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Old 03-08-2019, 07:58 PM   #1
Roxo
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Default installed a new 6:1 head now a tapping noise

I install snyders 6:1 head ( old one was cracked ). Started the engine and had a tapping noise. Checked valves and found a broken valve guide on #4 exhaust. Replaced all guides and springs. Lapped in #4 checked all clearances, ground #4 to specs. Still have the same tapping noise.

I thought maybe a exhaust leak, gasket looked like #4 and #3 were leaking.
Installed new intake and exhaust manifolds with new copper gasket. Still same tapping noise.

Ground out the Spark plugs. When Grounding out #3 the tapping stops.
Is this a bad wrist pin??
There was no tapping with the old head.
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Old 03-08-2019, 08:33 PM   #2
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Default Re: installed a new 6:1 head now a tapping noise

If you replaced a stock head you increased compression pressure by 50%,you basically made a bigger hammer.Given the wear in your valve train I'm going to assume the rest of your engine is worn as well.Higher compression is the best thing you can do to a model a engine to increase power (that,and carburetion),provided its in good shape. Unfortunately you have to go back in and find the root cause of the noise.
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Old 03-08-2019, 08:46 PM   #3
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Default Re: installed a new 6:1 head now a tapping noise

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Originally Posted by Railcarmover View Post
If you replaced a stock head you increased compression pressure by 50%,you basically made a bigger hammer.Given the wear in your valve train I'm going to assume the rest of your engine is worn as well.Higher compression is the best thing you can do to a model a engine to increase power (that,and carburetion),provided its in good shape. Unfortunately you have to go back in and find the root cause of the noise.
Yes I'm afraid what I might find. It's an older rebuilt motor, no idea what kind of mileage is on it since. It ran great with no out of ordinary noises. I thought it was very guite running. Now tick tick tick. the change in compression must have woke something up.
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Old 03-08-2019, 08:54 PM   #4
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Default Re: installed a new 6:1 head now a tapping noise

Same symptoms, much the same diagnostic path. Ended up pulling the motor and disassembling. Found #3 piston scored from rings down. Fortunately no damage to cylinder wall.


Now pistons/rings and back together successfully.


Good luck.
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Old 03-08-2019, 09:08 PM   #5
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Default Re: installed a new 6:1 head now a tapping noise

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Originally Posted by BillLee/Chandler, TX View Post
Same symptoms, much the same diagnostic path. Ended up pulling the motor and disassembling. Found #3 piston scored from rings down. Fortunately no damage to cylinder wall.


Now pistons/rings and back together successfully.


Good luck.
my cylinder walls where fine after pulling the head back off to do the valve work. I need to pull the oil pan and check things out. Thanks for letting me know what you found, I will check for that.
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Old 03-08-2019, 09:34 PM   #6
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Default Re: installed a new 6:1 head now a tapping noise

If you can save the babbitt its not too expensive to freshen it up.Going high compression is a slippery slope,hard to stop when you feel speed.. A mechanical advance distributor to avoid detonation,ping is murder on the center main bearing..a downdraft stromberg 97 or holley 94 provides the fuel the Zenith lacks..while your there,a B cam compliments both pretty good,and toss in a header for the added zip..60-65 horse,add a mitchell OD and you can drive on any road you want without annoying the prius behind you..
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Old 03-09-2019, 10:10 AM   #7
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Default Re: installed a new 6:1 head now a tapping noise

Does it tick when the engine first starts up, then does it ease off after the engine warms up?
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Old 03-09-2019, 12:41 PM   #8
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Default Re: installed a new 6:1 head now a tapping noise

It's possible a piston is hitting the head or gasket.
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Old 03-09-2019, 08:00 PM   #9
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Default Re: installed a new 6:1 head now a tapping noise

I had a tick, tick, tick that turned to a huge knock. It was my center main. Little did i know that when you raise the compression you need to retard the amount of full advance.
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Old 03-10-2019, 09:26 AM   #10
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Default Re: installed a new 6:1 head now a tapping noise

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Originally Posted by old31 View Post
Does it tick when the engine first starts up, then does it ease off after the engine warms up?
Its starts at startup and continues even after it warms up. It will stop for a few seconds then starts back up again. But just for 2 or 3 seconds.
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Old 03-10-2019, 09:29 AM   #11
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Default Re: installed a new 6:1 head now a tapping noise

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Originally Posted by Jim Brierley View Post
It's possible a piston is hitting the head or gasket.
Never thought of that. I did try both the graphite and the copper head Gaskets.
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Old 03-10-2019, 09:54 AM   #12
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Default Re: installed a new 6:1 head now a tapping noise

My big concern is why when I ground out #3 spark plug does the tricking stop? would that be a wrist pin or center main? This started after replacing the head with snyders 6:1 head.
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Old 03-10-2019, 02:49 PM   #13
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Default Re: installed a new 6:1 head now a tapping noise

Keeping an eye on this thread. A friend has a fresh engine that has a tapping sound also.Quite until the engine gets warm. We not had time to investigate as yet. He has a 5.5 Snyder head.
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Old 03-10-2019, 03:18 PM   #14
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Default Re: installed a new 6:1 head now a tapping noise

Hello Roxo,


Quote:
It will stop for a few seconds then starts back up again. But just for 2 or 3 seconds.
This is typical for so-called "piston tilting". This happens when the piston has a little too much wear in the cylinder diameter. Too much running tolerance between piston and cylinder. It tilts transversely 90 degrees to the piston pin axis.
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Old 03-10-2019, 03:36 PM   #15
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Default Re: installed a new 6:1 head now a tapping noise

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Hello Roxo,


This is typical for so-called "piston tilting". This happens when the piston has a little too much wear in the cylinder diameter. Too much running tolerance between piston and cylinder. It tilts transversely 90 degrees to the piston pin axis.
I believe what you are referring to is what we call Piston Slap.
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Old 03-10-2019, 04:50 PM   #16
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Default Re: installed a new 6:1 head now a tapping noise

I was also thinking it could be piston slap.
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Old 03-10-2019, 05:11 PM   #17
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Default Re: installed a new 6:1 head now a tapping noise

When individuals change heads, I wonder if they are giving any consideration to deck height. Know of an individual who had his engine rebuilt by a reputable engine rebuilder and after engine warmed up( which may have come from engine component expansion rates, experienced a tapping sound. It was found that the piston was tapping the underside of the head and shining it up a bit. If the deck height of a model A engine is unknown, which how many times has engine been decked? I could for see pistons playing tag with a head.
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Old 03-10-2019, 05:50 PM   #18
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Default Re: installed a new 6:1 head now a tapping noise

I think we mean the same thing. The piston clatters because it "tilts" diagonally against the cylinder wall with its pressure flank during the ignition cycle and then beats against the other cylinder wall during compression cycle.
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Old 03-10-2019, 06:32 PM   #19
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Default Re: installed a new 6:1 head now a tapping noise

With piston slap in mind here is what I know so far without opening up the engine again. There were no signs of ware on the piston walls as far as the piston body sliding up and down the walls. But again this just started.
One thing I did notice is there is a ridge on the top edge, on just one side of the walls on at least 2 piston cylinders (drivers side). Other side of the walls are smooth. Engine has been rebuilt, .080 stamped on the heads. I believe it's got a lot of miles on the rebuild.
Once I get the truck back together I will drop the pan and inspect from the bottom. Right now I'm pretty much rebuilding the truck from top to bottom. At this point I need to find out if rebuilding the motor should be on my list of things to be done.
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Old 03-10-2019, 07:33 PM   #20
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Default Re: installed a new 6:1 head now a tapping noise

Piston protrusion should be measured,the quench area should be .030 to .040 for ideal combustion.Factor the head gasket crush for correct dimension.I have a milled snyder 5.5 that I use with a zero protrusion engine,runs good..
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