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Old 07-21-2004, 08:42 AM
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Crazy 350sbc timing problems

Guys, I'm new to the board. Im having some crazy timing probs. Ok first off I will tell you what I have and maybe that will help the situation. I have a 72 Chevelle with a 350sbc bored .030 over. 13.1:1 compression pistons, Edelbrock Airgap intake, Edelbrock 750cfm double pump carb, complete roller motor 1.7 rockers, 1.8 and 2.02 valves on the heads with stock HEI ignition. this motor was dynoed 496 rwhp and 483 lb -ft of torque. Heres the problem. Last night I heard a valve tapping and so I imediately checked the timing. well it was like 20 degrees off, so I go to adjusting it and the vacuum advance was in the way get it back to 0. So I pop the distributor out, turned it just a little bit and put it back in and it went to 60. I pulled it back out in hope that I could get back to 20 but it didn't happen. Its still way off. Anyone have any ideas on how to get the timing back to normal. I have an inductive timing light, and it's still not helping me.


Thanks for any comments.

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Old 07-21-2004, 11:09 AM
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TIMING

I think you have some parts in your combo that are not a match, but thats another discussion.

You stated it was "20 degrees off" Where intial timing, total timing or both, What was the actual reading?????

What was the vacuum canister hitting on????

Got any cam specs on this motor???

I think you need to go back to square one. Get the motor on tdc (on the intake cycle). Set the distributor to the proper place and fire the motor. Then set you initial timing...


When did you here this valve tap??? Idle or while driving up the road????

Keith
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Old 07-21-2004, 11:43 AM
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Re: TIMING

From what I was told that is the specs on the motor. Also to get it tdc, do I need to pull the timing cover off, or is there an easier way? Also if I pull the distributor all the way out, there is supposed to be a mark on the bottom of it or whatnot correct? That notch is supposed to line up on what on the motor.

I heard the valve tapping whenever I would hit it off the line. Sounded pretty awful.


-Jon-
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Old 07-21-2004, 01:12 PM
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Do you have headers? If so are you sure it's not a header leak?

I'm not being a smart *** but from the souds of the questions you really need someone else to do the timing for you! Watch them and learn then do it for your self.

Just tring to keep you from having alot of grief.

Jim
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Old 07-21-2004, 01:53 PM
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fuel

what octane fuel are you running in this motor???

What was the timing at when you first checked it??

Keith
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Old 07-21-2004, 02:25 PM
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If that 350 of yours is putting out 496 rear wheel horses, I'd stop doing anything with it right now and go have a professional look at it. From the sound of it, the guy that sold it to you lied through his teeth, or you're dealing with a very high performance / high dollar small block which requires very delicate tuning. Mess with the timing too much and you're going to have severe detonation problems and destroy its precious internals.

don't take any of that the wrong way, I'd love to help you solve your problem, but when you're dealing with a chevy small block that pushes the limits like that, it's best left to someone with a LOT of experience tuning similar setups.

good luck

tbw
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Old 07-21-2004, 02:36 PM
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You may have a problem with the distributer the mechanical advance may be hanging in the advance position? or the outer ring on balancer has come lose in the rubber.
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Old 07-21-2004, 07:05 PM
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Half the problem is fixed

Ok well this is what is up guys. I finally got the timing fixed, it wound?(I think that is how you spell it) up being 180 degrees off so we got it fixed, however the valve(s) are still tapping. I have time slips of this motor running in a 83' model Chevy truck. It ran a 6.01 first pass, and then a 5.98 second pass. I know this motor is built right. But whatever happened to this thing I dont know. However it does have Hooker long tube headers on it. I still have to find out why the valve or whatever is tapping.
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Old 07-21-2004, 07:26 PM
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Quote:
I still have to find out why the valve or whatever is tapping.
what do you mean when you say "whatever" ? is the noise coming from a certain spot? is it only one "valve or whatever" that's tapping? try holding a stethoscope (read: screwdriver) to your ear and pinpointing where the noise is coming from.

if those headers you've got are wrapped with fiberglass tape, you might have a hole rusted out somewhere that can make a sound similar to what you're describing.

the more descriptive you can be when you post, the more information folks can offer ya.

good luck

the blonde weasel
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Old 07-21-2004, 07:34 PM
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What octane are you running?

Quote:
It ran a 6.01 first pass, and then a 5.98 second pass

I trust thats 1/8 mile times even still that is very fast for the hp you described
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Old 07-21-2004, 08:31 PM
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ET times

I do believe he said he ran 107 octane gas in the tank, and yes that was 1/8 mile with 20" rims and 4.56:1 gears in a Fab 9" positive traction rear end. I've seen the videos. I know I wont run that fast, but I should atleast be down in low 8's or high 7's not high 42's..
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Old 07-21-2004, 08:46 PM
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You said that you hear the noise when you hit it off the line. usually with a rocker arm out of adjustment, bad rod bearing or something like that you will hear it at idle. That's why everyone is suggesting a header leak. Don't for get about the collector, it can sound like something tapping also. If you have a bad motor mount the fan might be hitting the fan shroud when accellerating.
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Old 07-23-2004, 03:13 AM
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tapping noise when you launch?

At night, have someone watch you from the front and from behind. If a small spark or two falls from your starter area, then your flex wheel is flexing against your starter. It will make more of a quick meshing noise, though. But since you're kinda new at this, and different areas may produce slightly different sounds... it's something that will only happen during a launch. I also agree with the guys who say it's an exhaust leak of sorts. It can't be a bad one though, or you'd hear it at idle. Yet it's still bad enough if you can hear it at all.
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