simple shortblock build ??s

[Daeron]

Okay, I have been playing games with the various "calculators" for mocking up an engine build.. and I have a question.

 

What I am thinking of revolves around the head; I am pretty set on doing the P90 shaved 0.080" for an NA motor, compression goal is around mid 10s.

 

According to everything that I have used (and I know not to RELY on these things) if I use stock L28 crank, L24 connecting rods, and KA24 flattops, I should be at about 10:1 compression...... but I wind up getting a deck height of about -1.25-1.5mm.....

 

The reason I am posting is to ask: is this negative deck height going to have an adverse effect on the quench pattern that I am using the P90 head for in the first place??

 

Also, what sort of piston options might I have to still get my mild overbore/stroker engine, yet maybe tuck the piston tops closer to the cylinder head??

 

Obviously, I am asking questions while sitting in the midst of a cloud of ignorance here, but I am trying to read and do my research, and I really kinda want these questions answered before I read too much more.

 

thanks gang.

[texasz]

I just want to clear something up to make sure that you are getting the information you are seeking.

 

In your post you say that you are using the stock L28 crank yet later on you state that you are working on an overbored/stroker engine.

 

If you are using the stock L28 crank you are not building a stroker, if you are using the LD28 crank then you are building a stroker. Which crank are you using?

 

If the LD28 then you will certainly be getting the piston closer to the valve...so much so that you will have to use a 2mm head gasket (iirc) to prevent impact.

[(goldfish)]

Yes, that negative deck height will kill all quench of the head.

[Daeron]

well by using the longer connecting rods from the 240 it changes the throw of the piston... thus adding to the effective stroke. if the term "stroker" only refers to a longer stroking crankshaft, then please forgive the semantic error;

 

In any case, as I thought the negative deck height is a killer on this one.. what pistons might I be able to use to do a mild stroke job using the stock L28 crank and the 240 rods, that would give me a relatively flush deck height?

[silver280zx]

I have a 79 280zx, and i was wanting to do the same kinda setup, but i have heard that with the ld28 crank, l24 rods, and ka24de pistons, will build an awsome NA stroker, and wont give any problems. I have a Compcam's 280s, its 460 lift, 280degree intake/exhaust duration. i am running a ported n47 head, with oversized valves, i probably will ditch the n47 for an e88. well i was wanting to do the storker this summer sumtime, i would just appreciate some feedback. thanks.

[(goldfish)]

well by using the longer connecting rods from the 240 it changes the throw of the piston... thus adding to the effective stroke. if the term "stroker" only refers to a longer stroking crankshaft, then please forgive the semantic error;

 

 

Actually changing the rods dose not change the distance the piston moves up and down, that is purely the crank. So yeah, stroker refers to longer stroking crankshafts. The reason the "common" stroker build uses longer rods, is that the ka24de pistons have a much different pin height relative to the top of the pistons than l28s.

[Daeron]

well actually, i was totally misconceived because I had failed to notice that my gain in CCs up to almost 3 liters was from boring it out on the engine calculator page..

 

I was just trying to start getting a mock up plan in my head as a thought exercise. I have actually learned quite a bit beyond what I even asked in this thread, since I posted it. I just needed some pointers along the way, that was all

 

thanks though.

[zeiss150]

if you want to build an over bore short block thats fine ... just dont change to L24 rods.

 

If you want to use the stock L28 crank with L24 rods thats fine... lots of guys do it ... but not for a bigger stroke... its done to change the stroke raito. If you have an optimum stroke raito the you can rev faster/higher... At least thats what I remember, I looked into doing this a long time ago, so I sort of remember some stuff about it.

 

If you go with the L28 crank and L24 rods then you need the special pistons that arizona Z cars sells. they have a different pin height. the longer rods need the ?shorter/longer? pin height to be flush with the deck. I don't know if they sell 120 thousands over size to make it a 3.0 (2998cc or something like that) If they do then you might be able to get what you are working on.

 

I hope this helped.

 

Matt-

[speedstylez78]

Im curious as to what kind of performance piston options are avalible for the ka24. i found this on nissan parts

The KA24E cylinder head has an uncut (surface to surface) thickness of 90mm/3.898 inches. Piston dome and combustion chamber must be modified to achieve desired compresion ratio.http://www.nissanparts.cc/catalog/?section=324

my question is would modifing these piston's tops be better than decking the head .080.