'72 240Z Rebuild

[siteunseen]

I need advice, reassurance on my valves. I took all the rockers off so they were sealing with the springs tension. I blew into the exhaust holes on the manifold side. Tight! No leaking. The intakes were tight but I could tell air was getting past them, just the intake valves. Is that okay? My thinking thinks it is, just no leaking through the exhaust on the combustion stroke. Right?

Thanks for any thoughts.

Cliff

[rossiz]

you can check sealing by flipping the head chambers-up and pour some isopropyl alcohol into the chambers then look into the ports with a flashlight to see if they are leaking. if there's cruddy buildup on the back of the valves, you can soak 'em in solvent then use some masking tape on the stem, chuck 'em up in the drill press and use scotchbright 00 steel wool to get 'em clean & shiny. if they still leak, you can try lapping them, then next step is a valve job.

[siteunseen]

Thank you! Sounds easy enough.

Quite a bit of carbon on the valves. After a good cleaning they have to seal better.

[siteunseen]

That cam hook spring compressor would make centering the cam lobes onto the rocker pad a helluva lot easier, right?  And you do them one at a time until you get it right, then go back and install the right lash pads and button it up?  I'm gonna start with the .190s they sent with the cam then use .175s and some cut up pieces of a feeler gauge to stack under the lash caps for the right height to get them to hit the center, thanks for that tip Rossiz.

 

I bead blasted them today with good results, to me.

 

 

 

[Patcon]

I am no engine expert but I would think you would want zero leakage past the valves. If the intake or exhaust valves leak then you won't reach 9:1 compression or whatever as the build up in pressure will bleed back into the intake or exhaust manifold, whichever is leaking. The need to seal really well which is why valve lapping is sometimes necessary

[madkaw]

Yes - tools are good .

Please check ALL wipe areas before buttoning up

[siteunseen]

Which spring compressor do you use madkaw?  I think the one that hooks on the cam would be best for centering each lobe on the rocker pads.  Seems like it would be a lot quicker but I've never done it so I'm looking for ideas/tips from you and the others that have done this before.

 

Like this one,

 

Thanks, 

 

Oh yeah, I got my heads sealed with Eastwoods clear satin for bare metal.  I used a 1/2" China bristle brush rather than spraying it on.  After reading a good many threads, if you put on too much it will yellow and flake from the heat.  The best thing is to put some on and work it in with a brush, until it quits soaking in.  You can barely tell it's on there but I dripped some water on them and it beaded up like wax.  I'm happy so far.

 

Edited August 1, 2015 by siteunseen

[madkaw]

The compressor in your pic would be ideal. I just used a pry bar.

[siteunseen]

Rossiz says the same. I'll get one.

Have fun with the tranny install. Your helpers will always remember working on your Z.

Pain pills say not to operate heavy equipment. I imagine a locomotive fallls under that warning.

[siteunseen]

Want any opinions on these seals before I go any further.  Are they bulging too much?  The valves will stay up by themselves so they are sealing pretty tight, I guess.

 

I did #1 exhaust last night with a plastic piece of tubing to drive it down, bad decision.  A 13mm deep socket works better, more control and the socket is perfectly even top and bottom.

 

Thanks for looking.

 

 

[Patcon]

Cliff,

When you say bulging to what are you referring? I don't see any distortion. Can you point it out.

C

[siteunseen]

Those aren't made for an L head and if you drive them down too far the valve guide will cause them to "bulge" out between the little spring and the metal base of the seal.  You can see the gap at the very bottom between the inner spring seat and the metal base of the seals.  I'm worried I went too far.  I'll put another, uninstalled one beside these and take a closeup picture to help judge, my eyes are finally showing their age.