Valve job question -

[SteveH-CO]

OK - last night, I put 20 psi on several cylinders, and manually pressed open the valves with my hand. I 'burped' the valves numerous times. I then reapplied 100 psi. (I didn't do the burp test with 100 psi, simply because I cannot open the valves against that pressure).

The #1 intake valve is sealing much better, and #6 improved, too. So, clearly, I was able to get some debris out of the valve seating area. The question is now simply - do I just run it, or pull the head and double-check the shop's work, all down the line? I guess that one is for me to answer.

 

[TheEquineFencer]

OK - last night, I put 20 psi on several cylinders, and manually pressed open the valves with my hand. I 'burped' the valves numerous times. I then reapplied 100 psi. (I didn't do the burp test with 100 psi, simply because I cannot open the valves against that pressure).

The #1 intake valve is sealing much better, and #6 improved, too. So, clearly, I was able to get some debris out of the valve seating area. The question is now simply - do I just run it, or pull the head and double-check the shop's work, all down the line? I guess that one is for me to answer.

Take a hammer and tap the ends of the valve stems without any pressure on the cylinder to get the valves seated as if it were opening by the cam/rockers. Then recheck it for your peace of mind. I'd run the thing and not worry about it myself.

 

[madoc1]

i agree with equine but would add some air pressure like already did on some. the air should blow out any small debris in there. then run it. no harm done if you do all this and it might turn out just fine. good luck

jim

 

[Showkey]

Debris in the seat area is one theory ( maybe not the best considering recent work things should be clean). Loose valve guides allowing the valve to seat in a slight different position each time should be considered or checked if sealing issues continue.

Agree with fencer.......tap on the valve with a hammer ( brass or soft dead blow) multiple times to confirm the valves are sealing. If your getting inconsistent valve sealing in static testing it is not likely to improved when the engine is running.

If the sealing problem continues ......When you look at the valves.......are the installed height of the valve all the same.

 

[EdT]

FWIW I used to work with high pressure valves and did a lot of testing on lift vs. flow and you'd be amazed at what the curves look like. The amount of contamination between the valve and the seat required to produce a significant leak is amazingly small. Poppet valves have a very steep flow-to-lift curve and the first clearance that occurs in the lifting cycle produces the lion's share of the flow. Point is, a piece of dust or a fly leg between the valve and the seat will make a difference. Keep that in mind along with all the comments above. If it was me, I'd give it a go since it's all together.

 

[TheEquineFencer]

FWIW I used to work with high pressure valves and did a lot of testing on lift vs. flow and you'd be amazed at what the curves look like. The amount of contamination between the valve and the seat required to produce a significant leak is amazingly small. Poppet valves have a very steep flow-to-lift curve and the first clearance that occurs in the lifting cycle produces the lion's share of the flow. Point is, a piece of dust or a fly leg between the valve and the seat will make a difference. Keep that in mind along with all the comments above. If it was me, I'd give it a go since it's all together.

LOL, Fly leg? I love it! That's smaller than fly snot!

 

[BDT/NWMN]

I used to work in a machine shop doing engine rebuilding. Installed and cut many many stellite seats. You have to be able to face them to get the correct seat geometry to get the correct valve to seat contact for a seal. Properly cut seats and valves never need to be lapped in. Lapping is a bandaid repair method and is a relic from the distant past that has no place in modern engine work.

YES Professional Machine Shop that works on these jobs every day..

Also have them check the valve guides, stems, and overall condition of the head..

Have to keep in mind that the rest of the engine should be cleaned thoroughly. A small amount of carbon that is left loose in a cylinder will eventually make an exit through the exhaust valve. A small amount of **** in the intake manifold will be passing through both the intake and exhaust valves... After a Professional Machine Shop puts the head in good condition;;;;;;;;;;;;;sometimes you simply have to start the engine up and let it finish cleaning itself out......

 

[TheEquineFencer]

Update?

 

[SteveH-CO]

I think I'm going to just run it (rather than pulling the head) and see how the compression checks out. I can't work on it for a couple weeks, but will update this thread (for sure) when I see how it all shakes out.

 

[TheEquineFencer]

I think I'm going to just run it (rather than pulling the head) and see how the compression checks out. I can't work on it for a couple weeks, but will update this thread (for sure) when I see how it all shakes out.

Good move

 

[madoc1]

sounds like a plan. where in colo? we usually go to the springs every june-july. at 7k, that is about as high as i can go these days.

jim

 

[SteveH-CO]

Progress - got the entire truck back together, driven 30 miles, head bolts retorqued to spec, and valves adjusted. Compression is 115 (+/- 2 psi) across the board. This is at 7000' elevation, so ~20% lower than sea level numbers. The engine runs well, and starts a bit more briskly, and the idle quality seems better. The oil fouling due to oil getting past the valve stem seals is gone (as is the smell). So, I think the whole thing is a success. I wish I had gotten a bigger compression bump from the .030" head shave, but this is a tractor engine (so to speak) and it takes more than that, it seems.

 

[TheEquineFencer]

Progress - got the entire truck back together, driven 30 miles, head bolts retorqued to spec, and valves adjusted. Compression is 115 (+/- 2 psi) across the board. This is at 7000' elevation, so ~20% lower than sea level numbers. The engine runs well, and starts a bit more briskly, and the idle quality seems better. The oil fouling due to oil getting past the valve stem seals is gone (as is the smell). So, I think the whole thing is a success. I wish I had gotten a bigger compression bump from the .030" head shave, but this is a tractor engine (so to speak) and it takes more than that, it seems.

Keep us posted how it holds up over time...

 

[bulletpruf]

Progress - got the entire truck back together, driven 30 miles, head bolts retorqued to spec, and valves adjusted. Compression is 115 (+/- 2 psi) across the board. This is at 7000' elevation, so ~20% lower than sea level numbers. The engine runs well, and starts a bit more briskly, and the idle quality seems better. The oil fouling due to oil getting past the valve stem seals is gone (as is the smell). So, I think the whole thing is a success. I wish I had gotten a bigger compression bump from the .030" head shave, but this is a tractor engine (so to speak) and it takes more than that, it seems.

That's good news. Good thread. Lots of good tech here.

Scott

 

[sberry]

Modern engines are so much better, put a head gasket in one a while back, 106k on and didn't do anything to it and outlasted the car.