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Hi, I have started to have a go at modifying (increasing the chamber size and modifying shape) of an A Series (Classic Mini) Cylinder Head and was looking for anyone on here that could share some pearls of wisdom regarding valve seat cutting. I picked up a second hand set of Neway Valve Seat Cutters and am now in the process of confirming exactly what I need to achieve what I am after. The valve seats are for valve sizes 35.6mm Inlet and 29.2mm Exhaust, angles are 45 degree with a 30 degree top cut and 60 degree bottom cut. The Neway set I picked up has three cutters in it and I have hopefully found the newer versions of these on the Neway site and have linked them. One of the cutters is a Neway 285 and looks to be the correct size for the Inlet (Just had a quick play on an inlet) but is slightly to big for the exhaust as it fouled on the chamber side - although this may be OK if I moved the blades in a little and this was on an unmodified chamber, which may have a little wiggle room when I expand it? The other two cutters are marked 110 and 275: Neway 110: Neway 275: I maybe able to sell the Neway 110 and 275. I have modified one chamber on a test head and have increased the size by raising the chamber roof and enlarging the chamber walls. I now need to re-cut the inlet and exhaust seats so that I can seal the valves and measure the chamber size. So some questions: Can I cut valve seats from scratch with a Neway hand cutter? When cutting valve sets should I use some cutting fluid of any sort? Many thanks
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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DIY Valve Seat Cutting slater
@slater
Club Retro Rides Member 78
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The short answer is don't bother tbh. Theres reasons we all have proper seat cutting machines like Serdis. If you want a professional job you need professional kit.
I've not actually used a Neway kit specifically but I've used simlar and they are agricultural at best. They are intended for quick bodge ups on tractors and the like really. Not precision machining anyway!
What you have to consider is those type of cutters only support the cutter through the valve guide which allows the cutter to wander and chatter. Its just impossible for it to be ridgid enough for reliable results.. You then have to consider how you are going to get your depths all the same. Even more so if you are planning to use three different cutters to do the three angles (normally you have a single cutter than does the three angles at once).
I think you'd be better off flogging it and using the money to fund someone doing it properly.
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when I built my 2.2 gti6 engine I had my local engine machinists do a skim, seat and valve cut all for £130
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The short answer is don't bother tbh. Theres reasons we all have proper seat cutting machines like Serdis. If you want a professional job you need professional kit. I've not actually used a Neway kit specifically but I've used simlar and they are agricultural at best. They are intended for quick bodge ups on tractors and the like really. Not precision machining anyway! What you have to consider is those type of cutters only support the cutter through the valve guide which allows the cutter to wander and chatter. Its just impossible for it to be ridgid enough for reliable results.. You then have to consider how you are going to get your depths all the same. Even more so if you are planning to use three different cutters to do the three angles (normally you have a single cutter than does the three angles at once). I think you'd be better off flogging it and using the money to fund someone doing it properly. I am practising on an old head that someone sent me for £15. It was covered in rust and I cleaned it up using Citric Acid and it's not in bad nick and no visible cracks. The reason I started this is because I need to increase the chamber size in the head to get the correct Compression Ratio of 9.75:1. Current chamber size is 21.4cc and I need about 25.3cc. I have been getting advice from a classic mini expert on shape / size and how to achieve it. On the old head I have finished grinding the chamber to the correct shape and now need to measure the chamber size, however as most of the valve seat is now missing, the valves wont seal so I am having trouble as the measuring fluid is leaking out through the valve stem / guide, hence the need to re-cut the seat. Here is the head in its original condition: And here it is after I cleaned it up: And here it is ground out:
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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DIY Valve Seat Cutting slater
@slater
Club Retro Rides Member 78
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I would think you will get that to seal ok with enough grease. If you cant you can burette with water with a dash of fairy liquid in it and it wont dissolve the grease. It not as accurate as diesel or something but good enough for indication on the rough size at that stage. don't forget the volume is highly dependent on valve depth anyway so measuring it at this point to compare the chambers is largely pointless unless the seat depths are equal already which they wont be on that head..
Bit late now but a tip for anyone wanting to grind thier own head is to get a couple of spare valves and turn/grind the heads down so only the seat section is left. These can then be dropped in while you work on the chamber and you don't end up damaging the seat unessicarly. (You will need them when you come to finish the grinding after the new seat are cut unless your supremely confident at grinding)
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stealthstylz
Club Retro Rides Member
Posts: 14,812
Club RR Member Number: 174
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DIY Valve Seat Cutting stealthstylz
@stealthstylz
Club Retro Rides Member 174
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As Adam says you need a proper machine to do them properly. We charge £3.50+VAT per seat for cutting seats so it's not particularly expensive.
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Is it a 1275GT/Cooper head? I'm intrigued by the two little screws next to #4 cylinder, not something I've seen before on an A-series head...
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It's going to need inserts fitting anyway to cope with unleaded?
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Apr 12, 2021 19:52:10 GMT
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Not sure TBH? This is a head that was sold as scrap?
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Apr 12, 2021 19:52:59 GMT
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It's going to need inserts fitting anyway to cope with unleaded? With the increase in ethanol, most people are advising stick to addative?
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Darkspeed
Club Retro Rides Member
Posts: 4,642
Club RR Member Number: 39
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DIY Valve Seat Cutting Darkspeed
@darkspeed
Club Retro Rides Member 39
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Apr 12, 2021 19:55:22 GMT
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Give a go - with care and even pressure surprisingly good results can be had with manual tools - You have the benefit that your time is free.
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