Author Topic: 356 Camshaft measurements please  (Read 301 times)

Online Greybeard

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356 Camshaft measurements please
« on: 26.10. 2018 16:21 »
Peeps. Are you able to let me know what the base circle and lift should be for a 356 camshaft. Thanks.

Later: I've just found this graphic that shows lift figures. http://atlanticgreen.com/bsamain.htm

The lift figures I've obtained * from my (356) cam look about right according to that graphic; I've got approx 0.300"

I'd still like to see a figure for Base circle, please.


*I was not able to get a dial gauge to reach the camshaft, (I'd need an extension piece) so I used my digital calliper height piece against the edge of a steel rule which was held across the crankcases.

Offline coater87

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Re: 356 Camshaft measurements please
« Reply #1 on: 26.10. 2018 18:19 »
 Are you trying to do this with cam in the bike?

 I believe you can measure one lobe. Subtract the smallest measure from the largest, and that's your lift.

 I think the smallest measure you obtained is your base circle. *conf*

 Lee
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Re: 356 Camshaft measurements please
« Reply #2 on: 26.10. 2018 18:31 »
Are you trying to do this with cam in the bike?

 I believe you can measure one lobe. Subtract the smallest measure from the largest, and that's your lift.

 I think the smallest measure you obtained is your base circle. *conf*

 Lee
Thanks Lee. Yes, the cam is still in-situ. I have the lift figures. I also have a measured base circle, using a modified pair of dividers so I could get them on the cam. I'd like to know what an official base figure is. If you recall, I had trouble with the Inlet tappet adjusters having to be screwed in too far. If the base circle diameter is too small that would account for it. Mind you, as the lift looks ok, the lobes would also have to be undersized!

Offline Swarfcut

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Re: 356 Camshaft measurements please
« Reply #3 on: 27.10. 2018 08:50 »
 Hi GB.... Just have a used  356 cam to hand, so for what it's worth measuerd on unworn areas, sadly with a metric caliper.

   Lobe lengths heel to toe 31.6mm,  cam width  at the base at right angles to a line through the lobe... 24.3mm

  Bear in mind this cam has had some use, but looks to be relatively unworn.

  The actual lift a cam gives depends on the difference between the distance of the heel and toe from the centre of rotation.  When a cam is reground, to restore lift, material is removed from the back of the heel.  In effect the starting point for lift has been moved nearer the centre of rotation. This is what restores the lift.

  So if you have a reground cam, the heel/toe length will be smaller, but the overall lift should be back to standard.

   With a reground cam, the followers now sit lower in the tappet guides when they are on the heel, and now they may be bottoming on the retaining grub screws and centre guide. Unlikely, but worth checking.  We also assume the followers themselves are as they should be as regards
 the distance between the contact face and the top of the follower locating slots. 

  Swarfy.

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Re: 356 Camshaft measurements please
« Reply #4 on: 27.10. 2018 09:04 »
Thanks Swarfy. This is a new camshaft.

Offline Swarfcut

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Re: 356 Camshaft measurements please
« Reply #5 on: 27.10. 2018 09:18 »
 GB.. Apologies, I thought from the style of your original post that you had a reground cam. Looks like a very large investment here on a single component, so I can share your concern that all is as it should be. The information on cam regrinds will no doubt be of use to some of the forum members.

  How do my figures stack up against your new cam?

 Swarfy.

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Re: 356 Camshaft measurements please
« Reply #6 on: 27.10. 2018 10:18 »
GB.. Apologies, I thought from the style of your original post that you had a reground cam. Looks like a very large investment here on a single component, so I can share your concern that all is as it should be. The information on cam regrinds will no doubt be of use to some of the forum members.

  How do my figures stack up against your new cam?

 Swarfy.

My rather inaccurate method of measuring the base circle came up with 0.940". Your figure converts to 0.956", so I'm happy with that.

Calculating lift from your measurements:
Base to lobe = 31.6mm.  Base diameter = 24.3mm.
Lift = Base to lobe, minus base diameter: 31.6mm - 24.3mm =  7.3mm, or 0.2874"

My measurement got an average lift of 0.31", so close enough. The graphic I found online shows a value of just over 0.3" for the 356 cam.

This all looks good. I was worried that my problems were being caused by a dodgy camshaft.  *wink2*

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Re: 356 Camshaft measurements please
« Reply #7 on: 27.10. 2018 10:29 »

 Looking at your pic of the dial gauge holder and thinking you should be able to flip the thing over to go further in?? I have one the same, and it can be a dyslexlic nightmare at times.... *pull hair out*

 FWIW, I posted the measurements of my reground 357 not so long ago and the 0.940 figure sounds familiar but I think my irrelevant lift was 0.334" -0.338"
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Re: 356 Camshaft measurements please
« Reply #8 on: 27.10. 2018 10:36 »
Looking at your pic of the dial gauge holder and thinking you should be able to flip the thing over to go further in?? I have one the same, and it can be a dyslexlic nightmare at times.... *pull hair out*
There wasn't room to fit the body of the dial gauge into t'ole. If I had an extension I could have did it.

Quote
FWIW, I posted the measurements of my reground 357 not so long ago and the 0.940 figure sounds familiar but I think my irrelevant lift was 0.334" -0.338"
That looks about right according to that graphic I posted. Thanks.

Offline Swarfcut

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Re: 356 Camshaft measurements please
« Reply #9 on: 27.10. 2018 10:51 »
   

 Thanks GB, good that things are looking up. Swarfy.