Need help on choosing PISTONS for my project

[frank280zx]

He guys,

 

As some of you might now, i'm rebuilding my engine, and my goal is...more go!!!!!

so this are my 'tools' to work with.

I have an F54 Block, with original cranck and rods, N42 head witch will get a hot cam ( havent figured out the numbers, it has to be a good 'streetracer' jet), and will be ported an polished.

My intake will be polished and carry a 65mm TB for sure, maybe a and hopefully a 70mm, a custum feul rail and bigger 370cc injectors.

THe outlet side will have a Holly Hooker header 6-2 with a high flow daul exhaust

 

I will use a high pressure feul pump and a FPR, also i'm planning a MSD ignition, and a SDS type motor manegment sytem, but at first it has to run on the stock ECU, since sadly i don't have a money tree in my garden

so lots of plans for her. i'm aiming at about 250 orso HP, maybe with the use of NOS

 

But now the problem i want to get flat top pistons to improve the Compression

but since im reading about skyline pistons and all, i was wondering if there are 'bolt on' pistons that will higer the compression, but use the same rod, or what rod do i need, iw ant to keep my cranck at this point, unless i find a diesel cranck, but then i will be back to you guys.

Any of you guys have experiance with 'hybrid' pistons, and what do i need to mod? where would teh compression be?

 

Please don't come with 'use anoter head, or built a stroker, or go with boost', i also have a ZXT thsi will eb my next project. This are my ingriedients and i want to use em, finding parts in holland is hard as is so any help on the piston subject would be apreciated

 

thankz

 

Frank

 

[Lockjaw]

Aren't the pistons from the f54 flat tops? Find a ZX engine with a P79 head, and it has flat top pistons in and that will give you the compression you need.

[frank280zx]

Unfortunatly not all f54's came with flattops, some like the n42 came with dished, i will install flattops, unless i can find a better option!

 

Thanks for the reply

[Kevin Shasteen]

Just my .02c's worth....regarding your choice of camshaft.

 

You said in your initial post that you were thinking about running NOS; keep in mind that a high performance cam on a normally aspirated engine has excessive overlap whereas a highly modified turbo/supercharged/NOS engine will utilize a cam that doesnt have excessive overlap as in:

 

1) Shorter Duration

2) Wider Lobe Separation Angle

3) Correct Intake Lobe Centerline-relative to the Exhaust Lobe Centerline

 

The latter cam will close the intake valve sooner so as to trap the cyl.pressures as quickly as possible. Whereas the previous cam, with excessive overlap-on NOS, will bleed a good portion of the effect that NOS adds.

 

So, if you plan on running NOS and want a hotter cam-just try to get one where the Lobe Separation Angle is wider than usual and dont go to hog wild with the duration....providing you are going to go NOS; if you dont do the NOS thing-then go as crazy as you want-keeping things in perspective, of course.

 

Just my .02c's worth.

 

Sorry-not really up on I6's...but I do understand airflow.

 

Goodluck in finding what you need.

 

Kevin,

(Yea,Still an Inliner)

[frank280zx]

Thanks kevin

 

Well i'm not sure of NOS i want it to be a 'brutal' (what is brutal here) car with more go juice than a averange road car, the NOS thought is for the times i need that little extra, but in the far future, first i want a good MSD ignition, and a progammable engine manegment system and all, so NOS would be the ultimate when i still think she to slow.

 

But consider the Nos not being there, what would be a nice cam? duration and all, i heard a 270 duration is good, MSA states 290 duration cams are OK, but i dont want my car to be having revved to 4k just to keep her running at a traffic light, i do not mind a rough idle, but i have no cleu of cams, or the valves to use in that matter..

I'm reading all i can including the book how to modify you're Datsun OHC,

I understand the basics but thee is allot to learn

 

I read having bigger valves is a must on this forum, though i read the N42 head has big enough valves as is??

 

I will port and polish and match the head to both intake and header, are there more things that i could benifit from, as in optimizing the flow carateristics?

 

sorry tons of q's to all with wisdom

 

Frank

Frank

[Kevin Shasteen]

Comp Cams lists 6 different cams (older catalogue) for the Datsun/Nissan I6 from 240-292 Duration; with lift varying accordingly.

 

I believe you are thinking correctly in that a 260-270 Duration cam would be perfect for a street engine; if you want a decent lower idle.

 

As I said earlier-I'm not really up on the I6; but I do know this engine is basically 1960's technology and the secret to making good power down low is Cyl.Head Velocity-lots of it. Cylinder Head technology has warped light years ahead since then. The I6 is a good engine-but it is also a small displacement engine. This is why it responds so well to turbocharging....(or V8'ing )

 

Small displacement engine's are not going to make a lot of torque down low w/out turbo/super/NOS'ing that engine. Any OHC engine is going to be known for high rpm power-as most OHC engines, prior to the 90's, were usually small displacement engines; I'm speaking as an ignorant American here-who isnt privy to the European displacements and any other country: barring the expensive exotic mgf lines like the multi-valve 12 cyl's ect, ect. I'm trying to say that most OHV engines-available to the general public wer small displacements and with smaller displacement OHC's comes a known chracteristic of any small displacement engine-and that is minimal power down low; only to see its peak power up high...about 500rpms to 1000rpm's higher than any push rod engine of equal displacement/performance expectations.

 

Now throw in the characteristics of a DOHC & Larger Displacement-then you have real all round performance...this is basically what you are doing when you turbo/super/NOS a smaller displacement engine-you are giving it Deeper-Artificial Lungs.

 

I think what you are asking is how can one make brutal power w/out sacrificing low rpm power; normally aspiratingly speaking, for a stock 2 valve I6-you cant sorry.

 

Someone else w/more experience than I on the I6 will have to help you on your piston/cyl.head combo.

 

Good luck.

 

Kevin,

(Yea,Still an Inliner)

[Guest Anonymous]

frank ever think of making it a 3.1 stroker, just my thoughts