Sure it must've been covered previously, but looking for suggestions on where to install a servo take-off... Empi inlet manifold for Weber prog. I know there's a flat bit of casting on the short manifold for 3 & 4...is one take-off sufficient? Any advice most welcome... This ain't my engine BTW
The vacuum is about the same both ends of the manifold if everything is in balance in the cylinders. That end keeps it out of the way of the stock air cleaner. In the end the brake servo is meant to operate best with the throttle shut which means it is going to be much the same pressure throughout the inlet manifold at that point. To access manifold vacuum on mine I drilled a hole at the top of the riser on the manifold just under the secondary choke and JB welded in a pipe stub. It is at a lower temperature and on my setup it is used for operating the hot air control flap in the air cleaner (or actually snapping the actuator as its too much vacuum !)
I did indeed..@Dicky brought it up to Dubreeze this sunday would it not be more prone to fluctuations closer to just one cylinder? I'm fitting two take-offs...one for servo, one for a MAP sensor, so the central riser section has been bagsied....maybe fit both on the riser one above the other or one at the front, one at the side. The Empi riser section is split for the primary and secondary chokes until it merges about an inch from the bottom, so it's not as straightforward as I imagined...unless I'm worrying uneccesarily
wasn't this flat casting originally for a take-off? Now you've got me thinking....my bus has been so long non-standard, I forgot about a vacuum source for the air cleaner....is this source normally taken from the inlet manifold on a stock set-up? I'm thinking to reinstall the original air cleaner box, complete with pre heat etc, but modify the ducting from the box to mate with the carb top My memory's getting worse
To get most out of a 1776 twins would be a better option ,but I guess you already know that. Standard type 4 servo take offs are just above cylinder head but there are two connected by a balance pipe
When I had a 1776, I put a vac takeoff for my brake servo in that exact spot. Everything was fine. The engine didn't have any problems, the world did not end, the sky did not fall in. The engine ran for about 8-10k miles without any problems whatsoever, I then sold it on when I had my scooby conversion done, and as far as I know, it is still running fine in the van of its new owner.
...there's the rub! Think my riser's gonna look like 'Take-Off Central' I've a matched pair of IDFs waiting to be overhauled (again) but I'd like to see how far you can go with the progressive...I've a feeling people tend to write them off, performance wise, but maybe don't take as much time as they ought to set them up properly...it's a cheap carb at the end of the day, but pretty sure you can get it to work well
Yes, the brakes were fine. The previous engine had a different manifold, and the vac takeoff on the old manifold was blocked! Braking on the motorway was brown trousers time, so a working servo on that manifold was a revelation.
Think i'm going to use the new brazilian bay servo, as they're pretty cheap all considered....worryingly, when i asked Jk whether the original style Master cylinder for 71-79 servoed buses would fit on the Brazilian unit, they said "we've had a look and can see no reason why it shouldn't fit.." While that's a reasonable response, I was expecting a Yes or No answer tbh... Call me a worrier but having looked at a german company's website that specializes in classic brake systems, there's much more to it than meets the eye, in terms of cylinder stroke, diameter, pressure, servo ratio etc. As a kid I'd've just cobbled something together and hoped for the best, but now I'm starting to notice more grey hairs, the concept of 'brakes' and 'cobbling' are now mutually exclusive
