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?

[Mueller]

supposedly if you took a plumb-bob and went from the top of the windshield frame where it meets the targa top (middle of the car) and go straight down, that is roughly the spot....I was thinking you could lay on some spackling or something simliar, let it dry on the longs and do some quick and dirty tests to see where it cracks the most

[J P Stein]

supposedly if you took a plumb-bob and went from the top of the windshield frame where it meets the targa top (middle of the car) and go straight down, that is roughly the spot....I was thinking you could lay on some spackling or something simliar, let it dry on the longs and do some quick and dirty tests to see where it cracks the most

I have no doubt that the area described is the center of rotation for pitch & roll of the chassis.....which is no help in curing the problem.

The most effective fixes are fairly extreme.

A cage tied into the F & R shock towers.

Reinforce the inner door pannels of late model doors.....then weld them shut, both inner & outter pannels.

The weakness is the door openings. I've seen the bandaids for this and am unimpressed with their effectivity.

I did the fromer.

[drive-ability]

I don't have any sag problems but since I have a V-8 my feeling is to go with a cage. This is a street car, so I may only tie in the rear shock tower for now.

"supposedly if you took a plumb-bob and went from the top of the windshield frame where it meets the targa top (middle of the car) and go straight down, that is roughly the spot....I was thinking you could lay on some spackling or something simliar, let it dry on the longs and do some quick and dirty tests to see where it cracks the most"

Mueller
I did look where that spot, it looks like a thin transitional area. The use sparkle is a good idea. I want to give this car a little more structure.


JP,
Nice work, that cars not going to sag (IMG:style_emoticons/default/biggrin.gif)

[rfuerst911sc]

I don't have any sag problems but since I have a V-8 my feeling is to go with a cage. This is a street car, so I may only tie in the rear shock tower for now.

"supposedly if you took a plumb-bob and went from the top of the windshield frame where it meets the targa top (middle of the car) and go straight down, that is roughly the spot....I was thinking you could lay on some spackling or something simliar, let it dry on the longs and do some quick and dirty tests to see where it cracks the most"

Mueller
I did look where that spot, it looks like a thin transitional area. The use sparkle is a good idea. I want to give this car a little more structure.


JP,
Nice work, that cars not going to sag (IMG:style_emoticons/default/biggrin.gif)

I'm curious how are you going to tie into the rear shock towers on a street car? I'm thinking you have to go with bars thru the rear window? How do you maintain water intrusion protection? Trying to learn more. Thanks

[Bleyseng]

first add the Engman inner (IMG:style_emoticons/default/thumb3d.gif) kit which will help alot.

[J P Stein]

[quote name='rfuerst911sc' date='Sep 1 2007, 06:25 AM' post='941276']

[/quote]
I'm curious how are you going to tie into the rear shock towers on a street car? I'm thinking you have to go with bars thru the rear window? How do you maintain water intrusion protection? Trying to learn more. Thanks
[/quote]

First off, the rear window seldom gets wet....as I recall from the days I had one & went out in the rain.(IMG:style_emoticons/default/biggrin.gif)

A guy with a few fab skills could use a plexiglass rear window to seal it off......prolly not air tight, but close enuff.

The Engman kit stiffens the box structure around the passenger compartment....the front & rear box sections still flop around independently.

Draw your self a little picture that represents the 3 box structure of the 914 chassis or just look at the car with the doors off.
A tall box at either end joined by a long shallow box in between. The suspension is near the extreme ends of the tall boxes and where force is applied to the chassis.
Once you've done that, it's easy to see the weak points are and what needs to done to fix it. Simple to see, tough to fix. As I see it, it ain't worth the trouble for a street car.

[woobn8r]

My car is a street car...and I have a 3.2l Carrera engine to motivate her...
I have had enough of racing (15 years), and a at my age I will probably do only some fun lapping and the odd auto X...so NO CAGE for me...I wanted a 914-6 for it's fun factor (sold my '72 911 2.4 E).

Overall vehicle weight is not an issue with the 3.2 but power and flex are.

I plan on the Engman inner kit and also the "Mayeur?" outer long kit. I like the outer kit because it extends rearward past the "B" pillar (or "targa bar"). The CFR console re-enforcements are also a "must" IMHO.

At the end of the day, I don't want my 914 looking like a "boy racer" special....even though it might be one. YMMV.

[J P Stein]

I quite argee with the no cage on the street. I did that for several years and found out that the intrusion of the upper side bars can be painful. Fortunately, I had a helmet on when this happened.....but it still knocked me goofy....goofier?
My latest cage itteration has no upper side bars, but is impractial for the street...unless you leave the top off. (IMG:style_emoticons/default/biggrin.gif)

Power is not the "flexing factor", tire grip is the main culprit (& possibly a cast iron lump behind your head). I found out years ago that fairly grippy tires (the old Victoracers) couldn't be used to their full extent on the street....not if one has a lick of sense, anyhow.....just my .02, as is all else.

[iamchappy]

I put the Engman inner and Mulleur outer on my car with a sound chassis after I removed the rollbar. My auto power roll bar needed to be cut out, but it was still bolted into plates that were welded into the top of the long, I plan on modifying the roll bar at some point to be able to put it in and remove it if I ever do track events.
I am building my car as a comfortable street car so the roll bar had to go, but the added supports of both kits especially the Mulleur outer kit should be more than enough for the street.

[eeyore]

I'd say the longs are plenty storng, but the what they attach to at the front is the problem -- the single wall of the front inner fender.

[drive-ability]

Those are some interesting comments, I would like to forgo the cage for the inner and outer kits. I am not a racer but sometimes I wonder how this car holds up when I nail the throttle at 3K while going around 80 mph. I can just picture in my mind something letting go (IMG:style_emoticons/default/blink.gif) I think I am careful, most say I'm over complicating things (paranoid). I have done some work on the rear section pictured below.. Like that muffler in the last picture, well its now on my friends 55 Ford F-100. (IMG:style_emoticons/default/biggrin.gif)

(IMG:http://members.cox.net/stdotjohn/914%20Stiffening/Rear%20Frame%20work.jpg)

(IMG:http://members.cox.net/stdotjohn/Rear%20Frame%20supports%20finished.jpg)

(IMG:http://members.cox.net/stdotjohn/914%20Stiffening/914%20Frame%20stiffening%201.jpg)

[BarberDave]

(IMG:style_emoticons/default/smilie_pokal.gif)
Drive ability:

Christ if I had that fab ability, thanks for those pictures.

What a great 914

Dave (IMG:style_emoticons/default/slap.gif)

P.S. That's the only color God intended a car to be!!!!

[So.Cal.914]

I don't want my 914 looking like a "boy racer" special....

A cage is not going to make you any faster...A cage is going to save your life.

Well ok, my life.

[drive-ability]

I don't want my 914 looking like a "boy racer" special....

A cage is not going to make you any faster...A cage is going to save your life.

Well ok, my life.

So.Cal.914,
That's how I feel and my gut keeps saying do everything, long kits and cage even in a street car. Whats another 1K bucks, sounds like a good investment..
(IMG:style_emoticons/default/drunk.gif)

[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

[PRS914-6]

I don't want my 914 looking like a "boy racer" special....

A cage is not going to make you any faster...A cage is going to save your life.

Well ok, my life.

Although a cage is absolutely a must for a race car, I disagree with you for the street. Without a helmet, the cage may cost you your life instead of saving it. Picture your head slamming into a bar mere inches from your head and you will quickly understand my thoughts.

In addition, a cage is cumbersome for day to day driving. My vote....Leave it out until you hit the track.

[So.Cal.914]

Picture your head slamming into a bar mere inches from your head and you will quickly understand my thoughts.

Yes you are right, there are positives and negatives to a cage. Yes you can bang your head, this is probably why people put foam on them. I am more concerned with side impact and rolling/sliding. I am most concerned about coming around a corner and finding someone in my lane...going the other way or being T-boned in an intersection. I want to give myself all the chances I can.

In addition, a cage is cumbersome for day to day driving.

So is a saftey belt, but I wear that too. (IMG:style_emoticons/default/smile.gif)

[Brando]

I found getting in and out of a car with a cage really isn't that difficult --

If you're 5'8" and wiegh 135#.

[marks914]

I would tryt a Brad Mayeur long kit, do a search.

Mark