valve removal

[CMSMJ1]

Howdo,

Is it a fairly simple process to remove the valves form the NC heads? I do not have my haynes to hand and was looking in my garage earlier and found a spare head on the side...

I want to strip it and get dremel tastic with it but am wary of specialist tools for the valves etc.

Anyone care to advise? The basics als- is it worth getting the NC35 head or will a cleaned up NC30 head do just as well?

I know Cal44walker did it but that was on the old forum and a quick look was not enough to find anything about it.

Cheers
MARK

[chrisxr]

its very easy to remove the valves, for speed i use a tube about 20mm diameter and i cut a little off the side so if you look up the bottem of it it resebles a " C " shape, drill though the other end and make it into a T handle then i have a magnet on a tube, basicly put a rolled up rag under the combustion area and push down hard on th etop of the valve sprind holder till it releases the collet then push the magnet down to pick up the collets with the magnet.

To do the ports them selvs...........
open the inlet area to around 30mm for a little longer down the port, this will disturb low end pick up but aid with high speed runing, you need to clean all the bumps and rough castings down the port, the divider in the midle needs to be knife edged and kept as evern as posible, grind the inlet valve stems that pertrude a little at the sides to make a better flow path in this area, to be real clever roughen the area up then use a quality chemical metal to fill the area and reshape to create a smooth path uninterupted path. Gently match the area around the valve bowl so there no steps present in the direction of flow but dont take much out of this area. The main idea around porting is to create a flow increase at minimum valve opening this is done in the same effect as using a hose pipe if you reduce the end size of the hose water escapes at a far greater presure ie putting ur thumb over the end if you remove your thumb the water just escapes at a much less velocity. tuning many new design of engines ports are always reduced in size to see power gains so becarful how much you remove when touching your ports. Finish the port in a 80 grit no smoother if you make the port to smooth on a normaly aspirated engine fuel will hang on the port walls bit like condensation on a window and cause poor running. Once you have done the inlet put the intake rubbers in place and using a high speed abrasive roll of around 180 or higher grit clean the intake rubbers until they match the port shape you should be able to run your finger across and feel no change if done well.
Nothing realy to do on the exhaust port as gasses are always pushed out just explore the route out of the port and remove anything in the way maybe take a little off the back of the valve guide in a chamfered angle but not realy cutting the area away that holds the valve.

To be honest all that will be of very little gain for a massive amount of effort. More gains are made inside the combustion chamber and cylinder but i cant tell you these as i wont get any more work!

something you can do with your head off is cut the plug hole open to except a 10mm plug thread then run cr10ek s or something similair, also as the manual states make sure the valves are cut to the corect facing and sealing width. Just building all the components very well to tolerence will give great power results and much more reliability and stability in motor running.
Im sure many on here who have tuned there engines have other ideas as there is no set rules with regards to it as different combinations of things work for different reasons.

With regards to rvf over vfr its obvious the choice, there is a difference in them and the later do perform better.

Doing engines for my own vehicles used to be very enjoyable and great care was taken to create ports that matched each other perfect and not a blemish in the materials but after doing more and more it is becoming aparant that looks arnt everything when it comes to performance scruffy looking rough ports dosnt mean to say its going to run poor. Some places spend a long time making a nice pretty inlet port so visible work is veiwable and you can see work for your money but in most cases power is made in other less visable places.

[CMSMJ1]

Thanks Chris,

I have the heads spare so I will gve it a look. I have read some work from various sources about the flow and the velocity etc.

I am not looking to go crazy here but I will be removing the nasty casting marks and seeing how it goes from there. If I can get some RVF heads then I will do these properly but for starters I can practice on the spare heads I have.

I would imagine that the valves would all need reseating in an operation such as this?

cheers
MARK

[fumb]

I would imagine that the valves would all need reseating in an operation such as this?

I would since they are out. Its not a hard job to do and it can be quite theraputic. Some grinding paste and one of those plungers, mug of tea and your off.

[chrisxr]

doing valves to the correct seating is actually very dificult a 2 angled cutter will be needed if they are larger than the width stated. when lapping in valves be very careful to clean each stem and oil before spinning back and forth in the seat as any foreign material specialy grinding paste in the valve guide will cause smokey engine when done. When removing valves if they get stuck at the guide dont pull them through either you will need to de burr them around where the colet sits if not you will ruin your head valve guides are replacable but its very expensive and machining the valve seats after wards wil be required.

Check for wobble in the valve guides before you start if there is to much play in them (book tolerence for valve to guide clearence is very small) just junk the heads, chances are its the guide thats worn replacing valve seals only removes the excess oil for a small amount of time when they have bedded in it will be down to the guide to keep oil out of there. New valves may take up a litle play if any is there but another option is stainless ones, the ones i have used seem to have marginaly larger diameter stems than oem ones and it will help a work set of valve guides.

definatly try vfr on heads its not a massive difference between the 2 but the rvfs do make that little more power played with but gains can be made also on the vfr so dont be put off

idealy get it on a dyno do your bit then put it back on a dyno and leave all else as is and see what is actually acheived for your labour, you will be able to see wether what you have done works or dosnt

[CMSMJ1]

Cheers again Chris,

Sounds like fun...

I will arrange a baseline power run before I swap the heads out - this is going ti be a fairly long project for me to get started on as I have so much crap on of late... lapping the seats sounds fair enough adn i am sure that the stem seals and valve guide care will be obvious to me when I get into it.

Oh the joys of a 19yr old V4...would not swap it for owt! :D