guzziriders.org - moto guzzi forum Homepage
Forum Home Forum Home > Technical > Big Block Tonti
  New Posts New Posts RSS Feed - 850/1000 cylinder head valve oversizing?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

850/1000 cylinder head valve oversizing?

 Post Reply Post Reply
Author
Message
Zambuck View Drop Down
Falcone
Falcone


Joined: 17 Feb 2018
Location: Kent
Status: Offline
Points: 71
Post Options Post Options   Thanks (0) Thanks(0)   Quote Zambuck Quote  Post ReplyReply Direct Link To This Post Topic: 850/1000 cylinder head valve oversizing?
    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?
1000 Le Mans II Agostini
Back to Top
Brian UK View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 13 May 2014
Location: Surrey
Status: Offline
Points: 17641
Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 10:40
I'm fairly sure the casting is the same. But the similarity might end there.
Brian.

Better 5 minutes late in this world than years early in the next.
Back to Top
Jools View Drop Down
Senior Member
Senior Member
Avatar

Joined: 19 Aug 2016
Location: Milton Keynes
Status: Offline
Points: 273
Post Options Post Options   Thanks (0) Thanks(0)   Quote Jools Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 12:19
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! 
Jools

V1000G5
1972 T150V
1961 Royal Enfield Constellation
1971 Suzuki ACC50
erm... 1963 Philips Panda
(and other assorted detritus)
Back to Top
Zambuck View Drop Down
Falcone
Falcone


Joined: 17 Feb 2018
Location: Kent
Status: Offline
Points: 71
Post Options Post Options   Thanks (0) Thanks(0)   Quote Zambuck Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 18:14
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?
1000 Le Mans II Agostini
Back to Top
Mike H View Drop Down
Senior Member
Senior Member
Avatar

Joined: 21 May 2014
Location: East Anglia
Status: Offline
Points: 8733
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 18:33
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.



"Chicken nuggets don't dance on a Tuesday."
Back to Top
Brian UK View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 13 May 2014
Location: Surrey
Status: Offline
Points: 17641
Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 18:35
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.

Brian.

Better 5 minutes late in this world than years early in the next.
Back to Top
Mike H View Drop Down
Senior Member
Senior Member
Avatar

Joined: 21 May 2014
Location: East Anglia
Status: Offline
Points: 8733
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 18:39
And changing the shape of the combustion chamber? With no data to go by?



"Chicken nuggets don't dance on a Tuesday."
Back to Top
Zambuck View Drop Down
Falcone
Falcone


Joined: 17 Feb 2018
Location: Kent
Status: Offline
Points: 71
Post Options Post Options   Thanks (0) Thanks(0)   Quote Zambuck Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 20:49
Originally posted by Mike H Mike H wrote:

And changing the shape of the combustion chamber? With no data to go by?





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.
1000 Le Mans II Agostini
Back to Top
Zambuck View Drop Down
Falcone
Falcone


Joined: 17 Feb 2018
Location: Kent
Status: Offline
Points: 71
Post Options Post Options   Thanks (0) Thanks(0)   Quote Zambuck Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 21:01
1000 Le Mans II Agostini
Back to Top
BondEquipe View Drop Down
Senior Member
Senior Member
Avatar

Joined: 10 Dec 2014
Location: Summerzet
Status: Offline
Points: 1898
Post Options Post Options   Thanks (0) Thanks(0)   Quote BondEquipe Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2018 at 22:33
Originally posted by Zambuck Zambuck wrote:

Food for thought:


That was brilliant.  Did remind me of a Fosters advert with the 2 of them talking though!
Stephen
Black & Gold LM2
+ Other Bikes & Projects!
Back to Top
TonyF View Drop Down
Falcone
Falcone
Avatar

Joined: 29 Apr 2016
Location: New Zealand
Status: Offline
Points: 17
Post Options Post Options   Thanks (0) Thanks(0)   Quote TonyF Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2018 at 23:50
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.

Tony
Back to Top
BondEquipe View Drop Down
Senior Member
Senior Member
Avatar

Joined: 10 Dec 2014
Location: Summerzet
Status: Offline
Points: 1898
Post Options Post Options   Thanks (0) Thanks(0)   Quote BondEquipe Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jun 2018 at 10:49
Originally posted by TonyF TonyF wrote:

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.


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?
Stephen
Black & Gold LM2
+ Other Bikes & Projects!
Back to Top
Mike H View Drop Down
Senior Member
Senior Member
Avatar

Joined: 21 May 2014
Location: East Anglia
Status: Offline
Points: 8733
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 04 Jun 2018 at 09:32
Also I bet the dome is hollow underneath so risk cutting through and holing it. Expensive experiment!


"Chicken nuggets don't dance on a Tuesday."
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.094 seconds.