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Who can identify this front suspension??


Thehoffinator

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Remember this is a California truck (supposedly a '73) with a previous Buick engine swap.

 

Does the engine tag or door tag begin PL620 XXX,XXX or HL620XXX,XXX

 

 

 

 

The brakes are 720 but the spindle could be a '78-'79 620 as these hubs will fit the later calipers and rotors.

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The lower control arm where it mounts to the frame is about 1/2" wider on ball joint trucks. You actually can use the ball joint arms on the non ball joint frame. Can you see if there's a spacer between the lower control arm and the frame? Perhaps they might have put the spacer in the front or rear of the frame, or they could have done half on either side. Just curious. 

 

As for the upper shock tower, I wouldn't doubt that someone may have been able to modify the stock one or even cut off one from a ball joint truck and installed it (a lot of work, I'm sure). 

 

Or, as mentioned early on, the previous owner might have simply tried to bolt on the ball joint suspension, and the alignment is now really off. 

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Datzenmike - The door tag shows PL620, and shows 7/73 On the tag. Same VIN in the engine bay and on the frame

 

2wheel-lee - I just tried to look with it on the ground and I can't get under there far enough to check for spacers without putting it up in the air. You may be on to something though, the lower control arms and the hubs/calipers all have the same orange paint in some spots, indicative of a junkyard. Thinking these parts all came off of a truck and fit to this one. I'll be working on it tomorrow, I can verify if there are any spacers on it

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That tower doesn't look twisted back much to me in the photo below, but it looks like the frame has been hot at some point, also the lower back shock tower connection to the frame appears to me modified, no shock tower I ever seen looks like this one where it connects to the frame, but I don't really know much about the 620 chassis either.

20170817_190453_zpsfc1i5gn6.jpg

To know for sure I would have to see this in person, but that shock tower also appears to have the large upper control arm mount bolts, I believe that shock tower was welded onto that earlier frame, it likely has the first 720 version of the vented rotor disc brakes, but it could have the late 720/early hardbody disc brakes also, it's hard to tell.

The twist in the shock tower is very important, if it doesn't have any you will have to change them upper control arms to get the castor set close to stock, as for the negative camber, you will likely have to extend the upper control arms to make it align-able.

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What I see is the difference in paint quality. The paint on the upper control arm looks so much newer than the paint on the rest of the frame and suspension.

 

Hopefully whomever did the mods, knew what they were doing. There are a lot of potential problems to deal with during that kind of work.

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Thank you all for the responses and help with this. I believe I finally figured this out.

 

Here's a question, on the 620s, are the motor mounts and shock tower all one piece? Mine are all one piece.

 

Also, these do have the twist I found in photos of the 720 suspension, so I looked closer..and closer at the welds. There are very subtle differences between both sides as far as the welds go. They look good, but you can see a slight gap in the drivers side front motor mount pedestal where it is welded to the frame, that is not there on the other side. There is a bent corner as well that was there before welding, because the weld goes right over it. Not factory like that. Also, I found some grind marks on the passenger side mount where it rolls over the frame rail. All of this work seems to have been done many many years ago. So, I guess somebody adapted the towers and motor mount pedestals from a 720 frame and welded it onto the 620 frame, and is using factory 720 components. Seems effective to me, the alignment doesnt seem to be far off. I can drive it and it tracks straight, but I know the toe is slightly off (I eyeballed it)

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You said a Buick engine was in it so maybe the welding was to put the correct engine mount locations back to stock.

 

 

20170817_190453_zpsfc1i5gn6.jpg

 you will likely have to extend the upper control arms to make it align-able.

 

wano, if that shock tower was spaced outward and welded back on, that would effectively lengthen the upper control arm, wouldn't it?

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 the alignment doesnt seem to be far off. I can drive it and it tracks straight, but I know the toe is slightly off (I eyeballed it)

 

You can use a tape measure to check the toe, roll the truck back to front a couple feet to get the wheels as reasonably straight then measure the distance from the back of the wheel and the front of the wheel and that'll be the toe ( in or out )

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wano, if that shock tower was spaced outward and welded back on, that would effectively lengthen the upper control arm, wouldn't it?

 

If the 720 control arms are long enough the way it is then that is likely what was done, but as I have said already, I do not know much about the 620 frame/chassis, I always assumed the early 620 chassis was like the late 521 chassis, but they have differences.

He says it has twist in the shock tower so that gets the castor where it needs to be, the 720 control arms only have to be 5/8ths of an inch longer to work on a 1971 Datsun 521 to convert over to front disc brakes using late 620 lower control arms/tension rods and the ball joint/disc brake assemblies, but 5/8ths is right on the edge, if any shorter than that one would likely have a slight amount negative camber, but not sure if one could tell.

Also the lower one drops it, the longer the upper control arm needs to be, but if one uses drop spindles, then the upper control arm remains closer to stock configuration.

It appears that this conversion may have been done by someone that actually cared how it handled.

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Lower control arm on the ball joint 78-'79 were a different length than the earlier king pin trucks. The attachment point on the frame is located differently. If you swap the arms onto a king pin truck the camber is insanely wrong. If it was possible to do this somehow someone would have figured it out by now.... they haven't.

Correct!

Back in the late 80's I picked up a 74 620 for $250 Set up for a  sbc....and the only thing missing...is the motor, everything else, including all the hardware came with it.

Anyway...I dumped in a 283 and it was undrivable, at the time I found a whole front end off a 79 620 for like $50 and decided to swap it in, the major culprit (to my recollection) were the bottom a arms, so I had a buddy with a tig welder "adjust" them to size.....it worked.

Only god knows what happened to the truck by now....it was a neat peace of socal history.

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