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Pistons???


Mack

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Hello, I am building an engine with the tax refund money and I need a piston with a pin height of 33.5mm and a bore of 87.5mm, I know the Z22S pistons are 87mm bore witha 35.5 pin height, could I use these and take 1mm off and use a 2mm head gasket? or could I just take 2mm off the top of the piston without too many adverse side effects?

I am building this motor on a budget so, custom pistons are out of the question, and its going to be NA for a while, when I get money, I am going custom and turbo... So, anyone? how bout Norm? I know hes done some stuff like this...

 

thanks in advance,

McAdam Majors

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Mack,

 

I've been talking to one of my club members about having four sets of pistons made that have specs of 87mm diameter with a Pin height of 34mm and a 10cc dish. We are doing this for forced induction motors that will have a compression ratio of 8.48 to 1 when using a 1mm head gasket and a P90 head. Let me know if your interested as I'm sure the more we get the cheaper they'll be.

 

Joe

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Guest JAMIE T

Rags, Are these for a stroker? I need some quality forged pistons for my 3.0L. I want to use a 87, or 87.5mm bore and L24 rods with an LD28 crank. If so, I may be interested in some.

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If you plan to turbo it you should use a piston strong enough to take the abuse. Nissan N/A pistons don't have a thick enough top ring land to take the abuse that will come there way with a turbo. I've stacked a few ring lands but never on a stock turbo piston.

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I'm trying to put this together but we have to come up with a piston that is good for most of us. My plan is a piston that is good for a turbo that will yeild an 8.5 CR when used with a P90 and a NA motor that has a 10-1 CR when used with an E31. I'm shooting for a deck height of 0-1mm negative. Does anyone have a "limit" on pin height? Preference on ring land size?

 

Joe

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Okay here is what I'm looking at so far. 87mm diameter with a pin height of 32.35mm. This will yeild 8.5CR on a stroker with a P90 using a 1mm head gasket with the piston 1mm down in the bore and 10-1CR on the same motor using an E31. Preliminary pricing is around $500 for a set of six which includes pistons, pins, locks and rings if we can give an order of five sets.

 

Joe

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I'm interested, but timing is crucial here, lol. money doesn't flow that well for me, given a little lead time tho, I could scrimp together $500 for a nice set of pistons.

 

Heres what I'm doing, deisel block, Z20E rods length 152.2mm, deisel crank, which leaves me needing a piston of 87.5mm bore and a 33.5mm pin heigth for a Zero deck clearance. and I get my 2995cc motor with my 1.837 rod/stroke ratio. forged would be good, but if I use the stock replacement pistons in an overbore size and just go NA or a little boost for now, I'll be good. so, i dunno, sorry for rambling and let me know!

 

cheers,

McAam

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Guest JAMIE T

That sounds like a good price. We would definatly need to get a handle on our A/F ratio with that 8.5:1 compression. If this does happen, make sure to specify a turbo piston. That way they can spec thicker deck, and thicker ring lands. It may be tuff to get a "universal" piston for a NA, and turbo applications. They may be willing to actually do differant styles for the same price, if enough are ordered.

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forgot to add, Ross racing pistons offers fairly decent priced stuff. Like $550 foir a set of 6 and these are FORGED. and those are reg prices, not group buy stuff, anyone have anything good or bad to say about ross pistons??

 

cheers,

McAdam

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OK - I spent a little time playing with the Nissan Engine Builder program - Here is what I came up with for a good compromise piston which should work for N/A and Turbo - using LD28 crank/L24 rods/

Bore - 87.5

Stroke-83.0

Pin Height - 33.3mm

Piston Dish - 5.0cc

 

At this pin height it ends up .07mm below deck on the L28 block.

Here are the compression ratios

 

Gasket N/A(N42 head) Turbo(P90 head)

1mm 9.89:1 8.66:1

1.25mm(stock) 9.66:1 8.49:1

2mm 9.02:1 8.01:1

 

I'm not going to get into the head discussion today - I'm just trying to work it out so the pistons are usable in both N/A and Turbo. Another alternative is to mill the P90 for N/A - taking off .020" or .5mm gives you a compression rise of .5 to 1.

 

Your questions and comments - please. The $500 neighbourhood sounds pretty good. Ross sounds like quality parts from what I have heard. The other question I have is concerning the pins - I assume they are full-floating - so what has to be done to the rods to live with full floating pins? The other question is what Dia. pins are we going to spec?

Any engine gurus with the experience monitoring this post?

 

Cheers - Doug

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Doug,

 

There are two things that concern me. One is the 87.5mm bore. I picked an 87mm bore so there wouldn't be concerns with using these pistons on all l28's, not just the siamesed bore F54's. Second is the pin height you recommend. I had the pin height a little higher to move the piston down in the bore 1 full mm so there would be no radical cam to piston contact since there would be no valve reliefs. The cost of the piston goes way down if the piston is not dished. I'm still leaning towards 87mm diameter with a pin height of 32.35mm. I'll get the specifics on the pin diameter on Monday.

 

Joe

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