If i was to mirror polish the exhaust ports, make the inlet side a bit smoother, remove all ridges, casting marks and match the ports to the inlet what typical gains would be achieved by this work, the head is off the engine so i thought why not. If its only 1 or 2 ponies its hardly worth the effort for now.

 

you will get more power from putting octane booster in it. modern castings are very good and require little of the above. You need to turbo it if you want to make it faster

 

st170 benefits more from proper port work on exhaust side

 

then a remap to suit presumably? how much material and where is best to take it from and what shape?

 

tbh i would get someone who does it for a job and that has a flow tester as if it is done wrong it will affect the flow and loose power by doing so

 

how much more power will it make? 50 bhp? wouldnt bother my arse for 5 or 10

 

You don't want a mirror finish anyway, slows the airspeed!!
I would entrust the work to someone who does this as a business also, a lot don't use flow benches, just years of experience can tell them what they need, they may well flow it just to see the actual difference, but they have a very good idea without flowing.
tabetha

 

I thought a mirror finish on the exhaust side would aid the scavenging effect by speeding up the exhaust gas and prevent carbon from sticking and building up

 

if it made that big of a difference manufacturures would of done it from the factory. leave it alone or turbo it.

 

It dose help for sure have done this on many heads but as said modern casting is good removing lips and roughness will help and mirror finish is not needed the finnish you get with p80 is just fine cut backs on the valve is good but think your find its all ready done being a modern engine as for gains hard to say , ask tuners first what works get advice then do the work done this myself good resaults every time.

 

well they do ever heard of extruded honing ? mainly they dont because casting is very good these days and costs.

 

I assumed that the extra time and effort involved in making good a head during production was not worth the expense so the head is as cast, every head is unique with its own flaws.
Im building a seperate turbo engine at the moment but with the cost of living its going to be a long time till its finished so im looking at ways to improve the engine thats in the car for little or no money only my time.

 

new timing belt, oil and filter, change brake fluid, and make sure it has plenty of fresh antifreeze, strip and clean the brakes and make sure all the tyres are good etc, cant beat keeping a car in tip top condition, that is where i would be spending my time, not fannying about polishing heads for no noticable gains. Thats just my opinion of course and we are all entitled to that.

 

The cars just had a full underside nut and bolt restoration, the car is MINT, picking wheels up thursday from the powder coaters along with my freshly powder coated coilover springs. The car is tip top, easily one of the cleanest ST170's around, im just looking for something to do as there is nothing left to clean outside the engine lol.

 

i see, just drive it then!

 

Show us the photo's then!