mleadbeater Posted January 12 Report Share Posted January 12 Has anyone found a difference of clearances between a cold then warm engine? On my XPAG TD, there are no discernible differences. Mike Quote Link to post Share on other sites
Cew Posted January 12 Report Share Posted January 12 (edited) On 1/7/2024 at 3:03 PM, BlueTR3A-5EKT said: Does an eight cylinder use 17 rule and twelves 25 rule? I think on "V" engines you would treat each bank as a 4 or 6 cylinder engine, I have only come across one "V" engine where adjusting is actually done in a similar way as a TR and that is the Daimler SP250, most other "V" engines, like the Stag, use shims or have hydraulic lifters. Only my experience of course and I stand to be corrected. Edited January 12 by Cew Quote Link to post Share on other sites
Mike C Posted January 12 Report Share Posted January 12 (edited) 19 hours ago, mleadbeater said: Has anyone found a difference of clearances between a cold then warm engine? On my XPAG TD, there are no discernible differences. Mike I'd be interested in any comments on this. Personally I suspect the valve train components cool a fair bit between the start and end of the adjustment procedure, if the engine isn't dead cold to start with. Edited January 13 by Mike C Quote Link to post Share on other sites
john.r.davies Posted January 13 Report Share Posted January 13 (edited) Let's apply some science! The question is, will the thermal expansion of a hot engine close up the valve gap? The coefficient of linear thermal expansion "α" of steel is about 11 x 10^-6 / degree C , or 0.0000011 /degree C The change (dL) in length for a given rise in temp (dT) is given by dL = L x α x dT and dT is about 100 degrees C Consider a push rod, which is the longest part of the valve train, and is about 12", 0.3 metres, long. So, dL = 0.3 x (11 x10^-6) x 100 = 0.00033metres, or 0.33mm. Or 13 thou. Clearly a crude method, but provides a realistic result, to show, yes, you should adjust your tappets hot! As to cooling after warm up, I found this graph: Engine lubricant sump temperatures from a 1.6 l 4 cylinder S.I. engine during warm-up at 1500 RPM and 2 Bar BMEP and subsequent cool down. Samhaber C, Wimmer A, Loibner E. Modeling of engine warm-up with integration of vehicle and engine cycle simulation. SAE technical paper 2001-01-1697; 2001. It shows that, once hot and turned off, an engine will lose only10C in the first hour, and take two and a half hours to cool to half its running temp. Surely the first is plenty of time to do the tappets? John Edited January 13 by john.r.davies Quote Link to post Share on other sites
JohnC Posted January 13 Report Share Posted January 13 (edited) 2 hours ago, john.r.davies said: Clearly a crude method, but provides a realistic result, to show, yes, you should adjust your tappets hot! My original Triumph Repair Operation Manual (BL Part No AKM3646) states on p05-1 under Engine Tuning Data "Valve rocker clearance .... 0.010 in (0.25mm) inlet and exhaust. Engine cold" I guess that may not be correct for non-standard cams. In that case I suggest asking the cam manufacturer. Regards, JC Edited January 13 by JohnC Quote Link to post Share on other sites
Mike C Posted January 13 Report Share Posted January 13 (edited) 5 hours ago, john.r.davies said: Let's apply some science! The question is, will the thermal expansion of a hot engine close up the valve gap? The coefficient of linear thermal expansion "α" of steel is about 11 x 10^-6 / degree C , or 0.0000011 /degree C The change (dL) in length for a given rise in temp (dT) is given by dL = L x α x dT and dT is about 100 degrees C Consider a push rod, which is the longest part of the valve train, and is about 12", 0.3 metres, long. So, dL = 0.3 x (11 x10^-6) x 100 = 0.00033metres, or 0.33mm. Or 13 thou. Clearly a crude method, but provides a realistic result, to show, yes, you should adjust your tappets hot! As to cooling after warm up, I found this graph: Engine lubricant sump temperatures from a 1.6 l 4 cylinder S.I. engine during warm-up at 1500 RPM and 2 Bar BMEP and subsequent cool down. Samhaber C, Wimmer A, Loibner E. Modeling of engine warm-up with integration of vehicle and engine cycle simulation. SAE technical paper 2001-01-1697; 2001. It shows that, once hot and turned off, an engine will lose only10C in the first hour, and take two and a half hours to cool to half its running temp. Surely the first is plenty of time to do the tappets? John Don't forget the block and all other components are expanding/contracting with engine temperature as well as the push rods. . Edited January 13 by Mike C Quote Link to post Share on other sites
Jonny TR6 Posted January 13 Author Report Share Posted January 13 Whilst I understand and agree with the principle of adjusting whilst hot, I can’t help thinking that for a standard cam Triumph probably did this when they designed the engine and came up with 0.010 as the cold setting ? Quote Link to post Share on other sites
RobH Posted January 13 Report Share Posted January 13 4 hours ago, Mike C said: Don't forget the block and all other components are expanding/contracting with engine temperature as well as the push rods. Exactly - and the distances and materials are roughly similar, so the gap may close a little but that is all, as Mike says above. No doubt Triumph measured the results before specifying adjustment when cold. The cam will make little difference to the expansion so the method should still stand even though the specified gap may be different. Quote Link to post Share on other sites
Z320 Posted January 13 Report Share Posted January 13 (edited) 12 hours ago, Mike C said: Don't forget the block and all other components are expanding/contracting with engine temperature as well as the push rods. . In my opinion the only thing that rules are the expanding length of the valves… But why measure on the hot engine, when the producer tells cold? And who wants to bear the pain to adjust hot? Edited January 13 by Z320 Not „hit“ —> hot engine Quote Link to post Share on other sites
Jonny TR6 Posted January 13 Author Report Share Posted January 13 Just now, Z320 said: In my opinion the only thing that rules are the expanding length of the valves… But why measure hit, when the producer tells cold? And who wants to bear the pain to adjust hot? Pushrods will be the biggest expander when hot I’d have thought. Quote Link to post Share on other sites
Z320 Posted January 13 Report Share Posted January 13 (edited) 2 hours ago, Jonny TR6 said: Pushrods will be the biggest expander when hot I’d have thought. Yeah, I know… But I’m convinced they expand about the same like the hole engine block, the difference is about zero. Has this not already been mentioned before? Are we spinning in circles? Edited January 13 by Z320 Quote Link to post Share on other sites
john.r.davies Posted January 13 Report Share Posted January 13 Oh, for goodness sake, I said it was a crude method! YOU work out the effect of a hot block etc. then! The hot valves will further decrease the gap from cold, so with 13 thou extra length from push rods alone would close the gaps right up, if you adjusted for 10 cold! I doubt if the Triumph engineers could calculate it either, and did the measurements cold and hot. John Quote Link to post Share on other sites
Z320 Posted January 13 Report Share Posted January 13 I‘m totally relaxed and adjust valves cold… Quote Link to post Share on other sites
PodOne Posted January 13 Report Share Posted January 13 I suspect they came out of the factory adjusted "cold"? Quote Link to post Share on other sites
JohnC Posted January 14 Report Share Posted January 14 8 hours ago, Z320 said: But I’m convinced they expand about the same like the hole engine block, the difference is about zero. That's what I'd assume as well. My *assumption* is that the heat coefficient of expansion of the cylinder head and block is almost exactly the same as the pushrods and the valves. *If* that assumption is correct then the block (above the camshaft) and the head will expand the same amount as the pushrods, and the head will expand the same amount as the valve, with a net effect of nearly zero. @john.r.davies Please don't be offended if I've got this all wrong. What's your view? Cheers, JC Quote Link to post Share on other sites
john.r.davies Posted January 14 Report Share Posted January 14 JohnC, I chose the push rod for my very crude example because it is a very simple application of thermal expansion, which may be assumed to be heated evenly and as a thin rod requiring only length to be calculated. An engine block is very much the opposite, a complex casting that is heated at its centre and cooled via the walls by flow of coolant that is not even! Complex methods of estimating the expansion of such a shape are required, in particular Finite Element Analysis, which require computing power that is not beyond that of a desktop computer, but with expensive software and a LOT of time, neither of which I have! But it can be done, and this is an example: Athimakula, Kanth et al, Modeling and Analysis of Cylinder Block, RSP Science Hub 2 December 2020. https://rspsciencehub.com/article_6893_ebf8baa6ce8f5526775913ffc31ca5ee.pdf As this shows. thermal expansion of a complex shape induces equally complex stresses and deformation. Way beyond my capabilities! John Quote Link to post Share on other sites
mcgrison Posted February 23 Report Share Posted February 23 The noise of the valves disturbs me when I drive my TR4A and for this reason I had bought the aluminium cover which reduces it somehow. I noticed that the gap 0,2 mm ( 0,08 inch) warm is more or less equivalent to 0,10/0,15 mm ( 0,05 inch) cold. It is a very small difference but I already cheat a bit on the recommended gap which should be 0,25 mm ( 0,1 inch ) and do not want to risk. In spite of the above valve number 6 , starting from the battery side, is always a little noisier than the others. I suspect there is a small dimple in the surface of the rocker arm which alters the measurement but I don't want to dismantle the rocker shaft for a barely perceptible problem. Maybe I should get treated for paranoia first! Quote Link to post Share on other sites
Andy Moltu Posted February 24 Report Share Posted February 24 On 1/13/2024 at 5:19 PM, Z320 said: Yeah, I know… But I’m convinced they expand about the same like the hole engine block, the difference is about zero. Has this not already been mentioned before? Are we spinning in circles? If you are so inclined set them cold and remeasure when hot and note for reference. (Vice versa if your cam manufacture recommends hot setting) Quote Link to post Share on other sites
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