850/1000 cylinder head valve oversizing? |
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Zambuck
Falcone Joined: 17 Feb 2018 Location: Kent Status: Offline Points: 71 |
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Posted: 28 May 2018 at 09:35 |
I have an extra pair of the small valved cylinder heads for the Tonti 850 / 1000 and an extra Le Mans 850 engine with no heads. I would like to build a well specced Le Mans engine but pointless without the heads. Can a normal set of T3 heads be reworked to Le Mans spec?
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1000 Le Mans II Agostini
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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I'm fairly sure the casting is the same. But the similarity might end there.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Jools
Senior Member Joined: 19 Aug 2016 Location: Milton Keynes Status: Offline Points: 273 |
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As far as I'm aware, the small-valve heads have a 30mm inlet as opposed to the 36mm of the Le Mans-spec heads. These would need to be opened out to match the bigger carb size required, plus the valve seats machining at the very least to accommodate the bigger valves.
I believe that the camshaft for both the Le Mans and the 'soft' tuned G5, Spada, etc are the same (they appeared to have the same part numbers when I checked it out a couple of years ago). The heads can be re-worked by a competent tuner, but it would cost a serious amount I suspect. However, if it gives you the performance you require, why not? I wish my G5 had the performance of my mates old Mk3 - I just loved the sheer grunt of that old bike!
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Jools
V1000G5 1972 T150V 1961 Royal Enfield Constellation 1971 Suzuki ACC50 erm... 1963 Philips Panda (and other assorted detritus) |
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Zambuck
Falcone Joined: 17 Feb 2018 Location: Kent Status: Offline Points: 71 |
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Yes, performance gains are impressive on the enlarged valves and other tweeks. Does anybody know of a south eastern Guzzi friendly engineering shop that could do this?
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1000 Le Mans II Agostini
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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Le Mans have high domed pistons which need the Le Mans heads, which have correspondingly higher combustion chamber to match. Comp ratio 10.4:1.
Also the carb intake mounting bolt holes are M6 instead of M8. So "converting" T3 etc. not that straightforward and possibly lots of potential for cock-ups. Difficult without an actual LM head to look at and get measurements from. |
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"Chicken nuggets don't dance on a Tuesday."
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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Any place capable of putting in valve seats should be able to do it. You have to be a bit careful doing the inlet ports round the valve guides. Many years ago a friend of mine opened the ports on a Commando head. When he came to put the guides back in, guess what, they went in crooked. Scrap head. |
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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And changing the shape of the combustion chamber? With no data to go by?
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"Chicken nuggets don't dance on a Tuesday."
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Zambuck
Falcone Joined: 17 Feb 2018 Location: Kent Status: Offline Points: 71 |
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I could supply one of my cylinder heads as reference.... I could have sworn I read something like this somewhere on the interweb where the argument was for converting T3 heads into performance heads as they were easier to do than lm heads for whatever reason. Can't find that anywhere now.
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1000 Le Mans II Agostini
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Zambuck
Falcone Joined: 17 Feb 2018 Location: Kent Status: Offline Points: 71 |
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1000 Le Mans II Agostini
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BondEquipe
Senior Member Joined: 10 Dec 2014 Location: Summerzet Status: Offline Points: 1898 |
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That was brilliant. Did remind me of a Fosters advert with the 2 of them talking though!
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Stephen
Black & Gold LM2 + Other Bikes & Projects! |
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TonyF
Falcone Joined: 29 Apr 2016 Location: New Zealand Status: Offline Points: 17 |
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The lemans heads have wider and deeper combustion chambers (to fit the larger valves) than the small block heads. The lemans pistons then have high domes to fill the combustion chamber and give the higher compression ratio.
Converting small block heads to lemans spec is/would be expensive and you would need to find someone who really knew what they are doing. There is a school of thought that says that the small block heads can be made to flow very well if done properly, particularly on the inlet side - related to the shape of the back side of the valve. Lemans heads do come up for sale but at high prices. Here is an idea if you want to use your lemans engine! Have the small valve heads flowed. Then machine the lemans piston domes to bring the compression back to a usable level making sure that piston to valve clearance is okay and that squish is set at 1mm, you might need to machine the top of the barrel to achieve this. |
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Tony
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BondEquipe
Senior Member Joined: 10 Dec 2014 Location: Summerzet Status: Offline Points: 1898 |
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I'd have thought that the Le Mans pistons would be too valuable to do that too. Better to sell them and buy cheaper T3 pistons if going that way?
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Stephen
Black & Gold LM2 + Other Bikes & Projects! |
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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Also I bet the dome is hollow underneath so risk cutting through and holing it. Expensive experiment!
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"Chicken nuggets don't dance on a Tuesday."
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