Finally ready to get back to my 70 Challenger. Rebuilding the rusty rear half starting with new frame rails. I have the entire car sitting on a jig and all measurements are working off the factory diagrams but I noticed a discrepancy between all the Challenger frame measurements diagrams out there and the actual rear frame rails.
The diagrams show the rear frame rails with no upward curve but the actual frame rails do have a significant upward curve and that changes the measurement which is taken at the very rear of the rail. Wondering what others have done to get around this when rebuilding a rear body with new rails.
My original plan was to weld the rails in perfectly, followed by the floor, drop offs and wheel houses. Finally the quarters and rear tail panel.
If I cannot be certain of frame rail measurements because of a weird diagram discrepancy, then it looks like I'm forced to tack and screw everything together so I can fit the quarters and tail panel. Then if everything fits right, I could weld the frame rails in permanently.
Any ideas or other diagrams out there that show the actual upward curve?
so it's not just me???
I thought it would be easier for me to assemble the rear rails with the front spring mounts, shock cross member and rear cross member, and then install the assembly in the car. So... I built a jig based off the factory service manual dimensions. If you lay the rear rails out according to the factory dimensions, the rear cross member doesn't line up with the bumper bracket holes.
I stopped working on it until I can bring the car home and compare the jig to the body. I will still pre-assemble the rails before I install them.
I wish I would have just bought the assembly Dynacorn makes.... oh well.... :dunno:
Unless someone has a different factory schematic with a different dimension at the very rear, I don't see any other way around it then to tack and screw stuff together temporarily just so I can be 100% positive the rails are sitting at the right height. The new rails fit good and follow the contours correctly but I'd be pissed to weld them in along with the floor only to have the height of the floor an inch too high once the quarters and rear tail panel are in.
Your better off pre fitting everything now. :alan2cents:
I don't see the issue here? If you set up the datum line, as shown in the measurements and set the height of the rail to the shown measurement, where would you go wrong? Don't get me wrong here, I've been there and done that with the replacement panels and would likely hedge my bet by throwing the rails together with the rear crossmember. Toss the floor on too, while you're into it and see where it fits against the rails and wheelhouses. OR do it the way it was done at the factory and get high/pissed and just toss it all together! This works best on a Friday or Monday it's been discovered. Good luck :cheers:
The datum line of D shows it should be 18" but with the rail curving up instead of being straight as seen in the diagram, that measurement is closer to 19". The rest of the car is sitting on the resting points exactly as the diagram shows and it all measurements are just right. If I bring the rails down to the datum line measurement of 18" makes the rail fit horrible. I don't even need the quarters on the see how wrong it is. I'm certain it is all going together perfect but that datum line measurement at D can't be right.
Well, I'll get it together!
Quick question, is the car resting on the "seams" at the bottom of the rockers, or where the measurement holes are located? I only as because I've seen lots of folks who rest the car on a structure that amounts to beams going from side to side. The height of the seam would be around 3/4" and could account for the difference.
Just a thought.
:dunno:
I thought that at first but it's at the holes just like the diagram shows. I have a theory I'm going to check today. If the rail did not curve upward at the last 12-18" of the rail and remained perfectly straight as the diagram shows, then it would continue a slight downward trajectory. My theory is the measurement might be correct if the upward curve didn't exist. Easy to check. The rails are clamped in now so I'll put a straight edge along the underside and measure the datum line spot where the rail would be if there were no curve. If it checks out, and I think it might, then I'll know the height is correct.
What I was getting at, is the car supported in the yellow, or the orange? Orange, would have the car almost an inch above the yellow (where is supposed to be) and account for the difference. If you supported the car in the orange area, then you need to add that difference in height.
Moot now, but seems you didn't measure it all before taking it apart?
Anyway, that's all I got. Hope it works out.
-=C
Something else to consider is that diagram you have, and everyone has, isn't "drawn" well. The rails int he back aren't straight along the center axis. The dimensions, reflect it, but the drawing doesn't. Anyway, my point is, there is another diagram, that has different references and seems to indicate the measurements is taken 56.5 inches from the rear shackle on the same plane as the datum.
I'm not supporting the car at the rockers (the orange). Supporting at the alignment holes of the frame precisely where the diagram indicates. The other six locations have the car sitting perfect and all measurements check out so it's this last one at the back end that seems wrong. I've seen the diagram you posted but it doesn't help me since the car is just a shell. I would have taken measurements but the car was rusted apart and suffered a rear end impact throwing everything off. I'll get it. I just thought someone here might have noticed this rear frame rail discrepancy and had information to offer on it or another diagram with the correct measurement.
I know the one I posted simply cannot be right because it is showing a measurement at D given the frame rail as being perfectly straight when it is not. I don't think it's an artistic error, I think it's informational error. I used the same diagram when I rebuilt the front frame rails and afterward, I put the hood, doors and fenders on and found everything gapped out perfect.
Got it.
I have a vested interest in this as I'm working on learning the dimensions etc. before tearing into my vert.
What if you set it up so the measurement right behind the rear shock mount/cross-member is (18-9/16), where does the supposed 15-7/16 hit the rail?
I have the dynacorn rear assembly at home. I'll take some measurements and see what I come up with.
Measured my dynacorn assembly and have to agree, it looks way off. With the front of the assembly flat, the top of the frame arc is higher than the measurements show. if I tilt it back, the front section is at an obvious angle (not flat) and the rear is still about an inch high.
I'm not above learning I'm doing something obviously wrong, otherwise I'd think this would have come up before.
Anyone feel like measuring their car that's currently on a jig?
-=C
Well I measured the height off the datum line and realized I made the resting points about an inch high. Not sure how I did that but I did. I chopped them all down and repositioned the car like it should be and at first glance, the measurement at the rear rails is much closer. While the artistry of the diagram may not be accurate, it does appear the rear frame rail measurement might be correct after all.
"And they all gave a sigh of relief!" I'd still hang the 1/4s and check my door gaps. Good luck :cheers:
Even though everything seems good now, that's the message I got from this ordeal too. Trust nothing and double check everything before welding it all together.
Quote from: 70 Challenger Lover on March 29, 2020, 06:27:59 PM
Well I measured the height off the datum line and realized I made the resting points about an inch high. Not sure how I did that but I did. I chopped them all down and repositioned the car like it should be and at first glance, the measurement at the rear rails is much closer. While the artistry of the diagram may not be accurate, it does appear the rear frame rail measurement might be correct after all.
Well that's great! lol, totally agree the pictures suck, but knowing the measurements are good is helpful.
=C
Quote from: 70 Challenger Lover on March 29, 2020, 08:36:16 PM
Even though everything seems good now, that's the message I got from this ordeal too. Trust nothing and double check everything before welding it all together.
Allow me to congratulate you on your perspicasity! You could probably recoup some of the $ you'll sink into this thing, if you were to carve that statement into pieces of wood or plastic and sell one to everybody who's ever gone down the road you're now on. Misery loves company is the old saying.
You may think I like suffering but I actually enjoy doing this sort of thing. This car was probably not worth saving but I like the challenge involved plus it will be nice to say I did everything myself (except the paint!)
Quote from: 70 Challenger Lover on March 31, 2020, 06:14:04 AM
You may think I like suffering but I actually enjoy doing this sort of thing. This car was probably not worth saving but I like the challenge involved plus it will be nice to say I did everything myself (except the paint!)
I'm kinda in the same boat. Could have picked a better project to work with. Don't give up on the paint. At least rattle can it and then you can claim complete victory!
I can paint interiors, engine bays, trunks, that sort of thing and get pretty nice results. I just can't seem to get the knack for laying it down perfect like a pro. Not afraid to keep trying but this next project, I want it to look amazing. I have lots of plans for the car and plan to keep it a long time so not skimping on the finish.
@70ChallengerLover The difference between an amateur and a professional is a professional can fix there own mistakes. Wet sanding and buffing properly can make an alright finish into a great one. :alan2cents:
Quote from: JS29 on April 01, 2020, 05:35:41 AM
@70ChallengerLover The difference between an amateur and a professional is a professional can fix there own mistakes. Wet sanding and buffing properly can make an alright finish into a great one. :alan2cents:
Yep, :iagree: what the man said, BUT, make sure you get enough clear on it to accommodate that sanding and buffing! :cheers:
Alright, just beat this poor horse into the dirt a bit more.... This all got me thinking and checking my Dynacorn rear assembly. I have a hard time beliving it's messed up that bad so I am revisiting this to make sure I understand what I am seeing....
First pic is the measurement right behind the rear shock mount, per the drawing.
Second pic is at the rear of the frame rail.
I subtracted 6 inches from the overall dimensions since the thing is resting on the floor. They are 12-9/16" and 9-7/16" respectively. I did that because the drawings seem to assume a 6" datum line below the lowest points. If the front of the frame rail is on the deck and the shock mount area is at 12-9/16", then the rear of the frame rail "should" be somewhere "near" 9-7/16" but it's not even close. :thinking:
I did see a comment on that other forum where someone said that the "D" measurement should be closer to 18" and not 15" but that seems suspect too.
What exactly am I missing? :dunno:
That looks correct. You add 6" to your number and it's right where it should be
Do yourself a favour and cut a 6", 18 13/16ths and 17 11/16ths pieces and put the 6" piece under your rail right where the ghart shows, the centre hole, then take your 17 11/16ths piece and put it where it's supposed to go. Then see if your centre 18 13/16ths one doesn't fit where it's supposed to go. I suspect you've got a tip in the assembly and suspending both ends where they're supposed to be will allow you to remove that and check the centre. Good luck.
Quote from: jimynick on April 02, 2020, 08:28:31 PM
Do yourself a favour and cut a 6", 18 13/16ths and 17 11/16ths pieces and put the 6" piece under your rail right where the ghart shows, the centre hole, then take your 17 11/16ths piece and put it where it's supposed to go. Then see if your centre 18 13/16ths one doesn't fit where it's supposed to go. I suspect you've got a tip in the assembly and suspending both ends where they're supposed to be will allow you to remove that and check the centre. Good luck.
Where are these numbers coming from? I'll admit, the 17-11/16 seems right, especially taking into account other posts saying it should be "about" 18.
I assure you though the assembly is not tipped, if you look at the first pic, you can see the front of the rail flat on the deck. The center is right where it should be, but the rear measuring stick, at 9-7/16 is 6" shorter then the 15-7/16 shown on the diagram. It's just around 2" low, so your measurement of 17-11/16 makes sense. it's late, just got home, I'll verify it's level and check the numbers again.
As always, I appreciate the input. Most everyone here has more experience in this than me so when I ask where the numbers come from, it's not a challenge, rather a genuine question.
Thanks
Here is my chart.
I know everyone is hot on the premade assembly but I kind of like the idea of fitting individual pieces. If there was some flaw somewhere else, I could massage the rails this way or that to get it back where I want it. I'm sure your assembly is spot on though.
Is there another challenger you could compare to yours? If you test fit all your panels, you would be assured of the placement of everything. :alan2cents:
I just sold my a few months back. No regrets though. Got a great price and today is no sellers market.
Quote from: 70 Challenger Lover on April 03, 2020, 06:37:10 AM
Here is my chart.
Well there it is. Crazy how some charts float around for years with incorrect info. Hard to tell what's right and what's wrong. Mine must have a typo since it says 15-7/16" instead of 18. Easy to happen I suppose.
Here is the one I have....
http://www.cuda-challenger.com/cc/index.php?topic=106373.0
Thanks for the response.
If you search the Internet, you can find different years and those measurements vary slightly. I bought mine years ago off eBay but I have no way of knowing just how good the info really is. I'm definitely getting the quarters in place to check floor and rail heights prior to locking them in.
Another measurement you might check is the height off the floor at the very rear of the rail by the spring hanger. My chart shows 18 1/4" which is about 5/16" lower than the measurement behind the shock tower where you measured. The rails appears to slope downward very slightly as they go back and that would account for that slight measurement variance.
I think your assembly is absolutely perfect though.
Quote from: 70 Challenger Lover on April 04, 2020, 08:37:47 AM
If you search the Internet, you can find different years and those measurements vary slightly. I bought mine years ago off eBay but I have no way of knowing just how good the info really is. I'm definitely getting the quarters in place to check floor and rail heights prior to locking them in.
Another measurement you might check is the height off the floor at the very rear of the rail by the spring hanger. My chart shows 18 1/4" which is about 5/16" lower than the measurement behind the shock tower where you measured. The rails appears to slope downward very slightly as they go back and that would account for that slight measurement variance.
I think your assembly is absolutely perfect though.
Yeah I agree the assembly is going to be spot on, but when the measurements don't add up it's cause for pause...
I think anything within a 1/4" either way is probably fine assuming the gaps are good.
I'll get out and double check the measurements at some point.
-=C
Just got one of the quarters on. It's not even fit yet, just slapped on out of the box. I can already see the rails and floor are going to work out nice.
Beautiful, you should sleep better tonight. :yes:
This is part of the truck load of cheap metal I got from Tamraz two years back when they had that 50% off sale. The real reason I'll sleep better is I always wondered if these super inexpensive quarters were factory seconds that weren't gonna fit right! So far, that big purchase paid off huge.
That looks great.
Is the top front corner of the 1/4 sticking out from being flush with the door? My AMD 1/4's did and it required pie cutting wedges out of the flange to allow the panel to curve in sufficiently to make a good fit. Having said that, it looks like you got lucky with your purchase, so good luck with the rest. Hang ALL the tin and check your gaps, THEN and only then, do any welding. :cheers:
No, the top corner seemed fine. The bottom corner didn't drop in all the way but that was my mistake just not trimming out all the old lead well enough. There was zero fitting for this photo. Just tossed it in place. I plan to take my time with both quarters and the tail panel before welding anything. I'll probably put the decklid on too just for good measure.