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Old 01-23-2011, 10:38 PM
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SBC 350 idle issues

I just dropped a fresh 350 in my 74 nova (530 lift cam, 650 holley, HO 305 heads). I also had the TH350 freshly rebuilt and added a 3,000 stall.

The car cranks just fine, but it will only idle in park at 1000rpm or higher, and when I put it in gear the engine slows and dies in about 3 seconds.

I plugged all the vacuum ports on the carb so that shouldnt be an issue

The distributor is an HEI with vacuum advance but I'm not utilizing the vacuum. It isn't new so it could be worn out and causing the idle issues but I cant tell for sure.

If anybody has any good pointers or knowledge on this kinda problem I'd greatly appreciate it. Thanks in advance!!

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Old 01-23-2011, 11:39 PM
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question

have you set the idle with the trans in gear ? Somtimes with big overlap cams when the engine is loaded and slows the timeing retards and stalls the motor! high lift cams have low vacume! and need to idle higher. MAKE SURE SOMEONE HOLDS THE BRAKE AND HAVE IT IN REVERSE WHEN YOUR IN FRONT OF CAR DOING ADJUSTMENTS.
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Old 01-23-2011, 11:44 PM
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Hmmm havent tried that....I did try idling the engine up to about 1500 and putting it in gear ( I was by myself ) and got the same result.
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Old 01-23-2011, 11:48 PM
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what are cam specs? sorry i type slow 1 finger!
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Old 01-23-2011, 11:58 PM
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tech

if your alone jack up the rear of car jack stand it and make sure its secure and do your adjustments use a vacume gauge in gear ideling step on brake slow eng with brake see what vacume reading is just before it stalls it wont run if vacume is too low.
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Old 01-23-2011, 11:59 PM
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It was a friend of mine that put the cam in and he naturally lost the cam card....all I know is its a 530 lift. The thing chops some wood so its quite large wish I could give you more info on it i know the idle issue could be any number of things
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Old 01-24-2011, 12:05 AM
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tech

you may have a bad converter locking up early ive installed bran new ones did that and aspecialy used ones
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Old 01-24-2011, 12:11 AM
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teck

3000 stall conveter should have plenty of slipage at 1000 rpm if it still stalls at higher speed when brakes held in gear say 2500 rpm, but bellow stall speed your coverters locked when in nuetral your converter in free wheeling

Last edited by painted jester; 01-24-2011 at 12:17 AM.
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Old 01-24-2011, 12:12 AM
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What is your ignition timing curve?? Large cams will require mods to a typical HEI distributor, you will need to achieve a high initial timing setting like 20-24 but limit the total timing to 36-38.

The higher initial timing will allow the engine to idle much better. What you have happening is typical of big cams and unmodified distributors.
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Old 01-24-2011, 12:21 AM
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tech

hes right and vacume advance isnt much good on big over lap cams
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Old 01-24-2011, 12:24 AM
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I believe you may have answered my question ericnova72. I am in the process of having the distributor modified (i dont have a welder or proper tools or know what to do to it for that matter). Everything but the distributor and the alternator is either new or rebuilt so I'm assuming that's atleast where most of the problem is. I set the timing around 35 degrees and it still does it so hopefully the mods will help when I get the distributor back. Thanks to everyone for all your input I'll let ya know how it goes and please if you can think of anything else dont hesitate to let me know. Thanks again!!
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Old 01-24-2011, 12:26 AM
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tech

is the cam advanced , retarded or straight up advanced would increase vacume and idle better but you would lose some of the radicle sound
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Old 01-24-2011, 12:32 AM
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tech

if you set your anitial timing high with stock distributor already its not the distributor initial timing is initial no mater what distributor you have in it
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Old 01-24-2011, 12:34 AM
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good night & good luck
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Old 01-24-2011, 12:38 AM
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good night

total timeing is at speed usualy coming in at 3000 rpm on hi po engs initial timeing is at idle
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