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Car Forum / MINI / September 2003Installing new valves
Hi, I have a cylinder head and wanted to install larger valves. I was hoping that someone could give me some info on the general procedure, most importantly, can I do it myself at home or do I need an engineering place to do part of it? Do I have to replace/cut the valve seat? It's a 12g940 Mini head with 1 5/16ths inch inlet valves. I want to increase the size of the inlet valves to 1.4inch (as in the MG Metro which uses the same 12g940 head casting but is fitted with the 1.4 valves as standard. Cheers, Dave It would likely be cheaper and work better to swap the head. Maybe a rebuilder will take you old head in as a core and give you a good price on a rebuilt? I swapped the head on my old 1275 for one with the larger valves. If I remember right, the internal passages are larger as well to handle the increased valve flow. (this was on a late 60's vintage, things might have changed) Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's > Hi, > [quoted text clipped - 12 lines] > Cheers, > Dave This is pretty much a machine shop job - it's possible to do at home, but only with an investment in tools well beyond the cost of having it done for you. To make this work, you need to have the valve seat cut larger to suit the new valve size, you need to have top and bottom cuts to blend the new seat (the old "three angle valve job"), and you really need to smooth out and open up the bowl under the valve at least, to gain an advantage from the larger valve. If you have a cylinder head rebuilder do it, they will do a regular valvejob and refit the valves for you, but they probably won't do any of the flowing and blending work. You know of Minispares, of course - check out their website for remanufactured and prepared heads. When I was racing Mini's a few years ago, I did my first heads myself, then just bought them - cheaper in the long run! Cheers, Brian > Hi, > [quoted text clipped - 12 lines] > Cheers, > Dave > You know of Minispares, of course - check out their website for > remanufactured and prepared heads. When I was racing Mini's a few years > ago, I did my first heads myself, then just bought them - cheaper in the > long run! I'd say keep it in the 'family' and check out Dave Baker at Puma Racing who posts here. Seem to remember he's a wizard with A Series heads.  Signature*Fax is stronger than fiction * Dave Plowman dave.sound@argonet.co.uk London SW 12 RIP Acorn > You know of Minispares, of course - check out their website for > remanufactured and prepared heads. When I was racing Mini's a few years > ago, I did my first heads myself, then just bought them - cheaper in the > long run! Thanks fellas, I've looked at heads from Minispares etc but the prices are far to much for me which was why I fancied having a go myself. I've read and re-read David Vizard's "Tuning the A-series engine" and I'm ready to spend hours in the garage with a dremel enlarging, de-shrouding, porting and so on to Vizard's specifications. It just seemed a shame to do it on a head with standard valves. What would I use to cut the valve seat if I decided to do it myself? And what other tools would I need aside from the usual head rebuild stuff? Perhaps I'll just get a head of an MG Metro (already with the larger valves fitted) and grind that to the Vizard specs. snip > Thanks fellas, I've looked at heads from Minispares etc but the prices > are far to much for me which was why I fancied having a go myself. [quoted text clipped - 9 lines] > Perhaps I'll just get a head of an MG Metro (already with the larger > valves fitted) and grind that to the Vizard specs. You are right, a good option is to get an MG Metro head if you can find one. However there is a 'cheat' I heard about 30 years ago. First, get the valve seats recut for the larger valves. You then have seats that are wider than the lands on the valves. Then put some engineering blue on the valves and drop them into their new seats (you need the guides in of course). Take out the valves and you now have the dimensions of the new seats marked out in blue. The unmarked material needs to be removed. You may find the Dremel very slow - you need a decent flexible drive to attach to your meaty mains drill. Not expensive but get a good one as mine ran its bearings very quickly. Or do you have a pillar stand for your drill? This will give you a nicely vertical valve throat - just put a grinding stone of suitable size in the drill and bring it down into the throat. By this time you will have removed the old guides so you can do all the Vizard-style port shaping, for which you will need the flex drive. The advice about 3-angle ports is important but you have the Vizard book so you won't forget that. If you must cut the seats yourself you will need the correct cutters but not worth buying them so find a decent machine shop. This approach is not ideal but I used it on a 1098 Sprite head in 1972 and it easily blew my mate's Spitfire into the weeds. Later on though the head cracked between 2 seats so you might want to have it tested before you invest all that time. If this is for road use you can get away with standard valve guides. Apparently they last longer than the bronze ones, although the latter are much better for sustained high revs as in racing. > You may find the Dremel very slow - you need a decent flexible drive to > attach to your meaty mains drill. For information, B&Q have a rotary cutter under their PPPro range which sort of replaces the Rotozip, and this includes a flexible drive. It's also a router. The motor is 500 watts plus so should be up to the job. I've not used it for this sort of work, but it looks like it should be suitable in a DIY sense. Not sure about the price, as I got the older one at clearance time for about 50 quid. Signature*Suicidal twin kills sister by mistake. Dave Plowman dave.sound@argonet.co.uk London SW 12 RIP Acorn And Les Rose was sitting next to Elvis in the spaceship, which I thought was kinda strange, but then they turned to me and said: [...] > If this is for road use you can get away with standard valve guides. > Apparently they last longer than the bronze ones, although the latter are > much better for sustained high revs as in racing. Worth noting that if you're changing valve guides, you will probably need to cut the seats anyway after you've fitted the new guides. The standard iron guides are often bored well off-centre - replace the guide, and the valve isn't centred in the old valve seat any more. (All the bronze guides I've seen so far seem much more accurately made than the factory parts. Swapping a bronze guide for a new bronze guide usually leaves the valve still perfectly aligned with the seat.) Signature(-AD-) <uniqueid 'at' lineone.net> http://website.lineone.net/~uniqueid/ Hello? Anyone in here? > (All the bronze guides I've seen so far seem much more accurately made > than the factory parts. Swapping a bronze guide for a new bronze guide > usually leaves the valve still perfectly aligned with the seat.) Sorry to hijack the thread - whats the advantage of a bronze guide? Is it worth using when trying to build a bulletproof, reliable and slightly more powerful 1257gt based engine? I ask as I'm about to rebuild a head, and it badly needs new guides ( <http://www.raromachine.com/mini/enginestrip_200309/Engine%20Strip%20014- small.jpg> )- thought it already has hardened seats! splam And splam was sitting next to Elvis in the spaceship, which I thought was kinda strange, but then they turned to me and said: > > (All the bronze guides I've seen so far seem much more accurately made > > than the factory parts. Swapping a bronze guide for a new bronze guide [quoted text clipped - 3 lines] > Is it worth using when trying to build a bulletproof, reliable and slightly > more powerful 1257gt based engine? First off, a note of caution - there are two main types of bronze alloy used for valve guides, plain phosphor bronze (the same as is used in bearing bushes etc.) and Al-Si bronze, which is a much harder and more durable alloy (you can really feel the difference when you ream the guides after fitting!). In my experience, the Al-Si bronze guides last a lot longer than the cheaper phosphor bronze items. Good quality bronze guides tend to hold up better under extreme conditions (high speeds, high temperatures, large valve openings). Under extreme racing conditions iron guides can sometimes 'nip up' and prevent the valve closing (major OUCH!), bronze guides tend to be much less prone to this. The second big advantage is that they conduct heat away from the valves better (which is partly because they wear better - sloppy valve guides lead to overheated valves). Because of their extra toughness, they can be made shorter, so the end of the guide doesn't intrude into the inlet port as much. (Most of the bronze guides available off the shelf from competition parts dealers are the short bullet-nosed type) Finally, some valves are made of alloys that aren't compatible with iron guides at all, and you obviously need a bronze guide if using these. Signature(-AD-) <uniqueid 'at' lineone.net> http://website.lineone.net/~uniqueid/ Come to Sunny Morecambe! > However there is a 'cheat' I heard about 30 years ago. First, get the valve > seats recut for the larger valves. You then have seats that are wider than > the lands on the valves. Then put some engineering blue on the valves and > drop them into their new seats (you need the guides in of course). Take out > the valves and you now have the dimensions of the new seats marked out in > blue. The unmarked material needs to be removed. This sounds like the sort of idea I'm looking for, only I don't quite understand what you mean. Could you explain it again? I'm getting mixed up with which are the new and old valves and seats. Also, if I have the seats recut for the larger valves, why would I need to remove any more? Sorry for being a little slow on this one. > You may find the Dremel > very slow - you need a decent flexible drive to attach to your meaty mains > drill. Does the dremel not run miles faster than a drill? Or is torque the important issue here? > Also, if I have the seats recut for the larger valves, why would I need > to remove any more? Sorry for being a little slow on this one. Because part of the throat would now be smaller than the valve. It will be obvious when you strip a head. Signature*Why is the third hand on the watch called a second hand? Dave Plowman dave.sound@argonet.co.uk London SW 12 RIP Acorn >>You may find the Dremel >>very slow - you need a decent flexible drive to attach to your meaty mains >>drill. > > Does the dremel not run miles faster than a drill? Or is torque the > important issue here? Yes Dremmels turns a lot quicker than a drill -- power drill turns much too slow for port grinding even on cast iron heads, but Dremmel type tools really aren't up to the job what is needed is compressed air driven die grinder and a BIG compressor. > >>You may find the Dremel > >>very slow - you need a decent flexible drive to attach to your meaty mains [quoted text clipped - 7 lines] > type tools really aren't up to the job what is needed is compressed > air driven die grinder and a BIG compressor. This is what I used to believe. Last winter I did substantial work on a pair of 351 Cleveland heads. I got an expensive carbide bit and it ate cast iron like butter with the dremel. True, the work would have been faster using a larger grinder, but for just a pair of heads, and a few hours to spare, the result is just fine. I also used a B&D Power File, which is nice to get a smooth finish with, and it also reaches far into ports. Using a coarse belt, it is also fine for aluminum intake porting. Thomas > > >>You may find the Dremel > > >>very slow - you need a decent flexible drive to attach to your meaty mains [quoted text clipped - 21 lines] > > Thomas I may have learned something here! I will look out for a carbide bit and see how it copes with my inlet manifold. However I find that I need a range of shapes for a full head job and then it can get a bit expensive. >>You know of Minispares, of course - check out their website for >>remanufactured and prepared heads. When I was racing Mini's a few years [quoted text clipped - 7 lines] > de-shrouding, porting and so on to Vizard's specifications. It just > seemed a shame to do it on a head with standard valves. Standard A+ head is MUCH better than the average modified A series, same goes for the carb and manifd. There are a couple of ways to cut seats. Aside from specialist machines (like Serti, etc), the best way is to use a Bridgeport type mill with a carbide cutter. the mill is probably a couple of grand used, and the cutters, mandrels, holders, pilots, etc, are about a grand at least. This is a home shop job for some guys, but you and I aren't one of them! The next way is with a seat grinder - old technolgy, but still in use. You get grinding stones, a holder, a mandrel and a pilot, you need a dressing jig, and you use a tool that looks a lot like a die grinder or an angle grinder (but isn't) to spin the stones. You can get these used for about 500 pounds/dollars, depending on condition. That's what a lot of the more serious home shop guys use. Next is a hand cutter setup. You can get these, most often intended for small engines (lawn mowers, motor cycles, and up to Harley Davidson size heads. These work, but they also cost a fair bit. I get charged about $120 CDN for a basic "cut seats" job, maybe $200 for a complete valve job on a Mini head. I haven't yet been able to justify buying the cutters, etc, even though I have a mill. It's like boring cylinders - I can do it, but I can only cost justify it if my time is worth less than $10/hour. http://www.goodson.com has an excellent on-line catalog with all of the tools that you would use to do this sort of job, have a look. Brian > > You know of Minispares, of course - check out their website for > > remanufactured and prepared heads. When I was racing Mini's a few years [quoted text clipped - 14 lines] > Perhaps I'll just get a head of an MG Metro (already with the larger > valves fitted) and grind that to the Vizard specs. > Hi, > [quoted text clipped - 12 lines] > Cheers, > Dave Not the first to tell you this but Swap the head for a Metro one much easier, fitting bigger valves is major work even with the right seat cutters and a high speed die grinder. |
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