Spark Knock??
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Spark Knock??
1979 F-250, 400 engine, C6 Trans.
A few months ago I started noticing a knocking or ticking sound. It was very strong at part throttle or idle. I started with the rod bearings. They did not look bad, but replaced them anyway. No change in sound. I then checked the valves. Everything appeared to be in order, no bent push rods, but I replaced the lifters anyway.(just hoping) Still no change. I did notice a change in the sound when I was adjusting the timing. I have been reading about spark knock. I've tried to adjust the knock out with timing. This did not work. It seems to run fine, but makes awful noise. I've tried using premium gas and still no change. Good oil pressure. If anyone has any experience with this, I'm all ears.
A few months ago I started noticing a knocking or ticking sound. It was very strong at part throttle or idle. I started with the rod bearings. They did not look bad, but replaced them anyway. No change in sound. I then checked the valves. Everything appeared to be in order, no bent push rods, but I replaced the lifters anyway.(just hoping) Still no change. I did notice a change in the sound when I was adjusting the timing. I have been reading about spark knock. I've tried to adjust the knock out with timing. This did not work. It seems to run fine, but makes awful noise. I've tried using premium gas and still no change. Good oil pressure. If anyone has any experience with this, I'm all ears.
Senior User
Joined: Sep 2013
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From: Deer park, Wa.
Did you pop a couple of main caps and take a peek when you did the rods? How about the exhaust? A leak can sure sound like spark knock or a bearing for that matter.
How much advance are you running? Will the timing marks and dizzy line up with #1 on TDC on comp? Good luck with it.
How much advance are you running? Will the timing marks and dizzy line up with #1 on TDC on comp? Good luck with it.
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I did not check any main bearings. I didn't think it was necessary. Wish I would have now.
An exhaust leak was my first thought. I have a new exhaust system, so the only place it could be is at the welds or the header gasket. It sounds so much like an engine problem that I kinda ruled that out. I'll give it another check.
I'm running at 6 degrees advance right now. If I go to 4 the sound goes away at idle, but comes back during throttle. I also sacrifice on power at 4.
Will the timing marks and dizzy line up with #1 on TDC on comp? Not sure what you mean by this. Please clarify.
An exhaust leak was my first thought. I have a new exhaust system, so the only place it could be is at the welds or the header gasket. It sounds so much like an engine problem that I kinda ruled that out. I'll give it another check.
I'm running at 6 degrees advance right now. If I go to 4 the sound goes away at idle, but comes back during throttle. I also sacrifice on power at 4.
Will the timing marks and dizzy line up with #1 on TDC on comp? Not sure what you mean by this. Please clarify.
Senior User
Joined: Sep 2013
Posts: 329
Likes: 4
From: Deer park, Wa.
Pull #1 plug then put your finger in the hole and rotate the engine by hand till the comp pushes your finger out. Bring the piston to TDC then check to see if the balancer is lined up with the index pointer if not the ring could've slipped. Also pull the dizzy cap and see if the rotor is pointing at #1 plug tower. If it's not the dizzy could be a tooth off. You should be able to run 8 or 10 degrees of advance I would think. Good luck with it.
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