Thread: Sr20De(rr) with SR16 piston

You cant throw S4's (or highport cams) into a roller rocker engine. JWT makes the S3R cams that work in a roller rocker engine.

No it does not. Those flow numbers are real, air is air. It cannot be compressed, only flowed. Low ports flow more cubic feet meters of air than a high port does. Plain and simple. High ports benefit MORE from an extrude honing process because they are MORE inferior to begin with.

lowport flows ~240 cfm @ .500" and the highport flows ~190 cfm @ .500".

No matter how those tubes are designed, which is poor, the HEAD ITSELF CANNOT FLOW better and the lowport.

"The '91 thru '93 high-port engine had problems with "port wall wetting" (not to be confused with "bed wetting", though it's worse in the ARB's eyes), where the injector was far enough from the intake valve that some fuel was sprayed onto the intake port walls. When the throttle was snapped shut, the increase in port vacuum sucked this extra fuel into the combustion chamber and caused hydrocarbon emissions to skyrocket. In addition, low intake port velocity at idle also caused an increase in port wall wetting, leading to a similar condition. The PAIRV was there to introduce enough fresh air into the exhaust for the cat/con to burn off the excessive hydrocarbons.

The '94 and newer low-port engine moved the injectors closer to the intake valve and increased intake port velocity at low engine speeds. These changes were enough to allow for the elimination of the PAIRV. They were also responsible for the improvement in the engine's low-end power. "

SOURCE

A simple way to conclude the lowport flows more air stock is that it made the same hp (140 stock) as the highport with a less aggressive intake cam.

So the highport requires a more aggressive intake cam to attain the same power...

Seems pretty obvious to me that the lowport should flow better out of the box.

This was my next point, haha. Great job beating me to it. I was recently enlightened to the lowport being a better flowing head.

Not that I know enough to say this, but reading the thread I see US guys defending lowports/RR vs. EU guys stating highports are better. Correct me if I am wrong but from what I've read, JDM (UK) and USDM heads are identical but the cams (all three hp, lp, rr).
I own a lowport SR20 and I must say I know other guys with such engines (one of them has the exact same car as mine, just a month younger). Well honestly, not a single lowport or RR SR20 here which runs that good as highports do..
I've seen both heads as well and my understanding is that highport head is better build. However, we don't have a flow bench here and both heads were never tested to see which one flows better.

If I had a chance to start all over again, I wouldn't ever go building a lowport engine. Excluding the VE engine, a RR bottom end with 4CW crank together with highport head is how I see it. RR SR20s I think use the best intake mani as well. So pretty much this should be your goal - with SR16 pistons and any aftermarket cams it will great. But all this for the price of a VE which makes it sort of senseless, at least to me.

No, you can convert RR head to using highport cams by changing cams, springs, valves, etc. (dont know what else). It was done before. Andreas can tell more.

^ funny thread chaps

???

Yep, convert the mechanical lifters to hydraulic lash adjusters and then you can throw in S4's.