There is a lot of information around on what you need for porting a cylinder head. Some people state that you just need a hammer, others state that it is all impossible without at least a 5 axis CNC machine, A Newen Contour BB and Laser interferometers. I have ”invested” in tools that are primarily used for porting, some I would buy again. Some not. I’ll try to list some that I personally have found to be useful . If you want to earn money by doing this, without working 24 hours a day with it I’d suggest you skip all the silly grinding by hand and go straight to CNC and CFD and nevr go ner a castiiirn head ( whose core shifts for an A-series are so variable that it is pretty hard to do CNC on them). But that is a totally different story. I’m an amateur. I have a day/night job gassing people so I can afford to spend some cash on tools, but I feel that it should not get out of hand and for a lot of equipment it just does not make sense to have it yourself.
I am a firm believer in buying good tools. After being annoyed by a cheap battery powered drill I finally did the sensible thing and bought a proper Metabo one. It was about double the price, but unlike the other one it works. On the other hand, I have used and abused things like open ended spanners I bought at ALDI made by some unknown German company for years and they are fine, same for a socket set , the ratchets are quite sloppy but fully functional nonetheless. My dial indicator was made in soviet Russia and is fine ( but I have a Mitutoyo one as well).. the list is large. But when in doubt buy the good stuff first time around. My favourites are Gedore, Stahlwille And Facom. It just works.
Well the basics:
Any sturdy level surface will do. Ideally with a metal top so you can clean it better. Properly lighted. I bought a Vertex Light for use in a mill.. that is IP44 enclosed. Reason is that the old desk light I used before got filled with iron dust and it caused the switches short circuit..not good. With led lights being so cheap there are now a million was to make a suck light (a way to get light into to port while you still have a vacuum hose attached).
Dust Control: the more the better.
The engine build area should be separate ( kitchen.. should be clean and all the parts should be well clean enough to eat off anyway)
Grinders & Burrs
Plural, I have ported a few heads with nothing more than a Dremel clone and a flexshaft, a few carbide bits and lots of tiny stones. It takes ages, but on the other hand if you don’t have a very clear idea of what you are grinding, sticking in a big grinder will in all probability end in a trashed head and possibly serious injury.
Personally I find a flame type burr to be well suited to mini heads, in combination with a ball type about 10-12 mm diameter for roughing the guides. Also interesting is a reverse radius which I so far have not acquired but it makes sense to get a consistent short side.
I now use a Pro Tool SGP 30-8 die grinder with variable rpm’s . It is very powerful at 740 watts so potentially lethal. It works well, but it is rather expensive and the lowest rpm (13k) is still pretty fast for a carbide burr and with a long shank burr you tend to get scary amounts of tool whip. Maybe it is better with a better quality burr, but I cut my shanks quite a bit so that the overall length it now about 12 cm. That is a little shorter than you would want them, but otherwise they just where not balanced well enough. I need to get a few extenders made so that you have a long shank for stones as well. It is a piece of round bar about 10 mm diameter turned down to 6mm to fit in the grinder and drilled for 6mm so that you can glue in a mounted stone with locktite
An alternative would be the Hitachi GP5V but it goes from 2k to 8.5k which is good for burrs but not so much for stones that tend to need a speed of 20-30 m/s or 20-25K rpm given a 20 mm diameter stone. Anything without a long neck is near useless unless you fit a flex shaft and grind instead of cut. You really need to have a long lever to keep a big burr in check, and the long neck allows for a better view down a port as well as a sturdy grip.
A set of snap gages is handy in combination with a vernier calliper.
If you have a bunch of old valves you can have one of then them turned down to 87 % and 88% of the intake valve OD to be installed simply put it into the guide that way it is much easier to see where you have to grind (and NOT grind) in order to have a throat that is to the proper size where you want (or think you want 😉 ) it.
Marking fluid/machinist blue, carbide scriber. Sharpie/Edding or similar works as well.
If you have a good engineering company that can do them it makes a lot of sense to outsource this critical part. Trouble is that they have to know their stuff. A well cut seat should lap in about 3 seconds maximum. Otherwise the concentricity is off. Vacuum testing is pretty useless to test this because there will be a position where it will seal. Some builders loathe lapping btw, stating that the grit will embed itself in the seat. and y0u can’t get it off. My experiences with outsourcing have been mixed. The trouble is that you either have some capable folk cut a seat that is known to be functional , but you are stuck with that you chose. On the other hand the only other option, unless you are very friendly with the local engineering company, is to cut you own seats.
I have Neway hand cutters. Decidedly not high tech ( but pricing is ..) , but given care and time you can cut a halfway decent seat (laps in one revolution), and is alcohol/water tight for 20 minutes without springs holding the valve down. I always install new guides and ream them (the cast iron ones too) to help me along though. There are a lot of builders that are of the opinion that these things are only good for lawnmowers. I agree that there are a more fancy and much nicer tools around (Newen contour BB..) but of you have a tight pilot in a good guide, it is mechanically not all that different from a stone grinding setup (speed.. yes). I takes practice to get a decent seat this way and is very slow. To check I use a magic marker on the seat that way you can check if things are going lopsided. IMHO the ”trick” is to not ask the pilot to do a job it can’t: keeping straight when you lever away with a break bar. If you use very light pressure and a chatter spring below to stabilize things and use patience and an electric drill at slow speed ,with a flexible coupling (thick rubber hose) so you have minimal side loading , to turn it, it does tend to work for me. But it is slooooow.
A single point tool on the other hand needs a very very very rigid setup as the forces from wedging a three angle cutter in are stupendous. To be honest if you just quickly plunge a cutter in, I don’t think it is practically possible to make a set-up that is truly stable. So if you have a sloppy pilot and a clueless operator on a Serdi with a bit of miles on it, I would wager a guess that doing it the way I do it , is not all that bad at all.
Buy it again ? I don’t know.. you have to find a complete grinding set to do any better, or invest in 5000 euro worth of Mira cutter . It’s lot of money for a one trick pony.
An alternative is to cut seats in a mill. If you are not interested in speed it is probably one of the better ways to do it furthermore, If you have a lathe and a mill you can build a lot of stuff so they are usefull for a bit more. The problem is a useful mill for general engine use will weigh about 1500 kg, so no I don’t have one (yet). Although for an A series engine you do not need a lot of height like for a canted valve V8 head on a roll over fixture and if you don’t want to mill heads you probably could get by with a much smaller version and using something like a 3d system from Goodson or http://new3acut.com/ system. Total cost will be about the same as an entire mini.
SoI think you should see if somebody has a Newen Contour in the neighbourhood. It can cut any and bowl profile you want as it is a single point system and it is pretty independent of the operators skill from what I have heard.
I generally fit new guides as a matter of course. They are cheap and hard to measure properly, so I just stick new ones in. To do this I build a simple press from some heavy walled U bends and a 5 ton hydrolic pot jack. I have never had much work space and tools have to be stow able.This is small and has just enough punch to get very stuck guides out.
After fitting you do have ream to size. The proper size is 9/32 inch or 7.14375 mm which is of course silly so I use a 7.14.
The last 0.00011811024 inch does not really matter IMHO as there is no way you can get that kind of accuracy anyway (1/10 micron or 3.93700787 × 10-6 inches).
Reaming a bit less and then honing would probably be better in theory. There are people that start yapping that you should not do it like this and that there is not enough metal to take off to stabilize the reamer. In my experience the guides are so tight that they tend to get pinched a bit mid way with cast iron guides and bronze guides are generally tight all the way. You do need a very sharp reamer that means that you can’t expect more than a few heads from a HSS version (and the carbide ones are prohibitively expensive). Just as you bore and hone I can’t see you honing off this much material easily
I might get a few flex hones after all
Buying a head and simple economics.
Getting somebody else to grind for you 🙂 the ultimate outsourcing..
If you just want a decent head BUY one.. If you want to learn stuff like me.. BUY one and then start on doing you own 🙂 because otherwise you will never be finished .
If you want to save money.. SAVE MORE MONEY AND BUY ONE. I could have bought a really nice Swiftune all singing all dancing race head for all the tools I have bought through the years.
So once again: Save money ? NO WAY ! Learn lots of stuff , YES..
If you think the prices are high, you are right and you are wrong.. If a head is really done well and flow tested to the hilt I really get the 900-1500 UKP pricetag for a race spec head .. I honestly think it is a bargain! DO the maths. A Race head If you already figured it out fully beforehand (that will take a few months of hard graft as least, you will want to regain time spend somehow) how to do it, it will take a minimum of a full day to make, using some expensive equipment and about 10-20 ukp worth of material used for grinding and cutting ( a good burr cost about 30 quid each and they do not live forever when porting cast iron, same goes for 200 quid grinders). In the end, hourly about 70 UKP MAXIMUM..factor in the building etc. etc. etc. etc. .. maybe 20 quid.
What does a set of good V8 SBC ”budget” heads cost ? 1950,- USD bare. Only itake port is cnc’d then. A set of Darin Morgan Aussie pro stock heads cost $5600.
An A-series head is very hard to cnc due to the wild core shifts so unless you start of from new castings it is largely down to manual porting.
A lot of the US head porters downright refuse to cut a cast iron head any more.. it is that much fun!
This is all a very round about way of saying.. don’t whine,good stuff costs money. There are however some companies that want good money for not so good work. I have seen and fixed some heads that where done quite sloppy. I won’t be naming and shaming btw.
I would suggest one on the following two suppliers for NA heads.
Sadly I don’t think you can get just a head from Swiftune any more. You can get an entire engine however, and I’m sure it will go like stink. The tab will be quite hefty though.
They have moved their business to FIA race, historic racing , historic rally. People with the money to pay for the good stuff, not fast road tuner types that will want the world for tuppence and change. Shame for poor sods like me, but very sensible.
To the best of my knowledge http://www.cncheads.co.uk/ does their heads on a private label program.
Very good value and a very knowledgeable bloke that will try and help you out.
Keith ports small bore heads, GT and super sports heads for 1275’s, as well as some very nice cams and quality parts like non stretching IWIS timing chains.
Due to cam cores being very hard to source the cams are now ground on new blanks or billets as needs be. He can still do regrinds though (I asked) if you supply a good donor cam. Somewhat more economical than a new core, even more so if you have a few cams that need to be ground the same.
The GT heads are made to a price that is affordable so don’t expect a full race head, but you could do a LOT worse even for a basic race engine. He makes a mean race head and engine as well.
Furthermore has bravely ventured into having parts made that are really hard to get in a decent quality (like tappet screws) and forged 1.4 ratio rocker arms.
Other useful links:
The best resource on the planet for minis .Not only 5 porters but also the usual slew of K head conversions , a volvo 5 cylinder conversion and mad straight 2×6 multi engine jag powered back cab chassis) and turbo charging and banter. Especially fun if you have a sister.
Some of the build threads are awesome!
Mostly V8 stuff but a few years back it was the best forum on the web for engine building. Now sadly some of the regulars have left and some others have started the usual internet pissing contests but there is occasionally still some good info and searching will yield a lot of good stuff.
well I hope this helps out somebody somewhere