Can anyone confirm if the small 180b boosters actually make much of a difference when using 4 pot calipers. I remember driving with the old Girlock calipers with no booster and the brakes being hard and a sort of dead pedal feel. Now I have the 4 pots and the brakes still feel typically datsun. Is there bigger booster options out there that will fit in a 1600 with an SR???

yes the small can booster makes a big difference to pedal feel an if your going an SR your engineer will expect you to have one.

Yeah sorry I do have a 180b booster with a 7/8 master but I'm still having to step on them to get the brakes to work. What I'm curious about is the other options as far as bigger boosters go?

What 4 piston calipers are you running?
What rear calipers are you running?
Can you describe in greater detail what the problem is? - i.e. you step hard on the pedal and nothing happens, or you step hard on the pedal and the brakes lock?
Do you have a hard pedal or soft?

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
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#SR20Datsun @SR20Datsun

Ive got 4 piston Alcon superlight calipers with street pads
r31 rears (no air in lines)
hard pedal
When i step on the pedal i have to really push to get em to lock. Im just after some effortless braking like most newer cars, so is there any bigger booster you know of i can chuck on to help out?

Also i've heard the push rod on the outside of the booster that actuates the master cylinder can be adjusted out. This is something i may have over looked while assembling the brakes??

Final question before I can provide answers.
What is your pedal travel like?

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
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#SR20Datsun @SR20Datsun

Initially travel was close to the floor before adjusting the push rod that meets the pedal out. now i have a full pedal but still crappy brakes.

do you have the one-way valve the right way round????
it sounds like your booster isnt getting any vacuum

The one way valve is allowing flow toward the motor and no flow from the motor.

small can booster should be fine. is the booster diaphragm ok? to test start the engine for a few seconds, turn it of the pull the hose of the booster if you hear a sucking sound the booster is ko, if no sound time for a diaphragm kit.

I have the same issue, I am running a 200b booster (7inch) the biggest you can fit without major modifications. Same situation as yours, brakes all bred correctly. Mazda 4 pot calipers front, matching mazda rx7 rear calipers. 7/8 nissan master cylinder (which is same bore size as originally used on rx7). one way valve working correctly (and right way round) 17" of vacumm coming from 13b turbo engine at idle. These small boosters apparently need 17-22' of vacumm at idle to work to work maximum efficiency.

I have spoke to Baz at Datsport and he recons you wont get that new car feel with these small boosters. For example, the brake combination on my car was originally running an 11" booster on the series 4/5 rx7 they came off. Which an 11' booster obviously wont fit on a 1600.

I also spoke to local brake part supplier over here in Perth. He sells a product similar to these. http://cgi.ebay.com/ebaymotors/NEW-7-DU ... 5889d5b62c

http://cgi.ebay.com/ebaymotors/7-DUAL-D ... 5195f77920

Also if you have low engine vacuum supply try these first http://cgi.ebay.com/ebaymotors/electric ... ccessories

I still have not decided what im going to do yet. My vacuum is on the low side of whats needed but I cant see the extra vacuum making much difference. With the double diaphragm booster you would need a brake place to open it up and move the studs to suit datsun mounting centres and master cylinder mounting centres. And also would need to make sure there is enough room to fit the extra depth of this booster and check diameter width too . Maybe need shorter master cylinder ,in my case as i have exhaust/ and high mount turbo to clear.

This might be of help to you with SR20 tho?

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My build-
http://ozdat.com/forum/viewtopic.php?f= ... 89#p266789

Cheers RX510 for the ideas about the brake booster. Looks like an option and im sure making it fit wouldnt be too hard...although it would have been a S%^T load easier doing the booster mod while the motor was out...

No worries. Another thing i have been thinking about yesterday. Is to change the pedal ratio. here are a couple of good reads if you can be bothered.
http://www.deanoshiro.com/brakes/brakearticle.html

http://www.stoptech.com/tech_info/Pedal ... -Guide.pdf

I have measured the original dat 1600 pedal and it is about a 5-1 ratio. I have a 7" booster which has been rekitted by local brake place and is working correctly. According to the first link above it should make about 327 psi.
Where as the RX7 my brake setup came off was running a 9 1/2 to 10" booster which makes about 668 psi(he does state that they will probably make 85% of those figures).

Again according to the first link, if I work out which size master cylinder I am running which is 7/8 I can do a few figures(which I cant be bothered typing up here, but its all there on the links) and work out if I change the pedal to 7-1 ratio I can make up for the loss in booster sizes. To me in my situation with limited room in engine bay this should be the easiest way to get a nice pedal feel (THEORETICALLY it should work).

By changing the pedal pivot point (bringing pivot point lower down) I will be able to get the ratio I am after without having to change pushrod location keeping the booster and master cylinder in the original location.

This may help for you, I shall get around to doing this in the next couple of months busy with other commitments atm.

Also are you running the right size master cylinder for your brakes? I originally ran a 15/16 master and the pedal was just ridiculously hard (me thinking bigger is better not the case here), I was told to swap to 7/8 which is what the RX7 setup uses and it made big difference (but still not like a new car, you have to jump on them to bring it to a complete stop). Smaller bore creates more line pressure but if your running Skyline 4 pots I think they need more volume so you may need 15/16" if that's what they used.

Hope this helps..

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My build-
http://ozdat.com/forum/viewtopic.php?f= ... 89#p266789

Hey RX510 nice thread on brakes you posted. I'm keen to try the pedal pivot point change. It makes sense to me. Just have to work out a bracket that will pivot lower on the pedal but still run the pushrod square into the booster. I have the 180b booster and 7/8 master setup from datsport.
I wonder what the original 180b or 200b pedal ratio is?

i had a similar problem with the brakes on my 1600. (1"Bore Master, 180B Booster, C4 Corvette Callipers (F), R31 (R).

I found that changing pad material made a difference (from Bendix metals to Bendix street road track pads)
and made a extra reservoir tank which holds 2litres of extra vacuum