The PO had removed the old jack receiver tube and pyramid due to rust. I am going to replace these (not interested in leaving them off). The rust included not just the tube and pyramid, but also the exterior layer of the double wall longitudinal behind the pyramid. I have removed all of the rusted metal, but all that is left is the interior layer which is recessed into the longitudinal. I need to fabricate the exterior layer. The exterior layer also needs to be recessed but I don’t know by how much. If I go too deep the tube will be recessed too much. If I don’t go deep enough then it will not be recessed enough. I know I could just be safe and cut the end of the tube off if it sticks out too much, but I would rather just do it right and recess it the correct amount.

Here is the current situation. You can see the interior layer, but I don’t think (not sure) that the exterior is recessed quite as far back as the interior layer is.

Click to view attachment

I have replacement tubes and pyramids, so I know their dimensions. If someone could measure how far the tube sticks out beyond the flat surface on the top of the pyramid on their car, I can calculate how far to recess my replacement exterior layer. So in the diagram below, I know “A” and “B”. If someone can give me “C”, I can calculate “D”. If you can’t easily measure “C” then a combined “B” + “C” measurement (total height of tube from longitudinal) will work as well.

Click to view attachment

Thanks for the help!

Ever consider NOT using them and filling the rocker panel holes? I have and will again....

I have considered just finishing the job that the PO did and doing a "delete" on the jack point. It would actually be less work. However, this car is not going to see a huge number of road miles and I plan to do proper maintenance such as periodically pulling the rocker panels to ensure it's clean and free of dirt. I also like the idea of restoring it correctly and even having a usable factory style jack point. So they are going back on even though many people are removing theirs.

I bet if you posted a poll, the results would show that the use of the jack post is a bit dangerous and most owners go with a floor jack. "I" use the donuts at the four corners of the pan.

Either way, good luck in whatever you decide to do.

I would only use the factory jack points for emergancy use/last resort. I am all about using other ways to lift the car such as a floor jack. I think the main reason for removing them is rust prevention and I think that is a non-issue for me personally.

You mentioned the donuts, I trust the rear donuts to lift the car and use them, but not the front. I actually am not convinced they were designed for lifting purposes even if they are commonly used for that. The front ones are not supported very well from a structural point of view.

Anyone working from home today and have the rockers off their car?

Floor jacks from HF are chhep and they have a small one that you can keep in the front trunk. Just my 2cents. I don't like the jack hole or the plastic cover.

I'll look at my car when I get home and find out for you. That is, unless someone decides to post the measurement you're looking for beforehand instead of just trying to talk you out of your plans to replace the jack post.

How about measuring the other side to get a rough idea of what you want ?? Is this possible

Jaxdream

Thanks for the help.

Regarding the removal, use of jacks, etc. I figured I would have a few trying to talk me out of it even if I said in my first post I wasn't interested. But I am ok with that.



Doh! Why didn't I think of that...

...but I can't as the PO removed both jack points, so I have no reference.

Using algebraic formula to find the value of "C" all you have to do is take the equation: if A=73 and B=30 then C has to be 30 too. Right? .....ahhh bs!
I just measured a good used long I've got on the shelf, and C really is 30. I measured the entire projection from the aft edge of the support pyramid to be 60mm total, and the projection from the pyramid to the end of the jack spur, which is also 30mm.

Thanks Perry, that is what I was looking for. That gives an indent of 13mm which is close to what I would have guessed it was.

It's interesting that if you start to measure some of the small details on the car how stuff ends up with really nice even numbers sometimes. 10mm, 15mm, 30mm, 45mm, etc. I can just see the guy at Porsche drawing out the design and using those nice even numbers.

I use the stock jack posts all the time. There's nothing wrong with them as long as the car is free of cancer ...

Andy

PS: The "donuts" were never meant to be used to jack up the car. The ones in the front especially since they're on the underside of the rather thin floor pan and not anywhere near anything structurally sound.

I agree, it's the crappy stock jacks that booger them up. I still use my jack posts on my 911 because it's rock solid and I use a plug in jack pad. I just prefer the the donuts on the 914 which the 911 does NOT have.

Habit....