Spencer Posted January 7, 2014 Share Posted January 7, 2014 Vac advance chucks in a bunch of timing under cruise speeds (so high vac) its awesome and can save lots of gas. Once you go to individual runners and carbs/butterflies you are going to have different vacuum characteristics and the stock setup may work like poos. Sometimes a aftermarket (or modded) dizzy can be used on cars with a lower vacuum signal to still give some vac advance. Oh and if you have way too much base timing the vac advance is going to dial in wayyy to much advance at cruise speeds and it will shudder and lurch. Quote Link to comment Share on other sites More sharing options...
Ned Posted January 7, 2014 Share Posted January 7, 2014 word on the street is into the filter housing but i have no IRL experience with that personally, but thats what someone said in my bike carb thread Quote Link to comment Share on other sites More sharing options...
Steelies Posted January 7, 2014 Share Posted January 7, 2014 filter housing it is. oh yeah, so my slides dont seem to pop back down very crisp or quick manner when i move em up by fingers, it's like they jam slightly when they reach the top. they eventually come down and bottom 3/4 of travel is fine. it seems like more of an issue with the diaphragms (which were freakin tricky to reinstall) than a matter of slide friction etc. the spare set i have return a bit better. could i have got a set of carbs with incorrect diaphragms in them? they sat in the groove fine once i fucked around enough but wondering if i'm already up shit creek.. is there a way to test if the diaphragms are sealed correctly? i got as far as sucking and blowing gently in the little opening beside the throat, which moves the slides quite responsively. these are what i have, minus the kink and the scum Quote Link to comment Share on other sites More sharing options...
peteretep Posted January 7, 2014 Share Posted January 7, 2014 I have fittings in the runners for vacuum, all I use it for is vacuum advance. you might be able to take vacuum from the carbs but you should check to see what side of the throttle plates the signal is coming from, if it is upstream on the throttles then it will never get vacuum in our setups (normally these would be in an airbox and get some vacuum). If it is downstream of the throttles then you should be able to use the vacuum in theory. Also, if you want to take a vac line from the carbs, make sure it is vacuum and not fuel bowl overflow vac advance is used at motorway speeds to lean out under no throttle, ie is used for saving gas. I have mine hooked into all 4 runners and the vacuum diaphragm pulses at idle. If I fitted a vacuum chamber as seen in your pic then I would imagine the problem would go away If you want to use vacuum for a brake booster, just make sure that you have a check valve fitted in line so that vacuum is accumulated and wont drop at full throttle Quote Link to comment Share on other sites More sharing options...
Steelies Posted January 7, 2014 Share Posted January 7, 2014 check valve between runners and vac block, or between block and booster? stock valve is still in place just before booster Quote Link to comment Share on other sites More sharing options...
kpr Posted January 7, 2014 Share Posted January 7, 2014 stock valve will be all good Quote Link to comment Share on other sites More sharing options...
Ned Posted January 7, 2014 Share Posted January 7, 2014 it seems to me that if you have pulsing, that you just need a bigger collection chamber for dampening? Quote Link to comment Share on other sites More sharing options...
peteretep Posted January 7, 2014 Share Posted January 7, 2014 thats what I said above ned, In my case I dont have a collector fitted but the vac advance works properly just past no throttle so I havent been bothered to change it also, yeah if there is a check valve fitted as normal then you should be fine, maybe just check its still working. I dont know much about where/how they are fitted normally and whether its different between manufacturers Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 7, 2014 Author Share Posted January 7, 2014 Sweet I will certainly set up the vac advance as this is a road car and I'd love me some fuel savings! Quote Link to comment Share on other sites More sharing options...
Steelies Posted January 7, 2014 Share Posted January 7, 2014 chur yall! Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 8, 2014 Author Share Posted January 8, 2014 side note, a friend of a friend bought a ke30 with a 4age running mikuni BST36 (might be 38s) and says it runs fucking mint, so theres a bit of encouragement for you. 1 Quote Link to comment Share on other sites More sharing options...
cubastreet Posted July 3, 2014 Share Posted July 3, 2014 Thought I'd dredge this thread rather than start a fresh one. What do you guys do with the pcv when you use bike carbs? Do you plumb it into a vacuum collector or just catch can it? Quote Link to comment Share on other sites More sharing options...
Spencer Posted July 3, 2014 Share Posted July 3, 2014 Ideally you would want a common link between the runners and hook up a PCV properly. A bit of crud in the intake is worth it for the benefits of crankcase breathing IMO. But if the motor is a heavy breather and the PCV cant keep up then catch can it, I guess 99% of setups here have done that? 1 Quote Link to comment Share on other sites More sharing options...
peteretep Posted July 3, 2014 Share Posted July 3, 2014 yeah I removed the vacuum check part out of the pcv valve and ran the hose to a catch can and it works fine. Make sure you get a proper catch can with a tube inside it so that the oil and mist separate properly Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted July 3, 2014 Author Share Posted July 3, 2014 At this stage I simply have a breather filter on mine, if it makes a mess I'll fit a small catch can Quote Link to comment Share on other sites More sharing options...
cubastreet Posted July 4, 2014 Share Posted July 4, 2014 Ok I read up about pcv valves and the internet convinced me they're worthwhile. The original inlet manifold has the thermostat housing and a water channel between the heads (Subaru) so I might hook it up as a vacuum collector. Quote Link to comment Share on other sites More sharing options...
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