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AMC Pistons

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AMC Pistons

Post  Malfisher on Fri Dec 10, 2010 6:38 pm

Hello All

I and others have been engaged in discussing the piston situation for the AMC engines on here lately, most particularly the 20T engine, and it is getting rare. Kelvin (James 20T) mentioned getting some made, I dont know if any manufacturer would be interested to make a batch of these pistons, or if they were what the likely cost would be.

I do have knowledge of a few people getting h/comp racing pistons made for Royal Enfields, these are usually forged items. Accralite in West Brom are prepared to forge a piston, as are Ross in the USA and JP Pistons in Australia.

It got me wondering, how many AMC owners would be interested in buying a piston/s if they could be made? I suppose the question aught to be asked in the Directory as well, but I just thought it would be interesting to see what level of interest there is.

Malc.
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pistons

Post  piston 197 on Fri Dec 10, 2010 8:18 pm

From my experience with pistons ,i certainly would not be going to JP for piston manufacture,their pistons are enough problem in conventional engines!!! i would not risk them in something like the open ported 20T .Generally the problem with piston manufacture is the required quantity to make the cost viable.Accralite is a well respected name and may be suitable,but i think most manufacturers will shy away from the design.Another point to ponder i have had three AMC 250cc trials bikes where villiers barrels have been fitted,using the villiers piston,in each case an aluminium spacer plate with counter sunk cap head screws was fitted to the crankcase mouth using the existing stud holes,then more studs were screwed into this (villiers stud pattern)to accept the villiers top end.I have not seen this done with a 20T,but i bet it could be done with either an 8E or 9E top end(both the same bore as the AMC ,59mm)JH
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Re: AMC Pistons

Post  woodenhead on Sat Dec 11, 2010 1:17 pm

Hi
Sounds interesting do you know which barrel and piston was used on the 25T i've got a spare bottom end on the bench now and have been looking fo a barrel and piston.
This could be an interesting winter project
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Mike d.
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Conversion

Post  kerabo on Sat Dec 11, 2010 4:22 pm

Thats food for thought John

Please tell me more about this conversion. Do you have pictures. I notice the villiers engine I purchased has the same bore as my 20T. I suspect the transfer ports would be the hard thing to get right. If the bore is the same then an engine of the same capacity should have the same stroke so should just mean fitting the piston and barrel in the correct place to make the porting and TDC align.

Regards Ken
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villiers/amc

Post  piston 197 on Sat Dec 11, 2010 7:20 pm

One had a conversion done by john catchpole featuring a Greeves MDS square barrel,with his own head,the bore of the 20T is the same as a 197 villiers at 59mm,so the stroke is practically the same (199 v 197) near enough to make no difference,likewise with the 250 (both 66mm bore (249cc v 246cc) stroke almost identical,so basically if using villiers top end,as long as the piston top reaches to the top of cylinder then if using the villiers piston the porting will be correct.The stroke of the 197cc and 246cc villiers is the same (72mm) so i suppose putting a 250 villiers top-end on an AMC 20T would not be out of the question.

All the converted bikes i have had (3) all used aluminium competition top ends with through studding,but if that is possible then the iron top-end should also be able to be used? Villiers 250 top ends are available in two lengths to suit 5 1/4" or 5 1/2" conrods,presumably the villiers barrel is shorter than the AMC as all conversions i have had,had an aluminium spacer under the barrel.JH
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Conversion

Post  kerabo on Sun Dec 12, 2010 2:37 pm

How do they go John compared to the AMC head and barrel

ken
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AMC 20T and 25T pistons

Post  FB vincent on Sun Dec 12, 2010 2:44 pm

Although rebuilding an AMC engine with Villiers or other parts might be ok for experts, it does not help the rest of us who just want to keep the AMC engines going in their original state; in any case, I guess the replacement Villiers parts plus specialist flanges would not be cheap. We know that the going rate for an AMC piston may be up to 75, so what would be the cost of getting oversize blanks cast in both sizes (20T and 25T), for subsequent machining to the required oversize? The 20T engine was made from 1960 to 1966 and we know that there are many Falcons and James Captain's still out there. Is it possible to get some costings done to find out what a minimum order size would have to be?? Alternatively, would it be possible to sleeve the existing cylinder and use one of the remaining standard pistons? Sandy Ross

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Re: AMC Pistons

Post  Malfisher on Sun Dec 12, 2010 4:54 pm

FB vincent wrote:Although rebuilding an AMC engine with Villiers or other parts might be ok for experts, it does not help the rest of us who just want to keep the AMC engines going in their original state;

Sandy Ross

Yes, this is the real point Sandy, I for one, want to keep an AMC engine as is. And of course there is the future, and future owners, Im sure it would be only positive to have a source of spares.

Im sure that even if 20% of the AMC owners, both FB and James were solidly interested, it may well be feasible. I can only say that for an 87mm forged high compression racing piston, from Ross in the USA, on a short order of 4 pistons I think, the cost quoted to me from an Australian was US $223. That was in July this year.

I believe that Accralite/Omega may well forge a slug that could be milled? Anyway, the certain fact is there are people that can make the pistons, and it is worth asking about them, all that is needed then is sufficient interest to make the cost feasible?

Would this not be a good item to post in the Directory? Im sure there are many AMC owners that dont do the website.

Malc.
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Re: AMC Pistons

Post  Kelvin_20T on Mon Dec 13, 2010 8:53 pm

Hi

Would I be correct in assuming that 3 people are interested in a piston being made? that is myself, Malc and Sandy?


Regards, Kelvin
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Pistons

Post  kerabo on Mon Dec 13, 2010 9:18 pm

I may be intrested in having one but its going to be a guess as to what size to go for. If i am runninga +15 now then I am not likley to want the same size. I would think that once a program for a CNC machine was made the rest would be cheaper and copies could be made to that program. I know an engineer that makes stuff for cosworth and will ask his oppinion when i next wee him

ken
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Re: AMC Pistons

Post  Kelvin_20T on Mon Dec 13, 2010 9:20 pm

Many thanks for the reply Ken.

I'm not 100% sure about this, but if a manufacturing company knows the +15 size then making a +30 size should be no problem?

Regards, Kelvin
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Re: AMC Pistons

Post  Malfisher on Tue Dec 14, 2010 12:00 am

Kelvin_20T wrote:Hi

Would I be correct in assuming that 3 people are interested in a piston being made? that is myself, Malc and Sandy?


Regards, Kelvin

There may be more Kelvin, I appreciate your drive and enthusiasm, but we are at a very early stage in this enquiry. The size of the pistons is a valid questions as Ken points out.

Also, Ive discovered a few companies that offer custom orders tend to make forged pistons for 4-strokes, where we might struggle is the fact it's a 2-stroke piston and may be best cast anyway.

But we may be able to get a company like Wiseco in the US to consider it. I know they require a minimum order of 12 for a 2-stroke custom piston, and 4 for a 4-stroke one, that is if they would consider the design.

Malc.
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Piston

Post  kerabo on Tue Dec 14, 2010 1:17 pm

It may be best to have the largest size or one under then most barrels could be bored out but if you had a standard piston you could be stuck. Or as someone said if they make these with a cnc program i guess you could just alter the program.
I will have on as a spare providing the price is not silly.

Regards ken
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PISTONS

Post  piston 197 on Tue Dec 14, 2010 2:14 pm

wHEN PISTONS ARE MADE,THEY ARE ALL CAST FROM THE SAME BLANK,METAL IS REMOVED TO MAKE PLUS SIZES AFTER,LESS METAL BEING REMOVED ON A +060 THAN A STANDARD,PISTONS ARE FINISH GROUND TO PRODUCE OVALITY (AS THERE IS GREATER EXPANSION WHERE THE GUDGEON BOSSES HAVE MORE METAL)THE PISTONS ARE ALSO TAPERED FROM THE BOTTOM OF THE SKIRT TO THE BOTTOM RING,AND THE CROWN DOWN TO THE BOTTOM RING IS USUALLY ABOUT 1MM DOWN ON NOMINAL TO ALLOW FOR EXPANSION.
SO DON'T SEE IT WOULD BE A PROBLEM AS TO WHICH SIZE TO MAKE AS THE MAIN COST WOULD BE MAKING THE BLANK,THEN THEY COULD BE MACHINED ON A CALL-OFF BASIS I.E 4X 060 ,4X 040,4X 030 ETC,I STILL HAVE A FEELING IT WOULD BE COSTLY,jh
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AMC 20T/25T Pistons

Post  FB vincent on Tue Dec 14, 2010 4:14 pm

I would hope that any project to obtain new pistons is directed to the members of the FBOC via 'The Directory', since I guess that many members do not use this forum; however, the magazine has just been published so it will be another 3 months before this opportunity is again possible. Perhaps the British Two Stroke Club plus the two existing 2-stroke engine rebuilders should also be canvassed for their support. The FBOC Secretary is currently investigating the manufacture of replacement steering head races for the later frames, so hopefully the FBOC could manage and underwrite the manufacture of new pistons for those who need them, plus a stock for the future. For info, the original rebore sizes were plus 15 and 30 thou only; it was Hepolite who marketed the plus 40 and 60 thou pistons, and it is these sizes that are impossible to obtain. Sandy Ross

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Re: AMC Pistons

Post  Malfisher on Tue Dec 14, 2010 5:02 pm

piston 197 wrote:
SO DON'T SEE IT WOULD BE A PROBLEM AS TO WHICH SIZE TO MAKE AS THE MAIN COST WOULD BE MAKING THE BLANK,THEN THEY COULD BE MACHINED ON A CALL-OFF BASIS I.E 4X 060 ,4X 040,4X 030 ETC,I STILL HAVE A FEELING IT WOULD BE COSTLY,jh

Thats good to learn John, as it is a valid point as we would all likely be after different sized pistons, and to have a stock of all the popular sizes, std and OS would cost even more. I think they may well be expensive, but, the more were ordered the price would lower, by how much would be to learn.


FB vincent wrote:
I would hope that any project to obtain new pistons is directed to the members of the FBOC via 'The Directory', since I guess that many members do not use this forum; however, the magazine has just been published so it will be another 3 months before this opportunity is again possible. Perhaps the British Two Stroke Club plus the two existing 2-stroke engine rebuilders should also be canvassed for their support. The FBOC Secretary is currently investigating the manufacture of replacement steering head races for the later frames, so hopefully the FBOC could manage and underwrite the manufacture of new pistons for those who need them, plus a stock for the future.

Yes Sandy, thats what Ive been saying, it would be a lot better if all the club were canvassed, and better yet if it could be all done via the FBOC? But personally I think theres surely no big rush, this needs to be looked into right and discussed for many ideas. I also think the British 2-stroke club would be good to canvas also, never thought of them, thats a good idea. There surely must be a few hundred AMC owners about? It would be interesting to know.

Malc.

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AMC PISTONS

Post  myquest on Tue Dec 14, 2010 7:57 pm

Probably a daft question - but were these engines ever used in anything other than FB/James - even industrial?
If the latter, might be worth looking at stationary power unit supplies.

I'll get me coat....

Michael
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Re: AMC Pistons

Post  woodenhead on Thu Dec 16, 2010 7:47 pm

Hi
Just a thought,
Bantam John is reputed to have a stock of AMC piston would it not be an idea for the club to approach him to purchase his stock so that members when looking for piston dont have to suffer his negative couldnt care less I'm doing you a favour attitude.
In the mean time I will keep a lookout for pistons at jumbles as I have seen the odd one at Netly and Popham and if the price is resonable aquire them.
Regards
Mike d.
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Re: AMC Pistons

Post  Kelvin_20T on Thu Dec 16, 2010 7:55 pm

woodenhead wrote:Hi
Just a thought,
Bantam John is reputed to have a stock of AMC piston would it not be an idea for the club to approach him to purchase his stock so that members when looking for piston dont have to suffer his negative couldnt care less I'm doing you a favour attitude.
In the mean time I will keep a lookout for pistons at jumbles as I have seen the odd one at Netly and Popham and if the price is resonable aquire them.
Regards
Mike d.

I think this is a very good idea. I plan to join the club in January.

Regards, Kelvin
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industrial

Post  piston 197 on Thu Dec 16, 2010 8:40 pm

With regard to the question "were these engines/pistons used in anything industrial" No,the piston used in the 17T prior to engine No 3032 is unique to the 17Tcavalier and light cruiser,the piston used in the 20T and 17T (post engine 3032) are unique to the L20 ,L20S, Falcon 87 and later Light cruisers/cavaliers,the piston used in the 20T is unique to the commodore,cruiser 80/84 and although a different number to the trials and scrambles (25C/25S)pistons will double up in these engines,i still have a couple of 25T pistons,but the 20T ones are the difficult item.
As for BANTAM john's attitude,i personally have had no problem with him,but i appreciate others have!can't see any advantage in purchasing his stock and monopolising it !Chris Williams at Autocycle engineering still had some 25T pistons in stock,but only std and +015,JH
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AMC Pistons

Post  FB vincent on Fri Dec 17, 2010 8:33 am

The supplier you mention in Sheffield may (repeat may) have 20T pistons at plus 30 thou oversize, but after two years of discussions they have not been 'found'. However, as mentioned before, AMC did not offer 40 or 60 thou oversizes (they were only made by Hepolite) and allegedly the above supplier only has original AMC pistons. The hunt is therefore still on for the larger oversizes. Sandy Ross

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Re: AMC Pistons

Post  kerabo on Sun Dec 26, 2010 8:15 pm

I have a friend who has an engineering buisness and makes parts for Cosworth engines. I asked him how and where to get pistons made. His suggestions were.

http://www.ariaspistons.com/distribution.html For small orders

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=230566904757&ssPageName=ADME:B:SS:GB:1123

Regards Ken
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pistons

Post  piston 197 on Sun Dec 26, 2010 9:39 pm

I have some experience of ARIAS pistons in velocette venom ,they were excellent,with a very low expansion rate,JH
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Re: AMC Pistons

Post  Flo on Wed Dec 29, 2010 5:42 pm

STD., +15. +.30, +60. Nobody mentions +20, like the one I have sitting idle on a shelf.

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Re: AMC Pistons

Post  Malfisher on Wed Dec 29, 2010 11:58 pm

Flo wrote:STD., +15. +.30, +60. Nobody mentions +20, like the one I have sitting idle on a shelf.

They have been mentioned in the thread I think Flo, apparently Hepolite made them even-number sizes. Do you still have a 20T on the road? Or is the piston available?

Malc.
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Re: AMC Pistons

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