Ben's Z Posted November 26, 2012 Share Posted November 26, 2012 (edited) My god, can this build can any worse. So I got my Heli Coil in today with my cam towers and my N47 cam spun great on the P90. Reused the rockers from the N47 and kept them in order. I put permanent marker on all the rockers arms in prep to check the wipe pattern. Anyhow, I got all the rockers in and start setting the lash. I quickly found out even on base circle I couldn't get ANY feeler gauge on the rocker arm on ANY of the exhaust valves. The adjusters are all the way down. I was able to adjust all the intake valves and usually had about 1/2 to 1 full thread sticking out on the ball pivot past the jam nut. I spoke to a knowledgeable forum member who thinks the shop cut the exhaust valve seat too deep. .0015 was taken off the head by this shop and they felt as much as .0010 was taken off in a previous life. Holy crap I am getting weary of this... If they cut the seat too deep can they still use my valves and take some off of the stem or will that make the lash pad compress the spring retainer and not the stem itself? Are we look at custom valves on the exhaust side at the very least? It should be said they reused the valves (all but 1) out of my bad P90A head in this P90. Edited November 26, 2012 by Ben's Z Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 26, 2012 Share Posted November 26, 2012 Looks like no matter what you will deal with head saver shims... Or recutting all your valve stems shorter. What was the valve stem installed height again? This simple check would have told you if the valves were one right before all the reassembly. Quote Link to comment Share on other sites More sharing options...
Ben's Z Posted November 26, 2012 Author Share Posted November 26, 2012 Tony, cannot tell what the height was before hand. I am starting to distrust these hayseeds who run this outfit. With no exhaust adjustment should I go steeper than .015 on the shims? Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 26, 2012 Share Posted November 26, 2012 Measuring installed stem height will let you know! Quote Link to comment Share on other sites More sharing options...
Gollum Posted November 26, 2012 Share Posted November 26, 2012 This seems like quite the screw up by the machine shop. If they were going to reuse ANY valves after head shaving and valve seat grinding they NEED to see if the geometry is at least "in the window" of operation. I'd take it back to the shop and find out what they have to say. If they have a position of "it's not our problem" then raise hell. Even if they don't fix it, at least they'll hopefully have learned to be more careful on the next customer's head. Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 26, 2012 Share Posted November 26, 2012 (edited) Standard practice since I was trained in 79-80 was anything taken off the seat or the face was taken off the stem tip within a tolerance....then you told them they needed a new seat or valve! But you ask for cheap, you get cheap. Pay now or pay later. Or, as Gene Berg would say "If you don't have the money to do it right now, where will you get the money to do it over?" There is a "Valve Stem Installed Height Specification" --- this is supposed to be checked by any competent shop. Even an incompetent shop should be able to figure out the valve stems all need to be sunk the same just by measuring the stem height before removal. How do you shim your springs for correct installed height if you don't know installed stem height? This goes back to BASIC BASICS! Edited November 26, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
Ben's Z Posted November 26, 2012 Author Share Posted November 26, 2012 Thanks for the input. I will haul this back to the machine shop and let them handle it. To me, to save face, they ought to do the cam and rocker set up themselves now. This shop was recommended by two different guys I know. I can't believe they have been in business for something like 60 years doing crap work, but perhaps they are getting sloppy. Quote Link to comment Share on other sites More sharing options...
Xnke Posted November 26, 2012 Share Posted November 26, 2012 Just remember that you WILL have to adjust the valves several times the first several weeks of running. Probably the first 8 months or so, before they settle in. Leave yourself enough room to do several valve adjustments...The lash WILL GET TIGHTER AT FIRST. Then it'll level off, then in a few years you'll start to see it open up. Quote Link to comment Share on other sites More sharing options...
Josh280z Posted November 26, 2012 Share Posted November 26, 2012 Maybe they don't have experience with datsun heads? I don't know... Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 27, 2012 Share Posted November 27, 2012 Agreed that hey should have checked this - do you know what thickness your lash pads are? Quote Link to comment Share on other sites More sharing options...
Ben's Z Posted November 27, 2012 Author Share Posted November 27, 2012 Agreed that hey should have checked this - do you know what thickness your lash pads are? Do not, pulled them from my N47, my original motor. The rockers, and cam came from my original engine. Cam towers are the originals to the P90. However, I did use some other lash pad from another N47 and here is why. My old engine upon inspecting the lash pads was wearing the lash pads unevenly across the pad, but only on some of the pads. It was wearing a trapezoid shape, but the wider side of the trapezoid wear pattern would be towards the front of the engine. On top of that they had like small chunks of metal or pitting removed from where the rocker meets the lash pad. I didn't use those even though my old motor ran fine except for some oil use, which I blame on the valve seals. Basically I went through and use the best of all the original lash pads I had. Quote Link to comment Share on other sites More sharing options...
Ben's Z Posted November 27, 2012 Author Share Posted November 27, 2012 Well I dropped it off. Owner says .015 shims give you .030 in adjustment? Beyond my knowledge. I can see where he is coming from to a degree, but why do the intake valves adjust, just fine? I originally took them the original P90A head, and spare N47 for parts. The P90A had electrolysis holes so it was junk and and I took them a bare P90. Now I am questioning if they put the N47 valves in the P90. I say this because when I took them both heads in the beginning they rebuilt the N47 parts head, and I told them "wrong head buddy." need the bigger combustion chamber for the turbo. I took my extra valves from all of this and gave them back to them. They are going to take out the exhaust valves and measure it against the length of the valves in the parts box. If they have the correct valves in there and they wipe their hands of this, I will put in .015 tower shims. Once I check the wipe pattern, if I need thicker lash pads how do I go about knowing what size I need without buying a big assortment of thicknesses? When I use to dabble in Ford SHO's a shop sold a valve shims for the shim in bucket Yamaha engine and when you used the shims you needed you sent back what was left and paid for only what you used. Someone should do that around here. Quote Link to comment Share on other sites More sharing options...
Ben's Z Posted November 28, 2012 Author Share Posted November 28, 2012 Got my head back. Amazing how much more lash you get when the correct exhaust valves are in there. I don't think I could have cam tower shimmed my way to 2mm of clearance. I wonder if these guys put the rockers back in the right position? Quote Link to comment Share on other sites More sharing options...
Xnke Posted November 29, 2012 Share Posted November 29, 2012 Sure you can. It's done all the time by the guys who take a P90 or P79, shave the head .080", then shim the cam towers up 0.080", then they run the longer valves to match. Did you number the rockers before you dropped them off? Quote Link to comment Share on other sites More sharing options...
Ben's Z Posted November 29, 2012 Author Share Posted November 29, 2012 Sure you can. It's done all the time by the guys who take a P90 or P79, shave the head .080", then shim the cam towers up 0.080", then they run the longer valves to match. Did you number the rockers before you dropped them off? I left my head "complete", cam in, rockers in, when I dropped it off so they could see how there was no lash Quote Link to comment Share on other sites More sharing options...
Gollum Posted November 29, 2012 Share Posted November 29, 2012 I'm very glad to hear they fixed it and got it squared away. As long as the wipe patterns look good I wouldn't get TOO paranoid about rocker order. Quote Link to comment Share on other sites More sharing options...
z-ya Posted November 30, 2012 Share Posted November 30, 2012 (edited) I had a similar problem with an E31 head that I had 280Z valves installed in The machinist cut the stock exhaust seats to fit the 280Z valves, but had to install new 280Z intake seats. The problem was that now the exhast valve sat almost 40 thousands closer to the camshaft. Not as bad as what you are seeing, but to the point where you couldn't fit a 14mm wrench on the post when the lash was correct, so you couldn't tightned them down. It also offset the rocker wipe pattern to the point wher eit was just about off the pad. The correct way to fix this is to install new exhasut seats and machine them so that the inake and exhaust retainer heights are within a few thousands of each other. The assembled spring heights should match the FSM. The other issue with just machining the valve seats deeper into the head is that now the spring height is different, and therfore so is the spring pressure. So you end up having to shim the springs more to keep the same pressure. If you try to shim the cam towers to fix it, it will have a negative effect on timing chain tension, and cam timing, nevermind screwing up the rocker wipe pattern on the intake valves. Edited November 30, 2012 by z-ya Quote Link to comment Share on other sites More sharing options...
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