[Schroeder]

I picked up PTFBs subframe connectors (sfc's) and solid body bushings. I will be welding the sfcs in and need to make sure my body is straight. Has anyone done this without the whole front clip off? Ill I be able to loosen the subframe to body bolts and hammer or pry the subframe to where I want it? I think its slightly misaligned at thr moment.

[Rick Jones]

If you have a second gen. Firebird, yes you can. I put in the PTFB solid bushings on my '75 with the car completely assembled. I replaced one-at-a-time and used a floor jack and a piece of wood on the underside body of the car to make enough room to remove the old one and replace it. Install all loosely and you can align the subframe once all are in.

If you install them using the smaller bushing on top (positions the subframe 1/2" closer to the body, thus lowering the front end a bit) you will also need to loosen the bushings attaching the radiator support to the subframe too.

Once you get all four replaced, there are alignment holes on the subframe on the two front mounting points that should align with the same diameter hole in the body of the car. IIRC, a 3/8" socket extension is about the right size to check for alignment.

Rick

[Schroeder]

I always wondered if that small hole by the mounting bushing could be used to pry the body into proper alignment. I am doing standard mounting with the thick bushing on top by the way. Do u somhow wiggle it into alignment with the car on jacks? Seems like this will be hard to do with the car assembled. Im still not entirely sure how to ACCURATELY measure to make sure the frame is straight. Some pals on another forum explained it to me long ago. Ill have to go look that up. I remember being skeptical though.

[Schroeder]

Rixk, so u just align the body by getting those holes straight (concentric) and call it good?

[Schroeder]

?? Is this how u guys do it? Probably have to loosen the fenders and everything wont I?

[Rick Jones]

Schroeder, that is how I aligned both of my cars and they go down the highway like new cars (all new suspension bushings, ball joints, etc. too, though). The fenders are not directly connected to the subframe. IIRC, the only place they are somewhat connected is the fender wells, which are connected to the subframe and the fenders. You may need to loosen the bolts for the fender wells connecting to the subframe for adjustment. I can't imagine your subframe could be that far off, though.

thanks, Rick

[Schroeder]

Yeah that would be the route I was thinking. Ill give it a try. Did u do any other measuring on the car to ensure that it was straight?

My fenders and such seem all screwed up as far as alignment. The hood too. The shimming shows it as one side will have a inch of shim in a spot and the mirrored spot on the other side will have an 1/8". This occurred after I took the subframe off a couple yrs ago. It seems to drive straight though. I never thought the measurement techniques I was given to varify the sub frames straightness were that good.

[Rick Jones]

Schroeder, I didn't do any other measuring. After I replaced the subframe bushings, I rechecked the front end alignment (Herb Adams method) and have been running the car ever since that way. I even had the alignment specs checked at a shop and they were remarkably close. I set the caster by adding as many shims as I could to the rear bolts first. Then set the camber using an old school protracter level at -0.5 degrees and then checked the toe using a 6' level against the front tire(raised high enough to be above the bulge in the tire) and compared the level to the side of the car. I got this technique from Herb Adam's Chassis Engineering book.

The results from the shop were -.56/-.73 camber, just over 3/just under 3 caster and zero toe.

I think if you have the alignment checked/adjusted after you install the new bushings, you will be all set.

Thanks, Rick

[Rob B]

Fender/hood alignment is mainly related to the core support and its alignment to the subframe, not to the subframe itself.

[Doug1]

Originally Posted by Schroeder

Rixk, so u just align the body by getting those holes straight (concentric) and call it good?

I would not use the above method if you want to make sure you are square before welding.

I've done this a number of times now and within the last year, installed subframe connectors and solid body bushing on a Trans Am I built, though I used DSE connectors and bushings. The rest of my front suspension is from Dave at PTFB. The proper way to do this is to follow the factory manual to measure from the points in the frame for just this purpose. You measure from holes in the rear frame rails to holes on the opposite side front rails. I would suggest doing this before welding it in. The factory manual makes it very clear how to easily align the front sub-frame to the uni-body frame but the measuring points are past the wheels on both the front and the back in order to make sure it is square. All you need is a tape measure and a buddy to hold the other end. It takes less than 5 minutes.

Any sort of method to align the frame that uses alignment marks inside of the box formed by the 4 wheels is not going to be accurate. You might get lucky but I wouldn't count on it. Its much easier to make sure it is square before welding.

[Schroeder]

I do not understand the books method. The measuring points are not on the same plane so it is not easy yo measure from one to the other without plumb bobs and such. Point 1 may be 8" from the floor while the point 2 may be 15" off the floor with crap hanging off the car in between the two points. Am I correct? Thats y ive found the manuals method hard to implement

[Schroeder]

Just read the manual again. They do suggest using plumb bobs. Is my manual missing a page though? Mine does not give measurements for fbodys. G and a bodies are outlined. Heres what I see. Anyone got the alignment specs for fbodys? Most of the other sites suggest using the alignment holes too.

[Fishin2Deep4U]

On my f-body installs, I use a bolt through the lower control arm mount that has a center drilled hole. This allows my plumb bob to hang from the center of the hole.

I usually measure back from corner to corner using the body alignment holes and the rear suspension holes using a bolt or checking rod that has been turned to a point. This gives me a couple points of reference. I get it to within a 1/32" in most cases and call it good.

Then I burn a couple hard tacks into the connector and subframe until I get it torqued.

Then I burn it in good.

On the 68 I ended up doing the front section as a bolt in until the car is painted and the sub is powder coated. Then I'll burn it in as well.

My preferred method is to get the car leveled both directions and have plumb bobs hang to the floor and mark some painters tape on the floor. I string the plumb bobs with 20# or 30# fishing line and hang a fraction of an inch above the tape. Then I can lower the plumb bob onto the tape, make an impression and have a pinpoint to measure to. Far easier to measure to and easy to pull up the tape and try again if needed.

Dave

[Schroeder]

Good method dave. I guess ill have to do this. How do u guys go about moving the subframe around with all the weight on it? My car is fully assembles. I loosened the wheel wells from the fenders and will have to loosen the core support to subframe bolts. Then if I find that the frame is out of line, which im sure it is, what do I do to move it? A sledge?prying on something? I should have done a better job at this when the csr was apart and nothing was on the subframe.

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[Fishin2Deep4U]

It's not all that hard to get the weight off. You can jack up the car and support under the pinch welds. I have seen some guys use a block of wood under a jack stand under the rocker as well. But I don't trust that method.

Loosen the core support as you mentioned. And use a jack under the subframe. Take off a little weight and it'll move pretty easy. You can use rachet straps to pull it in line and help hold it there.

I don't like to bang on parts like this, but a heavy sledge on a piece of wood can get things moving.

Dave

[Schroeder]

Ratchet strap? So u support the car body, connect one end of s ratchet strap somewhere on the subframe, connect the other end to a tree or whatever, and then tighten the strap up to pull snd move the subframe? Conversely you could also jack up the sub frame and connect your ratchet strap to the rear end and pull on it if say the body had to move backwards realative to the subframe. Do I have this correct?

And really, do u have to support anything? Cant u just loosen the subframe to body bolts and pull on it like that with your ratchet straps?

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[Fishin2Deep4U]

That's correct.

A trucks hitch is a handy anchor point in the front. Use the frame holes in the rear or the axle. I prefer hard mounting points so I am not fighting something springing back. You don't have to support the car, but you will be fighting the friction of that weight trying to get things to move.

There's more than one way to do this job. The key is careful repeatable measurements and attention to detail.

Dave

[Schroeder]

Yea. Detail is something I shoulda watched more the first time around. I dont have much wiggle room for pulling. I already have the car lifted. I have it sitting on the blocks of wood so its supported by its on weight for the SFC install as I will be welding them in. Ill pry pull it with ratchet straps since my pulls will have to be very small and controlled to avoid pulling the car off the blocks.





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[Schroeder]

I measured the "H" dimension shown in the picture and in 5/8" short! Is there even that much adjustment in these holes? Also, should the "H" and "I" dimension on the opposite side be checked? They r not on the list of measurements to check but I think it would only make sense.




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[Schroeder]

Got my dimensions within an 1/8". I called it good enough. Any thoughts?