Securing Targa Top for Racing

GregAmy · 01-01-2016, 07:05 AM

How do you folks do it?

SCCA regs are not clear on targa tops, but in reference to convertibles, sunroofs, and t-tops the regs typically mention "securely retained" (sunroofs), "bolted or welded in" (t-tops), or in some cases "all latches shall be replaced with positive fasteners" (replacing convertible tops with factory hard top).

The previous owner left the front over-center latches in place and replaced the rear latches with an angle bracket and bolts. I'd be OK with that - after all, it got an SCCA logbook that way in 2003 - except the front latches are pretty damned worn out: there is no rubber interface left on either the header panel or the latch arm, and the latch arm is almost worn away on both sides. I like the tension of the front arms pulling forward, and would like to retain that if possible.

Just looking to see what others have done before I go engineering a solution.

GA

John Rogers · 01-01-2016, 09:12 AM

Since my 914 was going to be a full time race car I bolted my targa top solid in the rear. I used riv-nuts in the sheet metal for the bolts to thread into and 2 inch spacers to raise the rear of the top so air could escape the interior and break the vacuum that is created behind the rear window. This helps a bunch with cooling the engine and also provides some down force since the rear is not trying to lift up at full speed. I did also notice more air flow into the cabin area which is nice when racing on hot days. Here is a picture of what the raised top looks like. The front used normal top latches.

GregAmy · 01-01-2016, 10:12 AM

Thanks. Do you have a close-up of the rear mount? Below is what the prior owner has on the car.

I just pulled it all apart, and the fronts are definitely the stock over-center latches. Looks like someone welded on some material to the underside to build it up, but the hard contact with the ledge on the windshield header wore a "v" into the ends of the latches. I supposed I could get those re-welded.

But also, one stud each on the latches is stripped and the nuts won't tighten. Small little buggers. I may to either drill them out to put a through-bolt or maybe I'll see if I can find a couple of them used. Sad part is last summer I offered for free a spare targa top to the community, one I didn't think I'd need...as I recall, they had good latches (that's why I tell my wife I should never ever ever throw anything away...!)

I like your idea of raising the aft edge. This is an ex-ITA car that I'm going to be doing vintage/historics and ITEZ. I'm not quite clear on all the historics regs but I'll have to see if they'd tolerate a mod like that (or would even care).

John Rogers · 01-01-2016, 05:47 PM

Here is a link to a website that explains them. Essentially you drill a certain size hole for the rivnut, insert it and then fasten it. I bought mine a supplier in the San Diego are that sells most every type of fastener you could want and mine lasted for years. Remember to raise the rear of the top and it will most definitely make the car handle better at top speed with the vacuum broken behind the rear window. Another example is a Bonneville Speed racer who had a 914 with a nitrous boosted big block Chevy hooked to a 930 four speed transmission. The car ran in the stock bodied class, no spoilers or wings or such and when he would shift into 4th at 185 MPH and hit the NOS button the car would spin. I told him about the raised roof so he tried it and went 208 MPH top speed!

Rivnut Blind Fasteners Internal Thread Tubular Rivets

GregAmy · 09:22 AM

Thanks. I'm familiar with rivnuts, used them a lot on the "real" race cars. As an unrelated aside, I'm a much bigger fan of Click Bond's nutplates for fasteners in panels:

https://www.youtube.com/watch?v=Xl_zYF7l-1g

So you're still using the OE front latches? And the org(s) you run with have not given you any grief over that?

John Rogers · 01-03-2016, 03:25 PM

No issues over the front latches mainly since the top is forced into the front seal and unless the top could move backwards it would never come out. I did have three flat aluminum "clips" like those that hold a windshield in place.

larrym · larrym's Garage

circa 1994 SCCA OK'd my car with the stock factory hardware - but the rules change regularly,

sometimes it just depends on the preferences of the tech scrutineer

- and each vintage org's tech guys (usually volunteers) have different preferences, which change from season to season in my experience

John - what does PCA Club Racing say (if anything) ? - and is Rennsport the same rules?

.

John Rogers · 01-09-2016, 02:19 PM

I sold my race car a few years ago (2009 if I remember correctly) at at that time both SCCA, HSR, VARA, HSR-West and PCA all said the targa tops had to be securely fastened which all of them took it to mean "bolted solid" or in the case of the front "clips" and from what I remember all the tech folks would check to make sure the top was secure. At that time, in southern CA, tech was done by the same guys except for PCA and their head tech owned the shop that took care of my car so John made sure it was prepped correctly.

Most racers I knew would always get a copy of the next years rules over the winter time to see what had changed and adjust accordingly. I would always make sure to have to contact info for the head of tech so if there was any question, I would contact him to get an answer.

GregAmy · 01-10-2016, 05:45 AM

Well...I'm a nationally-licensed SCCA scrutineer and steward...and I have an engineering degree

So I'm personally comfortable with using the front over-center latch and replacing the rear mount with that L-bracket. I'm just looking to see what issues others may have come across.

I agree with the idea that the stock front latch pulls it into that tongue-and-groove and it should not move, especially of the rear bracket is designed such that it will not let the top move rearward if the front latches both fail.

I'm going to get the car inspected using the existing setup (it's not against the regs, but to avoid conflict of interest we do not sign off our own cars); I'm quite certain I can convince a fellow inspector that the setup is safe. However, I may look into incorporating something similar to what John noted, by adding two aluminum straps screwed into some Rivnuts in the windshield header and the top. I'd pull it forward with the stock latches then bolt it through the targa top, making it clear that the top cannot move backwards. It should be neither difficult nor expensive to do. Though it would kinda suck drilling holes through a good targa top...