Engine Knock?

[atkinson40]

I hear a knock that seems to be about once per revolution.

 

Its louder than a rocker arm noise, but not really loud.

 

When I put in new pistons and rings there was no play between the pistons and pins.

 

I don't remember any play down on the bearings.

 

What could be this noise?

 

Thanks kevin

[MicroMachinery]

Did you measure your bearing clearance when you put the engine together?

[atkinson40]

Did you measure your bearing clearance when you put the engine together?

 

Changed the bearings, but being lazy I don't remember doing any measuring. :blush:

[MicroMachinery]

You probably shouldn't be building engines then.

[Skib]

making sure you have the correct sizing is kind of important........

 

 

 

.... your laziness could have just cost you an engine.

[I'm BLUE]

Measurement per factory specs of everything ,,,

Torqueing to within factory specs ,,,

Being as clean as possible with internals ,,,

Verifying you have a GOOD torque wrench before starting ,,,

,,, and having the correct tools ! ,,,,

 

^^^ is everything when re-building/overhauling an engine.

 

 

-----I have learned to record and file all specs of an engine for future owner/issues...

per specific engines I touch or have had machined by a shop.----------------------------------------------

*cam re-grind figures (if applicable)

*pistons (brand as well)

*ring size (brand)

*ring gaps (all)

*bearing clearances (brand)

*special parts

*special notes

*receipts of work done

*etc

 

 

You're only harming your-self and costing yourself $$$ by not doing going through basics of engine repair/re-build.

 

A good used "running" engine is probably a safer bet ..

 

Good Luck

 

 

EDIT: Don't touch anything internally until you are willing to do it the right way !

[datzenmike]

That said.... if the old motor was running and more or less knock free you have to figure that fresh bearings will tighten up the clearances. (yes it's not optimal, but....)

 

As to the knock... is it constant or does it come and go with throttle? Rod noise is seldom constant and quiet(er) on deceleration.

[Sealik]

You probably shouldn't be building engines then.

 

Some so-called machinists shouldn't be building Datsun engines either

[I'm BLUE]

Some so-called machinists shouldn't be building Datsun engines either

or allowed to work in a machine shop

[Sealik]

or allowed to work in a machine shop

 

Apparently 'they' found employment at the shop I went to.... :lol:

Totally clueless with overhead cam engines, clearances.... etc...... emailed them a Racer Brown tech article, to no avail

 

'Datcaveat' emptor.... :D

[atkinson40]

As to the knock... is it constant or does it come and go with throttle? Rod noise is seldom constant and quiet(er) on deceleration.

 

Thank You Mike. I only remember it at idle. Not at higher revolutions.

 

There's another caveat. I've measured the compression in all cylinders. All read 110 +3 PSI.

 

I probably did the test wrong by not opening the throttle and didn't perform it wet as well as dry.

 

The caveat is that when I remove the plug wire to #3 cylinder there is very little engine change(at idle).

 

Removing #4 plug wire produces no engine change(at idle).

 

I hear a tick, tick, tick noise as I pull the wires indicating spark to the cylinder.

 

#1 and #2 cylinder plug wire removal(individuallly) produces a huge difference, but doesn't kill the engine.

 

Could I not be getting gas to those back cylinders?

 

Or could they have put in a wrong cam when they rebuilt the head.(they changed it)

 

The knock seems to be coming from the #4 area that doesn't seem to be firing at all.

 

Thanks kevin

 

PS: To the other responders. I turn wrenches for fun. I like it. Its a hobby. If I wanted to be THAT serious, I'd go back to being an electrical engineer designing and building stuff that goes on the space shuttle/satelites. :rofl:

[I'm BLUE]

uhhhhh....most of us turn wrenches for fun as well..... it is an enthusiast place is it not ? lol

Even though we all do it for fun/hobby = your torque specs and measured clearances = have to be accurate to be successful whether hobby or professional !

This forum wouldn't be worth :poop: if we weren't trying to be accurate where it needs to count either ,,, :rofl:

 

Compression at 110 + or - 3psi = hmmmmm time to rebuild/ or ... keep eyes peeled for a good running engine :)

IMHO .... This engine is not worth your time trying to run if the compression is super low and there are currently knocks ;)

 

Does the engine smoke or eat oil ?

 

Also make sure your compression tester is not faulty or leaky hose as well ! ( I have had it happen a couple of times lol )

[bananahamuck]

110 is really low , how many revolutions did it spin during test , You sure you got valves adjusted correctly?? I like to adjust them on the " very slightly " loose side on a new engine just to be safe..

[Sealik]

With all the plugs removed and a full charge on batt., crank till the needle in the tester stops moving.....that said, it should read around 75 lbs on the first rotation with a healthy motor.

Having the throttle plate/choke open only adds around 7% + -....not much in the grand scheme of things

[atkinson40]

Does the engine smoke or eat oil ?

No, not at all. Not even when I do the smoke test.

 

This engine also pulled this load.

 

 

Up this hill and into the mountains.

 

 

In fourth gear without breathing hard.

 

Some things don't add up. I'm trying to figure out why.

 

The head's been rebuilt. New pistons and rings.

 

All cylinders read comp the same. Why doesn't pulling the wires of any cylinder have the same result?

 

The last time I pulled the plugs, #3 and #4 didn't look tan as they should.

 

They looked kinda black and crudy.

 

Even if I had worn cylinders, I would expect the fuel and firing to be OK giving a tan plug.

[72240z]

I like to adjust them on the " very slightly " loose side on a new engine just to be safe..

 

You know that changes your cam settings quite a bit. Its an old trick to speck the exhaust open more to change the cam timing.

[Sealik]

Its an old trick to speck the exhaust open more to change the cam timing.

 

Or....a 'new cam' had the exhaust lobe center 'moved' by 1 or 2 degrees (relative to intake)...for a little more top end/flow???

Race app....

Can't remember...... :blink: .... :D

Was somewhat mute though if the exhaust pipe and EM were not also upgraded ????

[MicroMachinery]

If I wanted to be THAT serious, I'd go back to being an electrical engineer designing and building stuff that goes on the space shuttle/satelites. :rofl:

 

That's... unsettling.

[datzenmike]

Head rebuilt and new pistons and rings.

Compression ranges from 107 to 113. How is this possible considering the above statement?

 

#1 and #2 wires off cause change in idle

#3 and #4 wires off cause little to no change in idle

 

You said the pistons were replaced? You also said you didn't measure everything.

 

1/ Did you over bore the cylinders and fit oversize pistons and rings?... or

2/ Did you replace the pistons with standard size pistons and rings?

 

If you did 2/ did you measure the cylinders for wear? Did you use chrome rings or cast iron??

[Skib]

but being lazy I don't remember doing any measuring. :blush:

 

 

oops....

 

[atkinson40]

Head rebuilt and new pistons and rings.

Compression ranges from 107 to 113. How is this possible considering the above statement?

 

Thanks Mike

 

This is what is not adding up add I'm trying to figure out. I may have done the comp test wrong somehow.

 

I had the head rebuilt by a well respected motor rebuilding/machine shop here in San Diego. Motor Machine.

 

They replaced the cam in the process, hence my question about if they could have used the wrong one.

 

You also said you didn't measure everything.

 

I didn't measure the bearing clearance.

 

1/ Did you over bore the cylinders and fit oversize pistons and rings?... or

2/ Did you replace the pistons with standard size pistons and rings?

 

I also took the rods with the old pistons/rings and MM pressed on new standard size pistons and rings.

 

If you did 2/ did you measure the cylinders for wear? Did you use chrome rings or cast iron??

 

I measured cylinder bore and ring gap to be within specs. I think the rings were black....cast iron??

 

Thanks kevin

[datzenmike]

If re-bored they would be exact enough to use chrome rings. If only honing the bores cast are softer and break in better on an uneven surface.

 

 

I guess I should ask if you honed the bores?

[atkinson40]

I guess I should ask if you honed the bores?

 

I did.

 

I've just barely gotten ahead on the civic with cvc joints, head gasket, timing belt, water pump, struts and rack and pinion rack. B)

 

Next up is the bosses car, the camry, with cvc joints and a motor mount.

 

Then I can go back to the 620. Maybe pull the plugs and look at them. Redo the comp test.

 

I'm still stumped as to why all cylinders read the sam comp, but only two seem to not affect the engine when I pull the wires.

 

Thats why I asked if they could have put in a wrong cam. Its the only thing that fits. Thanks kevin

[datsunaholic]

 

 

I'm still stumped as to why all cylinders read the sam comp, but only two seem to not affect the engine when I pull the wires.

 

 

 

Because maybe those 2 wires are on backwards?

[72240z]

Because maybe those 2 wires are on backwards?

 

That sounds reasonable, if the comp, air and the fuel are there then spark must be missing...... Confirm timing and PROPER spark.