Curious if anyone has use the outer longitudinal clamshell reinforcement on a street car?

Did you have any unforseen down stream effects to other panels like the door jamb, or the rocker panel? Also thickens the upper flange and I'm wondering if this will cause fit issues later with the door stripping, or maybe even the cosmetic sill plates.

Starting to seem like this might be a good idea for race car prep but probably not ideal for just trying to fit up replacement sheetmetal and still have OEM fits.

I'm not in love with the additional weight either.

I can keep mocking up additional pieces but thought I'd see what the collective wisdom of the forum knows.

Check with Brad Mayer, he made some really stout reinforcement pieces
@914LTD

Chris Foley at Tangerine Racing fitted a pair of these on a street car quite awhile ago. I’m not sure if he’s a fan of them. You might Email or PM him for the pros and cons.

They’re probably not necessary if the longitudinals are repaired, particularly for a street car.

http://www.restoration-design.com/store/product/PP346R

Thank you for the lead. I'll reach to Chris. The part you've linked above are exactly what I have.

In my case, I've completely replaced the longitudinal (inside and outside) and the use of an outer clamshell like this is starting to seem to me like overkill for a street car.

I think I can get more stiffness out of the longitudianl by simply seam welding all the panels at the flange (in addition to the puddle welds). That will have more stiffness than the OEM spot welds had.

Look at Restoration Design set up, tight fitting, going to use on my car.

Why not interior bracing?

Bulkheads within the longitudinal box section would be highly effective to improve torsional bending (twist). However, with the heater tube in there (again this is a street car - I want heat) there isn't enough room for an effective bulkhead.

The reality is that the way the longitudinals connect to the wheel wells and the front of the door frame, the clam shell won't do much to resist torsional bending. The clam shell might help vertical bending incrementally but probably not much as we might think. Most of that vertical bending stiffness comes from the longitudinal box section itself, not the metal thickness. That is the beauty of unibody vs. a solid frame. Stiffer AND lighter.

Might be time to sit down and do the math to understand exaclty what it's worth.

However, in my case, as I mocked it up last night, I can see the clearnace to the front door edge is getting uncomfortably close. Had an idea last night when going to sleep about how to address it.

I'll try to post a picture or two tonight after work.

Yup, I have that part.

Although it is pretty "tight" in the sense that the contours match the outer longitudinal sheetmetal, it still adds 0.050" - 0.060" of metal thickness to the up standing door flange.

I need to dig out some of the costmetic welt that covers this and see if it will still fit properly with the extra metal thickness added into the door flange. Same for the sill plates.

I installed the RD clam shells and a mad dog inner kit on my brothers 914. The inner kit requires a lot more fitting work then the RD parts. The clam shells where real easy to install and I didn't run into any issues as of yet. Now his car is still under construction so can't say anything about weather stripping or sill plate issues. I can tell you that the doors and fender gaps have never looked better on his car. When you shut the doors it's solid. I also have a set of the RD clam shells that I plan on installing on my 914-6. I am not installing an inner kit like my brother did. I feel the RD parts should be just fine with adding some needed chassis strength.

My 914 body is a "rust free" example, my wife's '72 was a rust bucket that the PO repaired correctly and added the interior long kit plus some GT reinforcement parts. Just pushing the cars in/out over the shop OH door floor bump, with my palm on the windshield hoop/top seam, I can feel my 914's top wiggle around. The wife car is totally solid when I do this.

I'm going to do the inner long stiffener kit on my 914 next winter.

I have the Brad Mauyer external longitudinal kit installed on my Red six. I had it installed at the body shop when I got it painted.

The kit actually isn't that heavy, and everything fit over it with no issues. The car is so stiff I can put a jack under the jack point and both wheels come off the ground together. The top didn't squeak until after the 4.0 motor went in. Now I get a little body flex.

I can't use the factory jack points, but that is because the body shop didn't know what they were for and didn't install the correctly. My fault for not explaining the installation to them.

The stock long is a flat piece of steel, with a waffled piece welded to it at the points where they touch. The add on is a flat piece of steel welded to the top of the waffle piece. It is like making corrugated cardboard. If you peel the top layer off corrugted cardboard, it is flexy. With the top layer on it, it is really stiff and still fairly light.

When we finally get Betty's car done, it is getting a Brad Mauyer kit. After 400K, and lots of AX usage, poor old Frody is getting a bit flexy.

I originally designed the clamshells to support a rusty car that was way too rusted to consider restoring properly, Also, as a backup, someone could reinforce a racing car. The go over the original assembly so best installed by first removing the sill plate.
These days, with the value of 914s going higher and higher, very few choose to "patch" the cars, so the clamshells are frankly out of favor. All of the original panels are available and with a bit of welding and cutting skills, the cars are so simple that they can actually easily be repaired.

I put the Brad Mauyer outer longs support on my V8 car a 74 from what I can see on the rotisserie a no rust car with perfect longs before. I did this for the extreme strength for body for 400-foot lbs. of torque. I do not want any twisting with the big power.

I did more welding than Brad showed by drilling holes and welding extra on it in the field (center of the waffle raised areas). No bend perfect door gaps just the way it was when I got it from Greg at Camp914

Bob B

I'd share this opinion on the inners. Just something to be aware of rather than a deterrent.

Nice. Thanks Doc. I had no idea who desinged them you or RD. I guess that is answered.

Really appreciate the insight that they were designed to add strenght to an already weak chassis. That most certainly isn't my case after completely replacing the innner wheelhouse, the C-section of engine compartment, as well as both the inner and outter longitudinals.

I did use the short J-section of it that reinforces the transtion up to the rear suspension mount.

I hate the idea of adding any more weight to the car. The whole point of a 914 is light weight and mid engine handling. Weight just begets weight.

I'm a beliver in Colin Chapmans philosophy: “Adding power makes you faster on the straights; subtracting weight makes you faster everywhere”

I think based on your advice, I'm inclined to leave the rest of it off and see how stiff this puppy is 1st. I can always add the rest of it back on later when I completely return the car to OEM paint color but that is a few years away!

I did a little quick math this morning on the bending stiffness of a hollow rectangular tube and at best the stiffness gain is 30% maximum. However, that assumed I added 0.060" of section thickness to the whole section (top, sides, and bottom). In reality the clamshell only add thickness to 1 side + a small piece of the transition radius under the long. I'd need to do more CAD work and FEA to get the exact number but I'm thinking with only 1 side the improvement is more like 15% max. Not enough to justify the weight.

I ran them both. 914LTD, and Egmann kits, and a GT kit, which was almost worthless.

I could jack the one side at the mid point and I would pickup three wheels. I would have an 1/8 drop on the farthest corner.

I also ran a roll bar, and a petty bar, at that time, car was sold as a rock. I liked Brad's kick, and never had issues with other areas.

My experience, enjoy the car, btw my car was built for a class weight, so I just took something else out of the car. If I was running it for weight only I would still drop other items out and keep the kits.

I ran them both. 914LTD, and Egmann kits, and a GT kit, which was almost worthless.

I could jack the one side at the mid point and I would pickup three wheels. I would have an 1/8 drop on the farthest corner.

I also ran a roll bar, and a petty bar, at that time, car was sold as a rock. I liked Brad's kit, and never had issues with other areas.

My experience, enjoy the car, btw my car was built for a class weight, so I just took something else out of the car. If I was running it for weight only I would still drop other items out and keep the kits.

I made my own long inners... bent and welded to the floors, bent over the top shelf and welded near the seam, and welded to the rear bulkhead and inner fenderwells. Rosette welds all over the place too. It's now the stiffest 914 I've seen.
I also welded in triangular gussets between the inner longs and the rear bulkhead, like a 911 Targa.
I once had a Lotus Esprit V8 twin turbo. It was by far the worst sports car I ever drove. Awful torsional rigidity. I gladly give up about 20 lbs of weight in additional steel to gain even 20 percent more torsional rigidity. Besides, all the 911 engine and stuff is an additional couple hundred lbs.

I went down by 0.5" with my custom longs and increased stiffness by a calculated ~200% based MOI calculated in CAD for the new structure vs. original or changes with Engman reinforcements, etc. Note that I did not include weld stiffness though as I'm not that kind of engineer A little more involved than the manufactured parts though.

27lbs added in calculation...Forgot to weigh the actual metal

http://www.914world.com/bbs2/index.php?sho...p;#entry2127676

But have you driven an Elise or Exige? Esprit era was hardly a high point for Lotus.

duplicate post -

@JD74914

Damn James, you're going to force me to up my game!

Trying to the AutoCAD Invertor loaded back on my home computer after I lost it in a crash about a year ago. Then I can get a more accurate estimate on stiffness improvment from the clamshell.

As I tell the guys who work for me...my goal is to motivate people to be their best selves.

I work slow though...so you're waaaaayyyyyy ahead of me.

I've been debating changing it on the inner long side to something like rob mentions above, except with a two piece design which sandwiches the floor. That way I keep the extra 12 mm depth, floor at the same height, and increase torsional stiffness with the horizontal flange. That's a lot more work though, but since I've only got one side 'done' maybe not so bad.

Very interested to see what you come up with!

BTW: Don't remember if it's written in that thread but the reason I went the depth I did was because I was trying to make sure the ground clearance didn't drastically change. The height increase is really just offset by the loss of the lower flange on the original clamshell.

In reality the best would be to open the Log add a section down the middle from the front all the way up the rear to the rear suspension pickup. It can be done, it would take lots of work, and well weld it back up. I never had the car apart enough to do it.

Easiest way would be hide some DOM in there, you could even be crafty and retain heat while adding gussets to break each section into smaller sub sections providing even more strength. Or even square tube, as it is easier to fab and weld for beginners as it has straight lines, etc...

If you do not need heat or if you fell like it, and don't mind a bit of fab, adding small inner log gussets, partitions, or what ever down the log in several places will add strength and maintain your lite weight goals.

Think Chris Foley, Tangerine Racing trailing arm modification.

More food for the thought.

Or weld on a metal roof, and be done.

I have actually considered it. I don't particularly like convertibles, and we rarely take the top off any of the 914s. I am not a body man, so if someone ( @dr914 @autoatlanta.com ) were to produce a kit that duplicated the 916 top and seals, I would be interested in it.

I've never driven those newer Lotus. A lot of people I new raced them in SCCA, and they liked them. I saw one flip at Lime Rock around 2010, and the druver came out of it ok.