madkaw

Good find on the thread Cliff. Those notches look familiar. They look prettier than mine. Not sure I would worry about performance losses associated with notching, but oversizing ports for sure.

Cliff, If I were to do it all over again on a L24, I probably notch both sides but stay on the conservative side. You wouldn't loose much compression, and what you lost there you would probably gain in flow. Google bore reliefs for valves and you will see it has been done before on other engines. Maybe my pistons will be up for sale after all is said and done Cliff if you haven't bought any yet. I want to move on to the L28, but really wanted to dyno my L24 with the triples. So I might pull the other l24 out of the shed if need be. I just pulled apart my L28 and the crank and pistons look great. It had another 100K left in her easy. Looks like a hone, rings and bearings!

Well today was notch checking day-and they were all fine. My main concern was verifying that the notch did not extend into the ring area. The notches actually cleared more than what I thought they would. I verified by installing piston with top ring and using permanent marker around the bore. I ran the piston up and down in the bore until the top ring wore the marker off and that gave me a line of reference. I also checked my oil clearances using plastic gauge and they were in tolerance. Next issue is rings. My rings do not fit my bores. The gaps are excessive. I actually have two sets of NEW rings and both sets show excessive end gap. I have seen as much as .027 on the top ring. I have had discussions with the machinist and without going thru the whole conversation I have decided to take my block and pistons to someone else for a second opinion. I believe the machinist went to far overbore to fix scratches that his machine put in the bore. I don't have exact dimensions but it sounded that he went to the limit of the tolerance. The only way to be sure is to take it somewhere else. If this is the case, I might just move on to my L28. Or my other option is to pull my numbers matching block out and work it.

I was suprised the sanding drums cut the block myself. It's a slow process and you will burn up a lot of drums, but slow is better. Or you could start out with a steel carbide and finish out with the sanding drum. A plan is good

Great-your rockers look pretty. Just make sure you check the wipe pattern on BOTH the cam and valve stem. My rockers were supposedly new Nissans and my cam new Schneider. 12k miles later I am rebuilding me head. 99% sure it was the rockers not having parallel surfaces , but there is a chance the cam wasn't right. Very first rocker I checked was not flat side to side by .014 on the cam surface . The machinist found this using a dial indicator on a machined surface. Search you tube for Delta rockers and see. My point is to make sure you verify the regrind carefully

Might consider doing the notching now while everything is clearly marked. Your piston rings and HG have left you a perfect guide or line to NOT PASS while you are grinding. You can lay the HG on the head and mark a center line for the valve centerline and transfer that to the block. This will show you where the the outer radius or edge of the valve will be. Grinding now before cleaning makes sense too. As far as grinding tools , I used a 60 grit drum sander on a dremmel. It is very controlable and takes material off slowly and smoothly. If it happens to jump around it won't gouge anything like a carbide bit will.

Guy, that 79 looks great. What a good looking chamber .

Love to see the official build sheet on the engine too! Well at least what info is willing to share. I saw that to Zed, I presume .021 above deck, but would like to be sure. Anything done to the crank? Thanks for sharing the pics-engine porn!

Guy, they do look good-better than the ones I got back. The thing that caught my eye was my rockers didn't look like the ones I sent them. Another words, did they just swap out for others and were they Nissan rockers at all?

Booked from 15th-19th . Really looking forward to this and hope the Z cooperates. Last show I made was zcon2010 in Nashville.

Richard, your warnings are well noted. That's why I stated my disclaimer-. I really didn't exhibit any symptoms that I can say was directly caused by heavy notching. I fully intend to recheck that my top ring clears the notching as stated earlier. It is a bit of an old hot rodders trick to help make the engine breathe better, but like you said, it could cause dead spots for carbon build up. I don't believe I lost much compression, but we actually figured it in to my 9.5:1 CR. Didn't have issue with detonation either, but my engine didn't have a ton of miles. I didn't like the carbon build up I had, but this engine has been thru tuning hell with SU's and then triples. The length of the notch is following the HG, nothing more. I understand that it is waaayyy more than enough to just clearance a valve, but there was more to the notch than that.

I purchased OEM replacement rings from ebay and they were NOS Napa/Dana/tokeomi rings. Cast with the top ring having a special wear surface, but don't know if it is Moly, but I know it's not chrome. Rings looked okay with just a cast second ring, but i decided to get the matching Sealed Power rings to match the pistons. My machinist also insisted on a Napier second ring for oil control. I also found out that .030 pistons and rings are a bit tough to come by anymore.

Guy-they are scary deep actually. This will be checked during preassembly. I plan to dykam blue the bores and run the pistons thru their cycle and check for breach. This engine ran really well for years and I don't think there is an issue here, but everything will be checked. Don't see how anything would change over time regarding I will add that upon dissembly the markings from of the rings on the bores were very tight on the notches. The machinist did not believe there was any issue there. I sincerely believe all my issues were valve related -caused by rocker arms

I cleaned my pistons(tops only) with the Berrymans stuff before sending them to the machinist.I had some serious stuff baked on the top of the pistons. A combination of carbon from tuning up and down of my triples and such and add a dab of oil from valve issues and you get some serious gunk-see pic! Berryman's is good stuff but I wouldn't leave anything in that solution for long or at least monitor it closely. I have left carb bits in there too long and it discolors the aluminum or will remove the cladding on parts. The machinist scrubbed the pistons down with fine scotch brite after cleaning. The gasket remover is some nasty sh!t and it sprays, so it can get on your hands easier and burn. I like the control of the dipping process and leaving it in the shed out back so I don't have to smell it! It all looks pretty when it's fresh doesn't it. Kind of like the rest of my resto. Look at it closely before you pull it out of the garage for the first time because it will never look that good again-

That was a long time ago, but any unshrouding I did was probably before valve seats were replaced, but can't swear to it. Most of what I did was at the outside to get the full use of the combustion chamber using the fire ring of the HG as my guide. I also concentrated on smoothing the spark plug threads in that area and any other possible sharp edges. I believe the machinist blended the valve seats. I did NOT try to reshape the bowls as much as I was looking to give my bigger valves room to breathe around the outside towards the bore walls. Thus the large notching on the bores. Disclaimer; I am not an engine builder or do I proclaim my way is better. I did major unshrouding both on the bore and head -you might want to be more conservative. Unshrouding is not rocket science, but if you feel uneasy doing it the machinist should be fully capable or willing to do it. I was willing to push the limit and start back over if it didn't work out.

Sealed Power units and haven' t measured anything yet.

Zed, not really mad, but making a statement that Z l motors are zero deck engines is just plain wrong. Maybe the the OP is getting this info from the builder that doesn't know. He wanted zero deck because that's what these engine should have which should not be put out there. .020 out of the hole is about perfect and very close to factory.

Now you are putting out misinformation. What do the 4 cylinder motors have to do with this discussion anyway. Please read the attached thread and realize you turned down your pistons for nothing. And who are you supposedly quoting? http://forums.hybridz.org/topic/119593-pistons-protrude-from-block-thicker-gasket/

Yes this is the second time around for the little L. And boy I have learned a lot and probably forgot a lot too! First time around the machinist/builder did most of the work. He dissembled and assembled the block and head and I put the two together. I degreed the cam and everything else to get it running. It's an early E-88 head on a stock P30 block .030 over pistons. The head had a full Schneider stage 2 kit-cam,springs,retainers,rockers. The engine ran very well and dynoed 155RWHP with SU's. But then I had some issues that i could only determine as valve issues caused by faulty rockers. here's where the learning comes in and hopefully no forgetting. I think my machinist let the bad rockers slip thru by not doing a complete wipe pattern on the lash pads too. Anyway, since L24 rebuilds are trending on CZCC , I thought I would join in! The block went back to the machinist for re hone for new rings. There was some minor scoring in the bores, but it all cleaned up. Probably towards the max piston/wall clearance, but she will be loose!! I ordered sealed power rings to match the Sealed power pistons. The only rings I could find in .030 over that had the Napier second ring-which the machinist insisted on. I swapped out the crank with another one I had. The reason was I was running a speedi sleeve on the rear main nad I wanted to eliminate it. I pulled my crank from my original no# matching block. It cleaned up perfect with no grinding, just polishing. The pistons and rods looked great also. The motor only ran about 13K miles, so I was hoping they would be fine. Just scotch brited the pistons and checked the ring glands. So I bought new main and rod bearings, new rings, new freeze plugs. The plan is for a pre assembly to check oil clearances, thrust clearance, deck height, HG height, bore notching clearance. I will try and throw up some picsw every once in a while:) The attached pic shows what a work horse the Z really is! Also attached is the block from prior rebuild and also the head the first time around.

Okay-this thread has been a bit confusing. .020 it is, but why even shave the pistons? I think I got 30 by adding the deck shave -which looked like there was a total off .011 taken off. My question is, if MOST Datsun motors have positive deck height(.020) for a reason, why would you think you needed zero deck height? So now you have atleast .039 head to piston clearance, but maybe more like .049 with your HG. IMHO, you didn't or shouldn't have done a thing to the pistons. Not bashing, just stating.

any advertised thickness of the HG?

You milled .020 off the pistons that were .030 off the deck and now you are at zero deck?

I would also express a concern about rocker geometry an quality of the rocker arms. Whoever winds up doing the wipe patterns, make sure the wear is square on both the cam surface and the lash pad surface.

If the machinist doesn't want to do the work, find someone else. You need and want to notch the bores. Datsun motors aren't the only motors that practiced this notching. I notched my bores right to the limit of the HG fire ring, but you don't need to go that far. If you are careful and take your time you can do this yourself. Just don't go to deep or wide. Sounds like the machine work is all done and you just need better valve seals and a wipe pattern checked? I would think any competant machine shop could do this. I handed my machinist the "how to modify" book for a references. I just told him that I know he doesn't see these motors everyday and just thought he might want the book to look at.

I'm getting ready to pull the trigger on Kameari rockers. I have also found out the harder way the importance of valve train geometry and the rockers are the heart of that equation. My machinist didn't like the Delta resurface job at all. And knowing that my supposedly new Nissan rockers weren't right out of the box, he didn't trust these resurfaced ones either. I told him that we need to check these, but that's time I have to pay him. I told him Kameari rockers were 600$(chromoly), and he thought that wasn't unreasonable considering their importance. It's a hard pill to swallow