madkaw

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

So Cliff, is this the motor that's hauling you to Zcon 2015? If so, we are in the same boat. I was thinking of documenting my 'redo' of my l24, but maybe just throw some comparisons in on your thread? I'm a little further than you in that my block is sitting here cleaned and rehoned with my crank polished. You are having a machine shop prep everything?(rods, crank, etc...)

Sure is pretty!

Is my math off or does it add up to .011 that he shaved off the block. If so, then he has cut it to tight and you will have to do something different. My block I figured 22 out of the hole and another 5 off the deck gave me 22 clearance. The more you read about deck height though, the more number you get. But even at the small side of 19 out the hole, you would have 30 total leaving 19 clearance--IF my math is right.. ...and if my math is right, then shame on the builder unless it took that much to clean up the deck and he had no choice. How much cam off the head?

OMG-don't let him machine those pistons. That's what i ran on my L24(deck height), and was fine. It's a bit tight with a 1.25mm HG, but that's probably what the Felpro is. Like stated, most of these engines run about 22 thou deck height(what I have read from numerous posts). Then you shaved off 5-7 thou off the deck, so there you are with about .019 piston the head clearance. The only way to know is to measure. I bought two felpro HG's just for that reason. I am going to find out exactly the crushed height of the felpro.

Sounds right to me. You should be fine. 5-7 thousands-couldn't be more specific than that? Now this is where the HG really gets important. What's the crushed thickness of your selected HG?

I've been trying to get a straight answer out of RHD Japan about their headers, but good luck on that I guess. I inquired before asking about whether they do LHD headers, but they responded to only one of my questions. It's also crazy that they don't put actual pics of their products on there. The disclaimer reads that the photo might be generic-REALLY. Some of these headers are 1500$ and you put a generic pic on there. The smallest pipe they use is 1 3/4" though.

Dam-no more nismo gaskets. Hope the new felpro works. I have 2 new ones(felpro's) sitting home now, but I'm out of town so I can't describe anything. In the big picture, has there been a rash of HG gasket failures lately DUE to inferior gaskets. How many ways can a HG fail? Many! Especially when we are dealing with the variables of back yard maintenance-me included. Was the surfaces prepped properly? Was the head torqued propery? Was the head checked for flatness correctly? Did the engine get hot? Was there undetected detonation ?

What i am saying is that the oval shaped fire rings are big enough for the larger exhaust or intake valves to be intsalled. Most HG's have the oval shape already. It seemed the OP was concerned with getting a perfectly round fire ring on the HG . Well that might not work for anything other than stock. The only way to be sure is to lay the HG on the head to make sure it doesn't impede into the combustion chamber. If you have your "how to modify" book, look in there. The oval fire ring allows for some nice unshrouding which is strongly recommended on the L24. Cliff-you shouldn't use a 280 Hg

Revisting the oval/round fire ring aspect. The perfect round fire ring type HG should be avoided for the fact that most head rebuilts include installing larger valves that WON'T likely clear that type gasket, or clear your cylinder bore for that matter. Any unshrouding work would also make that HG useless.

Here's my collection. top to bottom: Old felpro(I believe) Nismo New Felpro(universal 1970-1980 Victor reinz 1983 stock HG All Hg have oval FIRE RING except new Felpro and 83 stock Nissan

I have HG's of every variety now for some reason and I will take some pics when I get a chance. The latest Felpro HG has turned into a universal gasket which covers 70-80 models. The Nismo was very specific to the e30 block with the HG being cut out around unused water passages. The Felpro has a decent reputation amongst the Z owners I have read. I have two of the Victor Reinz HG's and I wouldn't put them on-they look cheap to me. Oval bore holes? Hmmm. That's weird. You might think the combustion chamber was oval or something

Felpro or Nismo from Nissan?

Well everyone has pretty much told you that the stock ECU will probably not handle this combo-but-good luck trying it. By the way ,that combo yields 8.63:1 , so a mild shave probably won't be 10:1 Maybe you should find a local Z club and buy someones gas and dinner for a ride in a stock Z and make your decision then.

It should. Shaft sits in oil pump, pump connects to timing cover. Gear should be closest to the pump. Look at your FSM for timing. #1 cylinder TDC compression stroke Insert so dizzy tang is sitting 11:25 clock

TUNE TUNE TUNE. Without an aftermarket ECU, you just need to optimize your stock tune. I've driven a very nice 77 all stock and it ran good. Very torquey! Everything was in good repair and the tune was spot on. Gearing is also a good way to quicken things up too. Or just say hell with EFI and go whatever engine combo and slap on some nice SU's or triples better yet.

460 is the limit for stock springs and valve seals from what I have read.

You know you won't be able to just throw that cam in that head without lot's of other work. Need to upgrade springs and valve seals. Valve lash pads will not be correct so your valve geometry will need to adjusted. I would strongly recommend degreeing that cam and than check piston/valve clearance. Exhaust liners will be the least of your concern. Tuning and proper valve geometry will give you best gains. Why not try a smaller cam? That 90/47 combo should be stout and with good octane fuel and good tune should run great.