Roaring Forties #36 - Mark Worthington's GT40

[Mark Worthington]

Since I still haven't put a web site together I might as well throw a few images here in this post and document my build. Since I've posted several progress reports on my GT40 over at my other favorite automotive web site, www.corner-carverys.com/forums, I think I'll just cut and paste some of what I posted over there.

But first, a little about my GT. Like many others in this forum, I fell in love with the GT40 when I was a kid. I strted looking into replicas in ernest in 2001, and was fortunate enough to buy Bob Lawrence's kit in June 2002. Bob had started building one hell of a show car. Frankly, I was intimidated about carrying on the construction up to the standard he set. This car happens to be the first RF that was imported to the USA. Here's a picture of the car in my driveway when I got it home from Dallas:

[Mark Worthington]

This is what it looked like when I got it unloaded into the garage. Bob Lawrence had fit about 70% of the panels before I bought the kit. The rest of the car was down in the basement when this shot was taken.

[Mark Worthington]

After fitting, trimming, refitting, re-trimming, drilling, clecoeing, removing, etc. the panels more times than I care to think about, I got everything off to the bare chassis in April 2003.

[Mark Worthington]

I spent a lot of time on the rear bulkhead panel. The one that came with the car was just messed up enough to make me want to re-do it. After locating the proper alloy and gauge of aluminum sheet, I spent an afternoon cutting the new bulkhead out, and at least a full weekend getting it prepped and installed. One problem I encountered was how to locate the blind holes in the chassis that had been drilled for the previous bulkhead panel and accurately transfer them to the new panel. So I followed Ron Earp's excellent advice and made this little jig, which was simply a piece of aluminum folded in half, drilled, with a rivet then inserted from the middle. Here's a pic of the jig...

[Mark Worthington]

In the next photo I've clamped the bejeezus out of the rear bulkhead to keep it from warping (one of the problems with the original panel). You can see my blind chassis hole locating jig in action...

[Mark Worthington]

Here it is all clecoed in place...

[Mark Worthington]

And here's the finished rear bulkhead, along with the fitted engine access panel (which in and of itself took another weekend to fabricate and fit). The engine access panel is held in place with countersunk 8-32 x 3/8 stainless machine screws which screw into rivnuts installed in the chassis tubes. I used Cherry Q rivets everywhere I could on the rollbar, because that is the one piece of structure I really don't want to fail. I had to file the mandrel down flush with the rivet head on each one. I'm using plain, low-strength sealed rivets elsewhere. In addition to riveting, I'm also bonding the panels to the chassis. Man, it was nice to actually start using rivets instead of clecoes. Progress!

[Mark Worthington]

Here are the panels I made for the water pipe tunnel, all removeable thanks to rivnuts and countersunk screws...

[Mark Worthington]

I'm using an acoustic/thermal insulation product called ZeroClearance...it has a heavy foil and silica/polyester with a super sticky adhesive. You cut it to fit, peel the backing, and stick it on. It'l help keep heat out (GT40s can get toasty inside) and I hope it'll keep the interior reasonably quiet and prevent drumming of the larger panels. I'm using it on most all of the panels that face the interior. You can find it at www.coolandquiet.com. I'll probably add about 15 pounds to the weight of the car with this stuff.

[Mark Worthington]

Finally, I had my aluminum panels powder coated. I used a translucent blue color by Tiger Drylac called Candy Blue. After messing around with polishing for months, I punted and ended up prepping the panels with a fine Scotch Brite pad in a random-orbit sander. These pictures do not do the color justice...they came out looking fantastic.

[Mark Worthington]

After the panels were fitted, I installed the rear suspension on my car. The next picture shows a bunch of junk in my basement that became my rear suspension. Everytime I bring something up to the garage I consider it a small victory. Remember, the right front suspension was already on the car.

[Mark Worthington]

I probably didn't have to, but I upgraded all critical suspension fasteners to AN and NAS hardware. This next pic the AN8 (1/2 inch) stuff (Cd plated) next to the stuff that Roaring Forties supplied. Here's to you, Carroll Smith!

[Mark Worthington]

I ran into an alignment problem trying to match up the lower arm to the upright...it was off by 25 mm (that's an inch to you backwards SAE types ). Turns out I had two sets of lower drag links, and one of them was 25 mm shorter than the other, so I swapped them out and all was well. A nice touch that Bob Lawrence did here was to powder coat the uprights clear. This way they'll be easier to keep clean.

[Mark Worthington]

Here's the rear suspension setup on my RF. The upper and lower drag link front ends attach to chassis mounts near the firewall with AN8 pivot bolts, and the drag link rears attach to rod ends which attach to brackets, that have a high-tensile 3/8" bolt welded to them. The lower bracket goes through the lower upright, through the lower arm, and through a bracket which makes this a double shear attachment and the bracket also serves to locate the lower damper mount. The rear end of the lower arm mounts to the upright in single shear. The rear of the upper drag link mounts to a bracket which has a high-tensile bolt which runs through the rod end on the outboard end of the upper link, which then mounts to the upper upright. All the 3/8" fasteners use high-carbon-steel ferrules (sp?) where they attach to the rod ends...the ferrules effectively increase the diameter of the bolt and distribute the load.

I posted another thread on this forum about the pros and cons of chrome-plated suspension bits, but have researched the matter and concluded that, for a car that will only occasionally see track duty and that will be frequently inspected, I am not concerned about the chrome plating.

[Mark Worthington]

Remember that single-shear attachment where the rear of the lower arm mounts to the upright? Well, when I was at the Carlisle show I looked at a CAV stainless steel monocoque GT40. It was fitted with Gulf flares and wide rear tires like mine will be. Unlike the RF kit I'm building, it uses a rear sway bar, which I think will be a necessity on mine considering the increased rear track width and associated understeer. Anyway, the CAV uses a tab welded onto the rear of the lower arm as the attachment point for the sway bar end link. I wasn't crazy about the idea of having to disassemble, weld, re-plate, and reassemble my lower arms, and then the idea hit me. Note how the uprights are symmetrical, and how the brackets attach only to the front. Why not use those pre-drilled holes in the rear of the uprights and fabricate a simple U-shaped bracket that can not only serve as the attachment point for the sway-bar end links, but can also give me a double-shear attachment at the rear-lower-arm-to-upright point. A simple and elegant solution.

[Mark Worthington]

I took four days off of work in July 2003 to work on my GT40. Hershal Byrd was kind enough to accept my invitation to come out from Phoenix to help me with the fitment of the body panels. I can't say enough great things about Hershal...he is truly an amazing guy. My wife was reluctant that I had invited a "stranger" into our home, but she absolutely adores Hershal now, and we all look forward to when we can visit with him again (February 2004 in Arizona). Hersh is a true class act and his help probably saved me three or four months of head scratchin', cussin', and bein' pissed off at this body work stuff. Hersh is so knowledgable about so many things, especially cars, and especially body work.

The next picture shows the rear-clip-to-spyder-to-door relationship of the various body pieces. It doesn't look too bad in this pic, but there are minor misalignments that need to be fixed with filler and my new DA sander. I have to be careful not to drive myself nuts trying to get the body panel gaps to look like a Lexus. The original cars were actually pretty damn rough. I've decided to paint the car a bright white with blue stripes. I like the stripe scheme that Hershal used and will copy it verbatim, only in Daytona Blue (A Nissan color on the new 350Z). I think the white color will really bring out all the gorgeous lines of a GT40, but it will also highlight any flaws in the panel fitment.

[Mark Worthington]

Here's the car after Hershal departed, showing off that purty body work. Damn but it is a gorgeous car. Since then I've cut out and mounted the headlights, driving lights, perspex covers, door hardware, and done some more work on the brake system. I have enlisted the aid of Bill Hough (AKA Datonabill) who lives nearby to help me fit the Gulf flares next weekend, so I hope to have a nice update in about a week.