rear end questions and chassis question

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rear end questions and chassis question

Post  Rickytx630 on September 24th 2017, 9:15 pm

in the current process to start updating/rebuilding my father's car. its been backhalf in our drive way back in 99' with a 2x3 rear section. after selling my bracket car and a few other toys im looking to put this car under a chassis. its an 83 ttop hatch, nothing crazy to be done with the car other then bracket racing and maybe the yearly divisional that comes around, the current set up has a ladderbar but im looking to go to a 4link. is it worth and easier to cut the brackets off and weld the 4link brackets? or should i just start fresh? new housing and go fab? should i go ms or cm? i know that moly is stronger and lighter and will cert quicker, but if im just bracket racing it or on a t-stop is it worth going with the ms and put the money else where? looking for thoughts and ideas from people.

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Re: rear end questions and chassis question

Post  bosshoss on September 25th 2017, 4:05 am

If you are doing the chassis work yourself be aware that the Moly Cage will have to be tig welded. If you have the gear to do that then I don't think the difference in material cost is going to matter much in the grand scheme. Resale value and a bit of weight savings are a better benefit imho...

on the rear end housing about all you can salvage is the center part of the banjo. Just buy a set of new tubes. If you don't have a rear end alignment jig I would suggest you purchase a complete housing with brackets and bearing ends already welded.. Places like Moser and Strange can do that for you using your measurements.

dkp
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Re: rear end questions and chassis question

Post  DILLIGASDAVE on September 25th 2017, 4:56 am

IMO.......

(A) For the average bracket door car (say under 1000hp & only seeing 1 or 2 different tracks during the year) there really is no reason to ditch a correctly setup ladder bar suspension other than if the driver setback/seating placement & rear suspension packaging/space placement are trying to occupy the same space. If that's the case then a 4-link is the only choice to gain back some driver seating/leg room. On a short wheelbase low slung full chassis car it's almost always impossible to place the driver's seat back against the wheel tubs for a lot of leg room and also use ladder bars.
 
(B) For the average bracket door car (say under 1000hp) there really is no need for the added expense of a finished fabricated sheetmetal 9" housing (unless of course you don't have access to a welder & housing/bearing end alignment jig & housing table). A junkyard 9" truck housing (or some coil spring car 9" housings) with their bigger OD & thicker wall axle tubes from the factory will get the job done just fine in most cases with a little work. Weld on a back-brace, weld in some internal front-face to back-face bracing, and stitch weld around the folded seams inside the housing (folded seam around the front-face & folded seam around the rear-face & back cover) will usually get the job done.

(C) For the average bracket door car that will never be faster than 8.50 mild steel tubing is usually a better choice IMO. Mild steel can be either Mig or Tig welded (more choices making it easier for the average Joe to make repairs himself), but 'moly tubing can only be Tig welded. In this situation being a bracket car there really is no  reason for using 'moly tubing unless you're only priority is looking to possibly help increase the resale value of the car down the road.

(D) If going with mild steel tubing to save some money (over 'moly tubing) a "welded seam" mild steel tube (CREW or HREW in a .134" wall) is a better choice IMO vs the the much more expensive "DOM seamless" mild steel tubing in a .120" wall, (it's called "seamless" but depending on how it's made a welded seam can still be there even if you can't see it). The reasoning goes something like this.....If you can easily afford the more expensive DOM m/s tubing, then you might as well spend a few more coins per foot and go with 'moly tubing instead.

(E) Round tubing for the main frame rails is usually a better choice vs box/rectangular tubing (round tubing takes up less space, weighs less, etc). The down side to round tube frame rails is round tubing is harder to securely clamp to the chassis jig during construction vs box/rectangular tubing.

(F) If you are going to be 8.49 and/or faster, but still be slower than 7.49, (a SFI 25.4 or 25.5 chassis cert) then the 'moly vs mild steel choice can get a little more muddy. The above good reasons for choosing mild steel are mostly still there. But going with 'moly at this level of performance also becomes more & more of a good choice as well since cars at this level start to get very expensive & resale value becomes more & more important.

(G) If you are going to be 7.49 and/or faster in a full chassis car then round tube 'moly is your only choice (SFI 25.1 or 25.2 chassis cert) since mild steel isn't allowed at this cert level.
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Re: rear end questions and chassis question

Post  Rickytx630 on September 30th 2017, 12:14 am

thank you for the replys. im still a little between the two on the chassis as far as the m/s vs c/m, i wont be doing the welding ill have a shop do that part. the car will mostly be bracket raced like i said but with the idea of either supercomp or gas set up. throttle stop mostly alll the time. but if it was off id like to have the car somewhere between the 8.1x and 7,8x range, yes i know its more to it and its a big range. i was looking at either an s&w kit for the foxbody, or the chassis engineering kit. after talking with the guys at chassis engineering the kit they offer tucks in really nicely and close as they have files and data after building a car in shop as i was told. but a few people around here in my area told me to go with the s&w kit, has anyone use either and if so how you like them?

as far as the rear goes, is it easier starting fresh and what should i do with the et in mind? the fab housing sounds easier as itll be and out of the box and bolt up but would it be cheaper and stronger then sending a factory truck 9 out and having it cut braced etc,

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Re: rear end questions and chassis question

Post  DILLIGASDAVE on September 30th 2017, 2:45 am

The proposed ET range being faster than an 8.50 (8.10's to 7.80's) puts it needing at the very least either a 25.4 or 25.5 SFI chassis cert in either mild steel or 'moly.

IMO there are better SFI chassis kits out there (than Chassis Engineering and S&W) like from either Tim McAmis or Rick Jones/QuarterMax, but they are usually more expensive. The 2 things I really like about both the Tim McAmis & Rick Jones designs is the way they do the windshield bars at the dash bar, (no bend is used on the windshield bar at the dash bar, the w/s bars attach to the dash bar instead). And that they don't use a halo/loop style bar in the roof.

But if a SFI ms/moly chassis kit is the goal, and if Chassis Engineering & S&W are the only two choices, then IMO Chassis Engineering's SFI kits looks/are a lot better choice than the S&W SFI kits.
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Re: rear end questions and chassis question

Post  Rickytx630 on September 30th 2017, 2:26 pm

i would love to have a rj or bickel or tm but when i called they dont do a kit for the foxbody cars. only what they offer for bodies. unless i drop the car to them and then the build price just tripples. i would love to but the money just isnt there for that. are there other kits like the ones said that offer the better up to date stuff like the rj or tm stuff?

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Re: rear end questions and chassis question

Post  DILLIGASDAVE on October 1st 2017, 3:07 am

Meh, off hand the only other super big name chassis shop that I can think of that might still offer "kits" is Jim Geese's back-from-the-dead Vanishing Point Race Cars. But a smart person should probably 1st learn of the original VPRC's past history before deciding to spend money there (check out the old threads about Jim Geese/VPRC on yellowbullet for the dirt).

Now that's not to say that Jim didn't learn his lesson from that disaster, and then become a better person at R2B2 race cars, before starting up VPRC again....I can't say, I don't know anyone who has dealt with him since VPRC's rebirth.

I don't know how much his designs might have changed over the years but IMO......

(A) I really liked the way he designed & braced his frame/chassis structure (its self, not including the cage) from the 4-link brackets to the back of the car. They were super rigid/very stiff from the 4-link brackets back to the shock mounts.

(B) I never liked his main cage roof structure layout ("old style" halo/loop roof bars).

(C) I don't like his (or anyone's) front door car chassis design that uses a tri-pod top strut mount setup (vs the better "conventional" setup using the extra bar running from the top strut mount back to the windshield bar).


The biggest drawback to any cage design that uses the old halo/loop style roof bars is it can severely limit how tightly you can fit the windshield bars up-into the car to get them out of the way. But then IMO on a lot of the DIY/kit chassis builds out there quite a few people just don't ever cut out anywhere near enough of the factory inner body structure to really get a cage to fit inside the body super tight anyway.

Cutting out all the factory inner body structure also makes it a lot easier to get in there & re-bend/form the remaining OEM windshield & window channel/frame into a flush-mount lip for Lexan.



[edit] I guess there is also Richard Earl's Suncoast race cars. Not really in the same "big name league" as Bickel, McAmis, or RJ, but there seems to be a decent amount of sportsman racers over the years that like his stuff.
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Re: rear end questions and chassis question

Post  Rickytx630 on October 1st 2017, 7:55 pm

ive just did about 4 hours of research and reading, ive always like the vprc's stuff but wow... thats all ill say. i think im gonna call around to a few bigger name guys and have some talk with them, maybe ill just start over and build a new car, not sure atm now, but thanks for the replys and reviews and tips.

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