davekp78

Pictures would really help!

jkg2101

some follow-up in case anyone is interested -
i removed the shuttle valve device and cleaned it out. there doesnt seemt o be anything wrong with it. air blows freely through both side of it. the pressure sensor thing is centered, although it may not move much at all. i dont think that is a problem at all
i bled the system again after re-installing this valve. the pedal still feels soft, with a bit too much travel to me and another person with corvette experience, but it does not bottom out
when driving the car, the brakes work pretty well - the rears can lock up appropriately, but i dont think the front system is locking up with a hard stop.

there might be air still in the front lines, or maybe this is just how this system works/feels.

i will keep playing with it (probably bleed front lines for the 100th time again using pressure bleeder on master).

dplotkin

I can assure you that a 65-up manual brake C2 that is operating as designed has a firm pedal requiring insignificantly more pedal pressure than vacuum assist, no inordinate pedal travel and that will lock the fronts up solid if jumped on to avoid a child. If you don't have all three than you need to go back to the beginning. I would have changed the pressure differential switch since you had it out to rule it out. Consider that, and then start bleeding again. Perhaps put away the power bleeder and do it the old fashioned way. Power bleeder should be doing the job, but it could be technique or something simple you are missing. (Happened to me with my 56 Fleetwood, bled until early hours of the morning until I finally moved a drop cloth looking for something I dropped only to expose the bleeder on the master I missed).

Dan

Grampy

To answer your question. Yes, you can have air in the system and see 700 psi on the gage. At 700psi the air is compressed to about 2% of it's original volume which causes the squishy part. If there is too much air you run out of pedal travel before 700 psi is reached. Any air is undesirable as a solid system is needed for ease of control and modulation. As has been mentioned by others the hoses can expand under pressure and be a cause of a soft pedal and Willwood (or other) performance pads can take some heat to become effective.

C2Dude

My 2 cents for what it's worth (probably not much).
I brought my 66 vert home in the spring. OE manual brake set up. My impression was that the brakes were inadequate, The pedal was firm and the travel was fine but I had to jump on the brakes to stop the car and even then, she took longer to stop per unit speed that I felt was acceptable. Now mind you I have been driving "modern" cars for the last 38 years and this impression I had could have been similar to revisiting recirculating ball steering after driving with a rack for 30 years. Only the two front calipers showed any signs of age, everything else in the brake system looked like it just came out of the factory. Ultimately I replaced the two front calipers with OE style calipers with SS selves you can pick up from Ecklers or Corvette Central and re bleed, no joy. I swapped the semi-metalic pads out for organic pads, no joy. At that point I had the opportunity to drive another members C2 that had boosted brakes, stopped on a dime. I purchased a OE conversion kit with a dual chambered master (1 1/8" bore if memory serves) and booster. Bench bleed the MC out of the car, installed and followed the recommended bleeding procedure. Took her for a ride and she stopped on a dime with good pedal feel, none of that over-boosted feel early cars had. Bleeding I have to say seemed fairly easy. Used the old school approach with the wife pumping the pedal while I worked the calipers. Probably took 8-9 pumps per caliper, done. It is easy to buy into the marketing aspect of capitalism (were all vulnerable to that) and although there is merit to all aluminum calipers as a way to eliminate the intrinsic dissimilar metal issues of OE calipers, the ss sleeve seems to be a fix for the OE versions. Using a improved OE system generates very good braking and is probably cheaper that new sexy after market designs.

dplotkin

We all drive modern cars. We don't need to adjust our expectations (as we once adjusted our brakes) when going from an Audi to a vintage Corvette. A OEM 66 manual brake system should stop just fine, with only a bit more effort required in the absence of assist. I'd say your experience had to do with bad front calipers and not any design deficiency. The OEM disk setup that appeared for 65, in operating order to factory specs, needs no improvement and stops fine. If it doesn't it is not because it never did or cannot be made so, its because the owner has yet to discover what the problem is. Problems such as the one the OP of this thread experiences are caused by overlooking something, usually small and often simple.

Dan

427Hotrod

There's something missing here and it's going to take slowly going through it. Measure master cylinder to make sure you have a manual one. Make sure pedal rod is in right hole on pedal and it's adjusted properly into the M/C. That 300-500 PSI is way low and 700 with you standing on the pedal is nothing to brag about. The low spongy pedal sure sounds like air somewhere. it only takes a tiny trapped bubble to do it. Were they better before installing the Wilwoods?

I've got Wilwoods on mine and it's got a rock hard and high pedal...just like it had before with the stock calipers.

JIM

Westlotorn

I needed a new recovery bottle for my old brake bleeder. I found this one, It has a one way valve on it that might help burp your air issues. I just ordered this one. Allstar Performance ALL11017 Bleeder Bottle with Magnet and Check Valve

Drothgeb

jkg2101

yes, i unbolted and put the calipers vertically and still no difference. i might bite the bullet and just buy another master cylinder. i'm not sure where these fancy repro 67 ones are made, but it wouldnt surprise me if maybe there was a bad batch? i'll update the post when i find anything new. on hold now, since the steering control valve (the 3rd rebuilt one i have obtained) is leaking again, with no miles on it. will try buying a new one this time instead of rebuilt. fun stuff!

dplotkin

The only place I would go to buy those is these guys. They are the best at what they do.

https://www.larescorp.com/product-ca...ontrol-valves/

Dan

jkg2101

lares does sell rebuilds, and i think they are reputable
the vendors do sell a new unit, who knows where it is made.