Does anyone know what vacuum the servo needs ? It may be a little like 5Hg or need a near perfect vacuum ! The smaller the pipe the quicker it will achieve the vacuum as less volume .. I have the brazzy servo and twin 36 dells with the standard type 4 pipe .. all you been is a bit of rust to block you valve !
not forgetting part of the tube (front to back) is metal. My money is on it not actually being connected lol!
I wouldn't imagine it needs an outer-space absolute vacuum Really, it's atmospheric pressure being let in that does the business.
Don't think your engine would idle very well if that was the case It's obviously Brexit that's causing these problems. Or climate change.
[QUOTE="lhu1281, post: 2010309, member: 108"Quote] all you been is a bit of rust to block you valve ![/QUOTE] Hadn’t thought of this, ! As the system is over 50 years old and the pipe and valve was presumably dismantled this seems quite a possibility
https://autotechnician.co.uk/brake-servo-fault-finding-guide/ This generic diagnostic article from ZF shows about 600mB/20 inches vacuum in the picture. And notes that as a part of the tests that the non return valve should hold vacuum for 5 minutes. Meaning you can turn off the ignition. Wait, apply brakes and still have servo action. Works on my other cars which have servo brakes. Yes the non return valve keeps backfire/contamination out of the servo but also holds vacuum in the system. As mentioned in the description of operation.
All sorted ! They checked the valve first, on the right way and working . All connections on balance pipe including “ T” connected. No leaks on servo line. The manifolds came with the barbs in situ so no oversight on not drilled. But the vacuum was very weak. Pedal test confirmed servo not working. Following a suggestion by Way Out Westy the T was removed from the balance pipe which remained in situ. A separate Barb was installed on the front left carb ( there was a capped outlet there) and a pipe connected up serving only the servo. Eureka servo working well. A suggestion was made that perhaps the servo did not take kindly to being run of the 2 manifolds, perhaps fluctuation in pressure? I’ll leave that to others to ponder . Thanks for all the suggestions much appreciated
Fixed at last! I'd imagine the servo will buffer/filter the pulses - it just gets pumped up (actually sucked down) by whatever comes down the vacuum pipe. And it is very pulsey, picked off one cylinder. I tried fitting a vacuum gauge on the dash (don't bother btw), and I thought needle was going to fall off...
Glad you got it sorted Dave It’s quite a transformation when all those new bits start working together nicely Sent from my iPhone using Tapatalk
on my 914 the vacuum was a bit of a nightmare as it feeds into fuel regulator ,MAP sensor ,supercharger bypass valve , BOV all whilst trying to force 7.5 psi down it . luckily no servo but i do come off 4 manifolds and it needed an anti pulse valve to stop the massive bounce ..
you got me thinking - i just went out to check how mine's plumbed in (i couldn't remember) and yes its just like that - balance pipe between the two, but the servo line just comes of the left carb. apologies if this information would have been more useful yesterday ..
Good outcome! Not familiar with your set up but now you mention it I had a pair of solex pdsi aftermarket jobs I never fitted and the barbs were different bores. Didn’t think anything of it at the time and never fitted them!
Maybe another difference is that @Huyrob's engine is a single port, perhaps that affects the pattern of what goes on at the midpoint of the balance pipe.
