68 power brake booster

[Howard T.]

The buildsheet and all information I have the car was original equipped with powerbrakes.

Thanks

[Jack C.]

Re: 68 power brake booster

Howard. I took a look at mine this morning and tried to get a picture to you. Very difficult when the car is all together. I see the bellows and the mounting studs. The studs look evenly placed. Maybe someone has one under restoration and can get under there to snap a better photo. Sorry.

[Howard T.]

Re: 68 power brake booster

Jack,
Thanks for the responce.
I don't know what is correct, the bolt pattern on the fire wall shows 5 holes with the hole for the actuation rod centered between the top horizontal bolts. The AIM shows this pattern for the master cylinder, but a different pattern for the power booster.

My question is when the body was sent to the assembly line was their two different layouts for cars with power brakes and without power brakes? Or did the assembly line have to cut the fire wall when adding power brakes.

After checking the bolt pattern on the pedal assembly it does not match the power booster.

I,m lost any feedback would be appricated.


Howard

[John S.]

Re: 68 power brake booster

Howard:

so when you bought the car it had a power brake booster on it and now the replacement doesn't match the old one? Non-power brake cars had the master bolted directly to the firewall and there were two bolt holes and one large hole for the actuator rod all in a straight line horizontally. On a power brake car there are four bolts holes, two on top and two on bottom and if you draw an X in between the bolts there is a large hole for the actuator rod. here is a link to what the booster should look like:

http://www.vbandp.com/C2-C3-Corvette...e-Booster.html

you might call these guys at VB&P and see what they say, but it sounds like you are saying you only have three holes in the firewall which would mean a non power brake car.

Sully

[Howard T.]

Re: 68 power brake booster

Sully,thanks for the response.
When I received the car there was no power brake booster or master cylinder with the car. The car was in process of restoration. The firewall has 5 holes with the hole for the actuator rod on centerline with the top 2 horizontal holes, there is 2 other holes located directly below the top 2 holes about 3 inches lower.The replacement booster (MBM restoration parts)does not match the picture referred to in your posting the booster has the 4 mounting holes as stated but the configuration of the body is somewhat different it even has metric mounting studs.
I guess the next question is when the body went down the assembly line was there a difference between the fire wall for the power brake and standard brake vehicle my guess it was.
Howard

[John S.]

Re: 68 power brake booster

Howard,

yes there is a difference in assembly while going down the line. The firewall configuration is completely different with the mounting of non-power brake cars vs. cars with power brakes. This is why many have trouble converting to power brakes. Is the replacement booster that you have purchased similar to the one on the VB&P link i provided earlier? I fear your car may have come from the factory with non-power brakes and at some time has been converted. This is based on my knowledge of the 72 I have. The 68's are very very similar but could be different. Being a 1st of the run year model there may have been a slight diff like there is with the dash ignition or the outer door handles and locks. If I understand your descriptions of the two boosters you have, my guess is your car has been converted to power brakes.

Sully

[John S.]

Re: 68 power brake booster

what is the casting number of the master cylinder? non power should show 5455509 and power should show 5480346. That is if it is original to the car also.

Sully

[Howard T.]

Re: 68 power brake booster

Sully, the booster that I purchased from Eckler's which was packaged as a reproduction replacement.The booster was from MBM Restoration Parts, I would assume manufactured in China the configuration of the body (shell’s) does not match the one listed at VB&P web site similar but not close. The mounting studs are metric not standard as they should be. The mounting for the master cylinder is recessed into the booster not as the VB&P booster. I believe the one listed on theVB&P web site is a correct replacement.
As far as the mounting of the booster to the firewall does anyone have the layout of the bolt pattern?
I would like to check the layout that I have on my firewall.
Thanks for the information.
Your question in regards to the master cylinder I ordered a new one the same time I got the booster, I will check the casting number and respond later.
Howard

[Howard T.]

Re: 68 power brake booster

Sully, the master cylinder that I purchased from Ecklers was listed as a GM reproduction part the casting number is 5460346. The casting number is different then the casting number you listed as original. I don't know what the difference is, sounds like here we go again.
Thanks, for all your help.
Howard