87mm flat top pistons in N42/N47? - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 6 (permalink) Old 01-23-2018, 12:03 PM Thread Starter
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87mm flat top pistons in N42/N47?

Hey guys,

I have a spare L28 (N42 block, N47 head) that I'm working to rebuild. I originally intended to rebuild it completely stock, but I'm wondering if there's mild modifications that I can make to it to get a bit more power out of it if I'm rebuilding it anyways. I don't want to turbo the engine or go for a stroker build, since I want to keep costs/effort down.

I'm mainly considering flat-top 87mm (+1mm) pistons to replace the stock dished 86mm pistons, keeping everything else stock. This should bring the compression ratio from 8.21 to 9.9 using a stock Nissan gasket and increases displacement from 2.753 (stock) to 2.817.

Without any other modifications, is it realistic to expect a power increase from this alone? With the increased displacement and compression, do I also need to think about replacing the stock cam or making modifications to the intake manifold or the fuel delivery system? I'm planning to run the stock FI system from my '77 280Z.

Thank you guys in advance! Any suggestions or thoughts are welcome.
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post #2 of 6 (permalink) Old 01-24-2018, 12:04 AM Thread Starter
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any ideas guys? I could really use some advice from more experienced builders here.
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post #3 of 6 (permalink) Old 01-25-2018, 12:52 PM
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if the bores are within spec for standard pistons, all you do boring it is remove life from the block.

You will gain more with a proper tune up. Go take it to a dyno and then do a proper full tune up... If after that tune up you aren't at 140 RWHP, you're leaving something on the table, find out what it is and get it back.

Most people start with a car so far down on power and underperforming they THINK all the money they spend on hot rod goodies are to credit for their 'power increase' but when the spin up below my stock L28E they get a bit upset.

Power is in the details, not a magic bullet part you bolt on or install...

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post #4 of 6 (permalink) Old 01-25-2018, 10:40 PM Thread Starter
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Originally Posted by Tony D View Post
if the bores are within spec for standard pistons, all you do boring it is remove life from the block.

You will gain more with a proper tune up. Go take it to a dyno and then do a proper full tune up... If after that tune up you aren't at 140 RWHP, you're leaving something on the table, find out what it is and get it back.

Most people start with a car so far down on power and underperforming they THINK all the money they spend on hot rod goodies are to credit for their 'power increase' but when the spin up below my stock L28E they get a bit upset.

Power is in the details, not a magic bullet part you bolt on or install...
Hey Tony, thanks for your input. I do have another stock L28E that I've been working on that's running pretty well in the car right now. I get why your first reaction is "don't do anything, you'll just make it worse" but I'm just asking an exploratory question to which I'm hoping the experts here can lend some advice .

I picked up a separate L28 to rebuild from the ground up mostly for learning purposes, but I thought I might opt to do some "simple upgrades" while I'm at it. I heard that some people have good luck with 1mm oversized pistons, but generally I'm wondering if there's simple changes (i.e. no stroker/turbo) that I can make to the L28E given that I'm completely rebuilding the engine already.
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post #5 of 6 (permalink) Old 01-26-2018, 08:29 AM
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depends on what you really want your engine to do. really. you already have all the power you need. if you're not racing, no need to upgrade.
let the guys in the faster newer fancier cars just go by you... you'll have a cooler car than they do, regardless.
you're not going to see a big power increase unless you go full out with either turbo build or stroker. but the question is, will it be worth it?


I had a big stroker engine custom built for my 280 several years ago and it was the biggest waste of money I ever spent. my car was a daily driver not a race car. for me it was not worth doing. but, it really sounded cool. if you're building a track car, then that's a different story.


not trying to steer you away, but just saying you may not get a lot out of what you are trying to do with the money you will spend for upgrades.




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post #6 of 6 (permalink) Old 01-30-2018, 07:29 PM
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Keep searching the archives and get more knowledge. I understood Tony to say no need to bore if in spec's, wasting money and lessing re builds on block. Valuable insight from someone who posts often, and most importantly, correct information. [ I get why your first reaction is "don't do anything, you'll just make it worse"] I find your response odd, and I would think, incorrect. At the risk of being an ass hat, you might look at how you put off good information.

Have you checked bores? if so what did you find? within specs?
Tony and anyone else knowledgeable would ask this first. The "do I bore it?" is answered.
Changing to flat tops will increase compression, changing head can also affect compression, up or down. Dish are for turbo builds from what I have read. You can search the old posts, good for getting the big picture, and then go about each problem being dealt with. Like do I need new cam w/higher compression? Will it help?
If so do I need intake and port? I am sure all that info here...a ton!

'79 280ZX Daily
83 slicktop being built
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