Loud Knock After Replacing Intake Manifold

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tdsunderla

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Sounds like you may have some wires crossed. You shouldn't have disturbed much more than the distributor. Follow each wire to the plug in direction of rotation. 1-8-4-3-6-5-7-2
Checked wires and they are correct. Would a bad wire have the same effect?
 

brooksman9

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I have got a great video, with the sound, but how do I upload? When I go to attach a file I only see photos.
You could upload to Youtube and link to it.
 

Ricko1966

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Just replaced Intake Manifold. Started engine and timing was off and engine backfired twice, once extremely loud. Set timing and engine idles fine, but there is a loud knock. Any ideas on the source of the knock? Any help is appreciated.
Did these back fires happen while cranking or running? I'm assuming cranking. There are a lot of possibilities,I,d look at the starter and flex plate. If you damaged the starter drive the starter gear can be bouncing off the flexplate,and of you cracked a flex plate they sound horrible.
 

Drauka99

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oouuuffftaaaa that sounds bad. I'm thinking bore scope into the cylinders. Sounds to me like 1 of two things, something got dropped into a cylinder and its hitting or rod knock happened to happen at the same time as the intake change.
 

mtbadbob

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Usually, a rod knock is more of hard ringing sound. That just doesn't sound like a deep enough knock to be a rod to me anyway. Did you pull spark plugs?? Could be part a plug in the cylinder.
 

tdsunderla

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Usually, a rod knock is more of hard ringing sound. That just doesn't sound like a deep enough knock to be a rod to me anyway. Did you pull spark plugs?? Could be part a plug in the cylinder.
I will pull the plugs and check out the cylinders.
 

Ricko1966

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Going to check out each cylinder with a camera… stay tuned.
Do you have the camera? All you are going to be able to see is the tops of the pistons. Look at the plugs,are they beat up? Look at the flex plate, is it cracked? Look at the starter drive is it able to hit the flex plate? Drain the oil is there glitter or chunks in it?
 

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Sounds like 1/2 crankshaft speed. Would add to Ricko's checks to dump the lube filter and look for contamination.
 

tdsunderla

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Do you have the camera? All you are going to be able to see is the tops of the pistons. Look at the plugs,are they beat up? Look at the flex plate, is it cracked? Look at the starter drive is it able to hit the flex plate? Drain the oil is there glitter or chunks in it?
Already drained oil and changed filter. Oil looked good, no glitter. Will check flex plate and starter, but when cranking with coil wire pulled to check lifter operation, engine sounded smooth while cranking. Take a listen…
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GXPWeasel

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The video of it cranking over just isn't fast enough to produce that same noise it sounds like. I don't know, but I'm leaning more towards pushrod / rocker arm chatter from your fist video. What doesn't make sense though is if you only replaced the intake, you wouldn't have messed with the rocker arms, and then they shouldn't be out of whack. When my engine didn't have the rockers adjusted correctly, it sounded a lot like that... so I think it could still be your valve adjustment / rocker arm adjustment, IF you messed with that during the intake replacement.
 

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So hearing the video, I highly doubt its "mechanical" in nature. It sounds like an exhaust leak. The fact it only does it when running but not when cranking (with the coil wire off) is the clue. Also, this was probably caused when the engine backfired. Ensure the header gaskets (including the collectors) aren't blown. You could also idle the engine and pull the plug wires off one by one. The noise should quite down to the "cranking level with the coil wire off" level when you find it.
If you can eliminate the exhaust theory and prove me wrong, I would change my mind and think about something in a cylinder. First thing would be a compression test. If you find a dead cylinder, I'd suspect a broken ring land and damaged valve. That "whooshing" sound is indicative of air leaking past the valve seat. If these heads have ever had valve seats installed, that is another possibility too. I had a late model work truck that dropped a valve seat and it sounded very much like your video.
Another possiblity-Is this an auto transmission? If so, the backfire may have cracked the flexplate. I have had a cracked flexplate and it also sounded similar to that.
Are you sure you're not missing a 10mm socket?
 
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