Hi - Convertible Frame Stiffening

[Carman 1964]

Hi,

I own a 1964 Karmann Ghia convertible (the one in the picture of my profile) with 1,600 cc engine recently rebuilt, and I thought that it could be converted into a more fun to drive vehicle, with a more sporty behavior.

Before the power of the engine (which I also want to increase) I am interested in stability, that it transmits sensations, that it reports well what is happening in the contact of the wheels with the ground, that it starts to slide from the front, that it is predictable and reliable. And the first thing I have seen when I started to go fast with the Karmann, is that it lacks rigidity in the chassis, the suspensions are very soft and the front is too high.

As the Karmann is now, as soon as you go a little fast in a corner the car starts to flex rather than slide, so you lose the feeling and the car is no longer predictable. I have seen the very interesting post by FJ Camper in which he talks about reinforcing the stiffness and improving stability, among other possibilities, with:

- PUMA regulable front axle beam
- Bracing the front axle beam
- Use of a 19 mm front bar and new clamps
- Yelow Bilsteins dampers

And that's going to be the first thing I do. I don't know if there is something important that I am not taking into account.

I know that the PUMA regulable front axle beam is not the optimal solution, and that it would be better to change the dropped spindles, but the ones that are on sale at least reduce the height by 6 cms. and because of the little space between the wheels and the fenders when turning, I think if I lower the car those 6 cms. the car will rub easily. Has anyone tried it?

I have also thought about improving the carburetion and ignition, and get some more power from the 1,600 cc. engine that now carries a single 34 mm central carburetor.

Regarding the carburetors, I'm afraid that installing two too big carburetors could choke the engine at low revs. So I am in doubt, would it be better to install two carburetors or two double body carburetors, what would be the best carburetor caliber 34 mm, 40mm or other? And what brand do you like more Weber, Solex?

Regarding the ignition I have thought about Petronix or Bosh 009.

Has anyone made changes like these and can advise me?

Thank you very much.

[Max Welton]

Welcome!

If you have actual Ghia wheels ( et46? ) and not beetle wheels, lowering 6cm should not be a problem. That said, many of the drop spindle solutions also increase track in the front. You may in fact be better off with a stock width adjustable beam for that reason.

The chassis flex is common in the convertibles. I had a convertible bug many years ago that did the same thing. There should be stiffeners in the chassis somewhere around the rear seat area but I can't imagine they overcome the lack of a roof.

Max

[Carman 1964]

Thank you very much, Max

The wheels I have are 165/86/15, I think they are the original ones.

I'm glad you consider that adjustable beam is the best option; I also prefer it because it allows more possibilities in adjusting the height of the front of the car. Until recently I had a 1988 Porsche 911, which had adjustable height, and small changes produced big differences in their behavior, so I could adjust a lot in their behavior to my liking.

I think that given the similarities between the Porsche and the Karmann (wheelbase, boxer rear engine and weight distribution), the VW could be made into a vehicle as fun as the 911, with the advantage of being even lighter. My intention is to make it suitable for daily use and sporadic sport driving (but not competition), but greater chassis stiffness is a must.

You say that there should be stiffeners in the chassis somewhere around the rear seat area, but you can't imagine they overcome the lack of a roof. The same thing happens to me, I find it hard to imagine how to reinforce that part of the chassis to improve stability. In a FJ Camper's post he speech as well about welding on braces under the floor pan, in the jack pickup point area, the braces need to be at least two feet long; but it is not quite clear to me what FJ Camper is referring to. What would those steel braces look like? What shape and thickness of plate? Where would they be welded?

I also think it is important is to improve the carburetion and ignition, and get a little more power; I don't need a lot, just enough so that when the front axle starts to slide in a corner I can compensate with throttle, making the rear axle slide so that the front of the car points back to the inside of the corner. That seems to me the most fun aspect of driving rear wheel drive vehicles, with the mass distribution that our cars have, but it takes to do it a little more power than now provides the standard 1,600 cc. engine with a single 34 mm central carburetor. But I still don't know which carburetor to install.

Maybe later I'll end up increasing the displacement to 1904 cc, changing to a camshaft with higher crossover and installing cylinder heads Panchito or similar. But for the moment I have to see if with all these changes the car is more communicative, predictable and fun.

[Max Welton]

The wheels I have are 165/86/15, I think they are the original ones.

That is a tire size. I was actually talking about the wheels, not the tires. Beetle wheels are commonly found on KGs after all these years but they put the tires closer to the fenders. So when you lower the car there is a greater chance of interference with the fender.

Max

[Carman 1964]

Understood, Max.

I have a feeling that on my KG the tires are very close to the fenders.

Worst case scenario, I think in the event the tires end up rubbing, I can fix it by putting on some lower profile tires.

On the other hand, do you know where I could find a post talking about carburetion options for boosting a 1,600?

[Max Welton]

I was hoping one of the regulars here who know of such things would pipe up.

Meanwhile, try digging around the Forced Induction Forum:

viewforum.php?f=3

Max

[Carman 1964]

Well, from what I have been reading about non-turbo engines, it seems that for a 1600 engine the best options in carburetion may be the Kadrons Solex 40 and the Weber 40. The Weber have a profile that is better suited to the competition, but sometimes give problems at low revs and its proper operation requires a lot of maintenance; from what I have read, for daily use seem preferable the Solex.

On the other hand, between two dual carburetors, or two single carburetors with dual throats, I have read that several people prefer this second option, because it is easier to tune and more difficult to mismatch; without the difference in power between one possibility and the other being too relevant.

I don't know if anyone has a different opinion?

[Ol'fogasaurus]

Carman, I have not had the pleasure of playing with a Carman Ghia, only beetle based dune buggies. I am not sure on what FJ was referring to either but with what he is doing is well worth looking at his strings and posts.

But... for what it is worth maybe this would help... or not (this is an opinion for you to choose or not, again, assuming it could be done on the KG's pan). I am sure FJ would say a quick yes or no to it.

001.JPG

This is the underside of a VW Beetle pan after new pan halves and some other work had been done.

The VW pan is part of a VW "unibody" construction but instead of welding things together they are bolted the body and pan together. The style of the VW bug pan is called a "tunnel style" unibody. Again, not sure just what, if any changes VW made for the Ghia. With the a soft top VWs lose both the strength and load sharing capacity compared to the the vehicles with steel tops on them have so I would think they probably do something to make up for the changes.

In this pix, I had already built a solid body lift out of 1 1/2" X 3" w .120 wall tube and put it on top of the body mount structure in the pan but I wanted to add some additional strength so I took a piece of square 1" tube and kerf bent it to shape on the underside of the formed body mount structure but I I later found out that i made a mistake in choosing going with the 1" (I forget the wall thickness of the square tube but it was fairly thick) square tube but, then sitting in the car with no body bolts clamping the pan, the body lift and the 1" square tube together the 1" square was not strong enough by itself so it took a load bend "set" the whole length wise. Bolting the pieces the body, body lift and the lower piece together did work though and the set did pull up but still is partly there when the "clamping together" is loosened up.

After a lot of debate with myself... before I chose the 1" tube I was going to use a rectangular length of tube which I think would be the way to go but what caused me to change to the square tube was the rectangular tube hung down some and may have snagged on things (like tree roots or limbs that had fallen off the tree) as I drove over them. Again, this is for an off-road dune buggy.

As far as putting adjuster's on the beam they do work and in several different way too.

Again, this post is for "what it is worth" only.

Lee

[Max Welton]

In this pix,

Lee, was there supposed to be another picture attached?

Max

[Ol'fogasaurus]

In this pix,

Lee, was there supposed to be another picture attached?

Max

No, I put the pix first then the disclaimers followed by a discussion. Its just my way of doing things... get the attention first then the discussion. Sorry about the confusion.

Lee

[Carman 1964]

Hi Lee.
Thanks for the information, it's a pity that the explanation is not accompanied by pictures to make it easier to understand.
I agree that not having a hardtop my Karmann must flex more than the VW's with metal roof, and that is the main problem to solve to improve its stability.
You talk about reinforcing with 1" square tube, is it welded from the U-beam? Where does that reinforcement go and where does it go from?
Thank you very much

[Carman 1964]

Here are some photos of possible chassis reinforcement on the KG convertible, although I'm not sure if it's really reinforcement:

[Ol'fogasaurus]

Yeah, that is stiffening with flanged lightening holes for additional strength. This is the first time I have seen pix of what VW did to strengthen things up. Around where I live Ghia's were not that common to see and the soft top version was even less so. Thanks for the pix.

https://www.shoptalkforums.com/viewtopi ... 3&start=15

About halfway down the page is where I started the under pan doubler to give some additional assist to the 3" body lift.

The pan is sitting on a home modified engine stand to make modifying the pan easier. I did make a post on how I built mine which can be searched for (it is really old).

Lee

[Max Welton]

So Lee, your work was on the buggy, yes? No room for anything like that on a KG. And the Ghia that FJ races is a coupe so he doesn't have the torsional rigidity issues a vert does.

I suppose a box structure could be added to the bottom of the pan along the perimeter to stiffen things up. At the cost of some ground clearance.

Max

[Ol'fogasaurus]

So Lee, your work was on the buggy, yes? No room for anything like that on a KG. And the Ghia that FJ races is a coupe so he doesn't have the torsional rigidity issues a vert does.

I suppose a box structure could be added to the bottom of the pan along the perimeter to stiffen things up. At the cost of some ground clearance.

Max

Yes Max, it is a modified pan for a dune buggy which, like many race cars, does bounce around a lot and doesn't have a top... only a cage that needs finishing the design on.

If you go with an square inch tube (as said that I don't really recommend using a square tube) then it is pretty flush with the bottom of the pan. As you with a rectangular tube, say an additional inch or so thick , e.g., 1" X 2" then the underside of the pan' outside parameter, it does get closer to the ground. That's why a 1" X 15" rectangular tube would not work .

I know FJ races a coupe but I would suspect his knowledge of Ghia's and beetles, et al, is way beyond that too.

Again, it is not a "have to" suggestion but more of an idea that may, or may not be usable.

Lee