You are exactly right. I have chosen a 3" x 4" HSS that I will modify to add a sloping surface of 17 deg for the firewall, it will end up being 3" x 3 1/2" approx.

I haven't really decided how to tie the transverse frame to the upper frame rail. At the moment they just sort of intersect as shown.




I will have a 1 1/2" x 3" HSS connecting the transverse frame to the lower frame rail so perhaps I will design it to tie all three points together.
I also plan to put a large gusset on each side to tie the transverse frame, lower frame rail and firewall together.

edit: for typo's

[This message has been edited by Yarmouth Fiero (edited 01-25-2013).]

I'll snap some pics and post them here around 19:00-ish. In the meantime, is there a benefit to removing the existing transverse beam and raising the new one up in its place? Is it because it will show less? I don't think you'll have to worry about clearances to the SBC, but I'll take a photo of my 308 engine bay to give you an idea for sure. More soon.

Guys;

When you are working the rear fire wall be careful to not put it up too high as the sail panel/rear window of the 355 body sits on top of the existing Fiero firewall on these kits. Raising the firewall top too much means you will be cutting and reshaping the rear window area to get the rear clip to sit down on the frame better. On my convertible, I ran a 1x2 across the top for my convertible top mechanism and had to reshape the engine lid area and the rear quarter tops to accommodate the higher firewall top.

Frame reinforcements are looking really good Graham.

Cheers
Don

Thanks Don. As I have it drawn at this time, the firewall top edge will remain stock height. If I had a rear window, the frame would certainly be too high as the window ledge in stock position is about flush with the top of the upper frame rail.

To answer Blooz, no, there is no real reason to raise the frame up to the very top of the firewall, other than to gain that 1.44" in the engine bay. Well, also, that "Z" piece of sheet metal that helps support the rear window and edge of the firewall has a flange pointing down against the firewall so even though its only 1/16" thick, it would keep the transverse frame from laying flat against the firewall.

[This message has been edited by Yarmouth Fiero (edited 01-25-2013).]

quote Originally posted by Yarmouth Fiero: I imagine Blooz that we also must keep in mind that the 355 body ( rear quarters and engine deck) are going to be almost flush with the top of this transverse beam, atleast in my current configuration, so as the rear quarters come around and over the B pillar, they will start sloping downwards, possibly right over the upper frame rail so we'll have to keep the top of the transverse frame as low as possible on the ends.

As long as you stay only as high as the the top surface of the firewall, you should be safe. These two photos are the best I could do to show the relationship between the underside of the rear fenders and the top of the upper frame rail. Even though you can't see the upper frame rail, it is 25mm below the top surface of the firewall, so you should be able to visualize where it is in relation to the fiberglass. As you mentioned, if you allow your new crossmember to extend over top of the upper frame rail, you'll probably need to bevel the ends:





As for where the decklid sits in relation to the top of the firewall, here a couple photos that show more or less what you want, though when I disassemble the body to modify it, I'll have to change this area somewhat since the thin lower fiberglass window frame isn't supported by anything as it is installed right now. I will probably fabricate a metal window channel that is welded to the frame of the car and have the fiberglass simply act as a decorative cover. Even though you won't have a rear glass window, you'll still need a trim panel in the same area so you will be affected by this too. The first photo is just to orient you:





Currently, there is approximately 65mm between the upper surface of the decklid and the top of the weld flange on the OEM cross-beam, but like I said, I'm not far enough along to say for certain whether this should stay that high or not. You don't have to look closely to see that the lower rear window frame isn't straight so take the 65mm with a grain of salt. The 30mm dimension shows the location of the underside of the decklid in relation to the upper side.

As for how much room there is between the underside of the stock cross-beam and a typical SBC installation, it's tough to measure because of the angle of the valve covers, but here are a couple photos that show you've got lots of room:





Bear in mind that this is an '84 chassis so the wire bundles come out in a different location than yours will. That's all easily modified anyways.

[This message has been edited by Bloozberry (edited 01-25-2013).]

Thanks Blooz. That is very helpful. I guess I could just remove the 'Z' piece which would move the transverse frame up flush with the top of the upper frame rail and it would allow the transverse frame to sit tight against the back of the firewall.

BTW... PIP is very slow tonight.

I'm going to add the stock engine deck hinges to the drawing so see where the engine deck will be in relation to the top of the firewall. I suspect the engine deck height will be very close to the stock Fiero?

[This message has been edited by Yarmouth Fiero (edited 01-25-2013).]

Updated previous post now that PIP is back.

Thanks Blooz. Great shots. I think if I remove the 'Z' channel and let the transverse frame come up under the firewall / window flange, it should be safe. That puts the transverse frame flush with the upper frame rails as well so they won't interfere with the body in any way.

I just modeled the stock hinges for my drawing. I think the 84 wire glands in the fire wall are in the same general loaction as my 85.

Your 308 doesn't have a 3" frame stretch does it? I may have even more room.

[This message has been edited by Yarmouth Fiero (edited 01-25-2013).]

That's true, the 308 is stock wheelbase so you'll have even more space. Also, the wires pass through in the same location as all years, it's just that I had a senior's moment for a second. I knew something about the '84's wire bundle was different but now I realize it's not where the wires pass through the firewall, it's where the big C500 connector is. On the '84's it's on the firewall, but I remember now that I moved C500 to the same place near the battery as the later years. You'll be fine.

Great news.

I'll use your 65mm and lay a temporary engine deck on my drawing and see how it looks in relation to the top of the firewall and the roll over hoops. This weekend we will remove the rear window... finally. That sucker is stuck on there something fierce.

Hi Blooz..... to answer your question about connecting the transverse frame to the upper frame rail, I have added an angled flange 1/8" thick that will cap the transverse frame and wrap up over the top of the upper frame rail. This should give ample surface area to allow a wrap around weld (atleast were its possible to get at). I have shown the inner flange of the upper frame rail snipped away to make room for the angled flange to fit tight to the body of the upper frame rail. Also, I have removed the 'Z' piece from under the firewall flange to allow the transverse frame to sit flush with the top of the upper frame rail.

Its unfortunate that the top flange of the fire wall will prevent me from welding the whole assembly together before dropping it down into place. I don't really want to cut the top of the firewall off to allow that to happen....... but

Thoughts?

[This message has been edited by Yarmouth Fiero (edited 01-26-2013).]

IMHO, the weakest part of the Fiero chassis is how the rear upper frame rail is attached to the cabin. To begin with, there doesn't appear to be much of anything for the uppers to be attached to in the first place. Perhaps that's because GM wanted the rear section to be frangible from the cabin in the event of a hard t-bone collision on the back side, but then that might be giving GM too much credit.

I think your latest idea is good but it might be stronger to leave out the angled flange (grey piece) and leave the back and top faces of the new beam longer. The longer top section of your new beam would overlap the top of the upper frame rail similar to your current grey flange, and the longer rear face of your new beam would be bent backwards 90 degrees to give greater contact with the inside upper frame rail. You'd have to trim a little more of the weld flange on the inboard side of the frame rail, but that's not a big problem.

One other thing I noticed is that your latest drawings don't include the support brace that interconnects the underside of that joint to the lower frame rail. That will make a huge difference too.

I agree Blooz. Its quite shocking just how poorly the upper frame rail is installed. The only problem with leaving out the flange and leaving the transverse frame longer to overlap the upper frame rail is that its going to be tough getting it in there, especially if I leave the front of the transverse rail longer. As I have it now, it would slip right into place between the rails. I'll have another look. Yes, I left the vertical frames out for clarity to see the flange. I think once they are all in and tie all 4 frame rails together with the transverse frame as well as add the large gussets against the firewall, the chassis is going to be incredible strong and stiff.... much more so than the original chassis ever was. I hope I never regret builting it to NOT come apart in an accident.

[This message has been edited by Yarmouth Fiero (edited 01-26-2013).]

That's the idea!

Keeping the theme of the transverse frame with integrated flanges to tie to the chassis, I designed the additional vertical frames ( left and right) using 1 1/2" x 3" x 1/8" HSS and kept two flanges / tabs on the lower end to secure the vertical frame to the lower frame rail. The upper end of the vertical frame will be butt welded to the underside of the transverse frame. I also modified the large gusset that will help tie it all together and give additional strength to the transverse frame where the roll over hoops will be fitted.

When it comes time to install this assembly in the chassis, I may end up cutting out some of the horizontal flange on the upper frame rails to allow it all to drop in vertcally and slide forward behind the firewall.

quote Originally posted by Yarmouth Fiero: When it comes time to install this assembly in the chassis, I may end up cutting out some of the horizontal flange on the upper frame rails to allow it all to drop in vertcally and slide forward behind the firewall.

That's perfectly fine. The flanges are primarily there as a means to facilitate the automated spot welding robot's job on the assembly line. You can cut them off and bead weld the corners with negligible impact on strength.

I think the spot weld robots were trying to wrap the week up early when they built my chassis....... wow... those spot welds are seriously random in places.

Hi

Sorry I have been a little slack posting updates. Work has been crazy with new boats under construction and others being delivered plus a new ferry for Halifax to bid by next Tuesday.

But as you know, the best way to get an engineer's attention is to tell him he made a mistake. ha-ha-ha-ha.

You may be quite right regarding the length of the upper frame rail. I didn't draw the monstrostity of a B pillar yet because it's so complex in shape so I may have conveniently lengthened the frame rail to suit my needs. I assumed it went all the way forward to the firewall.

The only picture I have on my laptop is this one showing us removing the lower window support. When I get home tonight I'll get a shot looking up at that area. If in fact it is the way you say, I may have to rethink the end connection. I haven't cut the 3" x 4" HSS yet so I have lots of material if it needs to be a little longer.

How about extending your frame extension to the firewall. It's probably 20 spot welds to drill out, but you could replace that whole top rail and shape it the way you need it to be.

Bob

[This message has been edited by RCR (edited 02-14-2013).]

Hi Bob. Thanks for your input. I have been thinking about that all night. I am also scratching my head as to why I didn't extend the upper rail when I did my 3" chassis extension because there was a short 4" long piece of frame rail just hanging there in mid air.

I am also looking at the fact that I have to remove the upper portion of the B pillar for the spider and will have to cap the gaping hole which will be in the same plane as the new transverse frame so I may design the structure to handle both of these matters at once.

Its quite suprising just how little there is holding the frame rails to the back of the firewall..... literally 3/4" sheet metal taps spot welded on two or three sides of a square section frame. I can only guess that the rear chassis is designed to separate from the passenger cab in the case of a serious side impact. I know I've seen a few pictures on PFF showing Fieros with the rear ends missing after an accident. Its scary to think about that's for sure.

Watching Fieroguru's video of his LS4 coming to life inspired me to get my own V8 finished today.

Just have to top up the sump with some high grade Italian EVOO for lubrication and she's ready to spin.

While the chassis modifications proceed at what seems like a snails pace for us, we decided to tackle the topic of choosing wheels and tires for the car. While it's a long way off until the day they actually spin under power, the decision to finallize a wheel specification will allow us to begin the work of developing the requirements for the suspension components. Proceeding in this order presents us with the oportunity to select available wheels from a wider range of designs. As we all know, just dealing with the constraint of sticking to 5 x 100 wheels is bad enough. The only other aspect that we wanted to consider was keeping the selection of final tire diameter as close as possible to Blooz's selection as we are building similar cars from the same moulds. Now that he has taken the plunge and made his selection and purchase, we had a huge sense of confidence regarding the direction we were headed in.

If you think its hard deciding what wheels to go with, try adding the opinion of two teenagers into the mix. Unfortunately both my boys have exceeded me in both height and weight so there are times my 33 1/3% vote felt more like 20%.

As we have stated a few times, we are planning a black color for the car so we first agreed that the wheels would be black also. The next item was that we wanted the wheels to be as flush as possible with the outer edge of the rim. Looking at many many pictures of fieros, modified fieros, various beautiful supercars, we found that we liked this look and it made the car look a little more stealthy, especially as the 355 spider body will appear low and wide anyhow. After many hours of back and forth choices and much deliberation, we selected a couple possible candidates from the brand XXR. From this point we narrowed it down to the XXR 527 in flat black and last night we agreed that this was our final choice and assuming they are available when we place our order, that is what our future black 355 spider will be rolling on. Oddly enough, there was an article on MSN this morning regarding supercars and their 0 - 100 kph numbers and on the McLaren MP4, there were wheels very similar to what we had chosen. We think they look awesome so that gave us a sense of satisfaction that we had made the right choice.

So using several online wheel and tire selection tools, here is what we will be going with.

XXR 527 in flat black
Front Wheel: 17 x 8.25 ET 35mm
Front Tire: 225/45/17

Rear Wheel: 18 x 9.75 ET 20mm
Rear Tire: 265/35/18





As you can see the tire selector only uses one decimal point for the wheel width so it's off by 0.25" ......but its close enough for this execise. As well, we have not chosen a tire brand yet but it will be a summer tire that's nice and sticky as this will only be a fair weather driven car anyway.

Here is the McLaren MP4 with similar looking wheels and we think it looks amazing. Actually, that car could ride on wooden barrel tops and it would look amazing.



So that is our decision regarding wheels and tires. I'll update once we place the order and when they arrive I'll post some pics.
If you have any comments, please feel free to express your thoughts.

quote Originally posted by Yarmouth Fiero: Watching Fieroguru's video of his LS4 coming to life inspired me to get my own V8 finished today. Just have to top up the sump with some high grade Italian EVOO for lubrication and she's ready to spin.

Wow, what a flashback, I built one of those as a kid (a very long time ago, in what seems like a galaxy far far away.)

Joe

Excellent choice of wheels. They'll make your black spyder look even more sinister. While there is an argument to be made for dished and lipped wheels from an aesthetics point of view, flush wheels are an indication that the control arms are out at the four corners of the car where they should be, not tucked in a foot under the car. These wheels should allow you to design the control arms to maximize performance.

Nice choice on your wheels. You've got me re-evaluating my choices.

BTW, If it's not too late, LSD Motorsports seems to have better pricing, although shipping might be the equalizer.
http://lsdmotorsports.com/m...tBlack&gSize=&gBolt=

Bob

Thanks Blooz. Thanks for your help along the way. Its very exciting to finally make a wheel selection and we are satisfied with our choice. And if the selection can add to the design of the suspension arrangement then that's even better. I hope they are still available. ha-ha-ha-ha.

Hi Joe, the model was alot of fun to build and the boys learned alot about the inner workings of the IC engine. There are videos on Youtube where they spin the models to 5000 rpm and apparently they sound like a real running engine. I'm looking forward to trying that. I may build a plexiglass box to put it in... just to catch the flying parts.
It's been 40 years since I built a model kit and it brought back some fond memories. Except this time I had to use a lighted magnifying glass on a stand to see what I was doing.

[This message has been edited by Yarmouth Fiero (edited 03-10-2013).]