I think this is probably my last comment on this thread as I don't have sufficient technical knowledge to add anything of value. However, I would like to say that I have improved the amount of boost to the BTV and, as a consequence, reduced the amount of peddle pressure required of my ageing right foot. The problem, or a large part of it, lay in the type of brake hose I used.

To explain in more detail, when I fitted the reco'd BTV I also fitted new brake booster vacuum hose. It's branded 9mm ID and complying with SAE J1403 standard, however its OD is about 2mm less than the stuff I took off. Yesterday I bought some more hose, this time the bigger OD stuff and branded 11/32", and fitted that. It too states that it complies with SAE standard J1403 and, as 11/32" is 8.73mm, I assume the difference in performance has something to do with the wall thickness of the hose as there is nothing else obvious to me.

Although still a little on the firm side, I am a lot happier. Thanks to everyone who offered advice - I really appreciate it. Cheers, John

G'day Mates,

Further to the question about the stainless steel liner in the BTV rebuilt for me by Karps of CA, it was a stainless steel sleeve for the master cylinder bore. It wasn't absolutely necessary but was an optional extra to increase the lifespan of the reconditioned master cylinder. Cheers, John

Sorry, I can't answer the question about the BTV stainless steel liner but will try to find out. I know my ignorance is showing but the reason I had a US brake business rebuild a BTV for me was because I know bugger-all about them and wanted someone experienced with BTV's to do the job. Also, thanks for the heads-up about personal account details - I didn't understand I could/should do that and now have done so (hopefully). Cheers, John

Sorry Guys, when I read your comments it tells me where you're from and I assumed my comments would indicate likewise when you read them. On closer inspection, I can see that my location is not mentioned and I apologise for any confusion this might have caused. Like Mal says, I'm from Melbourne, Australia, have been on this planet for nearly 66 years and I bought my Patrician from Dick Benjamin of southern CA about three years ago.

I've just had a look at those Chevvy sites and would like to mention for what it's worth that Karps did fit a stainless steel liner into my treadlevac - well I hope they did as I paid extra for it.

Cheers, John

Regarding the wheel cylinders, at the time of getting them reconditioned I was unable to find any the same size locally. That doesn't mean there weren't any, I just couldn't find any then and there. While there are a fair few American cars are on the road over here (only 3 '56 Patricians, including mine), mostly our late model cars are locally manufactured or imported from Asia and Europe. I personally don't know of any that use the same size wheel cylinders as my Patrician. In any event, getting the originals re-sleeved didn't cost much more than new ones would have and the turnaround time was quick. As I had the part #'s at hand, I put them into the cross ref to help anyone else who might want to know them. Unfortunately, they didn't help me find new replacements when I went looking. John

G'day Brian,

Thanks for the advice and I'll certainly be looking into it further. To answer your questions, I took the vacuum reading at the hose end at the booster. That is, I disconnected the hose at the booster and hooked up the gauge to it. By doing this I reckoned I should be able to test the vac tank for leaks at the same time, and it seems to be holding pretty well, losing only 2" overnight. I had previously replaced the carby check valve with a NOS one, which seems to be working properly, and I've also replaced all the vac hosing with new brake booster vac hose. This all suggests that it has something to do with the booster itself, and I now have a few clues to follow up on. Thanks once again. Cheers, John

G'day Mates,

All constructive advice is much appreciated and I'll certainly investigate whether something is blocked. By the way, over here when overhauling wheel cylinders it's common practice to re-bore the cylinders and fit stainless steel liners into the bores, and that is equally commonly known as "re-sleeving". I don't think playing semantics with words is really constructive advice. Also the comment about no external adjustment for brake boosters was simply a statement of fact by Karps. That is, the unit needs to be removed and disassembled before any adjustments can be made. Thanks once again, John

G'day Mates,

Time for that mileage update I promised. Unfortunately, figures were a bit over the shop but I achieved a best of AUS 19.6 mpg (US 16.3) and a worst of AUS 13.2 mpg (US 11), the worst involving some urban areas and hills. Mostly it was around 18 mpg. This is better than before the distributor was redone. The timing was set at approx 9 degrees and remembering the vac advance is now approx 20 degrees, torque seemed to be pretty good and pinging was rarely experienced. However, I'm suspicious of the carby now as there was some hestitation during the speed build up phase, although it's fine at cruising speed (55 - 60 mph). Also, the carby is "wet" around the accelerator pump area and there is petrol staining on the manifold underneath. It's off to a carby expert methinks.

Cheers, JP

G'day Mates,

I somewhat reluctantly join this discussion because of a) my inadequate knowledge of power boosters, b) because earlier this year I installed a BTV that had just been rebuilt by Karps of CA and c) the obviously strong views for and against BTV's. I opted to stick with the BTV because the previous one had lasted for 27 years and even then, only the boost function had failed. That is, the brakes would work but took plenty of leg power to operate, more than I had to spare.

I have a '56 Patrician with push button auto and had just replaced the front wheel bearings, had the wheel cylinders re-sleeved and after bleeding the brakes, found I had no boost. My assumption was that perhaps the pumping for the bleeding had interfered somehow with the boost side of things. The replacement BTV was subsequently fitted, filled with Dot 4 low moisture absorbent fluid and has been driven for about 2,500 miles and given no major braking problems. The only issue I'm aware of, and it's certainly an annoyance, is that the level of boost is too low meaning required pedal pressure is too high, although nowhere near what it was with no boost. Previously, before the boost of the other BTV gave up the ghost, pedal pressure was dynamite and care had to be taken to keep my head out of the windscreen.

Karp's have since told me that BTV's have no external adjustment so I'm either stuck with it the way it is, try again getting it rebuilt, or look at an aftermarket replacement system. I'm not against the latter but would really have great difficulty with a system that requires much modification to fit. I've checked the level of vacuum at idle and it's around 22" of mercury, and the system only loses about 2" overnight which seems OK. I suppose I have to do some more serious mulling over about which way to jump. Cheers, John

G'day Mates, thanks for the advice. It seems what I was achieving previously before the distributor mod's wasn't too bad based on your results. The reworked distributor has been refitted and mileage will be retested in a couple of weeks when she goes on another run. I'll keep you posted on what happens. Cheers, John