J's 620 Posted August 1, 2015 Author Report Share Posted August 1, 2015 Stock master cylinder....although I do have the 280z master that I was going to put in if these brakes were going to work. Quote Link to comment
J's 620 Posted August 1, 2015 Author Report Share Posted August 1, 2015 I haven't changed the pushrod or even touched the master yet Quote Link to comment
mklotz70 Posted August 1, 2015 Report Share Posted August 1, 2015 When your brake pedal is up, at rest, there should be a tiny bit of play on the pushrod........you should be able to wiggle it a bit. If it's tight, either your pedal spring is not pulling the pedal arm up well enough(is it all the way up against the stop?) or the pedal stop is not adjusted correctly. Do you have an adjustable pushrod? On the 521's, they were not adjustable. If this is the case, then make sure that the pedal bump stop is not holding the pushrod in tight. You want about an 1/8" of pedal movement before the pushrod becomes snug. The symptoms of your problem sound like the push rod is not being released all the way back. If you pushrod is set correctly, then this is my next guess. In calipers, the square cut oring is supposed to be the "spring" that pulls the pistons back just a tiny bit........so, my guess at this point is the residual valve in your m/c is holding the fluid more than the calipers are expecting. Second vid on this page may help if you haven't torn apart an m/c before. I'm not absolutely positive the stock single reservoir m/c has the same valve in it, but most likely. The quality seems pretty poor.....guess I should try to find the master and load it to youtube at some point. I'm not exactly sure how your brakes will act if you remove the rubber pieces with the slit in it. Quote Link to comment
J's 620 Posted August 1, 2015 Author Report Share Posted August 1, 2015 Yeah load it and I will watch it! And guys, I really do appreciate all the input and advice. I am grateful that you took the time to reply to my post. I think I may have been having this problem before I swapped the drums for discs. The truck did feel like it had a drag....I just assumed it was the bearings (after seeing the bearings). The grease in there was all rusty and mixed with water. This poor truck sat for many years in an old man's yard along with other datsun vehicles. A guy bought it, did some shotty "restoration" and sold it to me shortly after. I actually want to keep it and do it right. It's a bit rusty and runs great. Quote Link to comment
J's 620 Posted August 1, 2015 Author Report Share Posted August 1, 2015 I haven't checked the pushrod yet. I don't know if it's adjustable. I will update later when I start working on it again. Quote Link to comment
J's 620 Posted August 1, 2015 Author Report Share Posted August 1, 2015 It is adjustable Quote Link to comment
J's 620 Posted August 1, 2015 Author Report Share Posted August 1, 2015 Yeah that rod is tight. Quote Link to comment
J's 620 Posted August 1, 2015 Author Report Share Posted August 1, 2015 This master cylinder is a two reservoir...... maybe it is not the original. Quote Link to comment
620Turbo4X4 Posted August 1, 2015 Report Share Posted August 1, 2015 In calipers, the square cut oring is supposed to be the "spring" that pulls the pistons back just a tiny bit........so, my guess at this point is the residual valve in your m/c is holding the fluid more than the calipers are expecting. That would be my guess too. Drum type master cylinders have a 10psi residual valve. Disk type 2 psi.... Using dot 5 silicone fluid can also cause brake drag. The silicone lubricates the square o ring mike mentioned too much and does not allow the o ring to stick to piston enough for them to slightly retract. I found this out the hard way..... The wobble might be a bur on inside of hub where races bottom out. If you used a hammer and punch to remove races, theirs a good chance you might of nicked it and race is not sitting flat in the hub? 1 Quote Link to comment
mklotz70 Posted August 2, 2015 Report Share Posted August 2, 2015 I forgot you were working on a 620....you should have a dual res m/c stock. Loosen up that pushrod so that you have a slight amount of play and see if that helps. Quote Link to comment
J's 620 Posted August 2, 2015 Author Report Share Posted August 2, 2015 The brake pushrod wasn't adjusted right. I seem to have got it now. The brakes stop the truck and seem to release properly. Although I still have that warped hub problem. There are no nicks inside the hub to make the race crooked. I did a good job of making sure I took my time and was very carful with the hammer and a drift punch. It's the hub itself that is damaged. Possibly the spindle as well. I will never know for sure untill I find hubs that are in good shape to compare with mine. Quote Link to comment
J's 620 Posted August 2, 2015 Author Report Share Posted August 2, 2015 I can use any drum brake hub from any datsun vehicle mklotz? Quote Link to comment
mklotz70 Posted August 2, 2015 Report Share Posted August 2, 2015 Can you take a vid of it spinning. I've come across bent hubs before, but it's always been on the wheel mounting surface. A bent spindle won't cause a wobble.....the wobble has to be coming from a rotating part. Quote Link to comment
mklotz70 Posted August 2, 2015 Report Share Posted August 2, 2015 Hmmm.....good question. It would obviously need to be from a truck. I would think so, but I haven't checked it personally. You have 620 drum spindles......so you want to make sure you use 620 drum inner bearings. The 620 hubs have metric studs.....the others will have Imperial. Quote Link to comment
J's 620 Posted August 14, 2015 Author Report Share Posted August 14, 2015 Hey Mike klotz......do you have a brake kit or brackets for the rear on the 620? I've found some 720 hubs and I'm going to order your front disc kit. Quote Link to comment
mklotz70 Posted August 14, 2015 Report Share Posted August 14, 2015 Sorry, I don't have a rear yet. I've been talking about doing it for at least 5 years now and I'm still determined to get it going this summer. I've got fronts finishing up now. 1 Quote Link to comment
J's 620 Posted August 16, 2015 Author Report Share Posted August 16, 2015 Something just caught my eye while doing some research on this mklotz kit..... my spindles on the 620 don't have that spacer that gets removed. Is that a 521 thing to have the spacer? 1 Quote Link to comment
mklotz70 Posted August 16, 2015 Report Share Posted August 16, 2015 Correct. The spacer is built into the 620 drum bearing. This should pretty much explain the differences. :) http://community.ratsun.net/topic/30875-320520521-inner-bearing-spacer/ 1 Quote Link to comment
J's 620 Posted August 16, 2015 Author Report Share Posted August 16, 2015 Yes very straight forward thank you. 1 Quote Link to comment
J's 620 Posted August 24, 2015 Author Report Share Posted August 24, 2015 Now since I am basically doing this brake swap all over again using the Klotz kit.....I will have numerous photos for all to see. I have even shot a vid of my old hubs turning so we can all see how they wobble. I will show the wilwood kit on the truck as well, right before it comes off. It does look cool. It will be up for sale. Thanks for shipping the kit Mike. Hopefully I have a project this weekend. Ya! 1 Quote Link to comment
mklotz70 Posted August 25, 2015 Report Share Posted August 25, 2015 Should be there wed/thurs. :) Quote Link to comment
J's 620 Posted August 26, 2015 Author Report Share Posted August 26, 2015 Ya it's here 1 Quote Link to comment
J's 620 Posted December 10, 2016 Author Report Share Posted December 10, 2016 My dead thread will go into my build thread someday. The wilwood kit will NOT be going back on for viewing purposes. Too much work and my 76 hubs were junk so I tossed em. My brake swap went smoothly and the truck stops very well. Thanks to all for the input. Sorry for the absence of pics. 1 Quote Link to comment
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