updating back half to full chassis

have an 83 foxbody, it was build over 20 years ago and nneds some updates, im looking to just update and go to a full chassis on it. have a few concerns and mainly being a t top car. also im looking for pointers on doing so. what to get whats more important and what can be skipped, im not after the lightest car but dont want a tank. carbon is nice but is it really needed? and not sure really what class ill be running with it, most fast brackets or some quick 16 stuff.

Probably not what you want to hear but for many reasons IMHO you're almost always better off selling the current back-half car and use the money to fund the start of a new purpose built full chassis project.

This is because the assorted differences between the average back-half and full chassis cars usually means you have to make a ton of compromises when converting a car from back-half to full chassis. This can often result in a finished "full chassis" conversion that doesn't really work like it should, then you quickly grow to hate the finished product.

If your only intent is to front half the car, BUT at the same time change NOTHING else about the current combo, (body/chassis ride height, engine placement, driver placement, front suspension travel numbers, etc, etc, etc all stay the same as before) then converting back-half to full chassis isn't as big a deal.

But if you intend to also do all the other assorted mods usually associated with a "full chassis" car (like much lower ride height, moving the driver back for more leg room, moving the engine placement/angle around, etc, etc, etc) you're usually going to be opening up a can of worms trying to make the old rear back-half frame/cage section work correctly with these additional "full chassis" mods.

And don't forget that if you plan for the car to be 8.49 or faster a SFI legal cage/frame will be required cuz a regular 8.50 & slower NHRA/IHRA cage won't be legal. Another reason to start a full chassis deal from scratch.

agreed x2. been there a few times.

dkp

thanks for the reply. im looking to cut the body and gutting everything and getting a kit. not sure if thats what you were talking about DILLIGASDAVE. with what you are saying, is that for me to just go from the back half forward? or from buying a kit and doing it from front to rear?

Rickytx630 wrote:thanks for the reply. im looking to cut the body and gutting everything and getting a kit. not sure if thats what you were talking about  DILLIGASDAVE. with what you are saying, is that for me to just go from the back half forward? or from buying a kit and doing it from front to rear?

the car is also a 2x3 back half if that makes a difference and not round like most are,

Ooops, my bad. From the subject line in your original post ("updating back half to full chassis") I was thinking your plan was to just add a front-half section to the old/original back-half section & turn it into a full chassis car that way. So yes, gutting everything and starting the "full chassis" from scratch is the best way to go IMO.

But I have to say that throwing away the back-half chassis is still a bit of a waste (if the back-half car worked good that is) just to reuse the body vs selling the assembled back-half car (chassis & body) and getting a new body to build the full chassis car with.

But regardless if you end up gutting the old back-half body, or get a new body, here are some things you might think about if you're going to be building the full chassis your self........

#1 If you don't have a tube bender to build the chassis from scratch, buying a weld-up full chassis kit is about the only option vs having someone build the car for you.  

#2 Some "kits" are better than others, (fit, finish, design, layout, etc). Some kits the bars are a generic "one-size-fits-all" bend/shape and don't always fit the body very tightly, and some kits fit very tightly and are well designed.

#3 Building the chassis on some form of a rigid & square chassis jig is the only way to go IMO. Trying to build a full chassis car "off the floor" sitting on jack stands is a major headache waiting to happen.

#4 Regardless of which way you go with the body, (back-half body vs new body) a "full chassis" car's body doesn't really need all of the original/factory inner body structure sheetmetal (like a back-half or stock suspension car does). So cut out as much of the inner body structure as possible, it will make the body lighter & allow you to fit the roll cage in there even tighter.

#5 Rework the windshield/window frames to flush mount the lexan vs using spacers in the factory window frames to flush mount the lexan. The spacer method always looks like siht IMO.

#6 Mild steel tubing vs 'moly tubing. The choice all depends on (A) what type of welding you have access to, ('moly tubing must be Tig welded, mild steel can be either Tig or Mig welded). Or (B) how fast you want the car to be legally certified to (m/s can only be SFI certed 8.49 to 7.50, 'moly can cert faster than 7.50 depending on which SFI cert is used).

#7 A number of "full chassis" kits out there are SFI legal for certing a car faster than 8.50. The SFI 25.1 & 25.2 specs call for only 'moly tubing, and it must all be round tubing. The SFI 25.4 specs can be either mild steel or 'moly tubing (or a combo of both), but the 25.4 spec is only good from 8.49 down to 7.50.

#8 4-link vs ladder bar. A 4-link is way more adjustable, but is much easier for the beginner to get lost on the setup/adjustment. A ladder bar is a lot easier to setup/adjust, but has much less of an adjustment window to work with. A 4-link setup pretty much also has to have an anti-roll installed these days to work without excessive body-roll happening. A ladder bar setup (depending on design, layout, HP/TQ numbers, etc, etc) might not need an anti-roll.

#9 Strut vs A-arm/spindle. Aftermarket short "drag" struts for a full chassis car are about as light of a front suspension as you can get vs A-arms. They also give you the most header room vs A-arm. But the A-arm/spindle setup is usually less expensive (depending of course on who's kit you get) than an aftermarket strut setup.

#10 etc, etc, etc....There is a lot more but it's late & my brain cell has locked up for now....

thanks for the info. the car was build a little over 20 years ago in a dirt driveway, its certed but the car likes to dip down into the high 8.9xs its its a 2x3 frame latter bar car.
i have been looking at the chassis engineering eliminator x kit. looks really nice and saw a few done, the struts i was looking at the strange medium duty kits. i like to go with a 4link, im looking for something in the 7.50 range. not looking to set records, not sure if i want to continue running supergas with the car or try and go faster. car weighs just about 3100, with big block and c6 in it. its got a 514 now (thats with me in it), but ill be replacing that with the chead 598 that i finshed. what dp you mean by rework the window frame? fillers? any pictures for ideas? also whats about floor panels seats steering wheelie bar length etc

Rickytx630 wrote:.........i have been looking at the chassis engineering eliminator x kit.............

The Chassis Engineering Eliminator X full chassis kit is OK IMO, as designed it's SFI legal IIRC ('moly = SFI 25.1 OR 25.4 & mild steel = SFI 25.4). A lot of things I like about their design, a few things I don't. It's not as good as a high end Tim McAmis kit, but it's better than the older generic S&W full chassis kits (again in my opinion).

Rickytx630 wrote:...........what dp you mean by rework the window frame?...........

For example, you take the deep factory sheetmetal windshield frame/channel/flange that held the thick OEM windshield glass and either (A) re-form (bend/fold) the OEM sheetmetal windshield frame/chanel to form a new shallower mounting flange to flush mount the thinner 1/8" Lexan windshield. Or (B) cut the OEM sheetmetal windshield frame/chanel depth off at an 1/8" deep, then weld a new mounting flange to it to flush mount the thinner 1/8" Lexan windshield. Method (A) only works if the OEM window frame is deep enough (has enough material depth) to bend a new flange from. If the OEM windshield frame/channel isn't deep enough to bend a new flange then method (B) is used.

Rickytx630 wrote:...........whats about floor panels seats steering wheelie bar length etc ...........

IIRC all the faster SFI classes require a steel/sheetmetal floor welded in on the driver side. The firewall can be eiter aluminum, steel, or Titanium depending on what class you aim for and/or how fast you want to go.

The Chassis Engineering X chassis can probably use most any "drag only" type seat like a single layer fiberglass, sheet aluminum, or carbon fiber dragster/roadster/wrap-around type formed seat as long as it incorporates a small tubular frame (and/or the FC cage structure) to hold the seat in the car. The "conventional shaped" type seats (like double wall poly & Kirkey type seats) are OK too. But the double wall poly seat is usually so thick that sometimes you loose too much head room clearance between the under side of the FC cage & your helmet (depending of course on driver height & how "big" the car body is).  

IMO wheelie bar length usually needs to be at least 70" long. The harder the car hits the wheelie bars, the longer they usually need to be to avoid unloading the slick. A car that needs wheel-speed at the launch vs a dead-hook launch also usually benifits from a longer w/bar vs a shorter w/bar.

i was looking at a few of the chassis kits offered by tim or bickel and a few others but they dont seem to offer a kit for the foxbody,

Rickytx630 wrote:i was looking at a few of the chassis kits offered by tim or bickel and a few others but they dont seem to offer a kit for the foxbody,  

I could be wrong but I believe they would build a kit for most any body style. I would at least call them and ask.

There was a post floating around on Yellowbulet following the build of a Fox Body Mustang with their new Eliminator II chassis. It was the test bed to get the kit details all ironed out. About 6 months or so ago. The guy on there that works for Chassis Engineering posted the build...

Based o the large volume of fox cars currently on the race track I would be willing to bet that any of the current chassis kit makers out there have the dimensions on file already. Depending on your skills and the tools available even a generic kit could be made to fit. Personally I have had good experience with Chris Alston Chassisworks stuff. I just checked his site and they have a very detailed custom order sheet online.

dkp

jbozzelle wrote:There was a post floating around on Yellowbulet following the build of a Fox Body Mustang with their new Eliminator II chassis.  It was the test bed to get the kit details all ironed out.  About 6 months or so ago.  The guy on there that works for Chassis Engineering posted the build...

This one......

http://www.yellowbullet.com/forum/showthread.php?t=1535793

i was just looking at that build today. amazing job and it looks like it fit real tight. the few big name shops would only want to build the full car and not just bent up a chassis it or weld a chassis together. when i called and asked them they said they will only do the body options on their site that they offered. sucks but thats ok.