GM hydroboost pushrod length

[brownge]

I'm putting a GM Hydroboost from an early 90's Astro van and a new Wilwood master cylinder (model 260-8556-P) on my '72. I bought the hydroboost from O'Reillys but it didn't come with the pushrod, spring, and retainer. Another member helped me find a site (http://www.tallonhydraulics.com/stor...ex&cPath=40_16) that sells these items but I need to know the pushrod length to order.

Do any of you have the same setup and could help with the correct pushrod length?

Thanks!

[Twisted78SS]

there are several threads on adding Hydroboost, I have the Astro unit as well, and searched the boards coming away with these.
I believe what your asking is in there somewhere..

hydroboost rod length
http://67-72chevytrucks.com/vboard/s...d.php?t=448895

How I got Hydroboost for under $80 (including lines)
http://67-72chevytrucks.com/vboard/s...ferrerid=28772

http://67-72chevytrucks.com/vboard/s...3&postcount=46




http://www.pirate4x4.com/forum/jeep-...oost-info.html

Hydroboost info
________________________________________
Well, I'm on a lazy search again... wanting to learn about hydroboost.
I'm going to post some links, and pics. I'd like to find out more info...
And for those that think this is not hardcore, you find better info!

I'd like to open this to people to post thier pics of different Hydroboot units.

The Bendix "Hydro-Boost" system dates back to 1973. The system uses hydraulic pressure generated by the power steering pump rather than engine vacuum to provide power assist. Still in uses today.

Delco also has a Hydro Boost system.

Why Hydrooboost over a vacuum canister? Hydroboost give you Variable gains available (4:1 to 8.2:1)

Best post I've found on Pirate4x4 for Hydroboost info: http://www.pirate4x4.com/forum/showt...ght=hydroboost
Best guy for answering hydroboost questions on Pirate -> VancoPBS
- his web page: www . vancopbs . com/ (Hint: High Flow is good for Ram Assist)
More Links:
http://www.hydratechbraking.com/forums/
http://www.babcox.com/editorial/bf/bf030542.htm
http://www.foundationbrakes.com/en-u...s/default.aspx
http://www.powerbrakesonline.com/

Edit Even More:
http://www.remanbrakes.com/pdfs/hydr...stallation.pdf
http://www.brakeandfrontend.com/Arti...t_systems.aspx
http://nastyz28.com/forum/showthread.php?t=134759 How to rebuild not finished
http://wallyandsue.blogspot.com/2009...-rod-seal.html How to rebuild
http://wallyandsue.blogspot.com/2009...surements.html How to rebuild
http://books.google.com/books?id=hRm...page&q&f=false
http://vintagetest.com/chassis/dch74/V2D748005.pdf
http://www.ifsja.org/forums/vb/showthread.php?t=106056

http://bepco.biz/Catalogs/VacHydCat/S5_A.pdf
http://www.cpptse.com/BH-101.pdf

Bendix sold the hydroboost to Bosch in 1994
http://rb-kwin.bosch.com/en-NA/start/nfz_brake1.html (Link now dead)
Internet archive http://replay.waybackmachine.org/200...fz_brake1.html (takes a while to load, maybe on tape?)

IMGs (Taken from other sites)
Hydroboost external accumulator design


The '80 - '85 Type II internal accumulator design:


spool valve


HUMVEE aka H1
bolt pattern of 4 1/4 x 3 3/8"


The "proper" way is to have the return from the HB go straight thru the "top" of the T and the Power steering gear needs to return thru the "Bottom" of the T. this provides for no back pressure into the HB unit.

[brownge]

Thanks Twisted but let me clarify what I'm looking for as I don't see it in the links. I'm looking for the length of the output pushrod that presses in on the master cylinder when the brakes are applied, not the input rod that attaches to the brake pedal inside the cab.

I see from the pics below that there are two styles, the long and short versions. Does anyone have the length of these two styles?

Thanks.

[racecougar]

brownge, did you ever determine the length you needed? I've just stumbled into the same situation. I wonder what the remanufacturer does with all the pushrods it removes from the cores. Sure would be nice if it was included with the reman'd unit.

[davepl]

I have a GM hydroboost in the cupboard - I don't know if it's long or short, but if there's something I can measure for you, let me know.

[racecougar]

Originally Posted by davepl

I have a GM hydroboost in the cupboard - I don't know if it's long or short, but if there's something I can measure for you, let me know.

If there's any chance you could measure the overall length of the booster to master cylinder pushrod, I would be very greatful.

[jeffahart]

Originally Posted by brownge

I'm putting a GM Hydroboost from an early 90's Astro van and a new Wilwood master cylinder (model 260-8556-P) on my '72. I bought the hydroboost from O'Reillys but it didn't come with the pushrod, spring, and retainer. Another member helped me find a site (http://www.tallonhydraulics.com/stor...ex&cPath=40_16) that sells these items but I need to know the pushrod length to order.

Do any of you have the same setup and could help with the correct pushrod length?

Thanks!

Seems like you should get a stock push rod and get it hanging through the firewall and then measure to the pedal. Someone has to have the exact same setup for firewall mount and same pedal. But would you still trust the measurement? I would assemble then assess the rod length. Or if that company has adjustable ones you might get close from someone's measurement.

[jeffahart]

Also, I have a k3500 booster out of an 86 cucv on my bench. The rod is 6" from end to hole center.

[jeffahart]

on that same booster from above, it's 15" from mounting face to master to rod hole center.

[jeffahart]

Oops! I thought we were talking pedal rod. Now I see it's an old thread piggy backed onto. Anyhow, my master is installed to the HB.

[racecougar]

Yeah, wrong pushrod.

Davepl, disregard my request. We scored one at the junkyard today. In case anyone looks this up in the future, the pushrod measures 3.450" long and 0.343" diameter.

Btw, Tallon Hydraulics is now under a new name. They still sell these parts, but they can't keep them on the shelves. I was quoted a three week lead time today.

[davepl]

Will do, sorry for the delay, glad you got what you needed!

[100%Chevy]

A little off the topic,but how do you get the rod back out once it snaps in the hole?
Mike.

[racecougar]

Use a pair of needle nose pliers to work the retainer out (be prepared for it to go flying...there is a spring behind it). The pushrod falls right out after that.

[100%Chevy]

Originally Posted by racecougar

Use a pair of needle nose pliers to work the retainer out (be prepared for it to go flying...there is a spring behind it). The pushrod falls right out after that.

Thanks,I'll try that !
Mike.

[racecougar]

By the way, if anyone runs into this same issue in the future (needing a pushrod, spring, and retainer for a refurb'd unit), shoot me a PM and I'll hook you up.

[Danny23]

Quick question my breakes are lucking up trying to figure out the problem i already try a new MC and nothing and pedal is rock solid but when i bleed the MC everthing was really smooth no locking ..my question is do the output push rod short one i think (my is about 3-1/2 long) the tip need to be flush where the MC mounts or it need to be futher in about 1/2+/-? My output push rod is sticking out about 1/16 from the mounting surface when i mount the MC and get it ready to bolt it is stick out about 1/2.do the out put rod need to be futher in so is some play in between MC and hydroboist?...

if this is the case then my hydrobost is stock i did remove the input rod from thebreak p pedal to see if it move but nothing the tells me is not my breake pedal holding or not letting the output rod coming back to normal

[jeffahart]

Originally Posted by Danny23

Quick question my breakes are lucking up trying to figure out the problem i already try a new MC and nothing and pedal is rock solid but when i bleed the MC everthing was really smooth no locking ..my question is do the output push rod short one i think (my is about 3-1/2 long) the tip need to be flush where the MC mounts or it need to be futher in about 1/2+/-? My output push rod is sticking out about 1/16 from the mounting surface when i mount the MC and get it ready to bolt it is stick out about 1/2.do the out put rod need to be futher in so is some play in between MC and hydroboist?...

if this is the case then my hydrobost is stock i did remove the input rod from thebreak p pedal to see if it move but nothing the tells me is not my breake pedal holding or not letting the output rod coming back to normal

Always get the master to match the booster, year make model all the same. And with the accumulator to match your setup; disc/drum disc/disc and such. That said there is a caveat regarding the long/short rod masters.

In post #3 the master on the far right shows shallow hole. How this is achieved in "some" of the re-manufactured masters is to use a 1" steel doweling plug to make it short rod. Check if your master has the plug in, if so and you take it out you have a long rod master.

[Danny23]

My MC is like the one on the right and my HB has the short output rod the only difference from the post #3 HB to my is that my rod is about 1/16 sticking out from the MC mount surface and the one on the picture looks like is not flush like more in like 3/8-1/2 im guessing ,rod plastic washer is there and is center all i can think about is go to autozone and tell them to show me one from the exact same truck and try my rod and see how far in it goes if it goes in more the means my HV is stock and once i mount everthing back doesn't let the pressure go back to the reservoir and eventually builts pressure.. im still gonna check when breaks locks unbolt the MC and see is they still lock if they do may be the ABS because is new dics rotors /pads all around and new rear calipers with all braided hose.
But tiday i did a test with out the MC and is not hard once i put the old or the new MC it locks quick but like i say my output rod is flush looks like it need to go in little more do is some play between the MC and HB.

[jeffahart]

What is your locking symptom, Locks up when you press pedal and pedal is hard. OR, locks up and stays locked. If you are staying locked then I think you have he wrong rod or have misassembled it. Hard pedal is possibly lack of boost, and I'm going there first because it's a new setup you are getting up. How is your hydraulics plumbed. Can you show your setup.

You mentioned something about stock! Were the brakes fine then, you swapped the master replacement now bad. I am under the assumption you did a conversion since this is the 67-72 area. But more likely you bought something not stock I'm thinking.

I noted ABS in your post. Also, are you sure you have a hydroboost? An, HV caught my eye there on your last post! What is your setup. You may have bought a custom rig with some nice components if you got ABS. If that's the case you could tickle the manufacture.

[Danny23]

Yea stays lock all the time or pedal is hard at all times ,,you got my attention when you say lack of boost when the hapoens the means is a bad PS? When i say HV i was trying to type HB
I did check the braided hoses if they are in the right lovation and they are..
Im gonba be honest this is on a 88-98 silverado that i did a hydroboost convestion and thats why i was asking about my rod been flush with the MCmounting surface and the one on the picture post #3 looja li NJ e is qay more in next to mywhen i sayi think is stock i was taking about the shaft the move ibside the HB where the rod seats nsybe stock and thats why my Rod is sticking out about 1/16..

[jeffahart]

OK short answer: My 86 booster has rod in a tad, maybe 1/8" or so. Now I blather on!... I'm pretty sure your rod tip should be inside a tad. That combined with the fact yours sticks out a tad, could be enough the translate to brake pressure. The translation from travel of pedal to master don't take much to get brake pressure. Also, if your power steering works then your PS unit is OK! Retrace your steps on everything you did when you replaced your master; and verify correct assembly.

[Danny23]

Yea will do the im re-checking my hoses and will try my rod on a new umit at autozone the will tell me righ away if what i have is righ or wrong or if the HB got stock aome.how or is bad is a rebuilt one i got it from my uncle but now that i think about who knows why it was seatting on his garage. My other uncle gibe to me lol.

[Danny23]

Here is a picture where you see the rod like 1/8 from MC mounting surface ,other picture on red is my HB and the one on yellow is just one i found.qith ahort rod online and also the gap between MC and HB if i just hold it like 1/2.

[Danny23]

Just for the record if anyones run into this problem my breake pedal was hard at all times and if i remove the MC was normal my output rod is the righ length i just end it up replacing the hydroboost and problem solved these one got me thinking simce the HB was new(rebuilt ) from.auto zone but i got a new one. I just need to purge the lines ..thanks for the help jeffahart.