wcsinx

I don't think it would matter. Both ports displace the same amount of fluid.

Bee Jay

Damn you guys are som impatient ****'s. I picked up the 2904 at lunch today and yes it will fit my hydroboost. The big 9/16' fitting is in the front, and the little fitting 1/2" is in the back. I'll bolt it in when I get home and let you all know about the lines. Stay tuned.
Bee Jay

Shark Racer

ARE YOU HOME YET?

AGVI

You're too much man.

Eddie 70

Subscribed. I have been wanting to do the hydroboost mod for a while and this could be icing on the cake.

AGVI

Cake is good Eddie.

scottyp99

I am not interested in the Hydroboost(tm) mod, but I am interested in using the newer style MC. Is the interface between the MC and the Hydroboost(tm) different than the stock brake booster?

Wait a minute!!!! Didn't someone post earlier about using the stock cast iron MC on their Hydroboost(tm)? Is that why you guys are all exited? It makes sense that if the stock cast iron MC fits the Hydroboost(tm), and if this newer style MC also fits the Hydroboost(tm), then........WHATEVER FITS THE HYDROBOOST(tm) WILL ALSO FIT THE STOCK BRAKE BOOSTER!!!!!!!!!

Can anybody confirm if this is the case? Should I hightail it down to NAPA and beat the rush?

Oh, wait, we are still waiting for BeeJay to let us know how it works out for him, aren't we? Well, I've lived this long with a cast iron MC, I guess I can wait a little longer. Take your time, BeeJay, when you hurry is when you make mistakes! But, definitely let us know how it works out, bro.


Scott

TheSkunkWorks

Same here Scott, I'm not interested in Hydroboost either. And, I'm strongly considering conversion to manual brakes, but plan on dumping the cast MC either way; preferring a factory appearance over anything aftermarket. A direct fit with C3 correct bore (per application) and plenty of reservoir to compensate for severe-duty pad wear, and that doesn't require adapting (fittings, mounting or pushrod) would be a great find IMHO.

Bee Jay

OK, OK, I'm home.
First the good news. The M2904 fits the hydroboost. Bolted right up like it grew there.
Now the bad news. Marlin was right, the stock MC has the 1/2" port in the back. Moving the 1/2" brake line to the back a couple of inches was easy smeezy. But moving the 9/16" brake line forward a few inches is impossible. It needs to be about 3-3 1/2" longer. No problem, just disconnect it at the distribution block, take it down to NAPA and have them make me a new brake line 3 1/2" longer. Also, the MC sits much higher than the stock MC. The plastic lid is right up against my screened vent. The hood closes fine and shouldn't be a problem. So the M2904 will fit either the hydroboost or the stock vacuum brake booster. The M2903 will fit only the stock vacuum brake booster. I'll have to wait until I get a new brake line before I can tell you all how the M2904 with 1.250" bore feels. But I know a very popular mod on my Porsche is to replace the 17mm bore MC with a 19mm, so maybe bigger is better.

Bee Jay

Scotty, here is a link to my hydroboost installation. Search is your friend.
http://forums.corvetteforum.com/c3-t...-the-hype.html

Will's'74VetteL-82

Ok....So let me confirm some info. The MC that was originally gotten by Bee Jay (the 2903) will bolt up, no mods at all to a stock C3 (74) with the vacuum booster and lines/fittings and have the same braking properties as a stock MC? If so, I might need to do this soon!

Will

TheSkunkWorks

Bee Jay, Captain Obvious wanted me to point out for viewers that some of that height relative to your hood is due to the MC's distance out from the firewall.

And, thanks for posting up. Whether I find myself on the same page with you or not, your threads are always good reading.

wcsinx

Does the Hydroboost setup move the MC farther from out from the firewall?

Kid Vette

I went with a Wilwood MC. Stock bore and everything bolts up. Very easy swap and saves a few pounds.

Bee Jay

Not really. The hydroboost is about the same thickness as the power brake vacuum canister.

Bee Jay

Yep, but you may have the same problem with switching the lines front to back.
Bee Jay

Bee Jay

Here is the line that needs to be lengthened about 4". The end that plugs into the distro block is smaller than 9/16" or 1/2".


I took the reservoir off. Maybe I can replace this reservoir with something lower. Maybe two cylindrical reservoirs with screw on caps. The hole is 7/8" and the distance between the two reservoir bases is 3 3/4" apart.

Bee Jay

This is what a C4 master cylinder looks like. I wonder if those reservoirs would fit? Where can you buy reservoirs only?
Also, the C4 MC bore diamerter is only .875". Now I know why every time I drove a C4 Vette, it seemed to take a lot more foot pressure to brake.

aussiejohn

Bee Jay,

Have you considered doing a "cut & shut" on the original reservoir? With a good, brake fluid resistant glue, it shouldn't look too bad, especially if the cut was just under the lid, which would make the join difficult to see with the lid on. It would more than likely still hold plenty of fluid, if the cut was only a half inch or so.

I'm planning on a Holden MC for mine, which has the pressure regulating valve built in to the MC, and the whole lot weighs only 1.1 Kg, 2.6 Kg less than the stock MC. It also has metric threads at the outlets, so I will have to make up new lines anyway to go to the stock distribution block. I will move the switch wire up to the Holden MC. I just have to work out how to disable the switch mechanism in the distribution block, or I will just use a Holden dist. block and do away with the Chev one entirely.

The Holden MC has only an inch bore, so more pedal travel, but this might make it easier to regulate the pressure applied to the calipers. If this doesn't work out, I will just replace the Corvette MC and re-use the old lines.

Any thoughts on this?

Regards from Down Under.

aussiejohn

Marlin

Anybody know, for us early 70's c3's, if the dimple master cylinders will fit the older style boosters?
Seems the older ones have the rod stick out 1.6" while the newwer, later 70's+, have just the dimple.