BritBike Forum logo
BritBike Sponsor BritBike Sponsor BritBike Sponsor
BritBike Sponsor

BritBike Sponsor

BritBike Sponsor
BritBike Sponsor BritBike Sponsor BritBike Sponsor
JWood Auction JRC Engineering dealers JWood Auction
Home | Sponsors, Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons, "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Photo posting tutorial

Member Spotlight
dommie90
dommie90
bac o burk qld
Posts: 181
Joined: April 2014
Show All Member Profiles 
Shout Box
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Who's Online Now
200 registered members (68 royalstar tony), 1,749 guests, and 569 spiders.
Key: Admin, Global Mod, Mod
Newest Members
iansouthoz, Lightning Sim, Simon.Holyfield, Bushcreature, Gary Shackleton
10035 Registered Users
Top Posters(30 Days)
Lannis 147
kommando 106
Stuart 65
Popular Topics(Views)
477,783 mail-order LSR
Forum Statistics
Forums33
Topics65,731
Posts635,379
Members10,035
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate Thread
porting a t120 #406060
11/28/11 4:33 pm
11/28/11 4:33 pm
Joined: Jul 2010
Posts: 258
devon
K
kevin large Offline OP
BritBike Forum member
kevin large  Offline OP
BritBike Forum member
K
Joined: Jul 2010
Posts: 258
devon
hi guys while i have the head off for twin pluging i would like to gas flow the ports any tips diagrams etc for best port shapes

Support Your #1 BritBike Forum!
Membership Type! Free
Member
Premium
Member
Premium Life
Member
Vendor
Member
Site
Sponsor
Recognition No Premium Member Premium Life member (5 years) Vendor Member Site Sponsor Membership
Post commercial threads No No No Yes Yes
Custom title No Yes Yes Yes Yes
Upload avatar & photos No Yes Yes Yes Yes
Link avatar & photos Yes Yes Yes Yes Yes
Private Message Storage: 10 100 100 100 100
Length of signatures 255 600 600 600 600
Removes this very advert island between post 1&2 No Yes Yes Yes Yes
Price Free $12.90/year $105.00 No End
$55.00/5 years
$210.00/year
($17.50/month)
Email
Click on button >>
  Premium Member Premium Life member Vendor Member Site Sponsor Membership
Re: porting a t120 [Re: kevin large] #406070
11/28/11 5:33 pm
11/28/11 5:33 pm
Joined: Mar 2005
Posts: 10,023
Boston, Massachusetts
J
John Healy Online content

BritBike Forum member
John Healy  Online Content

BritBike Forum member
J
Joined: Mar 2005
Posts: 10,023
Boston, Massachusetts
For typical applications, including road racing, the ports are to big already. Get someone to do a good three angle valve job with a single point machine like a Serid or Newan and leave the ports alone.

To get an significant performance gain from a T120 head requires a lot of welding, especially on the exhaust port side.

Just my opinion!


Re: porting a t120 [Re: kevin large] #406128
11/28/11 9:48 pm
11/28/11 9:48 pm
Joined: Aug 2001
Posts: 7,026
scotland
triton thrasher Online content
BritBike Forum member
triton thrasher  Online Content
BritBike Forum member
Joined: Aug 2001
Posts: 7,026
scotland
How about spending the porting money on a 750cc conversion, to make better use of the ports you have?


Amateur Loctite enthusiast.
Re: porting a t120 [Re: kevin large] #406137
11/28/11 10:37 pm
11/28/11 10:37 pm
Joined: Mar 2005
Posts: 10,023
Boston, Massachusetts
J
John Healy Online content

BritBike Forum member
John Healy  Online Content

BritBike Forum member
J
Joined: Mar 2005
Posts: 10,023
Boston, Massachusetts
Triton Thrasher: Bingo!!


Re: porting a t120 [Re: kevin large] #406176
11/29/11 2:41 am
11/29/11 2:41 am
Joined: Jul 2007
Posts: 253
Charlotte NC
R
RHall-HCV Offline
BritBike Forum member
RHall-HCV  Offline
BritBike Forum member
R
Joined: Jul 2007
Posts: 253
Charlotte NC
It depends on which T120 head you have....some were terrible on the intake side. The exhaust could definitely use to be welded but that requires seat removal and lots of work. That time is better spent on a stepped header system that will build velocity that is lost in the large ports. Several things to do to make a Triumph better. But a 750 with the right cams in the right place and some 34mm carbs on a good head can make 70hp on pump gas.


ROB HALL
HCV MOTORSPORTS
Re: porting a t120 [Re: kevin large] #406179
11/29/11 3:27 am
11/29/11 3:27 am
Joined: Nov 2009
Posts: 593
B
bon Offline
BritBike Forum member
bon  Offline
BritBike Forum member
B
Joined: Nov 2009
Posts: 593
I was always of the impression that the early bonnevilles were faster because the inlet ports were smaller and of a more suitable size to the capacity of the engine , compared to the later machines.
When i did my head all i did was to make sure there was no noticeable step between the inlet stubs and the head casting. Stan shentons book tuning triumphs has a chapter on cylinder head work and he doesn't recommend doing much more then that.

Re: porting a t120 [Re: kevin large] #406655
12/01/11 11:57 pm
12/01/11 11:57 pm
Joined: Nov 2011
Posts: 257
terra Australis
P
Pre Unit Offline
BritBike Forum member
Pre Unit  Offline
BritBike Forum member
P
Joined: Nov 2011
Posts: 257
terra Australis
the ' Tuneing Triumphs ' by Stan Shenton , of Boyers of Bromley .
is back in print .

Yes , its more 'cleaning up ' in respect of detail .
The porting in common with very few vehicals is pretty much right
as built .

However putting 1 9/16 int and 1 7/16 ex valves from a 750
in a 8 stud Bonneville head , will get them sitting out on
the unsunken area of the seats.

'Tuliping ' back , will get more advanced flow. A std. 3 angle
is a bit primitive.
P.M. for ' other ' details .

Mortified at a head shop newly taken over , that was once the best in N.Z. , as the propritor handed over a Bonne head to a
greaseball , with the words " Yea , those Triump Heads are pretty rough standard " .
A quick glance revealed he'd buggered the head and the two ports were butchered diferantly .
Not particularly unusual .

If youve got Monoblocks , theres a chance youll get it to carburate smoothly .

Substantial gains in output can be gained with exhaust modifications, and superb acoustics .

Re: porting a t120 [Re: John Healy] #406709
12/02/11 11:27 am
12/02/11 11:27 am
Joined: Aug 2001
Posts: 7,026
scotland
triton thrasher Online content
BritBike Forum member
triton thrasher  Online Content
BritBike Forum member
Joined: Aug 2001
Posts: 7,026
scotland
Originally Posted By: John Healy
Triton Thrasher: Bingo!!


I only knew that because you wrote it here!


Amateur Loctite enthusiast.
Re: porting a t120 [Re: Pre Unit] #406711
12/02/11 11:33 am
12/02/11 11:33 am
Joined: Aug 2001
Posts: 7,026
scotland
triton thrasher Online content
BritBike Forum member
triton thrasher  Online Content
BritBike Forum member
Joined: Aug 2001
Posts: 7,026
scotland
Originally Posted By: Pre Unit


However putting 1 9/16 int and 1 7/16 ex valves from a 750
in a 8 stud Bonneville head , will get them sitting out on
the unsunken area of the seats.



You make a good point: we're jumping to the conclusion that he has a big valve 650 and maybe he hasn't.

Putting those big valves you talk about into a Pre-unit head can also give the engine some power characteristics that the rider won't like. But I suppose you can say that about any speed tuning that actually has an effect.


Amateur Loctite enthusiast.
Re: porting a t120 [Re: triton thrasher] #406955
12/04/11 1:27 am
12/04/11 1:27 am
Joined: Nov 2011
Posts: 257
terra Australis
P
Pre Unit Offline
BritBike Forum member
Pre Unit  Offline
BritBike Forum member
P
Joined: Nov 2011
Posts: 257
terra Australis
Warp Facor Six , Scotty !

Re: porting a t120 [Re: kevin large] #407640
12/07/11 7:39 pm
12/07/11 7:39 pm
Joined: Jul 2009
Posts: 3,549
Vic. Australia
P
Pete R - R.I.P. Offline
In Remembrance
Pete R - R.I.P.  Offline
In Remembrance
P
Joined: Jul 2009
Posts: 3,549
Vic. Australia
I think it's worthwhile tapering the intake guide,where it enters the port.I finish it to about 0.030"-0.040" wall thickness on the end.
Intake valve shape is good,but I still do a 35 degree back-grind to get 0.060" width on the contact face.
The O.D. of the valve seats would be 0.020"-0.030" less than the valve-head diameter,with a seat width 3/32".

If you want more flow,the only thing stopping it is valve-lift.The 1-1/8" port diameter is plenty big enough.1/2" valve-lift would not be wasted,if you want to take advantage of the port size.At 1/2" valve lift,you could justify removing a small amount of metal near the valve-guide,to keep up with the rest of the port.Other parts of the port will still be too big.Where was the flow-bench when they made these ports? Did they just not know how to use it?
You're not likely to get 1/2" valve-lift,without some serious work. 0.400" lift,or less,is more practical.The port will still be too big everywhere,and the valve is choking it.

The port is just plain too big when you get within 1/2" of the valve seat.How much you can fill it in without losing flow depends on your valve-lift.1-3/16" diameter,or equivalent area,would be about right.

Anyone have any better ideas?

Re: porting a t120 [Re: kevin large] #407658
12/07/11 9:07 pm
12/07/11 9:07 pm
Joined: Mar 2005
Posts: 10,023
Boston, Massachusetts
J
John Healy Online content

BritBike Forum member
John Healy  Online Content

BritBike Forum member
J
Joined: Mar 2005
Posts: 10,023
Boston, Massachusetts
As far as port size goes a sewer pipe can flow a lot of air, but lacks velocity.

In a comparison to our ports. A big port might flow a lot of air, but if the velocity is low the valve will close before you can get all that air moving. Tuners today are looking for air velocity of .5 MACH.

Put your engine specs into this calculator and play around with port diameters:

http://www.wallaceracing.com/machcalc.php

or if this has turned into a sickness get your wallet out and try:

http://www.maxracesoftware.com/pipemax36xp2.htm



Moderated by  John Healy 


Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.6.1.1