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Slamming a 620..


Mathius

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So I'm new to the forum. But have been looking threw these pages for years.

I'm looking for some info on dropping the rear of my truck.

The truck is a 77' 620.

I've had a 720, and a few Hardbody's over the years.

Are these the same as far as drop blocks? 3 inch is all I can go before banging frame, or can I do a 4 inch?

I'm also looking for info on c-notching this thing. Weather it'll have to be a custom notch, or........

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620/720 frames are similar, D21 are different.

 

Three inch it is, but stiffen the leaf spring or it will bang and ride like shit. The 720 4x4 springs are stiffer and flatter so you may not need as much as a 3: block.

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One thing to consider, coming from the point of view of a full time fabricator, is the fit of the notch section.

 

The pre-fab notch kits you can buy for a Chevy truck are usually bolted in and then welded. Some of them even come with precision cut guides. This is important. A poorly fit cut (like one you may do with a torch or plasma cutter) can leave gaps that need to be filled with weld. When you weld gaps, the metal shrinks. If you want the frame to stay straight, there are a few ways you could do it.

 

1 - Using 1/4" thick steel, either a pipe section or bent steel flat stock, scribe the cut line and cut with a sawzall or a cutoff wheel on an angle grinder and then clean the cut to the scribe line, but no further. Then the piece you're welding in should fit perfectly.

 

2 - Make your own prefab notch with a flange welded on extending a few inches on either side, just like the Chevy notch kits. You should still try to fit the piece pretty closely to the cut.

 

3 - Use a solid piece of pipe, again, with a precision cut, and weld it in still round, then cut the bottom section off.

 

4 - You could even cut the entire section of frame out and weld in a square tube section above the frame rail. Or better yet, weld the section in first then cut out the old section.

 

Whatever way you decide to go, you should have some sort of reinforcement around the notch, either in the form of a flange or an extension to the top of the frame. As I mentioned in the wide body 620 thread, you should start this project only after you've put the truck up on jack stands and leveled it off. I would even drop a plumb bob to the concrete and mark the key areas on the floor. Take measurements to the floor too and write them down (either on the floor or on the frame). After all of this, make the cut, measure it, tack it, measure again, weld it, measure again.

 

This is a fun project. Good luck.

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I don't know if the way I did mine was the correct way, but I welded in a piece of frame above the existing frame, then I cut the circle notch out of the lower frame piece and then welded in the section of pipe, then I put plates on both sides with holes in them so I could simulate a spot welds.

 

The frame piece I welded into place over the existing frame.

DSCN1507.jpg

 

The outside pass side

DSCN1509.jpg

 

The inside driver side

DSCN1514.jpg

 

The hole I had to cut into the bed because of the notch.

DSCN1516.jpg

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BTW, I did some other stuff and even lowered it more, if the frame was not notched the frame would be resting on the axle now.

001.jpg

 

Keep in mind that other stuff will start dragging the ground, the cross member holding the carrier and e-brake hardware, if you don't re-index the torsion bars the ends will drag on the ground, the front ball joints will bind in their sockets if you have ball joints, the tension rods will hit the steering gear and idler arm, the front tension rod mounts on the frame/chassis will hit on just about everything, these are all issues that have to be addressed and more.

 

This is what I did for the rear shackle, I also used the 720 4wd leafs.

DSCN2106.JPG

 

DSCN2108.JPG

 

Then I used 1969-73 Datsun  510 wagon leaf/shock plates so the lower shock mounts would not drag on the ground if I got a flat, I am using 2 inch drop blocks.

DSCN2208.JPG

 

It's a lot of work lowering a vehicle, the front was lowered 6 inches, and the back was lowered 7 inches.

DSCN3449.JPG

 

 

 

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All really good info.

Thanx everybody.

Thankfully I can weld a bit.

I'm no expert.

But I can stick 2 pieces together, and I have friends with nice 220v gas units.. 

 

I found these on Ebay for $50.

I was thinking I could save some work, and just weld these in.

1/4" steel.

10" wide. By 4, 3/4" tall with a 5, 1/2" inside width.

20190919_010936_zps9zdmnfi6.jpg

Do you folks think they would work??

I haven't had a chance to crawl under the truck for measurements. 

But I'm gonna pull the box off one of these days, and I'll start tossing some build pictures around.

 

These are from when I bought it.

20190810_163451_zpshespmllx.jpg

20190810_111622_zpstmjtfdzg.jpg

It has a rebuilt L20B in it, and runs like new. It does drive as well, but needs brakes.

It was actually about to be crushed..

Still not sure why the PO abandoned the project?

20190810_163508_zpssk2xorll.jpg

 

My plan is to build a "Shako-Rat" pickup..

It's no resto, so it ain't gonna be pretty!

I'm gonna keep the details quiet till I get going on it.. lol

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10 hours ago, wayno said:

I don't know if the way I did mine was the correct way, but I welded in a piece of frame above the existing frame, then I cut the circle notch out of the lower frame piece and then welded in the section of pipe, then I put plates on both sides with holes in them so I could simulate a spot welds.

 

The frame piece I welded into place over the existing frame.

DSCN1507.jpg

 

The outside pass side

DSCN1509.jpg

 

The inside driver side

DSCN1514.jpg

 

The hole I had to cut into the bed because of the notch.

DSCN1516.jpg

That is a heavy duty looking C-notch!

The fishplating, and size are impressive. Theres no doubt that its strong.. lol

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I was thinking of boxing it as well. If for nothing more than piece of mind. I can get a 6" cutoff of Sched 40 pipe, and some 1/4" plate easy enough to rig my own setup.. 

The only reason I want to do the notch is for hauling stuff. But I'm still feeling a 4" block.

It's basically gonna be a parts hauler, and junk runner.

But I have a certain look in my head, and don't want to compromise. 

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