Tony Millward Posted March 24, 2013 Report Share Posted March 24, 2013 (edited) Hi all, I am in the process of rebuilding my engine and checking wear areas. I am using a TR5 camshaft and note the timing is 35, 65, 65, 35. Does this mean that the inlet valve actually starts opening at 35 degrees BTDC?. The reason I am asking is that I checked mine and the inlet valve actually starts moving (on the dial gauge), at 75 degrees BTDC. After moving 10 thou on the dial gauge it reads 35 degrees. Full inlet valve (no.1), opening is achieved at 105 degrees. The inlet valve is fully closed at 110 degrees ABDC...? I'm confused...Help. Cheers Tony Edited March 24, 2013 by Tony Millward Quote Link to post Share on other sites
smizgals Posted March 24, 2013 Report Share Posted March 24, 2013 (edited) Tony, I got the attached from this forum (not you?) some time ago. Which degrees are you refering to: crankshaft,camshaft or both? Stan Edited March 24, 2013 by smizgals Quote Link to post Share on other sites
peterq Posted March 24, 2013 Report Share Posted March 24, 2013 Hi Tony, I had the same issue as I did a rebuild on my engine, I changed sprockets and chain and lost my timing marks by buying new parts. My cam is different, it is a CR cam, timing 18-58-58-18. Please consider that it is difficult to determine the point where the valve starts to open in relation to the angle of the camschaft. Due to the profile the valve at first opens slowly, then faster. As far as I know this is the reason that some cam shaft manufacturers are giving these angles at a certain valve lift, for example at 1mm. But then again, there does not exist a standard for this, different manufacturer, different standard. Then the measured gap between cam (or rocker arm) and valve tip also changes the opening and closing angle. Assuming that opening and closing slope are identical, I used the maximum lift to check the timing. At maximum lift my gauge only moved slightly for 30 degrees (95 to 125). So the top of the profile should be at 110 degrees. I timed my cam at 110 degrees and then checked opening and closing. These were not 18 and 58, but opening was a few degrees earlier and closing a few degrees later. This makes sense considering the timing given at a certain lift of the valve (no standard). If the profile is correct (no wear) and the gap (rocker arm and valve tip) is correct, the the diffence in degrees at opening and closing should be identical, just as a check. I hope this helps. Kind regards, Peter. Quote Link to post Share on other sites
Tony Millward Posted March 25, 2013 Author Report Share Posted March 25, 2013 Hi Stan, yes, you did get that from me. I kept referring to it while I was adjusting my cam...which is why the opening time weren't making any sense. I'm going to update that chart with the actual opening times of the cams. Hi Peter, thanks for that explanation as it's exactly what I found. I'll time it on max lift and see how it goes. Cheers Tony Quote Link to post Share on other sites
John L Posted March 25, 2013 Report Share Posted March 25, 2013 (edited) I thought there was another way to do this......Resetting the rear 2 valves to something like 0.014 or it could have been 0.016 or could even be a different value, the turn the cam so that the clearance had gone on both valves, a true rocking point and then turn the crank to TDC, fit the chain and then double check. I may well be wrong but it seems an easier method..... I stand to be corrected please. John Quoted from the Brown Bible page 15 Item 9 reset the number 6 cylinder valves to 0.040" on compression stroke Turn the camshaft to the point of balance with the number 6 valves Turn the crank to TDC and fit the chain Don't forget to readjust the valves on number 6 cylinder on compression. Make sure that the timing marks TDC on the crankshaft pulley are truly at TDC with the crankshaft and pistons. Edited March 25, 2013 by John L Quote Link to post Share on other sites
john.r.davies Posted March 25, 2013 Report Share Posted March 25, 2013 John, You are referring to "Equal lift on overlap" method of cam timing. With No.1 cylinder at TDC (when No.6 will be at TDC as well) adjust the cam shaft so that both the No.6 valves are equally lifted. This is the situation at the end of one Otto cycle, when the exhaust valve is closing and the inlet is opening simultaneously. At this point a Triumph cam , or any other 'symmetrical' cam, will be correctly timed. The other standard method is that the cam grinder gives you a magic number of degrees for the crank to be past TDC when No.1 inlet valve is at full lift. You might be able to work that out from your data, Tony. John Quote Link to post Share on other sites
Tony Millward Posted March 25, 2013 Author Report Share Posted March 25, 2013 Cheers guy's, I'm off to see Andy (MK1PI) tonight to see if he can shed some light on it. Tony Quote Link to post Share on other sites
Tom Fremont Posted March 25, 2013 Report Share Posted March 25, 2013 I timed one in ( it was a 41/71/71/41 cam ) using the equally open @ TDC, inlet opening angle with valve lash set to specification and full lift centerline methods. All were within 1 degree of one another. I wouldn't have expected 40 degrees to lift 0.010" but if there wasn't any lash set 35 degrees is on the money at least. If I recall correctly 105 degrees centerline is correct too. Quote Link to post Share on other sites
Guest ntc Posted March 25, 2013 Report Share Posted March 25, 2013 Hi Tony Why the rebuild so soon? Quote Link to post Share on other sites
Tony Millward Posted March 26, 2013 Author Report Share Posted March 26, 2013 Hi Neil, I had some leaks to take care of which involved engine removal so I decided to check the timing on the cam. While it was out, I thought I would check a few things for wear and no, I'm NOT gonna respray it too... Hey Tom, the cam will be set for max lift on No.1 inlet at 105 degrees and leave it at that. The first few degrees of lift are basically ramp angles. Cheers Tony Quote Link to post Share on other sites
Guest ntc Posted March 26, 2013 Report Share Posted March 26, 2013 (edited) Hi Tony Good to know thanks,. The timing you have is correct for a std (good) cp cam and that allows for valve clearance in the ramp Edited March 27, 2013 by ntc Quote Link to post Share on other sites
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