L24/w24 pistons and ozdat calculator novelties

[kolonelklink87]

Hey guys,

I have a set of pistons from a late EFI l24 block(w24):

They have valve recessions and a very slight dish (~<1mm)

1: does anyone have any info on these pistons worth knowing? They look like stock nissan parts to me, the engine calculator ive been using (ozdat) indicated a significantly greater dish on l24 pistons =7cc.... even with the valve recessions i'd be suprised if these things broke 5cc.

2: is there a difference in the thickness of the piston head on valve recessed pistons that could be expoited for removing material from the non-quench side of the head? I'm interested on how this can be combined with ultra-thin HG's to decrease head-piston clearance without increasing compression significately.

3. along a similar lines has anyone tried using the longer rods on a l28 crank with a 3mm steel HG rather than machining (-)clearance on the block to acheive v. high compression on an l24/6? would this bring the the rings too close to the combustion chamber?

 

 

I've done some reading in the past to try to pin this one down but couldnt and picked up the pistons today with renewed interest.

 

Thanks in advance ,

-Pete

[Xnke]

Can we get some photos of these pistons? Also, if you can measure the diameter and depth of the dish, you can compute the volume, roughly, or you can measure it by packing it with clay and scraping the top flat, then measuring the volume of the clay.

 

I've heard of these pistons; but I've never seen them.

[kolonelklink87]

Can we get some photos of these pistons? Also, if you can measure the diameter and depth of the dish, you can compute the volume, roughly...

 

Don't have access to camera at the moment, I'm aware of that, this is wher ei got the ~5cc... i dont think i can be more accurate than this due to the very slight dish and my lack of accurate measuring apparatus (my calcs put the dish itself at only 3.5-4cc plus some additional volume for recessions)

 

i'll try to get a camera at some point

 

-pete

[kiwi303]

Can you grab a 5cc syringe from a nurse somewhere? fill it to 5cc, empty it into the level piston top, and see how much is left after the water is level with the top. Rough, but close enough for the job.

[kolonelklink87]

Can you grab a 5cc syringe from a nurse somewhere? fill it to 5cc, empty it into the level piston top, and see how much is left after the water is level with the top. Rough, but close enough for the job.

 

That I can do easily... just need some time hehe

[kolonelklink87]

4.5cc as close as i can get without a zero-surface tension measuring fluid.

i'll try to beg a camera for photos, any new input?

-poit

[Daeron]

 

2: is there a difference in the thickness of the piston head on valve recessed pistons that could be expoited for removing material from the non-quench side of the head? I'm interested on how this can be combined with ultra-thin HG's to decrease head-piston clearance without increasing compression significately.

 

Thanks in advance ,

-Pete

I'm not understanding this quite clearly. The valves and spark plug are on one side of the combustion chamber, and the quench pad of the combustion chamber (and the intake/exhaust) is on the other side. Correspondingly, on the piston, one side has valve reliefs, and the other side you want to keep flat and push it up against the quench pad as close as possible. So, a thin head gasket allows the flat top of the intake/exhaust side of the piston up close to the flat quench pad of the head. You ask about the "non-quench side of the head" and it appears to mean you are actually referencing removing material from the piston, on the non-quench side. That would be the side where your valve reliefs are.

 

The way to relieve compression (since you're running an ultra-thin gasket) is to carve out a recess in the piston, with the bottom equal to the deepest section of the valve relief. Extend this bowl as far towards the inlet/exhaust side as the combustion chamber is in the cylinder head. Shape it similarly, but smaller (if anything) than the outline of the "peanut" combustion chamber.

 

I'm just regurgitating information; but it is good information nevertheless. Take it, go play games with the calculator, and figure out:

 

-what rods you're using

-what compression you want.

 

Input the data and determine:

-how close you want to get to the head

-how thin you want the gasket

and find out what volume your recess needs to be.

 

My logic is, if you stick with the thinnest spot Nissan produced the pistons with, then you are likely safe.

 

Hope this helps.

[kolonelklink87]

I'm not understanding this quite clearly. The valves and spark plug are on one side of the combustion chamber, and the quench pad of the combustion chamber (and the intake/exhaust) is on the other side. Correspondingly, on the piston, one side has valve reliefs, and the other side you want to keep flat and push it up against the quench pad as close as possible. So, a thin head gasket allows the flat top of the intake/exhaust side of the piston up close to the flat quench pad of the head. You ask about the "non-quench side of the head" and it appears to mean you are actually referencing removing material from the piston, on the non-quench side. That would be the side where your valve reliefs are.

 

The way to relieve compression (since you're running an ultra-thin gasket) is to carve out a recess in the piston, with the bottom equal to the deepest section of the valve relief. Extend this bowl as far towards the inlet/exhaust side as the combustion chamber is in the cylinder head. Shape it similarly, but smaller (if anything) than the outline of the "peanut" combustion chamber.

 

I'm just regurgitating information; but it is good information nevertheless. Take it, go play games with the calculator, and figure out:

 

-what rods you're using

-what compression you want.

 

Input the data and determine:

-how close you want to get to the head

-how thin you want the gasket

and find out what volume your recess needs to be.

 

My logic is, if you stick with the thinnest spot Nissan produced the pistons with, then you are likely safe.

 

Hope this helps.

 

 

1. regarding my "non-quench side of the head" comment - I apologise, i'm not getting heaps of sleep these days... allow me to rephrase: the side of the piston corresponding to the combustion chamber of a quenchpad-equiped cylinder head

2. i agree with most of what you have said, I dont have a specific application in mind, I was just curious about this "line of thought"... I've previously considered removing a peanut dish from pistons however I have some serious concerns about comprimising the integrity of the pistons. Along that line of thought I'm very dubious of removing the full recess depth - do you have any precedent where this has been successful? the thickness of the piston crown to the ring is only 6mm so carving a full 3mm off of this (dish + recess depth) doesnt leave much metal behind in a significant amount of piston head. I understand your logic but I think having a couple of very small areas with this thickness(recesses) is a very different beast to having ~50% of piston head material removed from one side.

 

Any further thoughts?

 

-pete

Edited February 23, 2010 by kolonelklink87

[Daeron]

do you have any precedent where this has been successful?

No, honestly, I do not personally have any. Thats why I said my bit about regurgitating information above to be honest.

 

However, within the last ahhh, two or three weeks, I know I pointed ozconnection towards a few posts brian (1 fast z) had made regarding the topic that I usually take as holy writ until I see otherwise.

 

Let me see if I can find that thread..

 

EDIT here is my reply:

http://forums.hybridz.org/showthread.php?t=130872&highlight=quench

 

http://forums.hybridz.org/showthread.php?t=119151&highlight=quench

 

I take 1 fast Z at his word as my "quench and piston" expert, so his word is Holy Writ in this matter as far as I'm concerned.

 

I also want to add that I had envisioned a very shallow valve recess in these pistons; One would not, by any means, NEED to bore this bowl out that deep. Unless I am mistaken, in one of the two threads linked was mention of how thin you can and cannot get away with. At the very least, the post should be useful as a litmus test for you regarding these pistons.

 

the other one has nothing to do with piston machining, and only piston-to-head clearance. Two valuable threads to keep up the sleeve IMHO though.

Edited February 24, 2010 by Daeron

[ozconnection]

http://forums.hybridz.org/index.php?/topic/78714-32l-twin-turbo-l28-stroker/

 

Pete, this is interesting stuff here and what Daeron was suggesting to look for.

 

Cheers.

[Daeron]

Thanks, man! (or mate.. thats what I wanna call you but I hate to sound like a pedantic american so I use my own lingo)

 

by the way, oz, what is your proper name? Mine's shawn, and you;ve probly told me yours already but I can't remember it.

 

I'm having (if you can't tell) a foggy, AND beer-laden evening and I'm feeling lazy. I didn't even click through on my own links, I just went on my recollections of what you asked and what I posted.

 

Even still, I like to think I'm useful in recycling this kinda stuff.

 

(by the way by beer-laden, I mean I drink good beer. Michelob Amber Bock is my standard, but as a rule I mix things up, and never drink a beer unless it is noticably darker in color than my own Irish skin. So don't think i'm swilling down cans of American swine over here either. Burp.)

Edited February 24, 2010 by Daeron

[ozconnection]

Thanks, man! (or mate.. thats what I wanna call you but I hate to sound like a pedantic american so I use my own lingo)

 

by the way, oz, what is your proper name? Mine's shawn, and you;ve probly told me yours already but I can't remember it.

 

I'm having (if you can't tell) a foggy, AND beer-laden evening and I'm feeling lazy. I didn't even click through on my own links, I just went on my recollections of what you asked and what I posted.

 

Even still, I like to think I'm useful in recycling this kinda stuff.

 

(by the way by beer-laden, I mean I drink good beer. Michelob Amber Bock is my standard, but as a rule I mix things up, and never drink a beer unless it is noticably darker in color than my own Irish skin. So don't think i'm swilling down cans of American swine over here either. Burp.)

 

Cheers Shaun, have one for me!

Mate, man, whatever, it's all good

Cheers, Mark.

PS We love your contributions, keep it up!!