New semi-loud knocking

[lego126]

I read a similar thread on here, mike u said there now way oil wiuld be coming from there. So its def. Not leaking from there.

[lego126]

Would a head gasket blown between 3 and 4 xylinders cause a oil leak. I mean its not a bad leak, not even enough to cause me to add oil between OC. But i cant stand the "grimy" oil look on the block. Maybe it was to Valve cover leaking all along. 10-4 on the stem seal. I think they actually come with the gasket set from Ni$$an.

[lego126]

The blown gasket is identical to this thread... http://community.ratsun.net/topic/13039-1986-nissan-720-king-cab-with-24-naps-z-engine-carb-based-running-rough-suddenly/

[datzenmike]

The oil supply up into the head is on the spark plug side, no way it gets over to the manifold side.

 

Almost always it's the valve cover gasket.

 

Is the valve cover vent hose connected to the stock air filter?

[lego126]

Ok think i got photobucket working. Chevk out this valve. Looks ok but some buildup on top. Tried cleaning but best i could do.

http://s1070.photobucket.com/user/Lego12682/media/20170317_142259_zpstwybzh7a.jpg.html?sort=3&o=1

[lego126]

Is this normal? Im new to valves, this is a first for the valve seals. Am i ok to reuse u think?

[lego126]

Yes, valve hose commected to breather.

[datzenmike]

Valve is fine. replace the valve seals they are cheap.

[lego126]

K thanks gonna put the first one back in. I already have the seals thats why im replacing.

[lego126]

Alright yesterday before dinner i cylinders 1&2 intake. Cleaned up and everything looked good. Cylinders 3&4 intake this morning, and when the valve is going up and down with the springs removed its making a slapping noise as the valves comtact the seat. Im about 80% sure this is the noise i was hearing. 1&2 didnt make this noise going up and down, only 3&4. Maybe i can post on youtube and let some of u that have done valves before listen see if this is normal.

[lego126]

Here is link to the video. Maybe i should reseat? Sorry for the questions but this is the first time I've done valves.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.youtube.com/watch%3Fv%3Dn2_igU-YTbI&ved=0ahUKEwin0aDjyuDSAhWC7CYKHZucBo8QwqsBCBwwAA&usg=AFQjCNHBnbUxVi4MQNk-ZeS8zKwfoL1nGw&sig2=xA30Jj65oNc12WbuDlEuNg

[datzenmike]

They all do this.... normal. You won't hear that in a running engine.

 

Using a dial gauge against the installed valve without the springs and retainers, push and pull the valve end in parallel with the rocker arm and measure the deflection to gauge guide wear. It should be 0.004" new, allowable up to 0.008".

 

 

You had a blown head gasket and that can cause strange exhaust sounds... and the manifold was cracked. This was likely the problem and/or valve clearance not right.

[lego126]

Well intake valves are all clear, exhaust however,2 out the 4 are warped, bent or worn. When going in and out, in certain places they wont close all the way if i spin the valve. Unfortunately this is something ive gotta order. None of the local AMarket places have em. Good thing i went with your suggestion and started replacing the seals, or id have never found em. I guess that'll me time to have head shaved while i wait on UPS.

[lego126]

Intake side were all not bad, opened and closed good, VERY little play between stem and guide. Exhaust though im skeptical. Hopefully new valves will help with the play and i wont have to replace guides on ex side. But i wont really know until i get the new valves.

[datzenmike]

The valves are very hard material and don't wear. The guides are a softer material and replaceable when worn. If they are actually bent they would have had to have hit the piston top... which is unlikely. In the event they are bent and not just wobbly from guide wear then replace them. Might be best to have the guides replaced by a shop. The old ones need to be hammered or pressed out, the head knurled to displace metal for an interference fit for the new guides, the new ones pressed in and reamed to the proper valve stem clearance of 0.004" and last the valve seat re-cut or better yet replaced, ground and lapped. Not for the home mechanic.

[lego126]

Once again you've proved correct. Upon further inspection, the guides are rather worn. Several of the EX valves are pretty worn as well, with slight pitting on the piston side just below the guide if its closed all the way. Ive been reading alot today on how the guides actually work, and worn guides could have def. Caused some of my problems. (Excess PCV pressure, oil leak aroud the valves cover)

Ill take to work tomorrow and check the actual wear on the valve as well as the stem end play to see if im within spec. I quite certain im out on #4 ex guide, maybe the #1 ex guide as well. Ill let you know tomorrow what the numbers are.

If i ordered new valves, how much you think this would help fill the clearence? Guess it would depend on then valve stem wear.?

[datzenmike]

The valves are hardened, they have to be for what they do. The guides are softer and replaceable. 

[lego126]

I checked all my Ex .Valves after a very good cleaning, i'll check guides tonight with a split-ball

 

#1 top(rocker side) .3135

     mid                    .3135

     bottom (piston)  .3125

 

#2 top                     .3135    

     mid                    .313

     bottom               .313

 

#3  top                     .314

      mid                    .3135    

      bottom               .3135

 

#4  top                     .3135

      mid                    .313 

      bottom               .3125

 

[lego126]

Checking the FSM on valve guide clearance, stem end play, stem should be moved in parallel with rocker arm. Looking at head from the front, does that mean front to back, or left to right, passenger side to drivers side?

Reason im asking, my valve guides seem worn more at the tops and bottoms. Clearance in the middle is spot on, but at the ends its right at its max for recommended service.

[datzenmike]

Parallel or same direction as the rocker arms which are at right angles to the cam.

[720inOlyWa]

Do you know the expected service life of valve guides for tis engine?

[datzenmike]

I'm sure there are Z24s with hundreds of thousands of miles on them with the original heads on them. Things that would accelerate wear would be infrequent oil changes, overheating, incorrect valve lash.... basically poor maintenance and abuse.

[lego126]

Im good on all valve guides. Think i put it all back togather on my next day off. Ill update next week, thanks for help.

[lego126]

Finally got my split ball gauge for checking valve guides, everything checked out good. I was right at the limit on #1 exhaust valve but still good. Got everything back togather, only to realize my "new" EGR tube i was gonna put back in is too LONG cause its out a 4x4 KA . My old one was broke and ive had it taped up with exhaust tape for several years. So when i took the head off i just broke it off and unscrewed it. Classifieds here i come. Anyone have any exp. With the EGR block off?

[datzenmike]

Just pull the hose off the EGR to disable it and seal the exhaust tube. A pipe plug will work, probably metric thread. Take the old fitting in with you.