Booster push rod length

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Retro Boy
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Booster push rod length

Post by Retro Boy »

Does anyone have an XA - XB brake booster out of a car who can measure how far the push rod protrudes past the face please?
This seems the easiest way to establish the correct push rod length when using a 7" single diaphram Gemini style booster with the XB master cylinder.
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Harv
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Re: Booster push rod length

Post by Harv »

The earlier Gemini boosters are used, which have a horizontal bolt pattern (later Geminis used an angle mount). The booster is mated up to an XA/B/C Ford master cylinder, which is dual circuit (PBR part number P6258a). The master cylinder pushrod has to be extended slightly so that it protrudes 1.5mm from the booster face (in order to provide appropriate booster pre-load). I have seen different length pushrods in the Geminis, so each type may need to be extended a different length to give the 1.5mm.

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Harv
Retro Boy
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Re: Booster push rod length

Post by Retro Boy »

Thanks Mate. The push rod in my booster is flush with the face of the booster, so by the sounds of it all I need to do is hit the of the push rod with the welder and then smooth it off.
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Twin Spinner
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Re: Booster push rod length

Post by Twin Spinner »

Beware, you need to know the content of that push rod and the correct electrode to use :wink: And quenching it in water could be a grave mistake as well. I was a boilermaker/1st class welder for 60 years and have seen plenty of Bubba's handy work, just sayin :lol: :lol:
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zuffen
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Re: Booster push rod length

Post by zuffen »

Bear in mind if you plan to weld in the brake or steering system it needs to be done by a certified welder and be non-destructive tested to be acceptable.

Not as simple as it looks.
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Harv
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Re: Booster push rod length

Post by Harv »

The way I did mine was to send the pushrod to Hoppers Stoppers. They extended it, and sent it back to me. Passed NSW engineering with a fairly strict engineer.

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Harv
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jeffa
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Re: Booster push rod length

Post by jeffa »

I have the same combinatio on my Chev.
As luck would have it, I scrapped a Toyota Crown 1/2 cut for much of the parts. The Crown used an adjustable pushrod.
Not sure how many other Toyota models had the same.
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FRANK BASILE
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Re: Booster push rod length

Post by FRANK BASILE »

The weld bit should not be critical. This is just extending the tip of a push pin. Easy to scrounge wrecking yards for an adjustable pin if you can. And as mentioned it is important to keep some 1-1.5mm preload on the master cylinder, as they do not have a piston return stop circlip. No preload and you risk fluid leakage back, too much and you block the compensating ports.
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Retro Boy
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Re: Booster push rod length

Post by Retro Boy »

Hey All thanks for your replies. Turns out my aftermarket Chinese "Gemini" booster has an adjustable push rod!
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toprodz
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Re: Booster push rod length

Post by toprodz »

Retro Boy wrote: Tue Nov 28, 2023 5:01 pm Hey All thanks for your replies. Turns out my aftermarket Chinese "Gemini" booster has an adjustable push rod!
Happy days.
Hi Retro Boy, the aftermarket boosters do have an adjustable push rod, the only problem is that with the newer versions, when you wind it out to suit the XB falcon master cylinder, you are lucky to have 1 thread left holding it in place, I replace the original ones with a longer button head cap screw, that I narrow the head slightly in the lathe, then put it back in with the original lock nut,
Image
I have done dozens of them over the last few years. I hope that helps
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Retro Boy
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Re: Booster push rod length

Post by Retro Boy »

Thanks, I'll check that.
Cheers
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