1972 Demon - tire and wheel question

[1971 Duster]

Hey Guys,

Need your help.

I just picked up a '72 Demon - it needs a lot of TLC, but has potential.

Got some questions regarding backspacing and bolt pattern for wheels and tires as this car has been backhalfed and narrowed in the rear. It's a 340-4spd.

The current rear tires are 295/50-15 and need to be replaced. Also, the 295 profile is not wide enough. I have 17 inches from the frame to the outside of the rear fender - so I have pretty good space to mount wide tires.

However, I'm not sure about the bolt pattern and backspacing I should use since the car has been backhalfed.

When I measure from the top of the rear fender lip to the ground = 27 inches. Granted I may be able to raise the rear of the car higher - not sure. Keep in mind, having a back-half car is all new to me, so thanks for your patience with my questions.

Left side rear tire

Right side rear tire

Back Half

Pic of Car

 

[72bluNblu]

Uhhh, hate to rain on your parade, but the car hasn't been back halved, not correctly. Those are the stock frame rails!!! They appear to have been moved in, and your measurements would support that, but that's not the same as back halving. The wheel tubs, and all the supporting inner frame work, appear to have been removed. I don't know what's holding the back half of the car together, but I would sure want to find out if I were you. Looks like a hatchet job for sure, no rear supports for the frame, quarters, or rear deck are visible in those pictures. And since I don't see a cage, there can't be much holding your car together. The original rear frame rails get a lot of strength from being tied into the rest of the car, and yours do not appear to be.

The rear axle appears to be an 8 3/4, and in 1972 that might even be the stock 8 3/4 back there. Won't be able to tell you anything about bolt pattern or backspacing without measurements. If it's stock, the bolt pattern would be 5x4".

 

[1971 Duster]

Thanks for the feedback; it is disappointing to hear "it's a hatchet job". I'll learn more about the car as we start to fix things.

 

[torkflight]

can I ask what you paid for that car?

 

[OldmanRick]

The trunk area looks decent, but would love to see more extensive pics of the underside?

The pic below looks like the back end of some type of ladder/traction type bar? Seems too low, but not sure?

Don't take any comments personal, we're here to help. But if that means letting you know something is not right, it's not to be harsh, it's just because we care!
View attachment aaaa.jpg

 

[72bluNblu]

I do apologize for the hatchet job comment, that was probably harsher than I needed to be, but that car isn't right.

So, this is your car

Pay special attention to the area under the hinges. The hinges are not tied into anything, they just "float" under the rear panel. That's NOT good. Also, look at how the inner rail for the trunk is buckled in the middle...

Here's a stock car.

Notice how the hinges are tied into the wheel tubs? That doesn't just support the hinges, which is important because your entire rear deck is going to flex when you open and close your trunk. More importantly, they tie the inner structure of the car, which supports the roof and rear deck, to the wheel tubs and ultimately the frame rails.

Also notice the bracing on the outside of the hinges? That is the inner roof structure continuing down and tying into the wheel tub. Again, that structure supports the rear corners of the roof and the rear deck. You don't have anything there!!! So, where is the inner structure for the back of roof tied in? Is it just floating above the wheel tubs?

Here's another car that has been back halved, courtesy of HemiDenny's thread.

Notice how he tied those inner structures into his tubs? That's the way it should be done.

And this is what that back half looks like...

Now, HemiDenny is the man and does incredible work, above and beyond. So all back half's don't have to look that good to be functional. But, they should look a lot more like that than what I see in the pictures you posted. There has to be some serious additional bracing present to make the car even as strong as it was before, let alone strong enough to bother having tires that wide. And I don't see anything like that on your car. And the factory rails have no place being back there if they aren't welded into the floor and inner structures, they were not meant to stand alone, they're part of a unibody. Look at the rails under your car- there's nothing but air above them. Those rails are not meant to work like that.

Unless there is a lot more structure under there that I'm not seeing, I would be concerned about the structural integrity of the car.

 

[1971 Duster]

The trunk area looks decent, but would love to see more extensive pics of the underside?



The pic below looks like the back end of some type of ladder/traction type bar? Seems too low, but not sure?

Don't take any comments personal, we're here to help. But if that means letting you know something is not right, it's not to be harsh, it's just because we care!
View attachment 1714771870

Hi OldmanRick and Others,

Thanks for taking the time to read through my post. I'm new to Mopar, but not new to classics. I'm in the learning stage and wanted to get some feedback from other vets on my options based on their experience with these custom add ons.

This is quite an interesting car. It is a 72 Demon confirmed by VIN. It has a '71 340 with J heads and the a833 4 spd. Motor and Transmission is excellent. Car is from Alabama and I picked up near Houston from an older gentleman.

I understand it's not backhalfed and am not concerned about it. I don't know why they went through all the trouble to put in the wide wheel wells, but not complete the backhalf; maybe they ran out of time or money. The seller did not have that information.

The car is not mint; it needs a complete make over and there is only 2 drag seats - the rest of the interior is bare; thankfully there is only a few rust spots on the back quarters. Floor pans and trunk are good. The rest of the car is straight, but it shows time. I was able to trade my '81 z28 Camaro for this car and my z28 was also a project car, much like this one. My z28 was only worth $3.5k in today's market. So, I don't have a lot of money in the car and was comfortable with the reality of all the TLC the Demon will require. I just love the fact that the majority of the car is there and it's not a rust bucket. I love this car; it has so much potential. My goal is to restore it as a street/strip car. I'm in a good position to restore it and correct any bad ideas.

 

[2 Darts]

The original wheels and tires in a 72 Demon 340 were E70-14 mounted on 5½x14 rims with a 4¼ back space, 4" bolt circle diameter. When components get switched around, it's tough to say what is on the car now.

IMO, the reason to tub the rear wheel wells is to run slicks. A stock, straight 72 Demon or Duster can take 235/60-15 tires on 7" wide rims with a 4¼ back space. Some FABO members report being able to get a larger wheel tire combination on the rear axle without tubs, spring relocation or rolling the fender under.

 

[72bluNblu]

I understand it's not backhalfed and am not concerned about it. I don't know why they went through all the trouble to put in the wide wheel wells, but not complete the backhalf; maybe they ran out of time or money. The seller did not have that information.

I would be concerned. That 17" measurement indicates the stock rails have indeed been moved, if you measured from where I think you measured. And so does the amount of room around the 295's you have mounted. I have 295's on my Duster, and there is not even close that much room to the frame, springs, or quarter. They are quite obviously the biggest tires you can fit on my car, where as looking your pictures there's still plenty of room for more tire.

And, as I already pointed out, you're missing a lot of structural components that will have to either be repaired or replaced. I would strip the back end of that car down and inspect everything that's there very carefully before I went any further.

The original wheels and tires in a 72 Demon 340 were E70-14 mounted on 5½x14 rims with a 4¼ back space, 4" bolt circle diameter. When components get switched around, it's tough to say what is on the car now.

IMO, the reason to tub the rear wheel wells is to run slicks. A stock, straight 72 Demon or Duster can take 235/60-15 tires on 7" wide rims with a 4¼ back space. Some FABO members report being able to get a larger wheel tire combination on the rear axle without tubs, spring relocation or rolling the fender under.

You can fit 275's on a bone stock Duster or Demon without moving anything at all. 15x8, 4.5" backspace, 275/60/15's with an 8 3/4. No offsets, relocations, rolling or trimming needed.

I have 295/35/18's on mine, I only have a 1/2" spring offset and a trim on the quarter lips. Wheel tubs are stock.

 

[1971 Duster]

Hey Guys,

Just getting around to reading everyone's feedback.

72blu - the pics and commentary you posted are very helpful - thank you for being so specific and detail oriented.

The good news is that we can add additional structural integrity. My comment about not being concerned is the fact that these issues can be corrected, nothing on this car is too far gone.

I'm taking the car in this week to a race shop who will be inspecting all the funky rear end stuff. After that I will take the car to my body guy who also does a lot of fab work for race cars. I'm sure he'll laugh when he sees the work on the car and then pat me on the back saying "don't worry - I'll draw up some ideas to fix this mess".

Either way, I'm jazzed about the car. I know with a little time and money we'll get it right and have a safe car.

Will keep you guys updated when the fun begins.

 

[Dartn440]

I agree with everything above and would add this. The right rear tire has an exceptionally odd shape and wear pattern compared with driver's side. Couple that with what everyone has already mentioned and I would venture to say there is something really wrong there. I think you agree. Only reason I make mention is that the energy that bent the metal in one place stressed or bent something elsewhere. Good luck. Starting a 72 myself

 

[72bluNblu]

I'm taking the car in this week to a race shop who will be inspecting all the funky rear end stuff. After that I will take the car to my body guy who also does a lot of fab work for race cars. I'm sure he'll laugh when he sees the work on the car and then pat me on the back saying "don't worry - I'll draw up some ideas to fix this mess".

Either way, I'm jazzed about the car. I know with a little time and money we'll get it right and have a safe car.

Will keep you guys updated when the fun begins.

Sounds like a good plan to me, good luck with the build!:thumbup:

 

[hemi135]

Hi OldmanRick and Others,

Thanks for taking the time to read through my post. I'm new to Mopar, but not new to classics. I'm in the learning stage and wanted to get some feedback from other vets on my options based on their experience with these custom add ons.

This is quite an interesting car. It is a 72 Demon confirmed by VIN. It has a '71 340 with J heads and the a833 4 spd. Motor and Transmission is excellent. Car is from Alabama and I picked up near Houston from an older gentleman.

I understand it's not backhalfed and am not concerned about it. I don't know why they went through all the trouble to put in the wide wheel wells, but not complete the backhalf; maybe they ran out of time or money. The seller did not have that information.

The car is not mint; it needs a complete make over and there is only 2 drag seats - the rest of the interior is bare; thankfully there is only a few rust spots on the back quarters. Floor pans and trunk are good. The rest of the car is straight, but it shows time. I was able to trade my '81 z28 Camaro for this car and my z28 was also a project car, much like this one. My z28 was only worth $3.5k in today's market. So, I don't have a lot of money in the car and was comfortable with the reality of all the TLC the Demon will require. I just love the fact that the majority of the car is there and it's not a rust bucket. I love this car; it has so much potential. My goal is to restore it as a street/strip car. I'm in a good position to restore it and correct any bad ideas.

If you ever consider selling off that 340 and 4spd let me know. I'm looking for the whole drivetrain for my 72 Duster 340 4spd roller.....Thanks good luck with the Demon.