That makes sense. I am not a morning person so no morning work for me. After work, I am on kid duty so that doesnt work either haha. I have to wait until the kid falls asleep to be able to sneak off to the garage. No wonder it took me 2 weeks to swap the clutch on my Evo...
That must be rough with kids to work on the sled. It takes me forever to swap a clutch, I'm like 2 months doing it cause I get bored so easily. Sometimes I'm a morning person, sometimes a night owl.....lol. Depends on how long my work day was. What kind of clutch you running on the EVO? I'm looking at options for mine, it really hates launching with the stock clutch.
Ya having 1 kid is my 2nd full time job. Maybe when he is older and can help work on cars, things might go a bit faster. And ya my stock clutch didnt like the 5k RPM launches that I was doing either. Didnt last long under racing conditions. I went with the ACT HDSS setup with the 13 lbs chromoly flywheel. Thats what most of the 8-9 people run when under 500whp. Its a good solid and proven setup. I am sure they make the same thing for the 10. Pedal is just a little stiffer then stock but man, that clutch can grab. Made my launching so much more consistent and a lot less stinky.
Custom machined spring seats should be completed by next week. Head valve bowel & runner port work is completely finished. Combustion chamber polishing finished. I'm working on a fixture to vacuum test the valves on the head, sorta like a suction cup plate with a fitting for a vacuum pump.
Looking into an 80* carbide valve cutter from Neway. I'm waiting on the Nissan intake & exhaust valves to match when I'm cutting the seat angles. Now what this 80* angle cutter will do is open up the intake valve seat throat. It's hard to describe but the valve seat sort of overhangs into the runner like a doughnut, and the flow has to sort of roll over it to get into the valve itself. Not great for flow, and the diameter is also slightly restrictive as well. Now, I could open the valve throat with a die grinder but I prefer to have a concentric opening with the valve. The cutter is piloted on the valve guide, so the cut will be dead perfect. Currently the intake valve angles are 30*,45*,55*, & 75*. The 80* angle will technically make this a 5-angle valve job, though most would consider this a 4-angle I guess since the throat isn't usually counted. The importance here is that it'll open the valve throat from 1.020" to about 1.050", the most I can without completely cutting away the existing 75* angle. The best method of blending the angles is to maintain a 15* difference between valve angles for smooth flow, so the 75* throat angle serves as a blending angle into the new 80* throat. This will also increase the "Throat-to-Valve ratio" to the more ideal 85% for performance applications. This is effectively like running a +1mm oversize intake valve without the issues of having valve shrouding. Since there isn't physically room to add an oversize valve, a larger valve seat throat is the next best thing. The gain is potentially a 5% improvement in airflow, in addition to the port work in the bowels and runners which is unknown at this time without flowing the head on a flow bench.
Anyway, I'll toss up some pics of the head with all the polishing done to it.
Received my spring seats from the machine shop. They came out nice, a little more play than I wanted but at least they won't bind up the spring when it compresses. In the future I'd probably run tighter clearances between spring, seat, & cylinder head. For now, it'll work fine but there is always room to improve.
I finished up doing the 3-angle valve job on all the intake valve seats, pictures below. What you see are (3) angles, while the top 30* angle is shared between the aluminum cylinder head and steel valve seat so there is a color difference. The 45" seat cut is visible and then a very small 55" cut right below it, then the 70* throat is untouched. The carbide cutters leave a wavy surface finish which can't be felt but is visible, this is totally normal for these cutters and harmless. The goal during the cuts is to make certain all cut angles merge with each other so there is a sharp edge created, sounds weird. Any gaps means there is a bad surface match and that area would allow a leak or burn thru during use. I found a few like this and it takes successive cutting of the 30* & 45* angles to blend out any discontinuities. Some of this was also caused by sanding the combustion chambers and letting the sanding flapper wheel get too close to the valve seats......causes more work later to clean up. Next, I then polished the valve seats with mag polish by hand, then followed up with the carbide cutter again on a very light pressure pass just too smooth everything out, sort of like a plateau honing operation. Finally, I used a sharp pocket knife to scrape any sharp edge down that the carbide cutting blade left over on the aluminum surface. Once the valves start banging away they'll seat perfectly on the softer cut surface and it'll work harden after use and look really nice. I still have to fit new intake/exhaust valves and resize the seats to maintain the correct "margin", this I'll show at a later date.
I checked the valve guide I.D. with my tapered pilot shaft for the angle cutter using a micrometer and the intake valve guides are coming in around 0.2166", spec is 0.2165-0.2172. The actual intake valve stem measures about 0.2152". So the actual clearance is something like .0014". The spec shows a nominal intake valve stem/guide clearance range of .0008-.0021" with a max limit of .004". So the Intake valve guides are pretty much in the middle nominal range even after 80k miles of hard use . This is good. The exhaust exhaust guides are definitely beyond 0.2173" as my tapered pilot shaft is bottoming out on several exhaust guides. I'd guess around 0.2176" based on how they fit current against the pin. The exhaust valve stem measures 0.2149", although it looks worn too. The actual exhaust valve guide/stem clearance is then .0027". The nominal spec range is .0012"-.0025", max limit of .004". So the exhaust valves are running +.0002" above the new nominal range, but well below the .004" max wear limit. This coincides with recommendations online of clearances in the .002-.004" range for exhaust valve stem clearances. My decision point here would be to reuse both the intake and exhaust valve guides as is.
I'm going to have to buy a tighter fitting 5.52mm tapered pilot shaft to continue cutting the exhaust seats, up from my 5.50mm I'm using on the intakes.
So these are a few things to think about if you want to have your head refurbished or upgraded.
Thanks. Yeah, the (1) exhaust I did cleaned up nicely. I'm holding on the 5.52mm pilot from Neway before I finish off cutting the rest of the exhaust valve seats. The exhaust valve seats are heat hardened and a lot harder to cut than the intakes. The most important thing is to get all the pits out on the 45* seat, the 30* top cut has all these weird machine marks from the factory and it's OK to not cut thru all that since it's nothing but a way to transition into the 45* seating cut, if that makes sense.
I didn't show it but I used a black Sharpey to color the individual valve cuts and I can tell exactly where to cut based on how much black marker is leftover or the gaps between the marker lines . I might switch to a red Sharpey as it's easier to see. I'll show this when I start cutting the exhaust seats for those that want to see how you must continuously check the cuts as you go. The seat cuts must all be equal width on the 360* rotation, and concentric within the 30* and 55* angle cuts as well. And of course the 45* valve seat width must be within factory specs. This is important for spring pressures, valve bounce, heat transfer, carbon buildup control....etc. etc. Because I had to cut down to a clean surface, the pitting controls how deep the cuts actually need to go. In some spots I'm running higher seat widths than factory spec due to the deeper cuts but the higher spring pressure from the SuperTech springs will somewhat compensate for this. I'll attempt to bring these back into spec later by manipulating the 30* and 55* cuts above and below the 45* valve seat when I start setting the valve "margin" position which I'll go into later. When I blueprint the head I'm going to show the factory specs and then what my final numbers are so all this good kind of info is captured.
I'm using a plastic T-handle to rotate the carbide valve cutter, which was supplied with my custom kit, I left it out cause it blocked the picture a bit. They highly recommend using 2 hands to rotate it. I tried (1) handed to get more face pressure and it flexed the pilot shaft and the carbide blade dug into the 30* cut face. Took me 1 hour to clean that up again. RPM is slow since it's done by hand, maybe 15-20 rpm. On the final cutting passes they recommend a light cut and I do those at maybe 100 rpm to give more a polish look. I also used Windex to avoid chatter marks which is what you might see in the pics. It makes cutting more difficult so dry cutting works best with light pressure, but sometimes you gotta muscle it if the valve doesn't cut effectively. I believe the valve seats are some type of induction hardened steel or Stellite.........very high hardness material. They have a rotary machine that does it too but it's like $1400 or so. The machine has a flex head that doesn't allow any side pressure, just the physical weight of the head and the pilot guide do the work. I've seen someone do this with an impact driver gun and a ball joint extension and I suppose this would work as a cheap solution too. The trick here is that everything should be done slowly.
Anyway, did you ever get that Turbobay turbo? What's goin on with your ride?
The valve job is mostly done. I'm waiting on the new intake/exhaust valves. All of the seat pitting has been removed. I've used a steel knife to debur sharp edges on the intake/exhaust chamber . The seat O.D. dimension on the intake ports is set close to 1.210" , and the exhaust set around .990". The valve seat widths are about .065" exhaust, .060" intake. This is about the average nominal factory values or close enough for now that I can tune these values up later.
What I'm showing here is basically setting the valve margin. The idea is that the valve mating surface and the valve seat mating surface have to be set correctly. I'm using Prussian blue or Engineer's blue to essentially mark where exactly the valve and seat actually touch. For a street driven car, what you want to see is the mating contact maybe slightly off the upper and lower valve face edges and just about centered. Basically, the blue edge on the valve face should be centered with a bit of machined surface peaking thru on each side of the valve face. This will all have to be done with the new valves one by one, I'm doing this on the old valve for reference only. I'll then use the 30* and 55* or 60* top and throat angle carbide cutters to move the seating position around as needed to "tune-up" the fitment.
Why all the effort? Well, if done correctly setting the valve margin correctly will help improve heat transfer, reduce carbon buildup, improve valve seat wear, improve cylinder sealing/maintain compression, reduce valve bounce/float, etc. My cylinder head rebuild is more of a street performance setup, so I'm keeping the valve seat width generous to maintain reliability.
Hopefully you guys can see how much effort it takes to get the head cleaned up and refreshed. Once I'm done with this I will then conduct a solvent check and vacuum check of the valves to make sure they seal 100%. It'll go pretty quickly after this. I have some more cylinder head polishing I want to do on the exterior to make the head look factory new. Then off to the machine shop for a clean head gasket deck flycut, then some ultrasonic cleaning, then I'll start dressing the head and wrapping it up.
This cylinder head is driving me crazy. Right when I think I'm nearly finished, there's something else to do....lol.
The carbide cutter just can't cut a perfect surface enough to make an air tight seal for the valves. I ended up using some aluminum mag polish and an intake valve and lapped the valves in. Yes, most cylinder head builders would frown on this but they are also running rigid tooling that'll cut a face perfectly. I didn't use standard valve lapping compound as it's way too aggressive and would cup the freshly cut seats. The mag polish is very fine grit and knocks down any microscopic imperfections or burrs that were preventing a full seat contact imprint. The blue circular markings are the prussian blue that is lightly painted onto the valve and then transferred to the valve seat by rotating the valve on it's seat. The trick is to lightly paint the valve with this dye, otherwise it covers all the gaps. Takes a bit of practice but it works. When there is poor contact, the round mark on the seat has an open gap or thin line contact. The combustion chambers are now all fully mirror polished.
So, I just checked the valve seats with a light and there definitely is an air gap on the intakes. I'd guess maybe there is a .002-.004" air gap. I have lapped them and then recut them with the carbide cutter just to make certain everything is trued. The Prussian blue looks good, but it's failing the light test. On the exhaust the seal is pretty tight but not perfect. Only thing I can think of is that the intake valves are actually bent somehow or the valve face is warped. A typical valve job would also include refacing/regrinding the valves themselves, so maybe this is what's going on. I'm ordering up a valve seat concentricity dial indicator that will tell me exactly how good of a cut I made on the seats. The new valves I'm buying might show a better result. I'm going to check the valve face runout with my indicator to see what the heck is going on.
For sure, it sucks. But I was buying new valves anyway, it's just forcing me to check thoroughly. I'm certain it's the valves, cause the exhaust valves with the same carbide cutter are sitting nearly air tight using the same cutting process. Because the exhaust guides are more worn than the intakes, the exhaust valve can kind of lean over and make a better seal, the intakes are pretty rigid and sit there hanging up in the air if they aren't perfectly straight. I'm pretty certain that's it.
Folks.......send your heads to a professional cause this ain't easy. Seriously, cylinder head work is a massive time suck and there ain't no short cuts.
Checked the valve runout on (2) cleaned up intake valves......straight as an arrow with maybe .0005-.001" run-out if that. I’m thinking the 3 cutter blades on the carbide cutter is creating a potato chip shape on the valve seat. Kind of like when a drill bit cuts a funky hole. The cutter pilot shaft is also dead straight spinning with an indicator. The reason the exhaust looked better is probably because of the extra hardness of the seat while cutting, it almost scrapes into the face instead of digging deep like the intake seats did. Wish Neway mentioned this in their literature, they allude to it but don't mention it directly.
O.K., I switched up my technique. The standard carbide cutting blades are 2 styles, a 12 teeth blade with an aggressive rake angle and no heel (i.e. flat surface). Another has 6 teeth with a long flat heel surface a different approach angle on the cutting edge. The first style blade is great for diving deep and plowing out those burn marks and pits when using a 0* thru 55* cutter, but can plow the material sometimes. The smoother cut blades are actually meant for 60-80* steeper valve port angles so the cutter doesn't plow too deep or quickly. Well, I switched out the blades over to the 45* cutter, think of it as a finishing pass on a lathe. Additional, I marked the T-handle so the "t" lines up with each blade to stabilize it from rocking side-side, like training wheel, minimizing any gouging that might occur.
Finally, I'm starting to see how truly bad the contact seal was with the previous valve seat cuts I made. The picture shows my first cleanup cut on the valve seat face which still shows a thin black line.......not good as the seat is concave, this is after hours of cutting with the previously mentioned carbide cutter (45* with aggressive blades). It's taking a lot of time to basically scrape the valve seat surface flat. When I stop feeling the scraping sound, that means all cutters are sitting on the surface equally and just sliding smoothly past, unless I apply lot's more pressure to start the cutting action again. Then, I paint the valve very lightly with some blue dye (prussian/engineer's blue) and I "bounce" the valve up and down like a hammer, making sure not to rotate the valve which would smear the imprint. Now, this bouncing is kind of an indicator of a good seat contact. A badly cut seat will absorb the bounce due to side deflection and hit with a "thud". With a well cut seat the valve will bounce high a few times with a nice ring to it, this is mentioned in passing by expert head builders.
Alternately, some guys paint the valve seat on the head and let the valve make a machined imprint on impact. This method is nice because you see the valve seat contact point on the head, and simultaneously you see the valve seat contact and positioning on the valve face itself, killing 2 birds with one stone. Both are important.
Anyway, with the first method If it leaves a clean blue circular stamp mark maybe .035-.050" wide of equal width 360*, it's good to go. Sort of like a rubber stamp imprint. Right now, most of the valves just contact in a few spots, showing how really bad the cut actually was. If the blue dye covers perfectly, it'll pass the vacuum test with zero problems. I'm thinking another 1-2 weeks to clean up the seats and then get the seat positioned correctly with respect to the valve which is the final final step. If you have OCD, this is a perfect project. I'm going nuts at this point redoing everything 100 times.
O.K., so I'll follow up in a week or so once I get some good results.