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Discussion Starter · #1 ·
There is a distinct tapping sound coming from the intake manifold(new
Edelbrock 289 Performer).
This sound will occur even if I turned the motor over a few times with
the coil disconnected(no fire-up) so I dont 'think' its from a hotspot.
Have new heads on, engine has run about 10 mins total since rebuild.
Will a bad water flow/pocket make this noise?
Its not faint at all, sounds like the gerbils are trying to hammer
their way out....
Thoughts?
 

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Did you change cams? Check your push rods for straightness and make sure they have round ends (are they new?) and verify that the lifters are rotating. Check your valve train geometry. It could be steam pockets if it only happens when the engines hot, but I really doubt it.

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<font size=-1>[ This Message was edited by: bytemydust on 6/29/06 5:23am ]</font>
 

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Is this after you crank it and then it shuts down and makes noise? Or do you mean as you crank it it's making noise?



<font size=-1>[ This Message was edited by: thekingofazle on 6/29/06 5:29am ]</font>
 

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Discussion Starter · #4 ·
I have new heads and used the old rods as they seemed to be the perfect fit.
Cam was not changed.
How do the rods/lifters make this noise after shutdown?
 

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Discussion Starter · #5 ·
The noise is after shutdown for about 30 seconds.
I wouldnt be able to hear it during running...
Makes the sound like the old iron radiators in older homes -
almost rythmic.
maybe I have some air pockets in the intake?
 

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On 2006-06-28 14:10, MoNaH302 wrote:

This sound will occur even if I turned the motor over a few times with
the coil disconnected(no fire-up) so I dont 'think' its from a hotspot.
Sorry, I was going by what you said. If it happens and you aren't cranking it over, then I would agree that it's probably steam pockets hammering some where. Do you have a pressurized radiator cap?


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<font size=-1>[ This Message was edited by: bytemydust on 6/29/06 5:38am ]</font>
 

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Discussion Starter · #7 ·
I should note this is on my boat (1968 Trojan with ford 302 'Interceptor')with an open cooling system, so there is no radiator or cap, just raw water pumped thru the block. I think i will pull the hose off the intake manifold(the smaller fitting up on top) and run it till water comes out to see if I might get some air out of it.
Any and all other thoughts are welcome as to what this might be caused by.
 

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OOOhh. Now the plot thickens. Having run an old "crackerbox" with a hot small block brand X, I can tell you this is perfectly normal. If you have a jabsco pump or similar positive displacement pump you put pressure on the system when it's running, but not when it's shut off and you probably are hearing steam pockets forming. Cool boat, got any pictures?
 

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Good looking boat. I would pull the upper hose off, like you have already suggested, and get as much air out of the system as you can. Do you have a way to tell the engine temp or how much pressure the cooling system has on it? If not, you might try to rig something up to make sure it has a few pounds (2-3psi) on the cooling system. If it has that I wouldn't worry about it. I assume you have water cooled exhaust manifolds? These actually preheat the water before it hits the engine so you don't thermally shock the engine. I've seen people take these out of the loop and cause cooling system problems.
 

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Discussion Starter · #11 ·
My risers/manifolds only take the water FROM the block, mixed with some cold from the raw water intake pump to cool the exhaust. The block is cooled by raw water flowing into the 302 water pump. Its always been this way. I will get back to the forum after the weekend to let you know how i made out and if any changes happened after an "air purge".
 

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The 351c that I am now rebuilding for performance used to make that very same sound after I shut down the motor. Had no idea what it was.
 

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It's called a water hammer due to the system draining down each time the engine is turned off. You should have a closed loop cooling system cooled by raw water. Otherwise and crap that gets by your strainer gets in the engine. If you're in a SW environment, engine won't last long. Even a FW will eat the alum parts quickly.
 

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5,000 dollars later...
Lots of boats run open loops. It'll be fine.


How do the manifolds take the water from the block?
 

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yep they sure do and that's what makes parts suppliers and mechanics happy fixing them.
 

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Discussion Starter · #16 ·
Yes, its had an open water cooling system for over 35 years now and on its first semi-major engine work, so I think the open system is doing fine for me.
I wonder why it would decide to 'drain down' now as it it didnt before?
The water to the exh. manifolds comes from the thermostat fitting on the intake.
There is a 'T' there that goes to each riser.
 

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If it uses the ford water pump it probably has a foot valve (check valve) in the intake piping somewhere to keep it from loosing it's prime. This valve may have started leaking by and letting the water run back out of the motor once it's turned off, or if you changed intake manifolds it may have a different outlet height compared to the old manifold which may cause an air pocket or may cause a syphon effect when the motor is off. I'm no expert on any of this, just giving you something to think about.
 

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You mentioned new parts. Did you have this problem at all before the parts change? and what parts did you change, to help narrow it down. Also any cooling problems or temp differences compared to the old parts?
 

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Discussion Starter · #19 ·
Never heard his before the head change. There is also a new water pump and intake manifold. The exhaust s pumping out a good amount of water, temp gauge has shown no overheating so far, but she has not been out running WOT yet.
I noticed it again last night as tried to start it up, before the engine even had a chance to get warm. It SOUNDS like hot water hammering away, but the water was not even warm. Is this something the aluminum manifold might do more than the old cast manifold?
 

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Is the water pump the same as the old one? Does the discharge water amount seem the same as before the changes?
 
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