Chassis experts and subframe questions.

68converted · Jan 14, 2006

Ok, I have a '68 convertable. I have been kicking around design ideas for subframe connectors. The idea I have is to cut the lower seat pan front to back, slip in the strait subframes and then weld it all back together. Does that make sense? Any comments, concerns.

I tried to post a picture but I cannot get it to work. Everyone else can add images to their posts, what gives?

68converted · Jan 15, 2006

Bump- please, need to know if this is a feasable option.

chromedog · Jan 15, 2006

i think it would work... i did floors, inner rockers, front frame sections, etc. on a 68 rag not long ago, and thought how nice it would have been if that car had had sub connectors installed 15 years ago, it might not be collapsing in on itself! to take full advantage of this installation, measure carefully, keep the cutouts as small as possible, and weld everything up good and tight. (in other words, a couple tacks here and there wont cut it)IF the car is starting to sag in the middle (door gaps tighter at the top than at the bottom) you need to devise spreader bars to jack the unibody back into shape... get in touch with me and ill show you how i did the 68

mdjay · Jan 15, 2006

That sound like it would work. I've seen people make their own connectors and half in, half out of their floor pans.

IMO It just seems like a lot of work when you can just purchase a set and weld them on.

68converted · Jan 15, 2006

chromedog said:
keep the cutouts as small as possible, and weld everything up good and tight. (in other words, a couple tacks here and there wont cut it)IF the car is starting to sag in the middle (door gaps tighter at the top than at the bottom) you need to devise spreader bars to jack the unibody back into shape... get in touch with me and ill show you how i did the 68

The car is in good shape, with no sagging. My biggest concern is when I cut the metal. I am not sure what the "pan" panel is called. Anyway, I am going to place jack stands under each rocker, and at both ends of the sub frames. No weight on them, just precautionary. I am going to use a highlift floor jack under the rear center section to make sure the car is "weighted". And then start the installation. I figure if the car is going to implode it won't land on my head. I value that part a lot.

chromedog · Jan 15, 2006

what i did was, using a chunk of 1" tubing, 1 3/4"nut and a length of 3/4"allthread, i made a screw jack to pre load the unibody (keep in mind, i cut floor pans, inner rockers, torque boxes, and seat risers out)bolted to lower door hinge, and window regulator mounting pad, using 2x2 angle brackets. jacked tension into unibody, going past where it needed to be after tension was removed.(if you arent dealing with any unibody sag, just bring the jack up tight)go ahead and do your cutting and welding, and you should be in good shape when you drop the car onto the ground.this little trick can be used when you do floors, quarters, and is cheap insurance when ever you cut away at the unibody of any car, not just a mustang.

68converted · Jan 15, 2006

I was going to use this style: http://www.mustangandfords.com/howto/89059/index.html

to make my attachments. Then use cross beams welded to the plate and bolted to the main sub frames. Should be fairly sturdy. Yes?

chromedog · Jan 15, 2006

good deal... those should be plenty strong. i wouldnt hesitate to clearance the seat pans to fit those in.

68converted · Jan 15, 2006

What is used to seal them against the floor pans? I can imagine the rust issues with this much metal to metal contact along the length of the subframe.

chromedog · Jan 15, 2006

3m makes a seam sealer called fast and firm... check your local auotmotive paint supplier for it, OR a roofing supplier for a urethane based product used for sealing up flashings and the like (the name escapes me right now) i would choose the urethane my self, as it is not going to shrink up, and pull away from the metal like most of the others will. (also, it is a little bit more flexable after it fully cures)

HistoricMustang · Jan 15, 2006

68converted said:
I tried to post a picture but I cannot get it to work. Everyone else can add images to their posts, what gives?

Again: http://www.imageshack.us/

HistoricMustang
www.historicmustang.com

Worn out example..........................

68converted · Jan 15, 2006

HistoricMustang said:
Again: http://www.imageshack.us/

HistoricMustang
www.historicmustang.com

Worn out example..........................

Thanks buddy, I actually pulled up one of your old posts and followed the link from the picture, and then figured it out. What do you think about the sub frame idea?

68converted · Jan 15, 2006

chromedog said:
3m makes a seam sealer called fast and firm... check your local auotmotive paint supplier for it, OR a roofing supplier for a urethane based product used for sealing up flashings and the like (the name escapes me right now) i would choose the urethane my self, as it is not going to shrink up, and pull away from the metal like most of the others will. (also, it is a little bit more flexable after it fully cures)

I have four tubes of the 3M stuff. Guess I will just have to POR-15 everthing. Then use seamsealer/undercoating.

70vert · Jan 15, 2006

Jacking rails and subframes?

68converted,
My current thinking is to try to get something custom done with jacking rails. Or just order the Global West jacking rails separately from Mustang Depot and then get a custom subframe connector done that ties into them.

I think on a convertible the extra strength of tying the rocker panels into the subframes that in turn connect to the frame rails would give a pretty nice setup that could handle a lot of power. Also would be nice to jack up from the middle.

10secgoal · Jan 15, 2006

That's how I did mine. The subframe will fit perfectly in between both frames

68converted · Jan 15, 2006

10secgoal said:
That's how I did mine. The subframe will fit perfectly in between both frames

Do you have a picture? (s)

HistoricMustang · Jan 15, 2006

68converted said:
Thanks buddy, I actually pulled up one of your old posts and followed the link from the picture, and then figured it out. What do you think about the sub frame idea?

It will work...................have seen it on some road race machines.

I staying away from sub frame work to save the weight but that may be why my ride got the name "Flexible Flyer".

HistoricMustang
www.historicmustang.com

10secgoal · Jan 15, 2006

68converted said:
Do you have a picture? (s)

Try to get you one. About to do floor boards and clean up the crappy welds. Have a much better welder this times.

chromedog · Jan 15, 2006

believe it or not guys, the inner rocker is where all the strength is in the convertibles...also, you want to epoxy prime, por 15, etc. before you seamseal.

68converted · Jan 16, 2006

chromedog said:
believe it or not guys, the inner rocker is where all the strength is in the convertibles...also, you want to epoxy prime, por 15, etc. before you seamseal.

I won't be touching the rocker rails. The mod from the subframes to the rocker rails will have to wait until the car is up and running. Trying to get a few sections of crappy wiring hogged out from under the dash. Then I can tie in the fuel system and fire it up. I have to work on it part time and it is taking forever.

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