3s head on 5s Options

[Boss-Celica]

I got some extra cash laying around just waiting to be spent on my car. So I was thinking on puttting a 3S head on my 5S. Has anyone done this before?

[presure2]

ahhh i LOVE this stuff. EXCELLENT post, kwanza.
now, can you explain a little about what the diffrence is between a 5s based stroker (3s 2.2l) and a 3s based stroker is, ive seen a bunch of diffrent stuff posted on the mr2 boards (mostly chrisk's posts) about how he builds 2.1 and 2.2l strokers based on the customers goals ect..can you break some of that down for us?

[Kwanza26]

ahhh i LOVE this stuff. EXCELLENT post, kwanza.
now, can you explain a little about what the diffrence is between a 5s based stroker (3s 2.2l) and a 3s based stroker is, ive seen a bunch of diffrent stuff posted on the mr2 boards (mostly chrisk's posts) about how he builds 2.1 and 2.2l strokers based on the customers goals ect..can you break some of that down for us?

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I would only be in a position to make a hypothesis... but my first assumption will be simply... these strokers are all based on forced induction. When forced induction is applied, greater displacement can make more potential power, since more torque is available early on (ala horsepower formula). However, when it comes to an n/a engine, the engine must spin faster in order to make power because it's not being force-fed. The 5S block is limited in how fast it allows induction, based on it's stroke ratio, rod length, and various other little things. Even if you have a head that is a very capable breather, if the bottom-end cannot "suck" in enough air fast enough, no additional power is gonna be made. People should understand... the head does not breathe on its own... in fact... it does very little breathing. Breathing is triggered by the piston travel...

As for a 3S strokers... well, to start... the 3S and 5S blocks have different main journal sizes. I know the JUN 3S stroker crank is basically be a new crank with new rods and pistons (specs are nearly identical to the 5S). The 5S stroker is simply using the 5S bottom-end with new pistons. I'll guess that the 2.1 stroker is using the 5S crank in the 3S block. Because the 3S block doesn't have the same deck height as the 5S, some displacement is lost, hence 2.1 liters. I'm not sure exactly what these guys do... but based on that information... that's my educated guess. I do believe in displacement... but all things considered, 2.0 to 2.2 is small-time and is not gonna show huge results as some may think. I personally feel the 2.0 has many great advantages and is excellent as is... but many may want to do the extra mile for the additional torque (mostly between 2500-4500 rpms)... but it's all give/take.