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Longitudinal Repair & Reinforcement

Pelican Technical Article:

Longitudinal Repair & Reinforcement

Lawrence K. Bonkoski


2 weekends






Floor jack, jack stands, sawmill, MIG welding outfit, electric drill and assortment of drill bits, Sawzall, rotary rasp, hammer, flathead and Phillips screwdrivers, two huge C-clamps, metric socket set with various size ratchets, M-8 thread tap, two 2X4's, heavy duty tin snips, wire brush, wire brush bit for electric drill

Applicable Models:

Porsche 914 (1970-76)

Parts Required:

Brad Mayeur chassis longitudinal repair and reinforcement kit, gas for the MIG welder, welding wire, scrap metal for welding practice, 3M Weld-thru zinc primer, one gallon of Skyco Ospho, two quarts of POR-15, two 1-quart garden sprayers, small disposable containers, eight M-8 bolts with Allen heads

Performance Gain:

Your 914 chassis will be as stiff as new (if not stiffer than new)

Complementary Modification:

Replace your front sway bar
So.. your 914 chassis is flexing pretty bad from rust? Replacing the long itself is kinda tricky. Building a V-8 conversion and want to add some stiffness to your chassis? Your answer might just be Brad Mayeur's longitudinal repair/reinforcement kit.

Brad Mayeur ( is located in East Peoria, Illinois. He has created a kit that repairs and reinforces the longitudinal, and ties into the rear trailing arm. The kit is simple to install, and requires only basic welding skills. I've done two now with very good results.

Jim Sucharski (, when he lived in Cedar Rapids) convinced me that I could do the work myself. It's a two piece kit that covers the entire clamshell and then ties into the rear trailing arm. The older kits were one piece, but Brad says this system provides a better, stiffer fit. It's made of heavy gauge steel... about an 1/8 than inch. The idea of the kit is to "laminate" the exterior of the longitudinal from the seam up to just under the door sill.

I've made up this "how to" from experience and suggestions from the Rennlist. The second job went much smoother than the first, even though the car was in MUCH worse condition.

I've divided the instructions into 4 sections: Tools and Materials, Prepwork, Welding and Finish work.

Disclaimer: Please note... Brad includes instructions with his kit. If a suggestion in my message conflicts with his directions, call him and check.


Tools required:

  • The Kit
  • Welder (I use a gas MIG welder)
  • Drill and assortment of bits
  • Tin snips (left AND right are nice to have)
  • Patience
  • 4 jack stands
  • 1 jack
  • 1 Toolwench (Mine is named Pam)
  • Sawzall is great to have!!
  • 1 rotary rasp
  • hammer
  • screwdrivers
  • two HUGE C-clamps
  • extensive cursing ability
  • Metric socket set and ratchets (air tools not required)
  • M-8 thread tap

Materials required:

  • Beer (or your favorite adult beverage - indulge lightly when welding)
  • Gas for the welder
  • Wire for the welder
  • Scrap metal to practice welding on.
  • 3M Weld-thru zinc primer
  • a gallon of Skyco Ospho
  • two quarts POR 15 or Corroless
  • two 1-quart garden sprayers (cheapo - 10 bucks each)
  • small disposable containers
  • 8 each stainless steel M-8 bolts (I prefer allen head)


The more you concentrate on prep-work, the easier the entire job will go and the longer your repairs will last. Remember, for welding, the cleaner the better. Remove all paint, oil, grease, sealant, crud, rust, etc. The welding you do will help reinforce your frame. No use going to all this effort and have weak welds because the surfaces weren't clean.

1. Remove the plastic (or aluminum on early cars) door sills, door seals, seats and carpet. Clean, clean, clean. You might want to consider having your toolwench go to the local quarter-wash and giving the carpet a good pressure cleaning. It'll amaze you how dirty and matted the carpet is. Odds are, you probably don't need to replace it. Take the time to clean the interior.

2. Jack up car with Targa in place. Place 2x4 under front trunk with jack-stands. Place 2x4 just forward of rear firewall with jack-stands. Place jack under transmission.

3. Remove outer rocker panels. Clean, clean, clean. If you've never removed the outer rockers, the bolts might be rusted on. Just cut them off.

4. Check door gap. Adjust the transmission jack until you get a door gap you want. Open and close doors. Keep adjusting till you get something smooth. This is the time to make your door gap look "factory". Drink a beer in salute of your mechanical prowess and your new door gap. :)

5. Trim away rotted metal. Measure the exact position of the jack post and support - then remove. Cut away the step plate support. Look for the spot welds, you should be able to drill them out. Check your door gap again.

6. Skyco Ospho for rust repair (available at Ace Hardware - possibly special order):

a. Take your 1-quart garden sprayer, and spray Ospho up inside the longitudinal. Drill holes for access. This stuff is kinda splashy. Wear gloves and safety glasses and use a plastic drop cloth to catch it before it permanently marks your cement floor. Let it dry. Ospho will prep the metal for primer and paint, and convert rust nicely.

b. Ospho the pieces of the repair kit. They'll turn a nice flat gray.

7. POR-15 for rust repair: Take your other 1-quart garden sprayer, and spray POR-15 (or Corroless or your favorite rust converter) up inside the longitudinal. Drill holes for access. Use a mini-Maglite and a mirror. This stuff is VERY messy. Wear gloves and safety glasses and use a heavy drop cloth to catch it before it permanently marks your cement floor. Let it dry.

8. Mark a spot (I use a paint pen) on the rear trailing arm edge. Measure from that edge to the body. Make several measurements. Write them down. The goal is to be able to unbolt the rear trailing arm to install the kit, and still be able to put it back in the EXACT spot, and not require a rear wheel alignment. When you get under there, I think you'll see what I mean.

(Added by Jim Sucharski: "I made a tool to reference the trailing arm to, I forget, to somewhere on the body. It was just a little piece of metal fitted to help do the alignment. Your way probably worked just as well.")

9. Unbolt the rear trailing arm, remove the shims, and put the rear piece in place. The bolts in the rear trailing arm have probably been in there for 20+ years, be careful. (I broke one off, and they are a PITA to remove.) Get new bolts if you need them (55mm - M10 x 1.5) . Clean the shims. I let mine soak in Ospho to clean them up. Bolt the assembly back together loosely. Get your alignment as close as you can.

10. Set the longitudinal repair piece into place. It's long enough to cover the entire longitudinal, but you probably won't need it all. On both installations, I ended up cutting about 5-7 inches or so off of the forward end. At the most forward part of the clamshell, there's a raised spot. If it's solid, don't cut it away just to put the kit in place. Measure the piece twice.. cut once.

11. Check the piece for fit. Bend or trim away anything that doesn't let the piece fit snug. Check the seam sealant that's in the joint where the step plate meets the longitudinal. There are drain holes in the bottom of the long - crush them flat. (If you cut the top of them, they crush very nicely.) The more you work on this step, the happier you'll be when you start welding.

(Jim S. also adds: "You can "shift" the drain holes from the outer longitudinal to the inner part of the seam. I welded a small chisel, sized to just fit into the existing drain holes, to a piece of bar stock, at right angles to the end. Then I inserted the tip into the drain holes and whacked onto the end of the bar stock to hammer the drain hole toward the center of the car. When I was done, they looked just like original - only shifted to the inside part of the seam.")

12. Prep your welding. Paint the longitudinal piece with zinc primer. Use a wire brush (on a drill, if you have one) and clean the areas where you're going to weld on the car: the longitudinal ribs, the longitudinal seam, and the forward edge where the piece will fit against the car. Clean these areas to bare metal. Wipe them down, and spray with zinc primer immediately.

13. Remove the trailing arm piece. Use your rotary rasp to open up the holes a little bit. It'll make wheel alignments easier. Prime the entire piece with zinc weld-thru primer. Mask off the area that you know you'll weld plus 4 or 5 inches around that. Paint the rest of the piece.

14. Drill holes in the step plate, per Brad's instructions. Clean both sides of the metal around the holes. Prep with zinc primer.

15. Last chance to check your door gap. Then, put both pieces in place.

Install shims (minus one) and bolt together. Get the wheel alignment as close as you can. Use your huge C-clamps to clamp the longitudinal repair piece in place.

16. Check all your work. "Don't forget nuthin." Have your toolwench get you some beer - you deserve it!


Start welding. Don't hurry, you don't want to overheat the metal and warp it. In order, weld:

1. Spot weld the ribs. Start on the two outside holes and work in towards the middle.

2. Weld the longitudinal and trailing arm pieces together.

3. Weld the forward edge of the long piece.

4. Spot weld the holes you drilled in the door step plates. If there is a gap, fill it up with weld.

5. Weld the bottom edge of the kit, per Brad's directions. Don't weld the entire seam. Spot weld every 3 or 4 inches. Then, alternate 3-4 inches of weld with 3-4 inches of space. This is the WORST part of the operation. You're going to weld upside down. It's a real PITA. Remember step 11? The closer the pieces fit together, the easier the weld will be. Be patient. Go slow.

6. Weld your new jack posts into place.

7. Unclamp the longitudinals.

8. This is a good time to cut and shape patch pieces to fix any rust holes in your floor pans, or around your jack points.

9. Congratulate yourself on your fine welding job. Have your toolwench run out and get some Chinese food. Chinese food is excellent food for welding. In fact, I think that's what Chinese food was invented for.

Section 4: FINISH WORK

1. Reprime and paint, if you desire. You probably will.

2. Fit the rocker panel into place. Mark places for new holes. Remove the rocker. Drill and tap M-8 holes.

3. Redrill drain holes. Remember the ones you crushed flat in step 11 to make everything snug? You still need them. I drilled a bunch and primed/painted them to prevent rust.

4. Install your rockers with your stainless steel screws. I use antisieze compound. Lower car.

5. Install your squeaky clean carpets and seats.

6. Take your toolwench out to dinner for putting up with you. Maybe a nice San Marco bracelet would be in order. (Do ya think I wrote that line?? - Lawrence)

In Conclusion:

Oh yes.. one other thing. There were a couple of suggestions from the Rennlist ( about removing the engine/tranny before installing the kit. Brad told me it wasn't necessary, as long as you get the door gaps right. Did I mention the door gaps were important? A door that opens/closes smoothly and has a proper gap is the best indicator that you have your frame aligned correctly.

This whole process can be completed on two weekends. Some of the painting and cleaning can be shifted around a bit, I guess. Your longest wait will be for the POR-15 to dry. (I let mine dry two days.)

Brad Mayeur ( runs 914 Limited. The number is 309-694-1797. He's a real gentleman and knows his stuff. I believe the kit costs about 320.00, shipped (July 1999).

914's Forever!!!

Lawrence K. Bonkoski
83 944 NA - Metallic Moss Green 
74 914 Limited Edition - Bumblebee

(Special thanks to Brad Mayeur, Jim Sucharski, Rich Johnson and Gary Dodge for their help on this article.)


Rich Johnson ( adds:

"I've had a hand in installing two kits. Both went into decent cars rust free 914s and I now understand how much strength they add to the torsional rigidity of these flexy old roadsters. I believe Brad's original intent was to use these parts to fix cars badly damaged by rust. It's easily to see how these pieces that laminate the outer longitudinal add strength to a once rusted cars too.

The last kit was installed by Richard Fisher to add strength to his '73 chassis as he prepared it for the 400 + HP V-8 transplant it received. In addition a GT chassis kit was installed, the rear trans. mount were boxed and the dog-bone trunk brace was rebuilt to add additional twist resistance. The chassis's stiffness difference was amazingly different. I noticed it when I jacked up the car (no V-8 yet) by placing the jack on the front right lift donut. The whole side of the car lifted without a bit of twist or deflection in the rear of the car.

I'd suggest this as a consideration for anyone building a big HP car or a car needing added longitudinal support for any of these reasons mentioned above."

Gary Dodge ( adds:

"I broke the frame on my '73 last year and bought a somewhat rusted '72 tub to transplant into. To avoid a repeat of the same type of injury, I bought Brad's longitudinal kit and the chassis and trailing arm stiffening kits from Pelican. My mechanic had not done this task before, but he said it was actually pretty straightforward. He did have to call Brad a couple of times for clarification; he said Brad was very helpful (even on the installation of the kits from Pelican!) I didn't actually weigh all of the stuff that went in, but my estimate was about 60 pounds...more than enough to offset the lighter doors, etc. of the '72.

However, there is at least one other point regarding these stiffening kits that you should be aware of. PCA (at least in our region) allows reinforcement in Production class (but not Street); SCCA is more strict. If you are planning to use the car in SCCA Solo events (autocross or time trials), be aware that this modification will kick you out of B-Stock or C-Street Prepared all the way up to A-Prepared class. Without making other significant modifications to your car, your otherwise stock 914 will not be anywhere near competitive in this territory.


I made the conscious decision to give up on SCCA Solo2 in favor of a stronger and better handling car. You should make an informed decision for yourself.

Gary Dodge"

Comments and Suggestions:
VWTortuga336 Comments: Pictures would be great!
June 28, 2016
  Followup from the Pelican Staff: If we get a chance to take some we will add them. - Nick at Pelican Parts  
Dick Comments: Has anyone ever done this procedure using Panel Adhesive instead welding the pieces to the longitudinaL?
Panel adhesive is used extensively on new cars, instead of welding.
July 31, 2015
  Followup from the Pelican Staff: I opened a post in our forums. A Pelican community member may be able to answer your question.
- Nick at Pelican Parts
luis Comments: pictures
February 20, 2015
  Followup from the Pelican Staff: No photos we attached. Can you try again?- Nick at Pelican Parts  

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Page last updated: Thu 3/22/2018 02:18:47 AM