Hydroboost Pushrod length - Team Camaro Tech
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post #1 of 9 (permalink) Old Feb 16th, 09, 01:13 PM Thread Starter
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Jereme
 
Join Date: Feb 2006
Location: Vancouver, WA
Posts: 160
Hydroboost Pushrod length

Hello,

I have the following set up:

Mid 90's Astrovan HB, rebuilt from a guy on ebay. He provided 2 threaded brake pedal push rods, I am using the short one and the top hole in the pedal.
Nick Diprenda's mounting bracket
69 Corvette Manual Brake MC
C4 brakes in front
95 Camaro 11" brakes in rear

Having a tough time bleeding brakes. Have been using a combination of :

my girlfriend on the brake pedal conventional bleeding. Did not work...
AC style vacuum pump to evac line. Marginal success.
Mity-Vac - Best so far. Fluid to all wheels, but can't seem to clear all of the air.

Even after I got fluid to all wheels, I have not been able to get any resistance at the pedal or any brake pad movement. So I have begun investigating pushrod length more carefully. The Corvette MC should use the long pushrod. The cavity in the MC measures 1.655" deep, this should equate to needing the long pushrod which from what I have learned in this forum should be 4" long. I pulled the pushrod from the HB and it measures 3.14" One final point of reference is that when I push on the brake pedal I only see fluid movement in the front circuit of the MC.

I have read that these Corvette MC's are tough to bleed for some reason, so my current plan of attack is to install a 4" pushrod and coax my girl back over to press on the pedal. Any reason I should not go to the longer pushrod?

Thanks,

Jereme

1969 L78 SS396 (Engine Long Gone)
BBC 496, TKO600, Beautiful Stock 12 Bolt Posi (maybe the only stock thing left.
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post #2 of 9 (permalink) Old Feb 16th, 09, 03:13 PM
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EY
 
Join Date: Nov 2005
Location: Europe, Finland
Posts: 194
Re: Hydroboost Pushrod length

I just bought a MC for a later ~79 ('sh) vette it has the shallow hole pushrod piston for my HB unit. I thought I needed a MC from ~70 C3 but found out about the pushrod legths before I bought it, hence the ~79 model.

I believe you could fab a "spacer" or change to a long style pushrod also. Check Pozziracing.com

With the deep hole and short pushrod it wont work.

E.Y. Finland,
-67 RS
Orig: PG + 327/275 + 12-bolt.
Now: SBC409 TKO600
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post #3 of 9 (permalink) Old Feb 16th, 09, 07:20 PM Thread Starter
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Jereme
 
Join Date: Feb 2006
Location: Vancouver, WA
Posts: 160
Re: Hydroboost Pushrod length

Thx for the repy E.Y.!

I have checked out David's website and fabed up a 4" pushrod. I am now working on a banjo bolt leak on my rear caliper. Still no luck with the girlfriend... Maybe a bottle of wine will put her over the top I will keep you posted.

Best,

Jereme

1969 L78 SS396 (Engine Long Gone)
BBC 496, TKO600, Beautiful Stock 12 Bolt Posi (maybe the only stock thing left.
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Last edited by RedJet; Feb 16th, 09 at 08:20 PM.
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post #4 of 9 (permalink) Old Feb 16th, 09, 10:45 PM
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Fred
 
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Re: Hydroboost Pushrod length

Jer! Why didn't you call me?!! Not that I could help from here. And the camper is washed because it's going to the dealer for fabric change-out tomorrow. That means I'm tied up for a couple days. That and Jacque is coming over Thursday with the kids so I can R&R her truck. Maybe this weekend? Note to readers; We're family.

One owner 69 Camaro,(yep, bought it new
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RS SS Hugger Orange, L88, 4:10's tru-tack posi, ducted hood, Endura, spoilers.
TH400 (CX) with Coan 8" converter, GV-OD, 8 track still on console and best et 10.495,
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+ MT Super Scavenger headers & 3" full exhaust with X pipe. 3700 lbs. with me in it.
1000cfm AED and HD Harold-Lunati SR, 725 lift with shaft rockers too.
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post #5 of 9 (permalink) Old Feb 16th, 09, 10:50 PM
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Al
 
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Re: Hydroboost Pushrod length

Jereme - who recommended that MC? Not sure you'll be happy with it. I think it's a 1" bore. You'll likely get a lot of pedal travel with it. I'm using a 1 1/8" bore 69 Camaro disc/drum MC with hydroboost on a very similar system at the recommendation of Hydratech and it's dead nuts perfect.


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post #6 of 9 (permalink) Old Feb 16th, 09, 11:29 PM Thread Starter
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Jereme
 
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Location: Vancouver, WA
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Re: Hydroboost Pushrod length

Fred -- come on down! I can always use labor that is smarter than myself!

Al - I kinda picked it on a lark, based on what I was expecting from the hydroboost. I was also considering port location and compatibilty, maybe I picked a less than optimal, we shall see!

Hey if Fred comes down this weekend maybe we can get together and check out your car? Is it still in the couve? Let me know....

BTW- I have a rotten-stinkin-leak on my RH rear caliper that is frustrating me! Had to walk out of the garage tonight to get my sanity back...Ugh!

Best,

Jereme

1969 L78 SS396 (Engine Long Gone)
BBC 496, TKO600, Beautiful Stock 12 Bolt Posi (maybe the only stock thing left.
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post #7 of 9 (permalink) Old Feb 17th, 09, 10:21 AM
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Fred
 
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Re: Hydroboost Pushrod length

Jer, I'll keep ya posted,,,

One owner 69 Camaro,(yep, bought it new
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
)
RS SS Hugger Orange, L88, 4:10's tru-tack posi, ducted hood, Endura, spoilers.
TH400 (CX) with Coan 8" converter, GV-OD, 8 track still on console and best et 10.495,
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
128.79mph 1.428 60'
All with 1960's stuff. (except tires and converter)
+ MT Super Scavenger headers & 3" full exhaust with X pipe. 3700 lbs. with me in it.
1000cfm AED and HD Harold-Lunati SR, 725 lift with shaft rockers too.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


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post #8 of 9 (permalink) Old Feb 17th, 09, 02:09 PM
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EY
 
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Location: Europe, Finland
Posts: 194
Re: Hydroboost Pushrod length

Just to let you know here are the P/N's for raybestor master cylinders.

So these are for the C3 corvette and they "look correct" (almost) if you are duplicating period correct disc brakes (JL8). Both of these mc's were originally for a power brake corvette so they are equipped with a 1 1/8 piston bore. The only difference is the pushrod hole, it's either deep or shallow.

MC39018 CHEVROLET CORVETTE (1967 - 1976) (+many others!!)
{Professional Grade Bore Size=1 1/8" Number of Ports=2 Primary Outlet Size=1/2x20 Secondary Outlet Size=9/16x18}
Power Brakes
DEEP HOLE FOR LONG PUSHROD HERE



MC39052 CHEVROLET CORVETTE (1977 - 1982) (ONLY!!)
{Professional Grade Bore Size=1 1/8" Number of Ports=2 Primary Outlet Size=1/2x20 Secondary Outlet Size=9/16x18}
Power brakes
SHALLOW HOLE FOR SHORT PUSHROD HERE

E.Y. Finland,
-67 RS
Orig: PG + 327/275 + 12-bolt.
Now: SBC409 TKO600
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post #9 of 9 (permalink) Old Feb 17th, 09, 02:11 PM
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Al
 
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Location: Vancouver, USA
Posts: 10,511
Re: Hydroboost Pushrod length

Quote:
Originally Posted by RedJet View Post
Fred -- come on down! I can always use labor that is smarter than myself!

Al - I kinda picked it on a lark, based on what I was expecting from the hydroboost. I was also considering port location and compatibilty, maybe I picked a less than optimal, we shall see!

Hey if Fred comes down this weekend maybe we can get together and check out your car? Is it still in the couve? Let me know....

BTW- I have a rotten-stinkin-leak on my RH rear caliper that is frustrating me! Had to walk out of the garage tonight to get my sanity back...Ugh!

Best,

Jereme
Still in the 'couve! PM me.....


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