LCA seems really wide, have it cam doctored to be sure.
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| Can We identify this Cam? https://www.ausmini.com/forums/viewtopic.php?f=2&t=11044 |
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| Author: | Chris [ Sun Sep 11, 2005 6:55 pm ] |
| Post subject: | Can We identify this Cam? |
I have a Pommy billet cam of unknown origin in a 1275, I know it is a billet cam due to the finish between the lobes. It has a total lift of 270 thou with inlet lobe to exhaust lobe centres of 115 degrees. I never had to measure a cam before so I don't know if that is enough info, is it? |
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| Author: | justminis [ Sun Sep 11, 2005 9:05 pm ] |
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LCA seems really wide, have it cam doctored to be sure.
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| Author: | Chris [ Sun Sep 11, 2005 9:42 pm ] |
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Does anyone know of a page with cam specs? |
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| Author: | drmini in aust [ Sun Sep 11, 2005 10:36 pm ] |
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Chris wrote: Does anyone know of a page with cam specs?
Here's one, but it's local. http://tighecams.com.au/cars.htm As Steve said it's a good candidate for regrind. 
You need more info- a cam grinder could profile it but with specs you've given it ain't no fire breather... 
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| Author: | Chris [ Sun Sep 11, 2005 11:17 pm ] |
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Kev, how do I plot the profile using a dial indicator? This thing has 020 more lift than any I found on Tighe's page. I set it up in the lathe and put the DI on it to get my numbers. A lot of cam lift figures appear to be quoted at the valve not on the lobe. |
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| Author: | drmini in aust [ Mon Sep 12, 2005 7:23 am ] |
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Chris wrote: Kev, how do I plot the profile using a dial indicator? This thing has 020 more lift than any I found on Tighe's page. I set it up in the lathe and put the DI on it to get my numbers. A lot of cam lift figures appear to be quoted at the valve not on the lobe.
Set it up in an old motor, with only 2 pushrods & lifters (in #1 cylinder) and a new timing chain. Use the standard cam key. Put head on, but you only need nuts done up firm. Set the 2 valves at .019" (std rockers) and set up a dial gauge on the inlet valve cap. Set TDC with a degree wheel on the crank and a bit of wire for a pointer. and see how far ATDC the inlet reaches full lift. You can then see what the timing figures are for inlet open/close and exhaust open/close, also the valve lift. You can also see what figures are at .050" lift which is a common spec. That will give you duration- if you really want to plot the opening area get thee some graph paper and write down the lift figures and crank angles at 5* intervals. 
Figures are a bit rubbery really because there's no standard I know of for `checking clearance', apart from BMC spec of .019" or .021". Bear in mind the whole timing diagram can be advanced or retarded by using offset cam keys. Stock BMC production cams were mostly all 110* LCA- to fit a Kent or GR one at 104-106*, I usually have needed a 4 or 6* key to advance the cam. |
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| Author: | Chris [ Mon Sep 12, 2005 9:22 am ] |
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Thanks for that, but no can do I as I don't have a motor to put it in at the moment. I have used that method in the past to time cams. It is a pity no one has made some decent cam gears for these motors ala Triumph. That car had gears that had the teeth offset to the bolt holes by half a tooth (I think it was that much) and it was possible to change the cam timing 4 ways on one side or reverse it and 4 ways the other side. It was possible to get it really close without investing in expensive vernier gears or using offset keys. |
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