Triumphrat

GulfCoastDave · 02-22-2007

There is an article in the new Walneck's Classic Cycle about Britech and it's owner Jaye Strait. In the article, there is mention of "crankcase breather modification alone adds 5 hp at the rear wheels".
I am guessing that a piston traveling up & down must alternately need to suck & displace air and that air must offer some degree of resistance.
But is 5 hp really laying around there??
Anybody know about this?
Best Regards,
Dave

rambo · 02-22-2007

5 hp ?...at the wheel ?in your wildest dreams.way back in the sixties,some owners ran a large pipe out through the tappet covers.later bonnies breath out of the primary.again,some owners used a 1 inch breather pipe from the primary.
if you relly want a bonnie to go faster,stop eating food for a few weeks,get your weight down to 120 pounds.goes fast then and pulls wheelies.to get the best out of a t140,you need to fit late t120 cams.the t140 was strangled by pollution laws in the states :-D

okiecityflash · 02-22-2007

Hi Rambo and Gulf coast. Just yesterday I was reading a Classic Magazine, 1985, I had laying around. There was an article "The affordable classic, the t140". It mentioned the fact that the bearings they had for the first t140's wouldn't take the torque with the t120 cams installed, so they went with milder cams or something to that effect. This was the first I had heard about that. My next thought was if the '79 bearings had improved to the point that would allow use of the t120 cams? Any info from anyone would be appreciated as always. Okie PS I saw this. 7lbs.= 1 horsepower. A figure used by racers.

rambo · 02-23-2007

hi okie,my t120 has 750 big bore kit with gearing the same as a t140.with the t120 cams,it develops power much lower down.the original prototype t140s were fitted with the t120 cams and it developed too much power for the main bearings.mine at present,is working great.i have 8.5to 1 pistons in stead of the 9to 1s..t 140s were fitted with the triple primary at this time to last a little longer.mine runs a 2 row and again works fine.
a big bore t120 develops quite a bit more power than a t140.the standard clutch just about handles it.
often,t140s will only do 50 mpg and a t120 will do 70 mpg.the cams in the t140 restricted the power and made it less efficient.cams to use are the nitrided ones of 1969 on.

okiecityflash · 02-23-2007

Thanks Rambo, I'll keep that in mind if I have to do some engine work. I haven't had to pull the head since it was new, but I'd like to put some new guides and scrapers some day. I did that on my '78 FLH and got about 3k to a quart of oil. Chain oiler off of coarse. Thanks again

Mecchanica · 02-23-2007

If you have a T 140 and want plenty of HP, only change the exhaust cam to the 69-72 nitrided exhaust cam. The stock 750 intake is the Thruxton grind, with .334" lift and longer duration compared to the T120 .314" lift and 270 degree duration. This cam gives GREAT midrange and must be used with STD (.750") radius tappets. The T120 exhaust cam frees up the higher rpm hp and torque, compared to the T140 exhaust cam.
For more hp at the upper end, you can buy an exhaust cam that matches the T140 inlet. Norman Hyde is one source.
The problem with main bearings is the metric (6306) right side bearing....no problem with the MRJA 1 1/8 on the drive side. Heavier duty replacements with more balls (literally... eleven instead of eight) are available as are two different roller bearings. The "superblend" bearing from the Norton Commando is a good replacement for the stock 6306, but requires shimming the drive side of the crankshaft to get the end float to .010" cold. Check the centering of the rods in the cylinders if you use the superblend.

The mileage difference between the two was more due to the exhausts used. Fit some of those sexy 70 Bonneville mufflers onto the T140, rejet, and see how much nicer it is to ride.

[ This message was edited by: Mecchanica on 2007-02-23 14:09 ]

rambo · 02-23-2007

yea,what mecchanica says. :hammer: :hammer:

GulfCoastDave · 02-24-2007

Uhhh... looks like my thread went off to cam land.

My question was not about a plea for more HP. I know there are cams, valve mods, etc etc.
Again...
"There is an article in the new Walneck's Classic Cycle about Britech and it's owner Jaye Strait. In the article, there is mention of "crankcase breather modification alone adds 5 hp at the rear wheels".
I am guessing that a piston traveling up & down must alternately need to suck & displace air and that air must offer some degree of resistance.
But is 5 hp really laying around there??
Anybody know about this?

The question is about crankcase breathing... and is there anyone who knows anything about HP gains made from CRANKCASE BREATHING SYSTEMS?
Best regards,
Dave

johnnypence · 02-24-2007

nobody listens, dave. i'm sorry for my fellow human beings' behavior. :razz:

Blaine · 02-24-2007

With two pistons timed 360, the crankcase volume change from TDC to BDC is equal to the engine displacement. This is not the case in a 180 degree engine where one piston goes up while the other goes down. The volume of the Triumph twin crankcases is small relative to the displacement. Therefore, crankcase pressure changes significantly. This is one of the reasons these motors leak oil at the tappet covers and anywhere else possible. Use a one way check valve to let crankcase pressure out but restrict atmospheric pressure in. Fewer Leaks and more power, but I don't know how much. It would depend on rpm and engine condition. Hope this helps.