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1974 620 Air Cleaner Vacuum Line Connections are?

Cardinal Grammeter

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I thought this would be fairly simple:  an intake vacuum line to the Temp Sensor and a Clean Air Supply From Air Cleaner line to Evap and whatever else (I think there is one more item.)


But it appears the Temp Sensor and the Hot Idle Compensator each have their own vacuum line.


I was planning on using the only available vacuum fitting, the one on the EGR sub-manifold for air cleaner vacuum supply.


So there must be T's involved.


Checked Parts and FSM and no clear schematic (but I admit I only spent maybe 30 minutes searching.)


Since the L16 and L18 are so much simpler, I'm hoping this is an easy question(s) for someone to help me with.





PS.  As always, I have nothing to go by from the truck itself.  All this stuff was stripped off.

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Don't you have a post on hose connections?... http://community.ratsun.net/topic/67811-1974-620-need-vacuum-line-schematic-and-routing/ Can't this be added to it?





There is no reason to assume this truck is California emissions equipped.
All 620s had power brake booster and dual master cylinders.
If you had an automatic there will be a very small vacuum line to the transmission joining the bower booster hose near the intake fitting.
Of the two vacuum line fittings on the valve cover side of the Hitachi carb, the front one is for the distributor vacuum advance. The rear one is for the EGR and can used or simply be left off to de-activate this emission device.
There should be a vacuum line to the air cleaner housing. Keep this operational for two reasons.
1/ This goes to a thermal vacuum valve that activates the vacuum motor in the air filter housing snorkel that mixes warmed air from  the hot exhaust with the cold air from the inlet. This provides an air supply that is kept within a close range of temperature and allows the engine to run better when cold. It also eliminates carb icing on extremely cold and damp days. It's gets both cold and damp in Pittsberg? yes?
2/ It is also connected to a thermal vacuum bleed to prevent an over rich mixture when idling hot.
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Yes, I thought about adding on to that thread, but it never yielded the information I needed, I thought maybe a specific Air Cleaner thread would be warranted.


I guess that was a judgement call.


Tell you what, you're and admin right?  Kill this thread and I'll post on that one because your reply that you quoted does not agree with my air cleaner:  I have two vacuum lines coming from each the Temp Sensor and the Hot Idle.


I'm going to reply to your post on that vacuum line thread and maybe I'll get the answer through that thread.

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