Porting again

[Jono]

The porting is going really well and is very enjoyable/rewarding. Initial observations from a porting virgin:

1 Electric die grinders are indeed very scary - either on or off and will not stop for anything I've already broken the sacrificial link which is wisely designed in between the spindle and motor so have had to order a new one

2 Meanwhile have bought an air grinder and borrowed a larger compressor which even at 100 litres is still very hungry for air. I reckon a 250 litres 3hp version would be best but I'm not going to buy one of those. I must agree with the previous poster the air grinder is much more forgiving with an ability to modulate the cut compared to the on or off nature of the electric grinder

3 A pal of mine gave me a great tip told to him by a development engineer from Clacier bearings who used to port A series way back in the day when they used to but them in from BMC to use as test rigs for bearings during development (he used to port the engines before running them) - homemade spirabands, will post some pics but they work very well in a std electric drill

4 I am having an extension mandrel made up so that I can reach into the port with the cutters/flapwheels - I took this tip from the DVA Power website

5 I've almost got 2 inlet ports roughed out now and at a state I am happy with. Will be moving on to the others now I have a reference point

6 Managed to do the inlet manifold ports without breaking into the push port holes - took them out to 28.5mm wide and did not want to push my luck beyond that

7 One question - how far do you grind back the guide bosses into the port? Vizard says not to take them out completely whereas Hammill says take them out to the floor of the port (blending in to a smooth curve)

8 I made up a mandrel and knocked the guides out with a lead hammer - figured I will replace them along with the valves. New guides - bronze or cast iron?

I will post up some pics shortly once our broadband is working properly

Overall view is that you need a wide range of tools - electric high speed grinder, air grinder, slow speed drill with flapwheels/spirabands, an electric dremel with some stones for fine work.

Jon

[wantafaster1]

Try regulating the air to the minimum pressure needed for the air grinder to run at the speed you want, it helps.

[Ollie78]

Hi
Sorry I think it was me who was warning of the dangers of these grinders, hope I didn't sound like a kill joy, its just Ive had a few lucky escapes with them brought about through lack of respect and complacency that can develop over time.
There are alternatives to spending out on a big compressor.
If you are competent with electrics you could run an electric die grinder through a dimmer switch to adjust the speed, I think you would need one with the appropriate wattage though I can't advise on this as I know nothing about electrics.... or consider buying a variable speed die grinder. One of the metabo's has that but its a bit chunky.
I currently have a small-ish (6mm collet) cheapy die grinder that's around 250-300w and runs 12500rpm, it seems to be ok for now and was about £50. I find that a nice speed for around 10-12mm tungsten carbide burrs, maybe a bit slow but feels safer. The 30000rpm type I had before is too fast really and lethal. Its about the peripheral speed anyway which obviously increases with diameter, all quality grindstones should have the max rpm info available or stamped on them. I may be wrong but I imagine flap wheels are designed to run much slower.
Ollie

[wantafaster1]

Just trashed a 10 minutes old carbide cutter when I got it jammed. Having trouble reaching in and couldn't see with my hands in the way. I'm glad it wasn't an electric grinder though!

[Jono]

Some progress photos

Which guides should I use - Minispares cast iron?

Also valves - what to go for and any advice on cutting seats (will be getting this bit done by my engine man).

I will probably leave the seats and use an additive given that the car will only do around 1500 miles a year

Jon

[Jono]

some more..

[In the shed]

nice!

[rich@minispares.com]

don't forget that once you have refitted the guides you must ream/hone them to the correct size

[wantafaster1]

Brilliant, if I can do as well I will be happy. Love the home made paper holding tool, necessity is the mother of invention! Very good.
Regards my practice head I thought I had gone huge on the inlet but then dug out an old 12g295 and I still haven't gone that big. When I get started to the 12g940 it will take far far less work, hopefully can do general smoothing and tidying up in the ports to maintain gas speed and do something similar to you in the throats. And much more room to work on the 940 head too.

[Jono]

...the rubber hose with emery wrapped around is the tip from the guy who used to work in the development of glacier bearings and they used a series motors as test mules back in the day - it does work!

I was all over the NEC motor show at the weekend looking for cartridge rolls and spindles - there was only one firm selling them in the entire show and they are here:

http://www.thepolishingshop.co.uk/acata ... ptors.html

The cartridge rolls are brilliant in a slow speed drill for smoothing out the burr marks and obtaining a nice 'honed' finish without putting a shine on the ports. A 100mm mandrel is brilliant for getting into the ports with the cartridge rolls.

Rich - Paul Exon (ex MED and QED) will be reaming my guides and cutting the valves seats - I've got 2 Lotus TC heads with him for the same job - he manages to get them just right and my current Lotus TC engine does not burn a drop of oil (and no guides seals on a Lotus head).

I used cosilbro guides for the Loti - are these the way to go with an a series and who guides should I use - used Paul Ivey for the Lotus valves.

[ianh1968]

I used some of these on the last head I did...
http://www.ebay.co.uk/itm/Drum-Sanding- ... 7924f82d0a

I was attracted by the bargain price!

The mandrels aren't brilliant, but I improvised by "loose-winding"
some masking tape onto a 1/4" rod for the 3/8" bands. This also
meant that I could have whatever length I wanted for a shaft...

Ian