RogerH Posted February 10, 2018 Report Share Posted February 10, 2018 (edited) Hi Folks, how is the cam installation angle generated. On the Moss TT1104N is is 108 degrees On the Newman PH1 it is 110 degrees. I've had a look at the various numbers - duration etc but can't come up with an answer. Also why does the standard cam nit have an installation angle. I appreciate that the original cam had a centre punch mark to align things but a new one may not !!. Roger PS - just found this site. Doesn't help the above but a good read about cams. Edited February 10, 2018 by RogerH Quote Link to post Share on other sites
iain Posted February 10, 2018 Report Share Posted February 10, 2018 Hi Roger have you read this, it might help http://www.tildentechnologies.com/Cams/TriumphCams.html Iain Quote Link to post Share on other sites
john.r.davies Posted February 10, 2018 Report Share Posted February 10, 2018 Roger, The answer in my mind is so simple I fear I don't understand the question. "Correct" cam timing for a symmetrical camshaft, which both of these are, is achieved by the Equal Lift on Overlap method, both inlet and exhaust equally lifted at TDC between two complete four stroke cycles. Simples! The cam installation angle is used in the other method, where the No.1 piston is set to TDC, the inlet on No.1 is set to max lift, and then advanced (retarded? its a while since I did this!) by the prescribed angle. The two cams you mention have different timing, Moss, 31-67-67-31, Newman, 18-58-58-18, which must explain the different timing. Or else just different cam designers. Or did you mean something else? John Quote Link to post Share on other sites
RogerH Posted February 10, 2018 Author Report Share Posted February 10, 2018 (edited) Hi Iain, that table is very interesting - there are some wicked cams out there. From that I went to the Elgin site and that showed some very interesting info. Elgin do a cam with the same numbers as the standard TR4/4A cam.17/57 - 57/17. Hi John, I have used your balanced lobe method on a standard cam and it worked well. It also explained what the WSM was trying to say. Didn't appear to work on the TT1104N but then that had an installation angle - which t me is much easier to accomplish. However what I wanted to know is how do they generate the installation angle on the drawing board. Could it simply be a pragmatic exercise during design that with #1 inlet cam lobe at max lift a certain crank angle puts it in the right place. No correlation to cam numbers at all. Roger Edited February 10, 2018 by RogerH Quote Link to post Share on other sites
iain Posted February 10, 2018 Report Share Posted February 10, 2018 HI Roger I would double check your installed angle. If the cam is too advanced against its book value, idle will be lumpy but it will want to rev and generate more power at the top end. Too retarded the opposite. I once had a 1935 Singer Le Mans which was unbelievably sensitive to cam timing. Get it wrong and it was a dog. Get it right and it went extremely well. I m sure you know but you get get very close with a standard sprocket, by changing hole and flipping over, 1/4 of a tooth out is over 4 degrees of crank rotation as explained in this useful article http://www.macysgarage.com/myweb6/cam_degree.htm Iain Quote Link to post Share on other sites
RogerH Posted February 10, 2018 Author Report Share Posted February 10, 2018 Hi Iain, The actual positioning of the crank and cam was very accurate. However, as you say, the standard sprocket can only get as close as the attachment holes allow. So yes it could be a degree or so out even though one was trying to be spot on. I think I shall invest in a vernier sprocket. What the hell, it's only money. Roger Quote Link to post Share on other sites
oldtuckunder Posted February 10, 2018 Report Share Posted February 10, 2018 Not sure if you have time to be playing with this today if your driving to Stoneleigh tomorrow But maybe a good place to pick up a sprocket! Alan Quote Link to post Share on other sites
john.r.davies Posted February 10, 2018 Report Share Posted February 10, 2018 (edited) Roger, It has to be the relation of the two cams to TDC. I found a "Camshaft Lobe Center / Duration Calculator/Lobe Separation Angle" calculator at https://www.rbracing-rsr.com/camshaft.html Entering the timing in degrees of either of the 'shafts you mention gets a value that is the " Installed centerline" of that cam: Moss, 31-67-67-31, Moss "108 degrees BTDC" Newman PH1, 18-58-58-18 Newman "110 degrees BTDC" So, it is a calculation! The working isn't shown,but the whole text of the answer says: Your PH1 has an Overlap of 36.00 degrees and has in Intake Duration of 256.00 degrees. The Exhaust Duration is 256.00 degrees. Your Lobe Separation Angle is 110.00 degrees. The Inlet Cam has an Installed Centerline of 110.00 degrees ATDC. The exhaust cam has an Installed Centerline of 110.00 degrees BTDC. I tjhink it's this way. Looking at the conventional cam lobe diagram The cam centre, maximum lift, is at (18 + 180 + 58)/2 = 128 degrees past opening. Which is 128 - 18 = 110 degrees after TDC. Do it again for the Moss and you get 108 degrees. Either is the position of the cam at max lift after TDC. Thnak you Roger! I've always considered this figure that is supplied with a cam with no explanations as "Magic", AKA, a technology so advanced beyond mine as to be indistinguishable from magic. Now I've advanced thanks to your question! JOhn Edited February 10, 2018 by john.r.davies Quote Link to post Share on other sites
Lebro Posted February 10, 2018 Report Share Posted February 10, 2018 Hopefully by the time I get round to my engine re-build Roger will be able to: 1) recommend which cam, & followers to use, & 2) how to time it. Bob. Quote Link to post Share on other sites
Ian Vincent Posted February 11, 2018 Report Share Posted February 11, 2018 When I was rebuilding my engine I found a spreadsheet on the internet which did the calculation that John has outlined above. FWIW a Piper fast road cam has the same timing as a stock TR 4 pot one. Rgds Ian Quote Link to post Share on other sites
john.r.davies Posted February 11, 2018 Report Share Posted February 11, 2018 To be honest, Ian, after realising what the "Magic Number" meant (and if I got Roger's Q correctly) it really really doesn't need a spreadsheet to work it out! Does this graphic help? Start red, go green, then blue. John Quote Link to post Share on other sites
oldtuckunder Posted February 11, 2018 Report Share Posted February 11, 2018 Only out of interest but is it? theoretically possible that a cam manufacturer would specify a different angle to that calculated, as the start of the inlet opening is an absolute as ground into the cam, as is it close, but the opening and closing ramp angles are unknown as is the tappet clearance specified by the cam grinder, so the full lift point needn't be half way. Which starts to make sense to me why some manufacturers quote duration between 0.050 lift points. Alan only adding mud to the water. Quote Link to post Share on other sites
RogerH Posted February 11, 2018 Author Report Share Posted February 11, 2018 As Jimmy Cliff would say - 'I can see clearly now.........................' Sadly the fog still remains. Roger Quote Link to post Share on other sites
Darth V8R Posted February 23, 2018 Report Share Posted February 23, 2018 HI Roger I would double check your installed angle. If the cam is too advanced against its book value, idle will be lumpy but it will want to rev and generate more power at the top end. Too retarded the opposite. Iain Iain: You are correct about the cam timing affecting the power curve, but it is the opposite of what you outlined. I am sure there are exceptions, but the rule of thumb is advancing the cam improves the bottom end because the intake valve closes sooner, and trapping efficiency is therefore higher when the intake charge is moving slowly. Retarding the cam increases top end power, because the intake valve closes later allowing the engine to take advantage of the inertia of the incoming intake charge to "supercharge" the cylinder. Installing the cam "straight up" provides a more balanced top and bottom end power curve. HOWEVER, with modern CNC cam designs, I am not at all certain this is a hard and fast rule. Modern designs use steeper opening rams to get the valve open quickly, and gentler closing ramps to improve durability of the valve train. David Vizard, generally recommends installing the cam around 4 degrees advanced (See his book "Tuning the A Series Engine" - excellent). Comp Cams (an excellent OHV cam design company) now grinds their newest cams with 4 degrees of advance designed in. So if you install their cams by aligning the dots on the cam sprockets, it will automatically be 4 degrees advanced. Older designs do not have this little trick built in. So in this case the intake valve center line might be 108 degrees while the lobe center angle would be 112 degrees, for example. So cam technology is still evolving even for "obsolete" OHV engines. A state of the art OHV cam will have asymmetrical lobes, slightly longer duration on the exhaust lobe, and some provision for installing the intake center line in a slightly advanced position. Whew! Lots of stuff to think about. Vance Quote Link to post Share on other sites
RogerH Posted February 23, 2018 Author Report Share Posted February 23, 2018 Hi Vance, sadly the fog still remains !!! Roger Quote Link to post Share on other sites
oldtuckunder Posted February 23, 2018 Report Share Posted February 23, 2018 sadly the fog still remains !!! But the frogs have returned to the pond, silly buggers, didn't watch the weather forecast! Sorry way off topic! Alan (but inching closer to testing the ceramic coating, but at this rate the spawn will have hatched first!) Quote Link to post Share on other sites
RogerH Posted February 23, 2018 Author Report Share Posted February 23, 2018 Hi Alan, I was out frog hunting today but they were keeping their heads down. Roger Quote Link to post Share on other sites
Darth V8R Posted February 26, 2018 Report Share Posted February 26, 2018 Hi Vance, sadly the fog still remains !!! Roger Roger: It is a very complex subject, and no cam is a silver bullet as far as guaranteed performance improvement. Without a dyno, it is impossible to be certain you selected the correct cam, and installed in an optimum way for your engine. So what can I suggest? Select a dual pattern cam with 6-10 degrees more duration on the exhaust, and install it 4 degrees advanced. The difference between advertised duration and 0.050" lobe lift duration should be no more than about 65 degrees, otherwise it is a 'lazy' cam and is therefore obsolete. As to the duration and lobe center angle, for car driven regularly in stop and go traffic, 112 - 114 degree lobe center angle with no more than about 210 degrees of intake duration at 0.050" lobe lift (approximately 270 degrees advertised duration). Most cams will put you at about 0.440" total valve lift for a cam with these specs. While you may need aftermarket valve springs, no other machining is typically required. The result will be a good idle, minimal impact on emissions and economy, and 10-15% more power on a well tuned but largely unmodified engine. You will lose the "glass smooth" idle of a stock cam, but you will have good cold start drivability and very civil behavior in city driving. This should also work with an automatic transmission. Auto crossing, add 10 degrees duration (280 degrees advertised), with lobe center angles of 110-112 degrees. Expect to do some head machining and raise the compression. Manual transmission or aftermarket stall convertor is required. Will be a bit tedious to drive in the city. Fuel economy will suffer, and you may have difficulty passing emissions tests. Idle with be choppy. 20-25% power increase with raised compression. Full on racing, add 20 - 30 degrees duration (290-300 advertised duration), and bring the lobe center angle to 108 degrees. Head work, exhaust work and raised compression are mandatory. An automatic transmission is pretty much out at this point. Forget driving on the street, and idle will be VERY choppy, fuel economy will be non-existent. Vance Quote Link to post Share on other sites
TriumphV8 Posted February 26, 2018 Report Share Posted February 26, 2018 Only out of interest but is it? theoretically possible that a cam manufacturer would specify a different angle to that calculated Normally a camshaft has same lobe for inlet and exhaust. For some special purposes there are different ones. Again normally the inlet would be larger in those cases. Some like the Mini Cooper engines have a larger exhaust lobe. Modern cams have a steeper ramp on the lift side and a smoother release on the lowering ramp. Honda does sometimes that way. The reason is that the opening force is limited by the stiffness of the valve train what is very strong with OHC and cup lifters but the closing force comes from the valve spring. So with less spring force and less stress on the valve train resulting from that a larger and faster opening can be achieved with that trick. All that is not of interest for our cams. Newman does such a hybrid cam with different degrees on inlet and exhaust. GT does another one but that is gambling ........ Both are rare and I see no need to use them. If somebody wants to judge a cam the overlap is a good indication and the degree where the inlet closes. My earlier post explains the reason why a cam better is quoted and installed with larger valve clearane. Quote Link to post Share on other sites
PhilipB Posted February 27, 2018 Report Share Posted February 27, 2018 To be honest, Ian, after realising what the "Magic Number" meant (and if I got Roger's Q correctly) it really really doesn't need a spreadsheet to work it out! Does this graphic help? Start red, go green, then blue. John I made my own Cam degree wheel from this https://www.blocklayer.com/degree-wheel.aspx Enter Cam spec, select wheel size and print. I used a diameter of 200mm which seemed to be about the max useable size and stuck it to a disc cut from 2mm thick aluminium sheet Phil Quote Link to post Share on other sites
Hamish Posted February 27, 2018 Report Share Posted February 27, 2018 Very clever. I like their tip and print size to stick it to a cd. Quote Link to post Share on other sites
RogerH Posted February 27, 2018 Author Report Share Posted February 27, 2018 ....would a 78 do.......... Quote Link to post Share on other sites
Hamish Posted February 27, 2018 Report Share Posted February 27, 2018 ....would a 78 do.......... A 45 would Roger. Dig some of those out. H Quote Link to post Share on other sites
RogerH Posted February 27, 2018 Author Report Share Posted February 27, 2018 Quote Link to post Share on other sites
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