Author Topic: which cam to use?  (Read 3561 times)

Offline mark

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which cam to use?
« on: 03.06. 2010 07:10 »
I have a choice of using a 356 or a 357 cam in my '55 rocket.  It has the correct heavy big journal crank and I've just taken delivery of a set of Lightning billet conrods from Thunder engineering, the pistons are 9 to 1 Hepolites and until I can source the correct head I am using one from a super rocket. What thoughts are there on the pros and cons of the different cams.
Regards
Mark
55 road rocket




71 Norton Commando Roadster 750


Australia

Offline A10Boy

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Re: which cam to use?
« Reply #1 on: 03.06. 2010 11:17 »
It depends what you want from the engine, the 356 is perfectly good for an all round tractable engine, while the 357 is more sporty but gives a slightly less flexible engine.

Are you sure you have the right con rods, A65's are different to A10's?
Regards

Andy

1958 Super Rocket
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline MG

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Re: which cam to use?
« Reply #2 on: 03.06. 2010 12:21 »
Andy,

"Lighning" is the trade name of the rods sold by Thunder Engineering for various bikes.
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

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Online muskrat

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Re: which cam to use?
« Reply #3 on: 03.06. 2010 14:04 »
G'day Mark,
                     I agree with Andy. I use 357's in both the A7 and A10 but I'm a rev head. The power comes in at about 4500rpm which means at 60 mph in top I have to go back to 3rd to get motivated.. The 356 will give better mid range.
I'd stick with the SR head.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online bsa-bill

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Re: which cam to use?
« Reply #4 on: 03.06. 2010 15:22 »
I have a 357 in my project but reduced the gearing a very little bit to compensate for reduced torque and not really interested in top speed these days but would like a bit of umph at the lights ( just to surprise the boy racers)
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline mark

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Re: which cam to use?
« Reply #5 on: 03.06. 2010 23:52 »
Thanks for the thoughts guys. Since I plan to use a 22tooth engine sprocket it looks like the 356 will be better in regards to flexibility.
regards
Mark
55 road rocket




71 Norton Commando Roadster 750


Australia

Online chaterlea25

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Re: which cam to use?
« Reply #6 on: 05.06. 2010 22:16 »
Hi Mark,
Flexibility of the engine (in riding terms!!) has a lot of of factors influencing it!!
Carburation and ignition settings  have a huge influence, even the exhaust makes a difference.
My SR has a 357 cam, manual mag (BTH) and a Mikuni carb,
It will pull easily from low revs and will trickle along in high gear without complaint!!
Whack the throttle open and it leaps into  life and scorches off into the distance *smile* *smile*

I'm rebuilding another SR for an older owner and have fitted flat top pistons and a 356 cam as it will be more suitable to his needs, he also has a plunger A10 and a Harley and only recently sold his Gold wing!!! so I hope I'm correct with the spec I'm using ????
Cheers
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline A10Boy

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Re: which cam to use?
« Reply #7 on: 07.06. 2010 16:39 »
Yes, an old owner will love it, i do.........  ;)
Regards

Andy

1958 Super Rocket
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline A10Boy

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Re: which cam to use?
« Reply #8 on: 19.06. 2010 19:02 »
I was wondering, what sort of price are those Lightning con rods from thunder engineering? do they compare with SRMs?
Regards

Andy

1958 Super Rocket
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline mark

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Re: which cam to use?
« Reply #9 on: 20.06. 2010 08:16 »
The Lightning Conrods cost me 250 pound the pair. I'm not sure how they compare with SRM. I am impressed with the quality however but the real test is still to come when the motor is completed and running. I was speaking to a chap in New Zealand recently who told me that he used them in a motor that set some race record over there so I guess that is a positive reccomendation.
Mark
55 road rocket




71 Norton Commando Roadster 750


Australia

Offline A10Boy

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Re: which cam to use?
« Reply #10 on: 20.06. 2010 20:47 »
Thanks

SRM do BSA forged equivalents @ £189 a pair or high strength forged @£150 each.

Regards

Andy

1958 Super Rocket
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline trickytree

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Re: which cam to use?
« Reply #11 on: 20.06. 2010 22:25 »
For those of you down under (from me at any rate!) theres These guys

I bought my A65 billet rods from TMS at £280 a pair.
1965 A65 Bobber
A10 Bitza project

Offline wilko

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Re: which cam to use?
« Reply #12 on: 21.06. 2010 00:43 »
Yes  Ridgcrest even make them for Matchy twins.

Offline Rocket Racer

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Re: which cam to use?
« Reply #13 on: 22.06. 2010 07:17 »
Excerpt from one of BSA's adverts for accessories...
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline Rocket Racer

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Re: which cam to use?
« Reply #14 on: 17.08. 2010 08:50 »
I thought I'd upgrade my '55 road rocket motor from its stock 356 to a 357. In practice this required machining as there was insufficient space in the cam trough for the additional lift to let the cam rotate! I wasnt expecting it not to fit.
Likewise I replaced my small journal crank with an early LJ and found the big end lock nuts fouled the cases and wouldnt let the crack rotate fully. I had to fit the castled type nuts which were smaller to have a crank that spun. Presumably the super rocket motors have a bit more clearance for cams and big ends...
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand