Friday, April 18, 2014

What difference do Triumph green camshafts make?

This post starts off with a simple oil leak and ends up with a cam swap from Triumph green profile to blue profile. It means I now have first-hand knowledge of the performance difference between the two, all else being exactly the same.

Shimming the valves

7000 miles later
The oil leak from the cylinder head cover meant I had to remove and reseal it. I was surprised how dirty the cover had become, after having been so careful in my restoration and with the radiator cowls fitted. But that's because it seems like yesterday when I got Ruby back on the road when in reality a year and about 7000 miles have gone by since then.

Central bolts are awkward
I discovered that the cam retaining bolts were barely more than finger tight. I had torqued most of them down on reassembly. I guess the rubber washers under the bolts and large rubber gasket had settled. That was why I had a leak anyway. I was also reminded of how close the central retaining bolts are to the main frame tube. They are impossible to torque down because even my smallest torque wrench won't fit in the gap.

Oil had collected around the plugs
The leak was not just external. I found puddles of oil around the spark plugs where it had run down into the central wells in the cylinder head. These are all blind to the outside world so there is nowhere for any muck or fluids to go if they end up down there.


As I was dealing with the oil leak from my cylinder head cover, I decided to check my valve clearances. I do not have a special tool for swapping shims with the camshafts in situ, though such tools are available for about 60 pounds. I am happy enough to remove and refit my camshafts when the clearances need to be adjusted.

Two of my exhaust valves were out of specification, needing a change from 2.60 to 2.55. With the cams out, changing the shims is easy - lots of room to move and that in itself justifies the effort for me.

Camchain tensioner springs

It is necessary to remove the cam chain tensioner mechanism to get the cams out. I'd also wanted to replace the tensioner spring. Trevor at Sprint has started supplying replacements. The originals weaken over time and so can't make the internal tensioner ratchet take up the slack in the cam chain as Triumph intended. The picture below shows the difference between Trevor's replacment spring and the old spring I took out. It is photographed over the official factory manual with the minimum spring length.
Comparing old (top) and replacement (bottom) cam chain tensioner springs

Swapping T300 Camshafts

Whilst I was at it (famous last words for me) I decided to swap the original 'green' specification camshafts for the later 'blue' specification camshafts. This was just because I could ... the later motor I had bought had these camshafts in good condition and I wanted to try them out.

Blue cam (left) and green cam (right) side-by-side
The blue cams are far far milder - less lift (shorter lobes) and less duration (pointier lobes) as can clearly be seen in the two side-by-side pictures.
Cam Profile Blue Green Red
Inlet open 1 BTDC 21 BTDC 27 BTDC
Inlet close 30 ABDC 50 ABDC 55 ABDC
Inlet duration 211 degrees 251 degrees 262 degrees
Inlet lift 7.1 mm 8.9 mm 9.4 mm
Exhaust open 28 BBDC 51 BBDC 54 BBDC
Exhaust close 2 ATDC 25 ATDC 28 ATDC
Exhaust duration 210 degrees 256 degrees 262 degrees
Exhaust lift 7.0 mm 8.6 mm 9.3 mm
The table above shows cam timing in degrees relative to the extremities of the piston stroke: before top dead centre (BTDC), after top dead centre (ATDC), before bottom dead centre (BBDC) and after bottom dead centre (ABDC). The blue cams have relatively little overlap in period (58 degrees compared to 101 degrees for the green profile) meaning that the exhaust valves close early enough to maximise effect of the charge. The green cams overlap considerably.
Green cam (left) out and blue cam (right) in place

Manual says seal the ends
Plenty of Hylomar around the plug recesses
Finally, I was very careful to seal the cam cover with Hylomar, following the factory instructions. I was confident that this would work because the rubber gaskets have now thoroughly settled and I was more generous with the Hylomar (but still VERY careful) than last time.




So, what difference do blue camshafts make?


I have ridden about 500 miles since installing the blue cams. What difference do they make? A lot. Performance (better below 60mph, worse above) and fuel economy (between 5 and 10% better) have changed.

The engine now pulls solidly from 2000rpm. It is both stronger and linear, whereas previously it would pull but with some hesitation, especially around 2500rpm. The low-rev thrust is a transformation. That is a brilliant improvement. However, the cost as I suspected is that the old kicks at 4000rpm and at 6000rpm have gone. I am not surprised by this after having read contemporary road tests of the original and re-tuned Trophy 1200s.

I can live without the 4000rpm step because it was probably just a sign that cylinder fuelling wasn't working super well below that engine speed. However, the way the engine came on cam at 6000rpm was exhilarating and I miss it. Realistically, I might experience that once or twice on an average ride because the roads around here are not suited to high-rpm riding. But experience cannot be distilled into numbers like 'twice per ride'. I shall be reinstalling the green cams in the next few weeks when I swap the engine covers over for powder coating.

On the other hand, the blue cams make for a much more relaxing and secure riding experience so I have decided to use them in late Autumn and Winter when I think they would suit riding conditions perfectly.

Consequence: I now have two engine tunes available, one for summer and one for winter. Very nice.

7 comments:

Triumph T3 said...

Hi. I'm checking shims on my 900 Tiger,and noticed 'green' cams? Wondering if STD should be blue? Not complaining,bike runs nice. markroderick@tiscali.co.uk

Triumph T3 said...

Hi. I'm checking shims on my 900 Tiger,and noticed 'green' cams? Wondering if STD should be blue? Not complaining,bike runs nice. markroderick@tiscali.co.uk

LeT said...

Hi mark. Yes I think standard is 'blue'. I just checked my manual and it shows the same timings as the Thunderbird 900. Can you see green paint on your cams? The paint on mine has faded/gone, maybe over time and with the oil I have used. Keep on riding!

Anonymous said...

Hi, just of interest on the T300 engines (900/1200) where were the red cams used?. I dont know if the super3 900 had red cams as std? watching youtube videos the cams do not sound lumpy at idle. Maybe red cams were an aftermkt triumph race track item and not put in road machines, just a guess. Be interested to hear if you know, or another reader can leave a comment, thanks.

LeT said...

Hi Anon, red were factory fitment, not race only, and used for the 115ps Super III and the 147ps Daytona 1200. Some markets had a 100ps limit for bikes at the time so didn't use these cams.

I can't remember writing the red cams make for lumpy running. Since I wrote this post, I found a set and tried them in my Trophy 1200. The seat-of-the-pants impression was that they didn't feel so very different to the green in practice. Certainly peppy, made the engine want to rev. However, they used about 5-10% more fuel for the same kind of riding. I switched back to the green ones and am very happy with this.

Strangely, as I get older, I get more appreciative of the decisions the factory made in the first place. I've also geared the bike back nearer original spec now too.

Anonymous said...

Thankyou LeT for sharing your knowledge and personal feedback, interesting to know. Notes will go into my little book. I can appreciate your gearing comment as riders age, being a mature rider myself. Safe riding.

LeT said...

No worries and thanks. I was mulling it over yesterday as I was out on my Daytona 900. I'm trying blue cams (as fitted to Thunderbird and Tiger 900s) in that engine. It reminded me that the blue cams make the top end noisier. The blue profile is like a triangle rather than an egg in profile, so very little in the way of a ramp for opening the valves. For all that they are open for less time and do not open so far, it's like they smack down on the shims. The sound is quite noticeable with blue cams in the 1200 - like a tinkling rattle at idle. It was disconcerting at first. The green and red make for a much quieter idle. On the go, I couldn't hear it though so for most it would be irrelevant.

I haven't written much here for a while because the Triumphrat.net forum is so good. But it's great to know these posts are interesting and sometimes helpful to folks in the big wide world. Makes me feel like doing another :-)


Take care