Thinking of porting my spare heads

I've got my spare heads from my old engine and thinking of doing a DIY porting (smoothing the intake ports, polishing the exhaust ports and combustion chamber top) to improve over all flow

Your advice, tips and don't does please

I am having mine done at the moment (injected bike). Will let you know what difference its made if any when it comes back.

DIY...TBH i wouldnt. Even Steve who builds plenty of engines isnt doing it for me. Id get someone who knows what will work and what wont work to do it. I think what you actually have to do varies so much between bike to bike. I know some bikes dont actually benefit from it and some run worse for it.

Although if its a spare....but could it cause damage if done wrong. Are you putting it onto a spare engine you dont mind about?.

Id be sure about what your doing first, unless of course you dont mind about the motor your using!.

Let us know what happens.

All i was going to do was clean all the burrs and mould lines from the intake side and polish the exhaust side to stop coke build up, not open them up or make them bigger in any way, would this be a bad this?

[TSM]

If its just polishing i beleave that Rictus has done that on his old SV and there was no issues.

Originally Posted by svrash

All i was going to do was clean all the burrs and mould lines from the intake side and polish the exhaust side to stop coke build up, not open them up or make them bigger in any way, would this be a bad this?

In that case then cant see a problem. If your actually machining then its not such a good idea.

Polishing ports can actually reduce airflow albeit very slightly. With a highly polished surface the friction is berween the gas and the polished surface. With a rough surface a layer of gas is held against the surface and the main body of gas flows against this. In other words the outer edges of the gas stream shear off and stick to the rough walls of the port. The air against air friction is lower than the air against polished surface friction so the polished surface will have a reduced flow.

The above is from an engine tuning tuning book I read a few years back. I would strongly suggest that you take a look at a tuning book before starting doing any work.

Just my tuppence worth anyway

cheers

Stewart

The SV heads are very close to optimum right out of the box. My suggestion is to do a dyno run before and after and let us all know the outcome. As far as good value mods go, lots more power can be realised with big bore kits (using new sleeves) and higher compression.

Originally Posted by sdusk

The SV heads are very close to optimum right out of the box. My suggestion is to do a dyno run before and after and let us all know the outcome. As far as good value mods go, lots more power can be realised with big bore kits (using new sleeves) and higher compression.

why would you need new sleeves?

Course an even better method of getting free power is ditching power commanders in favour of getting the standard ecu remapped

[embee]

Originally Posted by stewart-250

Polishing ports can actually reduce airflow albeit very slightly. ........

G0lf ball principle. Flow separation etc

I've been in engine development for 25+yrs, and had the luxury of all sorts of flow bench, single cylinder research engines, combustion analylsis, and latterly computational methods for flow prediction.

You can't guess it.

Even simple flow bench methods don't really help much, so don't put too much store by claims from the users. Flow benches usually use steady state flow and they have an open cylinder under the head and often without valves fitted, none of which represent what really goes on. We used to do flow bench tests at a variety of valve lifts and pressure differentials, and it just gets more confusing.

Half the battle actually comes as the turbulence breaks down just before ignition as the piston appoaches TDC compression, which a flow bench won't tell you anyway.

You might be really lucky and better what Suzuki have done, but if I were you I'd buy a lottery ticket instead.

Simply a little bit of tidying is probably the best plan, you're unlikely to make anything worse and you'll feel better.

The most useful thing you can do is make sure the engine is set up as well as it can be and is running absolutely correctly. Often if the engine is absolutely spot-on it'll feel (and sound) unimpressive, so many times people think that if it's a bit temperamental and coughs and splutters then it must be highly tuned. No, it's just set up badly.

Ignition systems are absolutely critical. Valve clearances, clean the carbs etc etc

[21QUEST]

Originally Posted by embee

Simply a little bit of tidying is probably the best plan, you're unlikely to make anything worse and you'll feel better.

Ah... like a placebo effect then. Where would we be without that



Ben