Valve noise
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Joined: Feb 2008
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Valve noise
First time user great site! Problem 77 ford with a 390 600 cfm carb. If I set the timing to factery the valves rattle BAD when you hit the gas or pull up a hill and it also starts had after it warms up. I know it sounds like its advanced to high that was my first guess. Mybe timing chain? 
Postmaster
Joined: Aug 2000
Posts: 3,312
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From: Eldorado Ca. USA
I agree with RCcrawler, I think its detonation. Back off your timing a few degrees, and run higher octane gas. The proper fix would be to get your distributor re-curved. There are seveal writeups on the internet on how to do it yourself. Do a search on google for duraspark distributor re curve.
Also you might be running a touch lean? I dunno. Try backing off your timing first, see what happens.
Also you might be running a touch lean? I dunno. Try backing off your timing first, see what happens.
Postmaster
Joined: Aug 2000
Posts: 3,312
Likes: 1
From: Eldorado Ca. USA
So you are saying that as the chain stretches, the timing retards? I hadn't thought about the effects of a chain stretching, I would have thought that it would not give that much unless seriously worn.
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Post Fiend
Joined: Feb 2007
Posts: 7,191
Likes: 4
From: Blairsville,Ga
the will streatch a good bit and still run and the more wear the more timing retards
pretty easy to check with timing light
pretty easy to check with timing light
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Postmaster
Joined: Aug 2000
Posts: 3,312
Likes: 1
From: Eldorado Ca. USA
Originally Posted by rbaker6336
the will streatch a good bit and still run and the more wear the more timing retards
pretty easy to check with timing light
pretty easy to check with timing light
Logistics Pro
Joined: Jan 2001
Posts: 3,740
Likes: 37
From: Central NYS
I think of a sloppy chain as alowing the cam/valves/distributor to lag behind where they should be. Or, to say it the other way around, the crank gets ahead of the distributor. When the distributor calls for spark at, what used to be 6* BTDC, the crank is already at ATDC, causing the spark to be retarded.
To verify chain slop, rotate the engine until the timing marks are roughly lined up. Pop the distributor cap and watch the rotor. Rotate the engine CCW until the rotor JUST starts to move. Note the timing marks. Then rotate the engine very slowly CW until the rotor JUST starts to move. Read the timing marks. If you can rotate the crank over 10 degrees without the rotor moving the timing chain and/or sprockets are pretty loose.
To verify chain slop, rotate the engine until the timing marks are roughly lined up. Pop the distributor cap and watch the rotor. Rotate the engine CCW until the rotor JUST starts to move. Note the timing marks. Then rotate the engine very slowly CW until the rotor JUST starts to move. Read the timing marks. If you can rotate the crank over 10 degrees without the rotor moving the timing chain and/or sprockets are pretty loose.