s4 street port vs. s5 street port
 

well i want to street port a motor. but mine has 71k and i dont want to tear it down. this is my first rebuild/ port attempt so i want to buy just a core for cheap and rebuild it with a mild port. i cant seem to find any s5 motors but there are a lot of s4 motors for sale for like 100 bucks. so even if its my first rebuild ill still have my org motor in case anything goes bad. just want to know if i should wait to find an s5 motor or go ahead and buy the s4.
btw i have an s5 gxl.
thanks

You'll want a series 5, it's overall a better engine and due to the intake manifold/rotors, you'll make more power. Not to mention that you'll have to wrap the motor in S5 stuff anyhow to even make it work. If you want a full s4 block/intake manifolds it'll become alot bigger of a project then you'll antcipate.

Do it right once.

thanks alot. yea i wasnt sure. i knew that the tps was different but im not to familiar with different specs of s4 motors vs the s5.

people say the s4 manifolds are better for big port jobs. and s5 for mild/stock ports. just what ive heard though.

s5 rotors are higher comp, and lighter.
but its .3 raise in compression, thats not a huge increase. the best thing about the s5 rotors you can spin a bit higher because theyre lighter.
fd rotors are even better for revving, but theyre 9.0:1. same weight, but ive been told that the weight is distributed a bit better, not to mention the combustion pit and rotor sides are CNCed.

rx-8 rotors are 10:1 and even lighter, but you have to have the apex seal slots milled to make them fit in one of the old peripheral exhaust motors.

a properly built ported s4 will still work though. don't think fo the s4 as a POS just because of a few upgrades. a ported s4 motor will work fine also.

honestly, a standalone would really hit the spot. people seem to make a good bit of power on N/As with a standalone.

worry more about having a quality rebuild/clearancing and port job more than rotors. the s4 n/a's will do. s5's are always better if you have them and the counterweights. But I don't feel its as huge an issue as people (and myself) make it out to be.
I'm having my rotor faces ceramic coated, my internals fully balanced (clutch, flywheel, counterweights, rotors and eshaft) and have a pro building my motor.
its all OE mazda parts. stock 2mm 2 piece seals.

having your motor balanced would be nice, but this will be my first motor to have rebuilt, so ill let you know afterwards! not to mention im replacing my 8.5:1 rotors w/ 9.4:1 so ill have no turbo lag :D

-Ben Martin

I would be ok with either an s4 or s5. My dream n/a would have a streetport, plus bridged 5th & 6th ports with pineapple sleeves and a 50 shot of nitrous to compliment the bridge. This would give a very streetable car with great top end potential that could keep up to or beat any stock TII. The 50 shot of nitrous would also give the fuel enrighment the stock computer cannot deliver. A standalone would also be a great plus and good exhaust would be mandatory.

yea that helps alot. just as far as dropping an s4 motor into an s5 car. would that be harder to swap? i know the s5 would just go right in but what do you have to mod/change to make the s4 fit?

if it has nitrous its not NA, technically.

but that is a damn good idea, streetport then bridgeport the 5/6th.

has ayone done that before? what would be the wielded power gains?

probably insane high end seeing how when they open up you have that much more of a port. maybe?

i really like your dream n/a...

but with all that port action wouldnt you need to upgrade fuel because at 6-7 k rpms that would really be stressing things imo

Yes it's been done, it's called an auxiliary bridge, you will want some kind of standalone to get the full potential out of it though.

You can build a pretty fast n/a, just ask tofuball :p:

You would beat a stock TII. Just dont mess with any modded ones. :)