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bike carb manifold
rash12 - 11/10/11 at 11:24 AM

im in the process of manufacturing a manifold for a set of bike carbs for my pinto and was after some advice,
what size vacuum pipe should i use for the four take offs from each leg of the manifold, and what sort of size vacuum chamber will i need before the single vacuum pipe to the dizzy ??

thanks in advance

deezee - 11/10/11 at 11:49 AM

About 3mm ID will be fine for your vacuum take off. A reasonable sized vacuum reservoir / chamber would be around 2" diameter and 4 inches long.

RAYLEE29 - 11/10/11 at 12:03 PM

hi, is it really necessary to have a chamber and that seems excessive to me just for the vac advance on the distributor.
Ray

blakep82 - 11/10/11 at 12:15 PM

quote:
Originally posted by RAYLEE29
hi, is it really necessary to have a chamber and that seems excessive to me just for the vac advance on the distributor.
Ray


yeah, it helps to smooth out the vacuum from each runner on the manifold. if you just took 1, it would pulsate, so you need all 4 really, they still pulse though, so it helps smooth the pulses out to give a nice steady vacuum

RAYLEE29 - 11/10/11 at 12:34 PM

ta, but does the plenum really need to be that big? 2"od x 4" long? for mine i was planning on running the four pipes tee'd together then to the vac diaphragm.
maybe a plenum made from a 1/2" tube slung under the runners would be better and neater?
Ray

snapper - 11/10/11 at 03:34 PM

I've got a plenum made from 10pm pipe 100mm long, seems to work on my Megajolt ok

jacko - 11/10/11 at 04:36 PM

A mate of mine made one out of 22mm copper pipe about 70mm long and caped the ends with pipe ends, then soldered 4 tubes in one end and one pipe in the other ,
This worked very well
Jacko

rash12 - 12/10/11 at 06:54 AM

thanks jacko i had a similar idea in mind i was going to do the same with a shorter piece of 42 mm copper tube