mklotz70

'77 620 m/c should be a dual circuit and drum/drum. Keep in mind that the 521 lines are SAE and the 620 m/c will be metric. You'll need to add a line to connect the rear circuit to the rear brakes. If you can flare your own lines, then that line will be SAE at the firewall end and metric at the m/c end. The front line will either need a new metric nut flared on or you can use an adapter BLF-29C which you should be able to find at Autozone. You'll need a barrel to connect the new rear line to the existing rear line at the block on the firewall. Disconnect the stock rear line from the block and connect it to the new line with a barrel connector. Make sure to get a plug to block off the hole you just created in the block. Not the prettiest or best place, but if you add an adj proportioning valve to the rear circuit, you can use it in place of the barrel connector.

If you want to check the clearance to the hood....you can take a tape measure and set it on the flange of the carb so that the tape extends up towards the sky. Pull the blade out just a bit more than you think you have clearance for. Lock the blade. Now close the hood on it. The hood should push the tape in, but the lock should hold the blade where the hood quit pushing. You may have to play with the lock pressure and the location of the tape if you hood is closer than the tape's body.

ball joints and tie rods stay....just the spindle, caliper, rotor come from the '86 or later HB. You can use your hub. I would recommend just getting new rotors for the HB....by the time you pay for used rotors and have them turned, it cost about the same as new. You're not going to find new spindles on rockauto. If you want it lower, now would be the time to buy dropped spindles.

you can get rebuild kits for the calipers on rockauto and ebay. Didn't the 620 calipers have a short hard line connected directly to them.....accounting for the female end on the rubber hose. If you're going to spend some money on that front end, my suggestion would be to get spindles from a D21 Hardbody.... '86 and later. You get better calipers, vented rotors. You can use the hubs you have with the HB spindle. I'd avoid any spindle earlier than that because of wheel fitment. The swap is just disconnecting the upper and lower ball joints, tierod end and brake hose from the hardline at the body. Getting the rotors off....provided you're not going to reuse them(vid). If you're going to have them turned, put the bolts back in and don't try to remove the rotors. More info about the brake differences for scrapyard reference.... http://www.bluehandsvideo.com/hub-info.html If you haven't R&R'd bearings before, these vids should get you started.... More pics of your suspension might help solve the confusion over your frame/frontend. There have been cases where guys have bolted the disc arms to the drum frame. The shock tower on the drum trucks were inline with the frame. The towers on the disc trucks were at an angle. I'm not that familiar with the 620 disc frames to recognize if the entire frame has been swapped. Good luck

Do you have any pics of the m/c where the lines connect? Kinda sounds like you're missing pieces off the m/c. The fittings would be m10-1.0 if I remember right. If you haven't done any flaring before, this vid will get you started, but there's probably better ones on youtube. These are old, crappy vids, but it will show you the fittings at the bottom of the m/c that I think you're missing. http://www.bluehandsvideo.com/brake-master-cylinder-anatomy.html

You can download the manuals online in a few places, but they're also on my site. http://www.bluehandsvideo.com/manuals.html

Yep....I don't make them anymore and they were definitely the most expensive. The kit wasn't cheap and then the other parts needed added to the cost. If you can do any kind of machine work or have a friend that can do it, the older, steel bracket design is on my website.

I always wanted to make the next ones with more arch to the arms so there would be more clearance, but I don't see that happening now. lol The original design was for torsion bars, so the arch wasn't needed. I think it's pretty clear why I went with a bayonet mount and the reinforcement piece for the shock tower. 🙂

I must have gotten some numbers crossed. I was trying to show that RA was a good way to get part info. The National 1981 does say its for a '74 and up input shaft seal. ....and after looking them up again, I agree with you that it shows the same for input and output. I do know that when I had my NL, the output seal matched on every 4 and 5 spd tranny I had here.....even a D21 trans.

You can do a parts search on rockauto. They both come up. When it shows you an option, click on the info button and it will typically give you more info like dimensions. The factory number shows up in the list of alternate part numbers, but both numbers don't show up in either. The dimensions do not match.

Are those numbers for the entire assembly? They'd have to be swapped as an entire assembly. The mounting holes in the cross shaft maybe a different size on the 620 ones.

I'm nearly positive that the UCAs will interchange between the 520 and 521....even 620 king pin ones. The 320 should work, too, but I don't remember if the towers are a bit narrower on the 320. If so, the arms might be a bit narrower, too. To be clear, it's the complete arm assemblies that will swap. The nuts are shorter on the older(?) arms so the cross shaft is probably a bit shorter too.

I know this is an older thread. This vid helps to explain the lower fulcrum pins and their bushings. The "waves" inside the arm are actually threads. The "nuts/bushings" have a similar thread on their outside. The inside of the nut is a coarse thread and it's actually the bushing surface for the fulcrum pin's threads.

Thanks Mike. Socalman came up with an option....

You can download the factory parts manual here.... http://www.bluehandsvideo.com/manuals.html The exploded parts diagrams may help show where they go.