Need Help In conversion of Power Brake Booster

[Corzette]

Guys I found two part numbers an 8 1/2 inch booster for a 78 280Z #53-5104 from AutoZone and a 10 inch booster #53-5065. I am upgrading from the 240Z unit to this. My question is does the 280 Brake Booster have the same 4 studs coming out the front like the smaller 240 unit does that will be a direct bolt on to the 240 master Cylinder? They are the same right? Pete you out there? Any one else done this swap? PLease advise...

 

CorZette

[260DET]

On my '77 model, a larger 2+2 booster bolted straight on IIRC. Don't know about the part # but the 2+2 booster measures around 250mm (10") diameter at the widest part.

[Dave]

For a couple comparison pictures click Here

[Corzette]

Cool, thanks for the input guys. I guess I will go with the 2+2 280Z Booster since its bigger.....

 

[RPMS]

WAIT! You might not want to do that. When the booster in my 260 went tits-up (due to a leaky master cylinder) I replaced them with parts from an early ZX - a 1979, I think. That way I got the larger diameter brake cylinder (15/16", I think?) needed to push brake fluid through the Toyota calipers I'm going to install soon, and I got the extra power assist. It was also about 1/4 the price of the original part! The problem is that the boost is too great. When I hit the brakes, it REALLY hits the brakes. When I apply the same amount of pressure that stops my BMW in a safe and sane manner, I just about fly through the windshield. If you go with a larger diameter booster, you'll have to be mindful of your pedal pressure. Also, I distinctly remember there being a few different bolt patterns out there. They used style A for the first few years, then they went to B, then back to A, then to style C. If you're not going to get a direct replacement, be sure to take your old booster in to get the correct fit.

 

If you decide to try it, here's a few hints. After bench bleeding the master cylinder, vacuum bleed it. I had a mushy pedal that no amount of brake bleeding would cure until I did this. Also note that the booster has an adjustable um... nipple on the end that screws in and out depending on how cold it is... NO, wait, that's not right. It screws in and out to adjust how much slack there is in the brake pedal before the assist hits. If it's too far out, your brakes will stick. If it's too far in, your pedal will have an inch or so of slack before the brakes hit. I found that tremendously annoying, so I spent a couple of hours fiddling with my nipple until the problem resolved itself. Now my brakes are very firm.

 

If I had it to do over again, I'd probably do the same thing just because of the big price difference between the 260 booster and the 280 one, but I don't really like it this way. The booster on my last 280 was completely ineffective, and I enjoyed the feel of manual brakes. I've got squatter's thighs to begin with, so it wasn't any trouble to lock up the wheels if I wanted to. Maybe I'll go back to that, come to think of it...

[Corzette]

Roger that! Well I just bought a booster and MC from JT from a 280ZX. If the bolt pattern is different I will redrill the firewall to fit. I do need the extra vacuum cuz I have the front and rear disk upgrades. This may be dumb, but how do you bench bleed the MC? I always just pump up the pedal then open the nipples and close and repeat. Is that it?

 

CZ

[Mike C]

Your 73 should have the same booster/pattern as the 280 Z. My 72 did not, but I redrilled for the later booster. Not sure about the ZX,however. To bench bleed your master, you can clamp one of the ears in a vise, put rubber hoses from the bleeder screws into the reservoir with their ends submerged in fluid, then actuate the master. I use a large Phillips screwdriver usually. If you have an assistant, you can actually bolt the master to the booster, then connect the hoses to the bleeders with the ends of the hoses submerged, then have your assistant cycle the brake pedal until no more air bubbles appear.