normal strut cartridge, the piston is the lower guide for the strut rod and the outer rod seal at the top is the secondary rod guide. The problem long term with the original design is that as the strut takes up side loads either because of its rake from how it's mounted in the car or because of any issues with the upper bump stop design....the piston rod side loads its outer seal and the inner piston head and eventually wears out the outer seal first. This starts leakage from the outer seal and eventually causes the gas in the lower piston section to start leaking upward into the oil reservoir section and out the upper rod seal.
On one hand if the normal strut has lasted long enough...Bilstein and other strut mfs would not care because you just buy new ones!

So, this upside down design....and I finally found a detailed explanation or what it IS....basically has an upper shield surrounding the rod just like a normal two eye shock absorber like you would use on the front of an A-arm car that keeps the rod and rod seal totally shielded from view and from water and dirt.

BUT....what they have done is to polished the outer surface of that upper rod shield and add its own set of bushing/bearings inside of the strut body and put the shield inside of the strut tube instead of outside of the body like you would on a normal two eye shock. They then gave it an outer surrounding oil seal that you can see.

What this does is it gives the strut rod....two extra guide points. The inner set of what they fall "linear bearings"....bushings.....and that outer perimeter seal around the fat shield welded to the strut rod.

What this does is it gives the strut rod four guide points instead of the original two guide points explained above....and makes it very rigid against side loading, wear and leakage.

Why did they do this? Because it's one of the only ways to make strut cartridges with HIGH PRESSURE gas that perform and last a long time and have less directional change in sporty driving.

Which brings me to my point......how did these perform on your type 4 car? These are B6 spec for sports car level driving.
I would think....speculate.... that they would be rough on a 411/412....basically out running the stock springs and hammering the ball joints as well.

Great technology though! And I have found several listing that list them for the 411/412.

I will post the cross section diagram of these I found later.

EDIT:

Here is a link to the PDF explaining the Bilstein inverted shock technology.

Here is a screen shot of what they are talking about if the link does not work for you.

So looking at that diagram....I had part of it right and part of it wrong. The piston rod is actually bolted or welded to the outer tube....at the bottom of the tube. That fat upper shield...moves up and down so there are actually several points of lateral support. Great technology.

And, the bump stop is actually inside at the bottom. So it really is just a shock absorber suffed into a strut tube upside down.


Ray

[Jeremiah Berger]

Y

Yes as Ray has mentioned I welded a plate across the bottom section to strengthen it and allow for a good torque without collapsing (note I put it to tight and had to adjust the bag mount and shock bottom to work, don't do that)if I did it again I'd have made it a bit taller and allowed more room from the bottom of plate to the bolt hole.The top just mounts to the spring seat and bolts to frame just a couple holes drilled so nothing major that can't be undone.the hardest part of that was a custom angled washer to compensate for angle at one side of spring mount area and working through the tiny hole.I considered adding bigger access doors.You can also see where the air line goes in through here...

That's very interesting Ray I never really thought about the design much truthfully, I just said oh wow when I got it and made sure they worked and didn't consider much about why they where so different. Truthfully it wasn't the best ride up front but it wasn't horrible either and I was running them with e30 springs which did not give enough precoil? ( is that what it's called?)in my opinion and I thought it was more because of that. I have certainly cringed at the sound of my ball joints slamming in potholes but it wasn't too bad and it all bolted right up and got the nose down where I wanted it, and never really had many complaints the few years I drove it like that.

[hulken]

[quote="Jeremiah Berger"]

Since I have no access to my car at the moment, do you have the diameter and wall thickness of the tube and the thickness of the plate?
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[Jeremiah Berger]

Thoughts on the deluxe cam kit vs. deluxe PLUS kit? Do you think I need the chromoly pushrods, vale retainers and rocker studs and hd springs? Or should I just go with the deluxe? I definitely want to maximize any quality parts possible but keeping it less complicated and as stock as possible.I was always under the impression that chromoly pushrods where louder and where overkill if you don't need them... seams like I should just go all the way though?

[raygreenwood]

[Jeremiah Berger]

Thanks for the reply. That all makes sense I will definitely do the valve seat test....The heads themselves are very great condition 70 k miles in a 412 wagon the engine is definitely been babied and the pistons did not have any skirt collapse or signs of overheating, but the exhaust valve guides do need replaced and the seat is a little tiny bit beat.I planned on new exhaust guides and Valve job and all new valves...bit o will definitely check the seats first...I will focus on the heads first, all very helpful.Thanks

[Jeremiah Berger]

I did the drop test on the valve seats today and everything went fine othere then the smell.of an overheating VW im my kitchen...its a good.thing i do allmost all the Cooking. They seem to be holding well for now

Kind of a rookie move for me like usual. I am always learning two steps behind and even though after diving deep into type 4 valve seats last night at this point I would have probably just said hell and bought new heads but unless I wanna send back the Neway cutters and the valves and guides and reamer I already bought ..and all the work I've already put into the heads...I think I'm just gonna hope for the best and honestly they are quite nice heads.

I went ahead and got the rocker studs out today... decided that it was worth the bundle considering the parts I definitely want so I'll probably just order the deluxe PLUS kit now and if I have some extra PRs in the end it's not the end of the world.

Here's the heads. I've got them all stripped and exhaust guides pulled...intake valves seats just had a tiny bit of pitting, went ahead and lapped them with one of the better old valves once to clean them up.cleaned up the ports and the chambers and pulled the exhaust studs to replace.