cant lower idle speed on new slant 6

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whatadish

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just started totally rebuilt slanty yesterday...sounds great runs awesome but can not get the idle speed down. Easy to see throttle plate is closed all the way...new 1920 anyway. not a choke, timing. or vacuum leak issue either. It is a little too quiet for me in terms of valve lash. Although the machine shop set the cold lash at the shop, could too tight of a lash cause this issue. Petronic breakerless setup, just about everything is new. There was a similar thread on the slant6 forum that did not answer the question of too tight valve lash causing this issue. Once again this is not a carb or linkage issue, choke step plate is off and the throttle plate is completely closed...excellent steady vacuum as well. Any suggestions would be greatly appreciated. Yep there is some pics of the car in my gallery.
 
It won't be the valves, Too tight would make it Idle ruff.
Only thing I can think of is to remove the carb and check that the throttle plate is aligned and closing fully.
 
Is the throttle linkage tight, as in no looseness or slop in the linkage to the carb? Perhpas it has been bent and is holding the throttle palte opne a wee bit; it won't take much. As above, I can't think of a reason for the high idle except in the carb, certainly no the valves.

Havae you ahd the engine completely warmed up to test this?

The carb is suspect since it is new; could be the throtte shaft warped and hanging in the shaft bores. Can you expand on why you think the throttle is completely closed?

Another explanation is that there is an air bleed path in the carb that has opened up; dunno if these carbs have a power valve that could leak both air & gas. And, an additional small air leak (like a small vacuum leak) could be compensated with idle richness and still idle smooth.
 
Linkage/cable adjustment,good answer.
Maybe the base gasket? it only goes on one way.
 
Usually high idle is caused by a vacuum leak or wrong timing.
 
i had the same problem once and found that the cable to the carb needed to be adjusted. it wouldnt let the carb close all the way.
 
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