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MIRROR FINISH ON PISTON WALLS


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Hey guys it’s been a minute. 
 

soo my 77 280z has a glossy finish in the cylinder walls. Is this normal on a stock car or should there be cross hatching. 
 

I don’t want to build the bottom end.

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Glossy finish...  normally a good thing ... on paintwork... Not so much on a cylinderwall!  The cross hatching is for lubrication of the piston and.. is very poor now i think..  You need to take the pistons out and restore the cylinders.. or buy another block that has them and has a good compression..

Normally a wall is still good after 200000 miles provided that there has been good maintenance i think.. your engine had a lot more miles or bad maintenance.. not sure..

Here i have a pic of a wall with 120000km on it or 74,500 Miles..  (From my 280zx, just a clean up and new seals needed.)

20210902_162648.jpg

 

Maybe you can restore these with special tools and new rings?  somebody chime in with experience?  Some pics of your walls would be nice!

Edited by dutchzcarguy
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They're not a shiny as I remember mine being. How long since the car has been run? Nissan used chrome moly from the factory so it should be slick and more shiny in my opinion.

Take your thumbnail and go up down all the holes and see if you find any scractes, gouges. Your fingernails shouldn't get caught on anything. You can get some rags and lacquer thinner and clean those holes of the carbon. Be sure and take the oil pan off or drain it for sure before cleaning.

This pic looks odd, the carbon build up on that one side. The scraper ring should keep them clean. I'm guessing that engine hasn't been run lately ?????

Screenshot_20211118-155611_Samsung Internet.jpg

 

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14 hours ago, siteunseen said:

This pic looks odd, the carbon build up on that one side.

Can it be a reflection? some spots are a copy of the spots on the top of the piston.. 

Anyway.. i do see some hone stripes.. not so bad.. give it a good clean.

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Im 100% with dutchzcarguy. It looks a lot like reflection and hone cross hatch and that is a good sign. If you can't see any vertical scores in the bores, it shouls be ok.

Nissan had a good reputation with the iron they used in the blocks.

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Okok I’ve never seen an inside of a engine this up close and personal. The reflection threw me off. In pictures and videos it look like a stain ish reflex due to the cross hatches. 
 

thanks guys! 

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Only reason I took it apart was because the coolant was complete dried up wanted to make sure the jackets were good. One of the head bolts had a little rust next to a coolant jacket. So I’ll just clean it up maybe get some head work done for breathablity and keep the stock efi system and an electronic distributor call it reliable 190 hp 👌🏽👌🏽 

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I dont think I have an original source.

I would base that on people in the past who have tried to modify but can't get fueling correct. Vendors, especially cam vendors have also expressed similar sentiments. Only supplying relatively mild cams for the factory efi. The fuel mapping is so primitive. When the modifications require more fuel it's hard to provide, especially if the required fuel is not even across the board.

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I remember a guy on Hybridz that did a lot of testing and wrote an instruction on how to tune the standard L28 efi system. His conclusion was the standard efi manifold was your biggest challenge to improving the horsepower performance. 

He measured the internal diameter of the runners and his conclusion was the runner were somewhere around 55% of the intake valve. The N42/47 being maginally worse than the P82. The turbo manifolds being slightly better.

I don't think he was saying the efi system was not tunable, just the intake manifold was already at its limit and would limit the benifit of any "more than moddest" modifications.

I think he went by the naame Braap on Hybridz, but it's going 10 years back. I think I coppied the tutorial he wrote. I'm on holiday atm, can't seem to find it on my tablet.

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15 hours ago, 280zdude said:

The car only has 58k miles on it so I was really concerned haha 

The pic i put above is of a 280zx block with only 74k Miles (120kkm) so your cylinders should be even better than mine.  (My car had oil stickers (MOBIL1 ) even in the door so i think... that it had good maintenance.. the PO was a garage and a RDW guy.. something like someone that worked professionally with cars and knows alot of the subject.)

R.D.W. rijks dienst wegverkeer..  Sort of a very technical Dutch DMV? they do APK (= like a MOT.)  Also they decide what cars and other mobile stuf is road legal.

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My limited experience with new rings in an old bore was years ago. I cleaned the cylinders (that still had light cross hatching), used the original pistons with new moly rings. That combination worked well for another 20+ years as a daily driver. I'd do it again.

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7 hours ago, EuroDat said:

I remember a guy on Hybridz that did a lot of testing and wrote an instruction on how to tune the standard L28 efi system. His conclusion was the standard efi manifold was your biggest challenge to improving the horsepower performance. 

He measured the internal diameter of the runners and his conclusion was the runner were somewhere around 55% of the intake valve. The N42/47 being maginally worse than the P82. The turbo manifolds being slightly better.

I don't think he was saying the efi system was not tunable, just the intake manifold was already at its limit and would limit the benifit of any "more than moddest" modifications.

I think he went by the naame Braap on Hybridz, but it's going 10 years back. I think I coppied the tutorial he wrote. I'm on holiday atm, can't seem to find it on my tablet.

This might be it? Enjoy your Holiday. Just a few more days for me. :beer:

https://forums.hybridz.org/topic/95316-braaps-l6-efi-induction-advice-and-tips/

"The OE EFI will NOT tolerate larger than stock cams, (large enough to make any difference one would spend money and time to swap out), and there is no “reasonable” way around it. If you desire a cam for EFI L28, do yourself a favor and steup to aftermarket Engine management which will allow you to tune around the new VE curve the cam delivers and also delete the AFM from the air stream. The stock Z car EFI isn’t tunable enough to compensate for an altered VE curve. I’m sure someone could hack the resistors and caps in the ECU, but with Mega Squirt being so inexpensive and readily accessible now…

 

The OE EFI will barely tolerate extreme exhaust mods and minor head work, (those two items with the stock cam and stock EFI intake manifold don’t alter the VE curve too much and what they do alter we are able to compensate for with a variety of methods). The OE EFI will not tolerate freer flowing intake manifolds. Both of those alter the VE curve drastically enough that there is no reasonable way to keep the part throttle cruise AND WOT in balance. You will have to sacrifice one for the other and at that, if you spend too much driving around in the compromised region of the tune, the tune could be far enough out to actually foul plugs, which means that when get back into region that is correct for the engine, it wont run right due to fouled spark plugs.

 

In summation, if you have the stock EFI, keep the stock cam and stock intake manifold. If you desire an intake manifold and/or cam change be sure you also have an alternative engine management system that allows the end user to tune and make use of what the cam and intake manifold brings to the table in performance gains."

Edited by siteunseen
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Yeah, I like his fix for the idle. Attack the AFM with a dremel to increae air flow at idle. And then fix the next problem you created when the AFM vane drops to low and cuts the fuel pump....

Edited by EuroDat
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Yeah I was reading about it. I’m guessing they need a longer duration if pulse. And more fuel pressure. I’m not 100% but I believe the pulse is in relation to the distributor. Anyways I’m sure there’s a way with adding resistors or something to length pulse. Or you can just put a ecu instead of trying to work it analog  

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Find some carbs and you're good with a cut cam on these old cars.

An aluminum flywheel and port match performance exhaust is the easiest thing to do for the money. I have a 10lb flywheel on mine and it's like riding a motorcycle without all the hospital, funeral bills.

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