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Old 06-18-2011, 06:20 PM
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Idle Issue vs. Cam Selection

Hello again everyone, Jay Gadsby here. Recently, I got the engine running in my boat, all is well there. Got the timing right where it needs to be etc. But, I cant get the idle below 1000rpm no matter how hard I try. The idle speed screw is barely touching (just enough to keep some pressure on it.) As per the holley initial adjustment guide, said to lean out the mixture screws and back off 1.5 turns. Did so, not enough to keep the engine running. A little more fuel and it gets happier. My question is this. I have a Crane Cams p/n 114201 .450 lift on both, 284 duration and 114 separation. This is installed on a SBC bored .060 over, balanced with flat top pistons, vortec heads, and a Holley 4150 600CFM marine carb. According to the local engine builder the CR is about 9.3:1. Ignition is a Thunderbolt IV that requires 8* BTDC, and thats where she sits. Is it possible that its too much cam to get the idle and lower without stalling it out? Is that a possiblity? Oh, and I sprayed the entire silly intake with carb cleaner and so far no idle changes. So I am guessing no vacuum leaks. Is there any obscure areas I need to check for that? Any one have any ideas? Thanks in advance guys (no sort of pun intended there).

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Old 06-18-2011, 06:22 PM
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DId you ck the secondaries idle stop?
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Old 06-18-2011, 06:45 PM
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Yes I did. Does this carb require any sort of vacuum reference or anything. On the backside of the carb, there is a ridiculously large capped off port. It is rather hidden with the coil there and the distributor. The cap slid off rather easily and I gonna put a hose clamp on it and see. The rochester setup on the mercruiser that used to reside in the engine bay had no vacuum lines period. Thanks again!!
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Old 06-18-2011, 08:28 PM
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Thanks for the advice. As far as the 8* initial timing, I set it to the Mercruiser standard and supposedly it is going to add 22* at max that should be all in by 3600rpm from all I have gathered. I will look into all that very soon. Right now it is idling at 900rpm (750 is the high side of stock). I will have to pull off the carb tomorrow and get it adjusted up. Thanks again!
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