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Hi, reading various articles on the internet several racers have converted there ducati singles to 60 degree valve angle. It appears this has been achieved using pantah rockers. I would be interested in trying this mod. Is there anyone who can help with advise on this... Can you use any pantah opening rocker, can you use 600 monster rockers? Do they still use the standard type single camshaft (race spec non desmo) The pivot for the rocker doe's this need to be relocated or can this be left in the standard position. If it can be left in the standard position does this mean the rockers are not 1 to 1 ratio? Lots of questions but any information greatly appreciated.
 

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I don't know the answers, but I know a man who does: Eldert, of this forum, who builds the fastest Ducati Singles.
 

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Hi Terry

reangling is about a 200 hour job . relocating rockerarm pivet points , reworking
the pantah rockerarms and making a new camshaft ( the lobecenters are way of with a single cam ) . and offcourse making new better flowing ports , reshaping the combustionchamber into a semi hemi and relocating the sparkplug (a 10 mm one ) way up in the combustionchamber

i did 3 450 / 500 heads so far and i am working on a fourth one . i dont think there would be any HP gain in a 350 so forget about it

Cheers Eldert
 

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Discussion Starter #4
Hi Eldert

Thanks for the advise, I have down drafted a head but as always are looking for a little more. I was just thinking if I re-angled the valves i could improve the short side radius a bit more. We achieved a more down draft angle by basically pressing an aluminium pipe into the inlet then welding. The port inlet is 32mm. I tried to post pictures but couldnt get it to work?
Regards
Terry
 

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Hi Terry

i think a 32 mm port would suit a 250 better . with a 350 engine you can go bigger . as a rule of thumb valve size X 0.8 for the port at the manifold .
so with a 42 mm valve that would be 33,6 mm
for the inlet valve seat throatdiameter that would be 42 X 0.9 = 37,8 mm

i raised the roof of the port a little to much on my last 350 head . so i am reworking the rockerarm to get more room for the valve spring

Eldert
 

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[quote/]

i did 3 450 / 500 heads so far and i am working on a fourth one . i dont think there would be any HP gain in a 350 so forget about it

Cheers Eldert[/quote]

I'm about to collect my 'new' 250 this weekend. I'm interested in the comment that changing the angle on the smaller motor makes little difference. The reason?
 

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It's interesting that Lacey Ducati's new and very efficient cylinder heads keep the original valve angles. Maybe port down draught and shape is more important than valve angles?
 

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If the bike is for pure race only, then combustion shape is important. So can the air get in and out quickly with possibly smaller valves and a good megaphone?
 

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Hi Wallace

why not restore the Diana ? being a 1961 it is a four speeder .
a 4 speed has the DM250 prefix in front of the barrel on the rh case .
a 5 speeder had the prefix on the lh case

Eldert
 

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My how time files. I'm back to the 250, 6 years later from my last post. Anyway, I have stripped it all, vapor blasted the engine and bits and now remachining new bushes, making sure all the casing bits are flat, new bearings etc and am about to assemble the bottom end once I have the clearances correct.

I bought a new bigend roller cage as the original conrod and bigend showed no signs of wear. The rollers were 0.02 mmm undersize.

From a discussion with a fellow rider, it appears that the 250 may not benefit a great deal from major head work. Valves are quite big and piston diameter, small.

I will raise the intake port near the valve guide and change to 6 mm valve stems. I'm keeping the hairsprings so will have to fabricate new valve/spring retainers to suit the smaller cotters.
Just need to find a reasonably priced hot road cam.
 

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Will 6mm be big enough for the valve stems? I've not heard of any Ducati Single running smaller than 7mm.
 

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Will 6mm be big enough for the valve stems? I've not heard of any Ducati Single running smaller than 7mm.
Comment appreciated. In the past I have upgraded CB350s to 6 mm and never had any issues. These valves are slightly bigger. I'm not sure why the originals were so thick except that probably the manufacturing processes those days were not as good as today. The valves I have are a premium USA brand blanks which I will turn to size and lighten and make matching guides. I think valves seldom break on their own, its just the piston that nudges them along.
 

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with the coil spring set up i am using i can add about 6 mm to the spring base

welded up the bottoms of both ports . welded up exhaust seat area to put in a smaller beryllium bronze seat and make more room for a smaller 10 mm spark plug higher up in the combustion chamber .
valve sizes 40 intake and exhaust 35 mm .

Eldert

986999



986995
 

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Fantastic work Eldert, God knows how you do it. I don't suppose you have dynoed the 450? It would be interesting to see what rear wheel horsepower the engine turns out.

I remember talking to either you or your brother at Brands Hatch many years ago about Anthony Ainslie, and seeing your 480 senior bike circulating. I remember that your Ducatis were some of the very few that actually pulled when changing up out of Clearways, most of the others just went flat and went slower.
 

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Nothing as nice as Eldert's- but a similar mindset. It's a 350, so it won't get much more power, my chance to learn to TIG weld and play with a CNC. With the dyno gone, I may not have a chance to push the power back up; this shows about 95mph on the GPS, probably around 30HP.
 

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here a picture of a 450 head with a Pantah rockerarm . plenty of room to raise the port and still have a long valve guide .

Eldert


990501
 
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