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Discussion Starter #1 (Edited)
I am looking to wrap up my frame alignment in the hopes that my motor will soon be ready to be installed. As you know, it's a lot easier moving the frame minus the motor and trans! I have gotten things as square as I can and verified some diagonals to the rear end. Can not get it completely square. Front is within 1/8" measured from front gage hole to front of clip. Frame to rear axel housing is within 1/2" but when I try to compensate, it makes the front squareness worse. I am looking to find a happy medium.

Then I came across this diagram and am looking to see how my dimensions relate and if this is the proper way to go about it. My main critical figures seem to be "F" and "G"





My main question is, which hole is the mid car "gage" hole? Is it the round hole to the right hand side, forward of that elongated hole, inside of the leaf spring?



I was too beat last night to get under the car to measure. Will get under there next chance I get.

There are also some reference dimensions to the rear shackle area but no way can I get a straight line with the tape...


not sure what this hole is for...drainage?
 

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My main question is, which hole is the mid car "gage" hole? Is it the round hole to the right hand side, forward of that elongated hole, inside of the leaf spring?

not sure what this hole is for...drainage?
Q1: Hole on the right is the gauge hole
Q2: Yes, drainage

Today is the day for subframe questions. Posted earlier by me:

From Chris Alston's Chassisworks:

Aligning the Subframe
OEM subframes are easily aligned on the assembly line by using fixtures and two locator pins. Without the fixtures used by Chevrolet, the locator pins only serve as a rough guide and the subframe will still need to be properly aligned. The method utilized in this manual will align the subframe to the rear suspension by eliminating the potential alignment misgivings caused by distortion of the body due to accidents or body sag. This ensures the front and rear suspension is aligned to each other.

To align the subframe, first install these items on both the driver and passenger side:
 Upper control arms
 Lower control arms
 Knuckles

Next, raise the knuckle to the approximate ride height (hub centerline even with bottom of chassis main rail), and set to zero toe. Zero toe is simply rotating the knuckle until the hub face is square with the chassis. This can be done by clamping a 2’ length of angle iron to the hub, and measuring from each end to a flat area on the chassis. When the measurements from both sides are equal, the hub is square.

To ensure accuracy also raise the rear axle to the approximate right height. Now, check the wheelbase at both sides, and move the subframe until the wheelbase is +/- 1/4” of factory specs. If the subframe is difficult to move, slightly loosen the mounting bolts. Ultimately, fender placement and personal preference may dictate where the spindle centerline will be.

Once the wheelbase is satisfactory, it is time to check squareness between the body and subframe. Proper datums to use are the lower control arm bolt heads and either the leaf spring locating pins or the alignment holes located on the rear frame rails just ahead of the front spring mount. Measure diagonally between these points and adjust the subframe until both measurements are within 1/8”. The subframe can be adjusted slightly by a firm hit with the palm of your hand or a rubber mallet. Once the measurements are square, re-check the wheelbase. If the wheelbase remains within tolerance, tighten the subframe mounting bolts. If not, repeat the alignment process.
 

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If using the suspended parts for alignment keep in mind all of them are mounted in a flexable bushing and have variences. Using the holes the factory used to align the subframe to the body and then checking the alignment to the points you found in the Fisher Manual is the most accurate method.
 

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If using the suspended parts for alignment keep in mind all of them are mounted in a flexable bushing and have variences. Using the holes the factory used to align the subframe to the body and then checking the alignment to the points you found in the Fisher Manual is the most accurate method.
Time to re-read the last part... :yes: Wheelbase must be set first or you will be chasing measurements. Then square the frame to the rear.

Once the wheelbase is satisfactory, it is time to check squareness between the body and subframe. Proper datums to use are the lower control arm bolt heads and either the leaf spring locating pins or the alignment holes located on the rear frame rails just ahead of the front spring mount. Measure diagonally between these points and adjust the subframe until both measurements are within 1/8”. The subframe can be adjusted slightly by a firm hit with the palm of your hand or a rubber mallet. Once the measurements are square, re-check the wheelbase. If the wheelbase remains within tolerance, tighten the subframe mounting bolts. If not, repeat the alignment process.
 

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Discussion Starter #6
Took a mental health day to catch up on some work on the car. Was planning on finishing up the alignment procedure and realized that I should probably get my tie rods and wheel alignment done first. Am I on the right track here? I have the front end in the ballpark and everything torqued to spec. Have plenty of room for adjustment on the tie rods and am figuring I should get that set first, before the actual subframe alignment, correct? Otherwise it seems I may be measuring to steering hubs that are not in their final position.

I'll do some searching for general front end alignment procedures but if anyone has some quick tips, I'll be happy to hear about them. wondering if I can get things close with the car where it is....up in the air and no front wheels.

Also, should I hold off on inserting any cotter pins? or are the tie rod ends done at this point and I can pin them up. thx.
 

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Discussion Starter #7
Well, I finally got around to tending to my subframe alignment and ran into some issues. Here's what happened....

First I set my wheelbase at 111". So far so good. This was done with my steering box perfectly centered and the rotors totally aligned and parallel.

I noticed that the drives side gage hole alignment was off. In order to get it in vertical alignment I needed to shift the subframe back 1/2" on the drivers side. This gave me a 110 1/2" wheel base on the drivers side and a 111" wb at the passenger side (both front gage holes totally aligned vertically).

My first question is: which is more important at this time....gage hole alignment OR wheel base? It seems if I keep my front gage holes aligned, I could have some wiggle room when I redo the whole rear suspension...maybe get it rearward a drop.

I crossreferenced the dimensions per the chassis manual. The F dimension is supposed to be 79 1/16" and I have 78 1/2". The G dimension is supposed to be 69" and I have 681/2".

I'm close but something seems off. Any idea of where to start looking or since things are "in the ballpark" I was thinking of dropping in the engine and trans (once I get my new Wright pump), then getting the front sheetmetal on and take it from there.

thanks
 

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Once the wheelbase is satisfactory, it is time to check squareness between the body and subframe. Proper datums to use are the lower control arm bolt heads and either the leaf spring locating pins or the alignment holes located on the rear frame rails just ahead of the front spring mount. Measure diagonally between these points and adjust the subframe until both measurements are within 1/8”. The subframe can be adjusted slightly by a firm hit with the palm of your hand or a rubber mallet. Once the measurements are square, re-check the wheelbase. If the wheelbase remains within tolerance, tighten the subframe mounting bolts. If not, repeat the alignment process.
Wheelbase gets you close. But measuring diagonally between the lower control arm bolt heads and the rear alignment holes takes priority. Make sure you do this in a "X" pattern, both lengths should be the same.

Check the wheelbase after all this to do a "sanity check".

Don't fret too much about the factory book measurements F and G. They had special tooling to align the subframe - you do not!
 

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When I installed my frame, I made sure dimensions G and F for correct on both the left and right side. For the front, I only used the gauge holes on the frame. If your front frame is straight, it will will have everything lined up.

I was able to stick a ratchet exenstion bar up through the front alignment holes into the body alignment holes just to see how close it was. It was very close.
 

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I installed my frame recently and measured my wheelbase and it comes up to 111.5" I have no more room to move the frame back is this going to be a problem?
 
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