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I have seen people saying to be weary of removing the sub frame because of alignment issues. Does anyone have a good way of doing it correctly? I am talking about a gen 3.

I want to paint the top of it and the bottom of the floor pans. I was not sure if I can just lower one side all the way and paint it (like if that would be enough room) or if I should just take it all the way out.
 

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I have seen people saying to be weary of removing the sub frame because of alignment issues. Does anyone have a good way of doing it correctly? I am talking about a gen 3.

I want to paint the top of it and the bottom of the floor pans. I was not sure if I can just lower one side all the way and paint it (like if that would be enough room) or if I should just take it all the way out.
I wouldn't sweat it if the fenders are already off and the subframe is bare. Gonna have to re-align anyway. Pretty sure there are alignment holes in both the subframe and body to help out later.

Just spray a bunch of PB blaster on the threads of the subframe's firewall bolts (through the top) and do the best you can getting PB on the rearmost bolts too. Do it for a few days. The issue is that the bolts go in to "cage nuts" and if they are frozen up you can break the cage free, leaving the nut to just spin inside your floor pan.

Also, if you have an impact gun, that may be best vs. a breaker bar.
 

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How does all the control arm bushings and ball joints look? Now would be the time to replace them and rebuild the frontend.

It is not hard at all to remove and install the front subframe. It is also a good time to replace the body bushings.

I have done a few of them, its very easy

Here are a couple of good videos showing how to install and align the subframe. One is for a 70 Nova, and one is for a 67 Firebird which has the same subframe.

 

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I had that issue trying to get the front leaf spring holder out. The cage broke so now I am trying to figure out how to get those bolts out.
The spring holder nuts are not cage nuts, they are J-Nuts. Some guys cut the head off of the bolt and pull the holder out. The problem with that is the bolt extends out the top of the nut and makes it hard to remove the J-Nut to put new ones in. I have been able to drill the bolt out of the nut then put new ones in with new bolts. There are some cheap J-Nuts out there that sometimes strip out when trying to torque the bolt. I have had good luck with the ones from the GM dealer, they don't cost that much.
 

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I think most of the problems arise from not looking or checking things before things get taken apart.
If for example, everything lines up just fine and the subframe is removed but it was shifted one way to have the sheetmetal aligned just right, you then might do what work you want to do and then put the frame back in and then align it using factory specifications and methods only to find out you have issues as it is now not how it was before.
These cars we work on are old and who knows what might have been done to them through the years.

At the mounts at the base of the firewall, there are alignment holes towards the outside of the mounts to where if the car is on level ground, one can take a 5/8" rod and slide it through the alignment hole on the frame mount ear and then should go straight up into a hole at the base of the firewall and both rods should be plumb.

If you get a factory service manual/shop manual it should cover replacing the frame and also include measurements.

Here are the alignment holes and how a rod is inserted to align things:







You might also want to look at the bushings and bolts and see if they need to be replaced.

If you do replace the firewall bushings, you will also probably need to realign the steering column. Here too, look at the coupler/rag joint and see what kind of shape it is in.

Be aware that some frame bushings saying they fit a 74 do not unless you use the 68-72 firewall base spacer bushing.

Jim
 

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Just to throw in my 2 cents, I was also very worried about alignment issues. My approach was to do one side at a time. There's enough room that way - just barely - to slip a brush in and slap some good oil-based paint on the frame. It was one less thing for me to stress over by leaving one side bolted up.
 

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I had that issue trying to get the front leaf spring holder out. The cage broke so now I am trying to figure out how to get those bolts out.
I'm not sure if you were able to resolve this issue... but I had the same problem when I was removing the front spring perches several years ago. Four of the six "J" nuts broke.
If you look at the rear frame rails, you will notice that there are some access slots that are located in the vicinity of each "J" nut for the front spring perches.
I was able to take some large flat head screw drivers and insert them thru these access slots to jab them against the "J" nuts to keep them from turning while I loosened the spring perch bolts. Prior to doing the above, I sprayed the broken "J" nuts with a lot of PB Blaster (thru the same access slots) and let them soak for a couple days.
 

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How does all the control arm bushings and ball joints look? Now would be the time to replace them and rebuild the frontend.

It is not hard at all to remove and install the front subframe. It is also a good time to replace the body bushings.

I have done a few of them, its very easy

Here are a couple of good videos showing how to install and align the subframe. One is for a 70 Nova, and one is for a 67 Firebird which has the same subframe.

https://www.youtube.com/watch?v=GK0T-XTu-4c
https://www.youtube.com/watch?v=bmrrNXEbPKg
I did it as shown in the video. Matter of fact it was so easy setting the engine and tranny in and rolling it right in. You can see some of it in my build link. All the measurements seemed easy to get to. I'm not worried, I'll just have to go through the painful fender alignment but I had to strip it anyway.
 
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