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Old 08-08-2013, 12:24 AM   #1
Straight six
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Timing ?

I have a new crt performace hei. Also a edelbrock 1404 on a 78 inline 250. The issue is its deiseling for like 20 seconds after shut off and then one loud backfire like a cannon. Not sure how to handle this is it timing or the idle mixture on carb?
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Old 08-08-2013, 12:29 AM   #2
INSIDIOUS '86
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Re: Timing ?

Idle mixture can do this. Hot engine can do this. Timing can do this. Not enough octane can do this. I can be a hard thing to diagnose. So if you make changes do one at a time.

What's your initial timing set at First off?
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Old 08-08-2013, 02:21 AM   #3
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Re: Timing ?

i have a 292, and my engine did this for the first couple of months i had it. i was new to carbs and older trucks. talked a guy at work and tryed all his suggestions. got a new carb, kept doing it. it came down to my idle being too high. also i was leaking gas with the first carb, that caused it to diesel too.. it took a day or two of turning the truck off even when my idle was correct to stop dieseling. just my two cents. id listen to the guy above. hes helped me already a couple times since ive been on this site.
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Old 08-08-2013, 01:34 PM   #4
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Re: Timing ?

My engine did it a lot and it was the idle being to high. The throttle was to far open. I lowered it and it helped then I re adjusted mixture, since my engine is a v8 single plane the mixture distribution was off and a re adjustment fixed it more.

In the mean time you can keep it in gear and shut it off and see if that helps
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Old 08-08-2013, 02:52 PM   #5
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Re: Timing ?

If you can't reduce the idle then hook the vac advance to a manifold vac port. Increased timing will speed up the motor then you can turn the idle down on the carb.
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Old 08-08-2013, 03:13 PM   #6
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Re: Timing ?

And another thing that's strange is that I also have the idle screw all the way out and still idles about 900rpm
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Old 08-08-2013, 03:33 PM   #7
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Re: Timing ?

Manual choke i presume. How about the high idle screw on the choke. Is it backed off all the way?
Possibly the secondary throttle plate is hung open or you have a vacuum leak.
What intake you using?
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Old 08-08-2013, 05:27 PM   #8
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Re: Timing ?

No it's electric. I haven't messed with that screw so like half out. Offenhauser intake
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Old 08-08-2013, 05:30 PM   #9
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Re: Timing ?

Could possibly have an intake leak if the idle screw is backed all the way out
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3''spintech prostreet mufflers xpipe 1 3/4 headers
build thread !http://67-72chevytrucks.com/vboard/s...d.php?t=577217
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Old 08-08-2013, 05:47 PM   #10
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Re: Timing ?

Quote:
Originally Posted by Straight six View Post
No it's electric. I haven't messed with that screw so like half out. Offenhauser intake
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THat's probably the source for your high idle.
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Old 08-08-2013, 07:17 PM   #11
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Re: Timing ?

Do you guys thing the idle being a little high because I mean little by like 150 rpm is because the hei is to far advanced ?
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Old 08-08-2013, 07:31 PM   #12
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Re: Timing ?

What's the timing set at on the initial. Shouldn't be more than 12*
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3''spintech prostreet mufflers xpipe 1 3/4 headers
build thread !http://67-72chevytrucks.com/vboard/s...d.php?t=577217
Iroc gauge threadhttp://67-72chevytrucks.com/vboard/s...d.php?t=554511
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Old 08-08-2013, 08:25 PM   #13
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Re: Timing ?

I don't know just slid the old dist out and put the new hei the same way. I'm an idiot
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