I am knew to triumph and I am building a 66 t120. Just mic-ed the cylinders found big bore and at least 40 over already. Jrc warned of too thin to punch the bore out to 060 plus we would have to special order the pistons. Thinking of just buying another big bore kit but I was trying to keep the budget and I need some cams as well. What is the best factory cams and the best aftermarket options (w/out crazy mods) Also do I have to change followers/ tappets with knew cams? any help would be great.
snodt120
Hey guys I have read a few of these threads and still havent come up with a deffinet answer. I am going saturday to buy some parts for my triumph and the guy says he has a box full of cams... Well what am I looking for here for my 650? I see mention of 750 in ex out, but I am not even sure what this means or how to identify these. Are these the nitrided cams? Thanks let me know.
I've never liked the idea of used cams. I don't have the technology to check and make sure they aren't trashed, so I'll stick to replacing mine with new cams. If I had to run used cams in a 650, I might opt for a pair 3134 cams or any 70's cams with a big lobe -they look way different than the earlier cams.
From what I understan, a cheap way to get good midrange power is to leave the stock 650 exhaust cam in place and replace the intake cam with aT140 Cam...of course later///hardned etc. Has anyone done that here???
Jay Straight of Brittech told me that the 750in/650ex combo is as good or better than any expensive set of cams for the street. He builds some powerful race motors so I am inclined to believe him. My current build will utilize this combo. I will have to let you know what I think this spring!
No need to go from .040" to .060" or to buy another cylinder. Just have the cylinder bored until it cleans then have Venolia or another piston maker make you a set of pistons to fit the bore.
You can also run the stock cams with "R" followers to pick up some added duration and power the cheap way.
If you go to non-Triumph cams be sure to put the cams and crank in the left side case and check that there's enough clearance between the cam lobes and the crank flywheel.
My advice (worth every penny you paid) is to do only mild tuning and keep the motor at least close to stock. Generally, the more highly tuned a Triumph is, the less it gets ridden. Personally, I like stock or lower than stock compression.
Too, if you're building a bobber, taking 20 or 30 pounds off the bike is the same as adding 3 or 4 hp, so it's going to run plenty strong with a stock motor.
You can also run the stock cams with "R" followers to pick up some added duration and power the cheap way.
If you go to non-Triumph cams be sure to put the cams and crank in the left side case and check that there's enough clearance between the cam lobes and the crank flywheel.
My advice (worth every penny you paid) is to do only mild tuning and keep the motor at least close to stock. Generally, the more highly tuned a Triumph is, the less it gets ridden. Personally, I like stock or lower than stock compression.
Too, if you're building a bobber, taking 20 or 30 pounds off the bike is the same as adding 3 or 4 hp, so it's going to run plenty strong with a stock motor.
I will rebuilt a 1970 Bonneville T120R motor with a Morgo 750cc big bore kit. What cams would you recommend? I thought the Jomo 15 or the improved Sifton 390 would be a good choice? What do you guys think?
The bike will be used only on the street (no race bike) but should have some "power & performance reserve" if you know what I mean.
The bike will be used only on the street (no race bike) but should have some "power & performance reserve" if you know what I mean.
This opened my eyes when I was researching about cams.
It is not possible to add low end power - commonly referred to as torque - and top end power, commonly referred to as HP at the same time to a naturally aspirated engine by installing a different profile camshaft. The whole concept of torque/HP is a marketing concept. Power is power. You get top end power with RPM; you get low end power with displacement.
THe only way to get both at the same time on a conventional engine (no adjustable valve/cam timing, no adjustable intake volume) is to increase displacement and/or compression and make whatever changes required to keep the engine able to spin the same (or more) RPM. When Norton increased the 750 to 828, they boosted the low end because displacement increased but they could not increase the top end since the engine couldn't safely spin to 7000 anymore. They didn't want to (or couldn't) make the necessary component changes to allow this.
Although exhaust and intake tuning also affect the power curve, all the cam change can do is shift the power band within the bikes RPM range. It CAN inrease max power over stock AND it can increase the power anywhere in the range that you want, based on the profile. BUT it CAN"T add top and mid and bottom at the same time. If you add power to the top end, you will loose power at the bottom. Obviously, changing the cam may - depending on what you are trying to do - typically requires many other changes to produce the results you want without creating a hand grenade.
So it's best to determine what you want the engine to do and then determine what is necessary to accomplish that. It may turn out to be impossible. Also consider rideability - hot cams NEVER make vehicles easier to operate.
http://www.johnsoncams.com/jc_t_cams.html
Your choice but with a race cam you'll lose the ability to snap open the throttle in top gear at 80km/h to pass a car, meaning your once torquey brit bike will be like a jap bike to ride, no torque until it comes 'on cam', but they've got more than 4 gears to be changing, that's what the bloke above means by easy to operate.
T75 ( 2 x 750 inlet profiles) can be easily timed using 750 timing pinions, a few blokes I know dig the T75's but there's heaps out there who swear by what they've got as well, the sifton 390 sounds alright.
You'll have to change the crankcase breather too, here's a pic of mine, a BMW reed valve in a home made housing, first it filters through 2 SS pot scrubbers in the cavity.
It is not possible to add low end power - commonly referred to as torque - and top end power, commonly referred to as HP at the same time to a naturally aspirated engine by installing a different profile camshaft. The whole concept of torque/HP is a marketing concept. Power is power. You get top end power with RPM; you get low end power with displacement.
THe only way to get both at the same time on a conventional engine (no adjustable valve/cam timing, no adjustable intake volume) is to increase displacement and/or compression and make whatever changes required to keep the engine able to spin the same (or more) RPM. When Norton increased the 750 to 828, they boosted the low end because displacement increased but they could not increase the top end since the engine couldn't safely spin to 7000 anymore. They didn't want to (or couldn't) make the necessary component changes to allow this.
Although exhaust and intake tuning also affect the power curve, all the cam change can do is shift the power band within the bikes RPM range. It CAN inrease max power over stock AND it can increase the power anywhere in the range that you want, based on the profile. BUT it CAN"T add top and mid and bottom at the same time. If you add power to the top end, you will loose power at the bottom. Obviously, changing the cam may - depending on what you are trying to do - typically requires many other changes to produce the results you want without creating a hand grenade.
So it's best to determine what you want the engine to do and then determine what is necessary to accomplish that. It may turn out to be impossible. Also consider rideability - hot cams NEVER make vehicles easier to operate.
http://www.johnsoncams.com/jc_t_cams.html
Your choice but with a race cam you'll lose the ability to snap open the throttle in top gear at 80km/h to pass a car, meaning your once torquey brit bike will be like a jap bike to ride, no torque until it comes 'on cam', but they've got more than 4 gears to be changing, that's what the bloke above means by easy to operate.
T75 ( 2 x 750 inlet profiles) can be easily timed using 750 timing pinions, a few blokes I know dig the T75's but there's heaps out there who swear by what they've got as well, the sifton 390 sounds alright.
You'll have to change the crankcase breather too, here's a pic of mine, a BMW reed valve in a home made housing, first it filters through 2 SS pot scrubbers in the cavity.
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