Mooser

Started installing the hydroboost unit (94/59 astrovan) and I don't have the rod /spring /etc that goes between the hydroboost and the master cylinder.



I'm being told those rods where different lengths so I need to find out how long it should be as I go hunting for a replacement.

Anyone happen to know the length\diameter of one?
Thanks
M

7T1vette

Don't know anything about Hydroboosts.... But, would think the strategy for sizing actuating pin would be the same.

For regular boosters, that pin must be the same length as the space available, when the parts are assembled. If too long, it will always be partially applied; if too short, there will be a dead spot in pedal operation.

Measure the depth of the pin recess in the hydroboost AND the recess in the master cylinder. Add these (include gasket thickness if one is used), then size the pin to the same distance +.000/-.010. That should work for you.

If others know some specifics about hydroboost pin, please chime in.

colesweat

I think you can buy that pin adjustable, what year vette is this going on? Let me know how it works out

Mooser

OK, so I've found what appears to be a stock pin length of 3.340" for short MC pistons

7T1, yes that seems to also apply to the hydroboost units (Tallon Hyd. suggest .010-.020 gap but basically the same)
I was after a ballpark length since I hadn't pulled the Vac unit from the MC and could only get the depth from the hyd unit.

I couldn't find any mention of adjustable length ones so I ordered an over-length version and I'll machine it to fit once I get everything on the bench

Thanks all.
M

7T1vette

Same thing I did for a replacement master cylinder.

Ibanez540r

mooser be sure to post your results when done! Will help me out when the time comes.

Andy Tuttle

How about posting some pics as you do the changeover? Would love to see how that goes! Going by your other work, I am sure it will be top-notch!

MN80Vette

A number of guys in our car club converted from vacuum to HydroBoost. Rather than modify the length of the rod, we just used a spacer between the firewall and HB.

It has been quite a few years since I switched to HB, but I used a HB from a '97 (?) Silverado. The rod was too long, so I added a custom spacer to make the length from the firewall to the center of the clevis hole the same as that length for the vacuum booster.

It REALLY helps when one of yous sons is a CNC machinist.

Mooser

Because it's not quite done and there's other threads

I'll likely put something together once it's done (soon I hope)

So far


Converting the pedal end




Installing the Tallon pushrod & spring


Checking rod for rough sizing


Reverse the mounting studs, astrovan has the same bolt spacings


Dryfitting


Adding non-functional bling


Anyway I'm ready to make up the hoses now. Just need to run some rubber ones to get the path worked out and then I'll assemble the braided ones.

Hope this helps for now. I know you were looking for options
M

MN80Vette

Nice work, and good pictures.

Is that a new pressure reserve cylinder or a cover for the original?

Thanks.

Mooser

Just a cover I made up to change the looks
M

Mooser

The rod that got shortened here was the one that goes between the HB unit and the master cylinder since this was a re-manufactured unit. Shortening it was simple once I actually got something to work with.
Spacer would work for the one that goes to the brake pedal(???)

M

Andy Tuttle

Mooser - thanks for the pics! That gives me a much better perspective. Will be watching as you get the hoses done too. None of the other posts I went through (and it was a bunch of them!) had very many pictures. Lots of info, few pictures. Getting more visual in my old age I guess or I am keeping up with younger generation! Anyway, really appreciate it! Keep it up!