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:

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.

	intake		exhaust
	open	closes	opens	closes	lift		measured clearance	tappet radius
	btdc	abdc	bbdc	atdc	intake	exhaust
650cc	34	55	55	34			0.002
6T DU.101 on	25	52	60	17	0.305	0.305	0.020
TR6 DU.101 to DU.44393	34	55	48	27	0.314	0.296	0.020
T120 DU.101 to DU.24874	34	55	48	27	0.314	0.296	0.020	0.750 (STD)
T120 DU.24875 to DU.44393	34	55	55	34	0.314	0.314	0.020
T100S	34	55	48	27		0.296	0.020	0.750 (STD)
T100T	40	52	61	31	0.314	0.314	0.020	1.125 (R)
5TA to H.49833	34	44	48	27			0.020
TR5T	34	55	48	27			0.020	0.750 (STD)
T100R	40	52	61	31			0.020	1.125 (R)
TRIUMPH 750 SHORT ROD	26.5	69.5	61.5	35.5	0.350	0.350	0.020	1.125 ? What Cam ?
TRIUMPH 750 INTAKE (T-75)	40	74			0.345		0.020	1.125 Matches M20416 T140E intake
JOMO 15	43	74	74	43	0.355	0.355	0.020	1.125 (R)

Note: Megacycle says “When ‘R’ followers are specified, you can also use STD, which will produce more low RPM power”.

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:

	intake		exhaust
	open	closes	opens	closes	lift		measured clearance	tappet radius
	btdc	abdc	bbdc	atdc	intake	exhaust
Tricor “Q” E3134	34	55	55	34	0.314	0.314	0.020	1.125 (R)
Factory “Q” E3134	34	58	58	34	0.310	0.310	0.020	1.124 (R)

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

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

Part#	Code	Casting #	Intake/Exhaust
E3134		E3134
E4819	X	E3134	Inlet
E5047	YCP	E5048	Exhaust
E5162	XCP	E4602	Inlet
E10040	XN	E10040	Inlet
E10041	YN	E10041	Exhaust
E4038	SG	E3838	Inlet
E4039		E3838	Exhaust
E4678		E4679	Inlet
E5044	YCP	E5045	Exhaust
E5047	Y*		Exhaust
E5163	CP	E4679	Inlet
E6965	Y	E6642	Exhaust
E10043	N	E10043	Inlet
E10047		E10050	Exhaust
E11063	N	71-0040	Inlet
E11064	N	71-0043	Inlet
E9983	YN	71-9986	Exhaust
E9984	YN	70-9987	Exhaust
E9989	YN	70-9990	Exhaust

Note:
1. Running clearance .002 in. intake and .004″ exhaust.
2. Take readings at .020 in. follower lift with “std” radius (3/4 in.) followers
3. Lobe Center 100.5 °
4. Duration 269 °
5. Lift .314 in.

Group 2 – High speed touring – E3325 Cam Form

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

Part #	Code	Casting #	Intake/Exhaust
E3325		E3325
E4818	X	E4997	Inlet
E4848	Y	E4560	Exhaust
E4855	Y	E4561	Exhaust
E4931			Inlet
E4022	SG	E3838	Inlet
E4023		E4679	Exhaust
E4786	Y	E4679	Exhaust
E10046	YN	E10049	Exhaust

Note:
1. Running clearance .002 in. intake and .004″ exhaust.
2. Take readings at .020″ follower lift with “std” radius (3/4 in.) followers
3. Lobe center 100.5Â°
4. duration 255Â°
5. Lift .296 in.

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

Part #	Code	Casting #	Intake/Exhaust
E3275		E3265
E3838	SG	E3838	Inlet
E3839		E3838	Exhaust
E5341	Y	E5342	Exhaust

Note:
1. Running clearance .010 in Intake and Exhaust.
2. Take readings at .020″ follower lift using “standard” followers.

Group 4 – Modified ramp form (racing)

Thruxton Bonneville

Part #	Code	Casting #	Timing
E4220		E4220	Valve lift at TDC with nil clearance 0.195/0.175″ Intake
E6267		E4220	Valve lift at TDC with nil clearance 0.205/0.215″ Intake
E6147	Y	E6146	Valve lift at TDC with nil clearance 0.165/0.175″ Exhaust

Note:
1. Running clearance E4220 .008 in. E6267 & E6147 .013 in.
2. Valve timing taken in inches of VALVE lift at T.D.C. with valves set at nil clearance for checking.
3. E6267 and E6147 must be used with 3″ radius cam followers and special guide blocks.

Key to Codes:

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

“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

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

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)

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

FACTORY “Q” E3134-E4819:

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

Megacycle cam grinds

Triumph 650/750 twins:

Cam Number	Lobe Height	Duration at .020″	Lobe Centers	Tappet Style	Description and Application	Intake: open/close Exhaust: open/close	Running Clearance
510-05	.348″ .348″	282 282	100 102	“R”	Best for low-end and some mid-range increase. Street / road performance 2500 R.P.M. to 7000 R.P.M. Should clear pistons. Check clearance. Uses stock springs.	41 btc/61 abc 63 bbc/39 atc	.010″ .010″
510-15	.355″ .355″	297 297	105.5 105.5	“R”	The legendary Kenny Harman #15 grind. (Also known as JOMO 15). TT, flat track, all around use. Must use modified springs.	43 btc/74 abc 74 bbc/43 atc	.007″ .009″
510-xl	.401″ .401″	308 308	102 106	“STD” only	Reproduction of Sifton 460. Racing use. Mid-range to top-end power.	52 btc/76 abc 80 bbc/48 atc	.008″ .010″
510-65	.355″ .355″ TDC lift	292 295	101 104.5 .163″ in .150″ ex	“R”	For 650 or 750. Best all around street and road cam. Broad power band, mid-range and top-end. TT style performance. Use modified springs. (Recommended by Motorcyclist Magazine)	45 btc/67 abc 72 bbc/43 atc	.010″ .010″
510-75	.400″ .400″ TDC lift	326 326	102 105 102LC=.159″ 105LC=.146″	“STD” only	Racing use only. Must remove material from tappet guide blocks to install this cam. High R.P.M. power. Must use racing springs and pistons. Check clearance.	61 btc/85 abc 88 bbc/58 atc	.008″ .008″
510-x2	.375″ .375″	296.5 296.5	103 105	“R”	New race profile. Best all around road-race. Best peak performance. May need to trim flywheel clearance. Use racing pistons and springs. TDC lift in = .174″ @ 1.1 rocker ratio/with lash
Base circle diameter=.812″					ex=.153″
510-95	.400″ .400″	340 340	108 108	“STD” only	Full race only. All racing components required. High R.P.M. drag race, grass track, competition.	62 btc/98 abc 98 bbc/62 atc	.008″-.014″ .008″-.014″
Stock 650	.322″ .322″	272 272			.322″ 278 .322″ 278	Stock for your reference. 750 short rod

Triumph 500 twins:

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

Cam Number	Lobe Height	Duration at .020″	Lobe Centers	Description and Application	Intake: open/close Exhaust: open/close	Running Clearance
512-05	.348″ .348″	282 282	100 102	Designed for stock pistons and springs. Good throttle response/all around performance.	41 btc/61 abc 63 bbc/39 atc	.010″ .010″
512-65	.355″ .355″	292 295	101 104.5	Best all around street/road race profile.	42 btc/67 abc 72 bbc/43 atc	.010″ .010″
512-x5	.293″	296.5		1938 Triumph 500 Twin stock reproduction.
512-x8	.375″ .375″	296.5 296.5	103 on “R” 105 on “R”	Best competition road-race profile. Maximum peak horsepower and throttle response. Must use racing pistons and valve springs. Trim flywheel for clearance.	44.5 btc/71 abc 73.5 bbc43 atc	.008″ .010″

Triumph and BSA triples:

Cam Number	Lobe Height	Duration at .040″	Lobe Centers	Tappet Style	Description and Application	Intake: open/close Exhaust: open/close	Running Clearance
511-05	.345″ .345″	282 282	98 102	“STD”	Best all around profile, road and touring. Use modified pistons and springs. This was the factory road race profile used by Dick Mann at Daytona. Smooth power band.	43 btc/59 abc 63 bbc/39 atc	.005″ .007″
511-x5	.375″ .375″	287 287	104.5 107.5	“STD”	Road race profile. Strong mid-range, top-end. All out racing. Use modified pistons and valve springs.	39 btc/68 abc 71 bbc/36 atc	.008″ .010″
511-35	.346″ .346″	268 268	104 104	“STD”	Short road race where throttle response is most important. Less top-end than the 511-00. Very strong mid-range.	30 btc/58 abc 58 bbc/30 atc	.008″ .010″
511-75	.400″ .400″	274 274	108 108	“STD”	Full race. Must trim tappet guide blocks. High R.P.M. race application. Race components.	29 btc/65 abc 65 bbc/29 atc	.008″ .010″
511-95	.400″ .400″	288 288	100 100		Special application race profile.	44 btc/64 abc 64 bbc/44 atc
Stock	.328″	262			For reference.

Johnson Cam Grinds

T100R Daytona

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE				R	272	40	52	.020
EXHAUST				R	272	61	31	.020

T120 “E3134”

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.314				269	34	55	.020
EXHAUST					269	55	34	.020

Triumph 750 short rod

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.350	111.5	.010		278	26.5	69.5	.020
EXHAUST	.350	103	.010		278	61.5	35.5	0.020

Q cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.316	105	.002	R	271	31	60	.020
INTAKE	.316	105	.002	R	251	21	50	.040
EXHAUST	.316	105	.004	R	271	61	30	.020
EXHAUST	.316	105	.004	R	251	51	20	.040

Jomo TT Cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.310	105	.002	R	276	33	65	.020
INTAKE	.310	105	.002	R	255	21	53	.040
EXHAUST	.310	105	.004	R	276	62	35	.020
EXHAUST	.310	105	.004	R	255	52	23	.040

Harmon&Collins 7054 Cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.326	105	.002	R	267	31	56	.020
INTAKE	.326	105	.002	R	246	20	46	.040
EXHAUST	.326	105	.004	R	267	61	26	.020
EXHAUST	.326	105	.004	R	246	50	16	.040

Connely #1 Cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.353	105	.002	R	280	31	69	.020
INTAKE	.353	105	.002	R	261	21	59	.040
EXHAUST	.353	105	.004	R	280	61	39	.020
EXHAUST	.353	105	.004	R	261	51	29	.040

Johnson J360/264 Cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.353	102	.006	R	305	51	73	.020
INTAKE	.353	102	.006	R	277	73	60	.040
EXHAUST	.353	110	.006	R	305	83	41	.020
EXHAUST	.353	110	.006	R	277	69	29	.040

Triumph T-3 Cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.328	102	.006	R	393	44	69	.020
INTAKE	.328	102	.006	R	264	30	54	.040
EXHAUST	.328	105	.008	R	293	72	41	.020
EXHAUST	.328	105	.008	R	264	57	27	.040

Triumph T-65 Cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.344	105	.008	R	280	36	64	.020
INTAKE	.344	105	.008	R	255	23	52	.040
EXHAUST	.344	105	.010	R	280	66	35	.020
EXHAUST	.344	105	.010	R	255	53	22	.040

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.

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.345	105	.010	S	294	40	74	.020
INTAKE	.345	105	.010	S	270	29	61	.040
EXHAUST	.345	105	.010	S	294	71	44	.020
EXHAUST	.345	105	.010	S	270	59	32	.040

Jomo 15 Cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.354	106	.006	R	289	37	72	.020
INTAKE	.354	106	.006	R	267	28	60	.040
EXHAUST	.354	106	.008	R	289	69	39	.020
EXHAUST	.354	106	.008	R	267	59	29	.040

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.

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.352	105	.008	S	290	39	71	.020
INTAKE	.352	105	.008	S	267	28	58	.040
EXHAUST	.352	105	.008	S	290	69	41	.020
EXHAUST	.352	105	.008	S	267	58	28	.040

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.

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.350	105	.006	R	305	49	77	.020
INTAKE	.350	105	.006	R	274	33	61	.040
EXHAUST	.350	105	.008	R	305	79	47	.020
EXHAUST	.350	105	.008	R	274	63	31	.040

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.

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.400	105	.008	S	306	49	77	.020
INTAKE	.400	105	.008	S	283	37	65	.040
EXHAUST	.400	105	.010	S	306	79	47	.020
EXHAUST	.400	105	.010	S	283	67	35	.040

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.

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.410	102	.008	S	303	50	73	.020
INTAKE	.410	102	.008	S	279	38	61	.040
EXHAUST	.410	110	.008	S	303	82	41	.020
EXHAUST	.410	110	.008	S	279	70	29	.040

Johnson J481 Cam

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

	LIFT	CENTER	LASH	TAPPET	DUR’N	OPEN	CLOSE	AT
INTAKE	.443	102	.008	S	316	57	79	.020
INTAKE	.443	102	.008	S	290	44	66	.040
EXHAUST	.443	110	.008	S	316	89	47	.020
EXHAUST	.443	110	.008	S	290	76	35	.040

Cam Timing - Half Race Camshaft Set PN# 70-3134 70-9989 E3134 E9989

Frequently Asked Questions

What is cam timing on a classic Triumph motorcycle?

Cam timing describes when the intake and exhaust valves open and close relative to crankshaft position. Classic Triumph cam specifications list these events in crankshaft degrees, together with information such as lift, duration and the checking height used to measure them. When comparing specifications, make sure the measurement conditions match. Our guide to the camshaft in your Triumph B-range engine provides additional background on this engine component.

What is the difference between cam lift and valve lift?

Cam lift is the movement produced at the cam follower or tappet, while valve lift is the movement at the valve after the rocker arm transfers that motion. They are not necessarily equal: the rocker ratio changes how much the valve moves. Before comparing Triumph camshafts, check whether each specification describes lift at the cam or at the valve. The Cam Timing Notes guide explains why this distinction matters when reading different cam tables.

Why are Triumph cam timing figures measured at .020, .040 or .050 inch?

Different cam specifications use different checking heights or checking-clearance procedures to define when an opening or closing event is recorded. A duration measured at .020 inch is therefore not directly comparable with one measured at .040 or .050 inch. Also check whether the stated measurement is taken at the tappet or valve. For example, Megacycle’s Triumph 650/750 twin specifications explicitly list duration at .020 inch, so that measurement basis must stay with the figures.

What do BTDC, ABDC, BBDC and ATDC mean in cam timing specifications?

BTDC means before top dead center; ABDC means after bottom dead center; BBDC means before bottom dead center; and ATDC means after top dead center. These abbreviations identify crankshaft position when a valve reaches the specified checking point. In a typical intake listing, “41 BTDC / 61 ABDC” means the intake opening is measured before top dead center and its closing after bottom dead center. You can see this format in Megacycle’s Triumph twin cam tables

What is the Triumph E3134 “Q” cam, and are all E3134-profile cams identical?

The E3134 designation is associated with a Triumph cam profile used across multiple camshaft applications, rather than identifying every camshaft’s complete fitment. The article also distinguishes Tricor and factory versions, so an E3134 reference alone does not establish one universal timing specification. Check the actual grind, application and measurement procedure before using published figures. See our E3134 cam profile notes and the 70-3134 / 70-9989 half-race camshaft set for related information.

How do I identify a Triumph camshaft from its casting or stamped numbers?

Distinguish the raised forging or casting number from the stamped cam identification. A forging number identifies the blank used to make the camshaft, and the same blank may support several different grinds. It cannot reliably identify the finished profile by itself. Compare any stamped identification with the relevant parts information and measured cam characteristics. Our Triumph cam forging-number reference explains this distinction and lists examples.

What is the difference between “R” and “STD” Triumph cam followers?

In Megacycle’s Triumph twin specifications, “R” identifies a follower with a 1⅛-inch contact-face radius, while “STD” identifies a ¾-inch radius. These describe the curvature of the working face, not the follower’s outside diameter. The specified follower type matters when interpreting cam timing and application information. Check the individual grind’s requirements rather than assuming the two types are interchangeable; the Megacycle Triumph twin reference identifies the follower style for each listed profile.

Is valve clearance the same as the checking clearance used for cam timing?

No. Running valve clearance is the adjustment specified for engine operation, while checking clearance or checking lift is part of the procedure used to measure cam timing. A cam specification may require zero checking clearance or a particular measurement height even though its running-clearance figures are different. Follow the instructions for the exact camshaft and engine, then restore the specified running clearances after checking. The Megacycle camshaft catalog illustrates these different measurement conventions.

What tools do I need to check Triumph cam timing accurately?

Accurate cam timing checks generally require a crankshaft-mounted degree wheel and a securely mounted dial indicator, used according to the cam manufacturer’s measurement procedure. The specified measuring point matters: a procedure based on tappet movement cannot automatically be replaced with one based on valve movement. Megacycle recommends degreeing cams with a degree wheel and dial indicator; see its camshaft installation guidance alongside our Cam Timing Notes—Part II.

Which camshaft is best for a classic Triumph 650 or 750 road bike?

The appropriate camshaft depends on the desired power range and the engine’s pistons, valve springs, followers and available clearances—not simply the largest lift or duration figure. Megacycle describes its 510-05 as a street/road profile emphasizing low- and mid-range performance, while the 510-65 targets a broader mid-range and top-end power band and specifies modified pistons and springs. Use the manufacturer’s Triumph 650/750 application table to compare requirements before choosing a grind

Do performance Triumph camshafts require different pistons, springs or engine modifications?

Some do, but the requirements vary by grind. Megacycle’s Triumph twin tables include profiles intended for stock components, others requiring modified or racing pistons and springs, and racing profiles requiring additional clearance work around the tappet guide blocks or flywheel. Even a profile described as likely to clear stock pistons still requires a clearance check. Consult the specific Triumph camshaft application notes before buying parts or assembling the engine.

Can I use Triumph twin cam timing specifications for a Trident or BSA Rocket 3?

No—Triumph and BSA triples need specifications for their own engine and camshaft application. The checking height and follower requirements may differ from the twin-cylinder tables. For example, Megacycle’s triple table lists duration at .040 inch and specifies ¾-inch-radius followers for most listed grinds, with an exception for the 511-X6. Use the Triumph and BSA three-cylinder cam specifications rather than transferring figures from a Bonneville twin.