the valves are in really good condition not a hint of pitting , im gonna stick with them, will probably renew the springs tho. will defo polish exhaust ports, but am undecided about wether to polish inlet as well, reason being i understand about fuel condensing on poilshed inlets, but reckon that would only happen when engine is cold, an audi wur would take care of that, a good friend of mine whos a trained ducati mechanic reckons itll only condense on a cold engine and to polish em 'after all you want it in there as quickly as possible'. i think he has a point!! so it seems that ideally the inlet ports WOULD be polished up to the point of the injector, then left rough(ish) to promote turbulence, any thoughts on that theory much appreciated!! any ideas about the saab fuel pump??
Polishing is unecessary. A fine, smooth finish is more than good enough. It's the shape thats the important part. Ensure the valve springs match the cam you use, the supplier should be able to advise, though standard GTi springs are normally ok with mild cams and rpm around 7k or less. A standard fuel pump & metering head will be fine at the power level yr looking at. Maybe with a modded w.u.r to fine tune the fueling.
ok wicked, i have a habit of getting too involved with these projects! im planning to use a set of internal calipers to measure the ports to get them even across the cylinders. and get an accurate shape to fine tune the fueling i figure the audi wur will do just that, i really like the idea of a non ecu management system thats set up well! mr hillclimber do you know the blue hills section down at trevellas in cornwall?? ive done it meself!!
Good idea with the calipers. No cant say I do, where abouts is it ? Never heard of it used as a proper venue.
more for classics i think but tricky believe me, first time i tried it i ended up just off vertical and crapping myself scroll down to this bit in the following link ''The sting in the tail of the Lands End Trial is Blue Hills Mine.'' http://www.jlclassics.com/phdi/p1.nsf/supppages/jlc?opendocument&part=4 im trying to find the proper link atm ive started the head 2day cleaning and polishing the gasket areas on the outside, down to 800 wet n dry followed by autosol then rinsed. gonna buy some new gaskets 2mo to use as templates and bolt em down , what dyou recommend to use as a good clean scribe on alloy, im a joiner so used to wood, hard steel or something softer?
Ahh... Slightly different form of hillclimbing to this one... http://video.google.com/videoplay?docid=7536319202742738850&q=mk1+golf+hillclimb+car Try and get some engineers blue and a scribe (bit like a dentists tooth pick) from a motor factors and mark out inside the gaskets a line as a "max" to go too, though you should'nt to open out that far depending on yr measurements (especialy on the exhaust side).
Have a "good" read of this before getting stuck in.... http://www.popularhotrodding.com/tech/0610phr_cylinder_head_porting/
Also worth a look here for some basic principals.... http://en.wikipedia.org/wiki/Cylinder_head_porting
Great thread... keep that info coming... The article by vizard repeats some basic rules that he also puts forward in the tuning the a series book, but it's interesting to read in the context of a different engine...
started by cleaning er up before after had some trouble removing exhaust inlet bolts so locked two nuts up and out they came using wire brush on a drill wet n dry down to 800grit then autosol to polish cleaned port face got me spring compressors coming later so will have the valves out for a proper look ive checked the faces are flat with a metal rule, just got to nuy the gaskets then ill start shaping the ports thanks for the links above, some really good stuff there!
be careful about removing too much material from the bends in an 8v head, the water galleys are not that far away. tip for valve refurb..... caefully put it in a drill chuck and spin it against your chosen cleaning material. I got an almost mirror finish on mine with some wet and dry, got rid of all the cr'p that was stuck to them
how far away?? i dont intend to take more than a couple of mm off will that be ok? cheers for the advice on polishing the valves thats a good un, will mount them in the drill press bolted gasket down and scribed it off valves out loads of crud in here and a bit more shiny blingy have now started cleaning the ports up ready to grind away and shape em!
Just a quick question I cant get my head around, how do you get at the short turn inside the ex port?
i dunno yet!! probably thro the valve side, i need to get a dremel with extension really, but this is more of a long term project so that will have to wait till chrimbo!
It's fiddley but possible, and best if you use a round cutting bit, but use the opposite edge to what you would normally, if that makes sense.
A ball shaped stone on an iron head (a stone will clog with ally heads) so a ball shaped cutter would be ideal and attack it (carefully) from both sides.
Before you start cutting away the ports, concentrate your efforts in the valve throat area. Ideally, have the guides pressed back so you dont damage the ends (or remove them compleatly if worn and fit new ones when yr porting is done) when thining down the guide boss.
No probs... Figure on an inlet port size of around 80% of the valve size, for the throat area (the bit below the valve seat), around 85% of the valve size will be big enough for road use. On the exhaust side, work to a throat size of around the same (85%) with the port around 90% of the exhaust valve size. If it looks like neither size can be achieved without hacking out large lumps of ally then use some restraint. I'd also leave the chamber alone for this exercise.
there seems to be a natural lip just past the seat in the throat, removing that would put it around 85%ish. theres a lot of founding marks, really suprised at the amount tbh. ive noticed the guides are at slightly different depths so will have them pressed out, and fit new as said. the injector shroud cuts deep into the inlet by about 6mm, i know the injector has to sit well in, is it worth building up the port in front of that to straighten it out or does it provide the turbulence? does the injector have to sit that far in? ive noticed that some of the ports are not quite true, i know they pan in at an angle but one or two are slightly out, gonna measure the peak of the apex against the block and even them up, im goin to extend the inlet port up and reduce the short turn radius so straightening it up a bit. a theory.... if the exhaust manifold were stepped out to the block, it would create an area of low pressure after the exhaust leaves the block helping to clear the port. what dya reckon?
