Building a race bike

I did something simular on a 3c Head, but don?t get into the Valvespringseat. Where should be the Valvesprings here?
I don?t know 750 Heads, there all have Steel Skulls?
This is for a Racebike not suitable! The Camber gets far too hot, it will Ring like a Bell!
 
hochkoenig said:
I did something simular on a 3c Head, but don?t get into the Valvespringseat. Where should be the Valvesprings here?
I don?t know 750 Heads, there all have Steel Skulls?
This is for a Racebike not suitable! The Camber gets far too hot, it will Ring like a Bell!
Click to expand...

I recall he's planning for it to be on metho, in which case heat is not the same problem it is on petrol.

Nice work Julian, will be very interesting to see the results.
 
Wow! Very interesting stuff. You've gone a similar route to me with the overall port angle, Julian, but I'm sticking with a high, curved port floor. 95% of my work will be on the roof. Started with a small valve head and used Phils pics as a guide as well. I have no idea how mine will work - 44mm inlets and 39mm ports. I'm not going short stroke, and I want fat midrange and decent top end, so different kettle of poissons to yours.

Hopefully I can compare with my 'std' ported head at some stage (although the larger skull OD for the OS pistons makes that difficult.
 
Marty that concept for porting is not only in the 6 plug bike, but it's also been done to yours and my 3C. Mine needed some mods to Reds alloy adaptors to fit his Mik Carbs to keep the downdraught effect working. Done by his CNC bloke. Its also got a set of rubber carb mounts from 40mm Guzzi Delordos that flow smoothly with no steps from those alloy manifolds to the Mikunis. Early on it had the carbs popping off these rubber mounts, Brett found a fix for that.
 
Problem with your and my 3c is it is let down on the exhaust side. 6 plug racer has custom made pipes to overcome standard pipe problem. Exhaust port is also flowed. Building up the floor of the port is half the equation, doing 95% on the roof?
 
My reply to that is I remember Will needed to get some TIG welding done to my exhaust port head exit as he couldn't get the pipes to seal, I think mine was too big. I have a set of Reds big bore headers, what is the 6 plug bikes headers like compared to our 3Cs.
 
Hi all,

If you look closely you will see that the port floor has been raised up quite a lot,
Also because the valve seat has been dropped into the new chamber by about 4mm, this has the effect of raising the floor even more, thus allowing a quite nice (but not yet perfect) short side radius,  far better than original and far better than I think you could get without doing something similar. 
Lay a standard port over mine and match the valve seat positions, you will then see how high my port is compared to standard.
I have seen what others do and do pay attention, however, "I do what I do"  only my results matter to me.  I have worked very many years on a Superflow SF600 and have a fair idea of what works and what does not, and am actually on the hunt for another one.  This combustion chamber and port shape etc absolutely has worked for me in the past on several winning race engines so am relatively sure it will not be a failure,  however, as mentioned, "the bulshit stops when the flag drops" 
The standard head does flow fairly well but absolutely not as good as it can do. Believe me, that inlet port will not get me the power I am shooting for.
Exhaust, of course this will be a one off, just for my engine and as much work will go on here also,  calcs have already been made for a base design but real world dyno testing will be the final word.  This engine will be right when it hits the track.
Spring seat,  there is enough room, let me worry about that.  :D

Thanks for the interest,
PS.  44mm inlets and 38mm exhaust, however I may go down to 37mm exhausts,

Regards,
J
 
Twin plug chambers.

In my opinion, the only need for a twin plug is the situation where you have a very large wide combustion chamber with little squish and / or a high domed piston intruding into and masking the combustion chamber, all contributing to a poor burn.
Twin plugs are then used as a "Sticking plaster"
The real answer is to re-shape the combustion chamber to a point where it burns better and has less distance to travel, while burning a well mixed fuel air mixture.  The flame should ideally start closest to the hottest part of the combustion chamber and finish close to the coldest part, thus avoiding the chances of detonating the furthest part of the gasses before the burn reaches them.  My piston will have a 3mm crown with a 317mm ball radius.  so almost no crown at all.  and 12.5: CR 
Lots of work left to do.

Julian
 
Thanks for the interest,
PS.  44mm inlets and 38mm exhaust, however I may go down to 37mm exhausts,
Click to expand...

Hi Julian - i used 44mm inlet and 37mm "penny on a stick" exhaust valves on my 870cc motor.  I like the "I do what I do" after noting others philosophy. never get anywhere if we all did the same - Regards - Phil
 
yeah - I was told so many "will not work" advices before I started my project 20 years ago just to find out that 99% of them were wrong. Maybe some modifications I did were unnecessary, maybe some should have been done more radically, but 110 HP out of standard modifcations with lots of low and midrange power is exactly what I wanted. So - we'll see if you can crack the 100 HP, almost anything below was already done...  :D

 
Absolutely!  If you believe in something, give it a go, at worst we learn something.

I'm aiming for 100hp from a true 750cc,
The class we will be racing in consists of the top bikes giving about 85 or so,  mostly Tridents, Nortons and Weslake/Nourish headed twins.

Trying to get it the lightest bike out there also,  really trying hard here. Hope I'm not disappointed.

Of course though, I want to see as much power as possible with a good mid range punch so more will not be complained about ;o)
The Dyno will tell.

Jules
 
Love your thinking Julian. And no doubt you have considerable experience and expertise to fall back on. Any rad work on an SF is joy to me and I can't wait to see, hear, learn how it goes. We all love to do it (no, Chris, not 'it'!) Sinatra style  :D

Really interesting the work you've done on that port short side (not apparent from pics).

Don't think FCRs are seen anywhere near the class Julian is aiming at!!
 
phil37 said:
Hi Julian - i used 44mm inlet and 37mm "penny on a stick" exhaust valves on my 870cc motor.  I like the "I do what I do" after noting others philosophy. never get anywhere if we all did the same - Regards - Phil
Click to expand...

Depending an the Cams, the big nice Valves will touch each other, as they look verry close allready.
What is the Epoxy in the Compuson Camber for? Just a terminal attempt, or you run it like that?
And I would like to see where your Springs are sitting....
Good Luck!
 
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