Storm wrote:Mirror finish polishing does nothing good for a street engine, for a full on drag engine its a different matter cause the idea is to get the fuel into the engine asap and its nearly flooding in anyway.
Rough casting hinders air/fuel movement and can in some cases cause turbulence that negatively impacts on atomisation because the fuel can get caught in the roughs and puddle.
ExtrudeHone or
AbrasiveFlow Porting is the new technology that seems to be getting brilliant results. It evens the individual port flows so each port is flowing similar to the others, it takes out rough castings allowing air/fuel to flow unhindered thus stopping puddling, it does not mirror finish the port, and it helps to create a near optimum valve throat profile.
A vortex will never be formed in a square or rectangle port. Vortexes are created in the valve throat and many factors including valve stem thickness, valve seat angles, combustion chamber shape, and the engines compression ratio have an effect on it.
Realistically what is required is a clean port that flows the amount of air the engine requires for the revs it pulls at the highest velocity possible. with everything else even a small port will have a higher velocity but a big port will flow more air. If you have an EA engine that is going to pull over 6000rpm continuously go the biggest port you can muster, if you just want a street engine then port matching, valve throat and bowl cleaning, and a good 3 angle valve seat profile will give you what you need.
The correct finish on ALL engines is a fine abraded finish such as that obtained by using "cartridge Rolls" as sold by Standard Abrasives.
Extrude hone etc is in reality about as usefull as so called CNC porting available on many aftermarket V8 heads a starting point and no more.
It is as always a method for lowering labour costs,But in truth there are so many variations no two engines even from the same engine family are identical,For instance with an engine with tight radius bends in the exhaust header section you deliberately try to make one section of the port flow more and to turn it so the exhaust gas swirls as it enters the header pipe section,This aids better fkow around light radius bends and is not something you achieve with so called abrasive hone porting terchniques.
Putting it into a perspective cpuntry people especially can relate to that type of so called porting is akin to a river it will always take the easiest path not necessarily the right path,Hence how many of the Billabongs formed on the Darling river.Logically when yoy think about it it does not translate that well to engines with specific design traits such as deliberate offset of ports to clear pushrods etc.
Now back to the EA81~82 in both cases bigger ports is not the way to go because of fuel dropout,So called Pocket porting,Carefull reshaping and blending behind and after the valve seat area will be worth the effort,either go slow pay for it to be done or buy a dremel and learn carefully.
Increasing compression such as EA82 MPFI pistons after all just how easy is it to get EA71 pistons these days,definately a good way to go.
Camshafts what you gain in one area you tend to loose elsewhere,more top end less bottom end so to speak.
Advantage of EA81 motors is torque so improve breathing by pocket porting,Better exhaust system raise compression with EA82 MPFI pistons and dial in the ignition system with correct timing after testing uphill with a stopwatch or a dyno.
Timing options include 2WD distributor or springs from same for faster response mechanical advance curve,Better Coil as mentioned previously and the point all forget replace all the connections at coil and distributor with new ones or preferably make up a new subharness as it will be old and baked hard by engine heat.
Voltage drop causes issues,drop 1 volt more than original factory spec and lose 10 percent of lighting output with headlights ,the same ratio applies to ignition systems so make sure it is A! not dodgy platic crimp connectors from repco or supercheap use Utilux from a good electrical wholesaler with Lucar Covers etc.
Oil if the engine is fresh then use a decent 10W40 Oil of semi synthetic stock as this will improve performance and economy.
Hint Motorcycle oils are best these days as modern car oil standards are junk where the Greenies have mandated Catalytic Converter life is more important then engine life so the latest standard for car engine oils means they are RUBBISH for engine reliability and life due to lowering the ZDDP content.
ZDDP ~Zinc and Phosporous additives are the ANTIWEAR additives in engine oils.
Motorcycle Oils have higher levels of these additives for they have to live in a gearboxs as well as an engines and have become firm favorites among the Hot Evo and WRX turbo guys for those reasons.
For those with issues as related earlier with Weber Carburettors having poor cruise manners look at the size of the Auxilliary venturi in the primary throat it is likely too large,The Auxillary is the small section in the middle of the carb throat and it controls when the main circuit starts to operate,some searching on sidedraft webers will give a good explanation of the relationships between different sections when tuning carburwettors