521 to 620 frame

[BACKWOODS DAVE]

I have a 521 truck and I was trying to hunt down how close the y are to 620 frames. So I decided to just ask. Will a 521 body bolt on a 620 frame? I know someone on here has to have this answer.

[BEEBANI]

Well, your answer is yes and no.....the bodies of the 2 trucks are a little different width and length, so the body mounts may not line up perfectly. I had a 521 frame sitting here when I first started my 620 project and took measurements off of both of them, and they are very similiar. The biggest difference is the carrier bearing x-member; most (if not all) 521's had a 1-piece driveshaft so there was no need for a carrier bearing.

 

I'm sure you can do it with very little modifications. Can you access both rigs to do some measurements? If so, that would be your best bet. I'm assuming you're looking to put your 521 on a disc brake 620 frame?

[BACARDI_DWB]

I have a carrier bearing/ 2 peice driveshaft in my 70 datsun 521. am i lucky?

[Gensaiken]

I have a carrier bearing/ 2 peice driveshaft in my 70 datsun 521. am i lucky?

 

I was about to say this as well. My 521 was made in 70 and I believe it also has a two piece driveshaft.

[datzenmike]

The cab looks like it will be close. There are 6 bolts holding it on.

 

LOOKING AT THE 620 FRAME MOUNT HOLES:

CAB: The pair at the front on each side of the rad are basically the same distance apart as the 521, so that's good.

 

The middle pair by your toes, are almost an inch closer to the front ones AND 2.5" closer side to side (than the 521)

 

The rear pair at the back of the cab are the same distance forward to the middle ones by your toes, but are 2" closer together side to side (than the 521)

 

BOX: The side to side distance for the box mounts is very close but distances front to back are different, plus I can't find a distance between the rear cab mounts and the front box mounts for the 521. The 620 is 6.89" if that helps.

It's a box so just make it work.

 

The middle and rear cab mounts are on extensions away from the frame. A flat piece of metal could be welded onto this and new holes drilled in the proper places.

 

Hope this helps.

[BACKWOODS DAVE]

I knew you guys would have the answer. The reason I was asking is because my plan is to put air bags under the 521. And I found a 620 frame that was Notched set up for a four link with the rear end and all the mounts on the front end already done. So I was hoping it would be a direct swap and I bought it to save me some work. But it looks like I might have just traded areas of work. Anyway I have seen a few trucks that have been bagged on Ratsun but anyone with knowledge please enlighten me with your wisdom so maybe I can save myself some headaches.

[/img]

[/img]

[BEEBANI]

That's why I said "most" 521's have a one piece. I think my '71 had a 2-piece now that I remember correctly.

 

I bagged my 521 as well dave, any questions you have don't hesitate to ask.

[BACKWOODS DAVE]

Beebani, thats good to know, was there any major fabrication differences between the two, or things that you would do different? I also would like to do disk brakes up front any advice for that would be great. Between my brother and me there is not anything we are afraid to try or scared that we will be in over our head so any ideas are appreciated.

[kansascity1]

I also bagged my 521, so if Beebani can't answer any ?'s I will try to help out as much as i can.

 

 

Beebani-How did you do the front of yours? I had to make new UCA mounts for bag clearance. I did mine pretty much the way Dwight did his. I also dished the frame for bag clearance.

[kansascity1]

Here is a link to Dwight's build. This is how my frontend is setup.

http://forum.ratsun.net/showthread.php?t=38

[BEEBANI]

I kept the upper and lower control arms stock on my 521, but notched the frame quite a bit for bag clearance.

 

Dave-not any real differences between the 2, the main thing is to take it down to bare frame if you can, the tranny x-member and carrier bearing x-members both have to be notched or shaved in order to lay frame and it's easier to do without the cab on.

[BACKWOODS DAVE]

I plan on striping the truck down to the bare frame. But I need to stack enough coins together to buy the bag setup before I just blow an entire truck apart in the middle of prime shop realistate. The 620 frame has aready been dished in front for bag clearance. but the bag mounts need quite a bit more reinf. so when I get them both bare and side by side I will have to make the call on wich frame is going back under the truck. I guess I am just trying to get as much info from those who have done it, so I can research it, and do it right the first time. I plan on this being a daily driver so I need reliability and I would like it to stop. when I get a chance I will snap so pictures of the 620 frame and post them. thanks for your help guys.