Cam Timing Notes

**Disclaimer: This information has been compiled by a resource independent of The Bonneville Shop. Please conduct your own research and verify that the information is correct before utilizing any of the information in this post.**

Also, check out our other tech blogs:

• Cam Timing Notes – Part II – The Bonneville Shop
• The Brain of Your Triumph B Range Engine- the Camshaft – The Bonneville Shop

Note that cam lift numbers are sometimes specified at the valve, and sometimes at the lifter (follower/tappet), which will be the same as the lobe height. Triumph rockers generally (as far as I know) have around a 1:1.1 ratio. This means that the valve lift does not equal the lobe height – lift at the valve will be higher than the lift at the lifter.

Cam timing is sometimes quoted at 0.020″ of valve clearance, sometimes with 0.040″ of valve clearance, and sometimes at 0.050″. 0.020 is the older way, but 0.040 is used because that’s almost exactly 1mm, and modern (IE metric) cam timings are specified with 1mm of clearance.

Triumph part number conversion:

Factory cam timing numbers

These numbers are from various shop manuals (Triumph, Haynes, Clymer, etc), which most likely originally come from the Triumph manuals. I think the lift numbers quoted are measured at the tappet (IE the cam lobe height), but it’s not explicitly stated.

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Notes on the legendary Triumph E3134 “Q” cam

• The E3134 cam wasn’t (always) a specific cam, it was a cam profile that was used on many cams for many years. There may have been a cam with the part number E3134, but there were many other cams that used the E3134 profile.
• To make things more confusing, there were two E3134 cams – Tricor and Factory. The Tricor profile (34/55 55/34) is the most common.
• The E3134 may have been the hot thing many years ago, but it’s no longer considered a high performance profile.

This is the E3134 profile:

Group 1 – High Performance – E3134 “Q” Cam Form

• Intake opens: 34 BTDC – Intake closes: 55 ABDC
• Exhaust opens: 55 BBDC – Exhaust closes: 34 ATDC

Group 2 – High speed touring – E3325 Cam Form

• IO 27 BTDC – IC 48 ABDC – EO 48 – BBDC – EC 27 ATDC Inlet or Exhaust

Group 3 – Ramp cam form (standard) – Quieting ramps

• Intake opens: 26.5 BTDC – Intake closes: 69.5 ABDC
• Exhaust opens: 61.5 BBDC – Exhaust closes: 35.5 ATDC

Group 4 – Modified ramp form (racing)

• Thruxton Bonneville

Key to Codes:

• X = Breather
• Y = Contact breaker
• CP = Copper plated
• SG = Spiral gear (distributor drive)
• n = nitrited

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“Specs for Stock Triumph 750 Short Rod”

• Intake: 26.5* – 69.5* 111.5* lobe center
• Exhaust: 61.5* – 35.5* 103.0* lobe center
• measured @ .020″ tappet lift
• running clearance .010″ intake and exhaust
• valve lift: .350″ 278* duration

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Random cam numbers I’ve run across:

• M20416 – 71-288? casting – 750 intake
• M20360 – 750 exhaust
• E5048 – T120 exhuast – E3134 profile – use R followers
• E3059R – “R” follower
• E1485 in/ex 1938/9 5T
• E3275 in/ex 1953-8 5T
• E3325 in/ex 1955-8 TR5
• E4819 – Bonneville E3134 profile intake
• E4855 – Bonneville E3134 profile exhaust.
• 70-7016 – T140 intake
• 70-7017 – T140 exhaust cam
• 70-9990 – T120 exhaust, mate to 71-1063?
• 70-9986 – 1970 T100C exhaust cam
• 70-9989 – 67-72 T120 exhuast cam
• 70-9989 – 650 Exhuast cam
• 70-9989 – T120 exhaust cam late unit
• 70-9989 – Exhuast cam, half race
• 71-0040 – Cam, intake
• 71-0041 – Cam, exhaust
• 71-0043 – Forging blank for 71-1064, 70-9986
• 71-0046 – Cam, T100, exhuast
• 71-0046 – T100C exhaust cam
• 71-0049 – T100 ex cam 68 on
• 71-1063 – T120 intake – Nitrided E3134 profile – use R followers
• 71-1063 – Cam, ’70 and later
• 71-1063 – 70-72 T120 intake cam
• 71-1064 – 1970 T100C intake cam
• 71-3011 – T140 intake – up to 1975.
• 71-3012 – T140 exhaust – up to 1975.
• 71-7016 – T140 intake cam
• 71-7017R – T140 spitfire exhaust cam
• 71-7182 – T140 exhaust cam
• 70-3059 – ‘S’ cam follower
• 70-3059R – ‘R’ cam follower
• 70-8801 – cam follower
• 71-7008 – cam follower
• 70-8801 – 650/750 exhaust follower oil feed
• 71-2297 – B50 cam

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Cam forging blank numbers

These are not cam numbers, they are the part number for a blank that a cam profile is ground onto. A single blank will often be used for a number of different cam grinds, so this number doesn’t actually tell you what cam you have. The forging number should have raised numbers, the cam grind number should be stamped in. Either number is sometimes omitted.

• 71-0040 – Forging blank for 71-1063
• 71-0042 – Forging blank for 71-9990
• 71-2887 – Forging blank for 71-3011
• 71-0042 – Forging blank for 71-3012
• 71-3012 – Forging blank for 71-3012 (really)

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Someone recommends “put a T140 inlet in the exhaust using a modified rev counter nut/drive to spin a one off Boyer rotor. FWIW, I clocked up
the cam and it’s almost identical to Nourish’s Z cam, so I used his timings of 102 degrees.”

TRICOR “Q” intake cam is also named E3134-E4819:

• intake 34-55 deg,
• exhaust 55-34 deg
• cam lift .314″
• duration 269
• lobe center 100.5 deg

vs

FACTORY “Q” E3134-E4819:

• intake 34-58 deg,
• exhaust 58-34 deg
• cam lift .310″
• duration 269
• lobe center 102.5 deg

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Megacycle cam grinds

Triumph 650/750 twins:

Triumph 500 twins:

All cams listed below will work with “R” or “STD” tappets

Triumph and BSA triples:

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Johnson Cam Grinds

T100R Daytona

T120 “E3134”

Triumph 750 short rod

Q cam

• Factory speed kit grind for 500’s of the 50’s, also used in the 650 TT
• Specials of the 60’s.

Jomo TT Cam

A little more duration than the Q cam, gives a little more top end power.

Harmon&Collins 7054 Cam

A little more lift than the Q cam. For more mid-range torque.

Connely #1 Cam

Lots of torque off tight corners. Tight TT, short Motocross, not good at high rpm.

Johnson J360/264 Cam

Johnson designed for 750 Triple Road racing, and by coincidence is a modern version of the TH6.

Triumph T-3 Cam

Stock 750 triple cam. Has always been hard to beat and works well in 500 twins also.

Triumph T-65 Cam

Between a Q and a Jomo 15. Good for hot street, short track, and TT in 650 and 750 twins.

Triumph T-75 Cam

Stock 750 twin intake. Use in exhaust also, for hot street motors and racing, where endurance means more than the last HP. Good to 7000rpm with stock springs. Similar to Nourish Z.

Jomo 15 Cam

This cam has long been considered the classic “all around” racing cam for the Triumph 650 and 750 twins.

Sifton 390 Cam

This grind is an improved version of the Jomo 15. With less seat to seat timing the motor makes more torque, and runs “crisper” down low.

Triumph TH6 Cam

Developed by Doug Hele for the factory 500 twin road racers of the late 60’s, also used in the 750 triples of the 70’s.

Sifton 460 Cam

For 1/2 mile and mile flat track and real racers. NOT FOR THE FAINT OF HEART! Must trim flywheel and tappet blocks.

Johnson J 46

Johnson Design for a smoother, modern version of the Sifton 460mcam.
This grind was developed to be easier on springs, tappets, etc.
Must trim flywheel and tappet blocks.

Johnson J481 Cam

Johnson design drag race cam. It is not recommended for anything other than drag racing. Must trim flywheel and tappet blocks.