Weakest area of the longs/Flex point, Searched but came up empty Options

[drive-ability]

I know I read some where on the forum about a certain area of the longs where it seems to flex more. I just can't seam to find the Picture/information. Can anyone show me where that area is?

[John]

It has always been my belief that there are 5 main problem areas with the original longitude design all are important:

1. The holes in them where the jack posts are. With both jack posts and rocker panels removed, it is possible to look straight through the car (through the lower firewall). Since this is one of the joints in the "3 box design", this is a high stress area. Short of going to a cage, the only solution in this area is to strengthen the existing design (which moves the weak point someplace else). This is the area most rusty 914's sag and causes door/top misalignment in flexy cars.

2. The area where the front of the longs attach to the front "box" is another high stress area, but this one seems to be a little better off than the rear joint. Short of going with a cage, I have not determined a real good way to reinforce the area.

3. The middle of the longs (just as described by others) is another area of high stress. The chassis (even with stiffeners added) will begin cracking here. The ones I have seen have the crack propagating from near the floor seam up the inner long. Once the crack begins to form, it will grow fairly quickly. The metal at that point becomes brittle (assumed to be work hardened). I have noted this in street cars as well as track cars. They seem to crack in just about the same spot. The only way to eliminate this weakness is to stop the cyclical movement of the metal (not very practical if you want to drive the car). The engman inner long kit (or something similar) should slow the process down drastically as it would probably more than double the wall thickness of the tube (long).

4. The area where the rear shock towers are tied into the rear portion of the longs can begin to form cracks when spring rates are increased. There used to be some threads that addressed the resolution of this issue a long time ago. The repair involved opening up a cross-member, adding some welds between formed sheet metal sections, and closing up the cross-member.


5. Rear suspension consoles will form and propagate cracks when wider/stickier tires are used. They can be braced, reinforced, fish plated, etc. These areas are highly stressed and there is only so much that can be done to slow the process down.





After running the same chassis for 20 years on the track (with 2 drivers), it becomes obvious where the weak points are/were.

There are other weaknesses in the 914 design, but these are the major ones that I have also witnessed in street driven cars.

I fully understand why you want to avoid a cage in your car. The same reasons that my silver car (street 3.2) does not have a cage. I wanted a STREET car. If/when it gets a cage, it will probably become a track car. I hate cages in street cars.

By the way, the windshield frame also likes to form cracks down in the corners where it meets the cowl.....

just my $0.02