Peter Cobbold Posted January 2, 2017 Report Share Posted January 2, 2017 (edited) Hi Iain, This may not help but who knows: I had a knock at hot idle with my TR4 in 1974 ( sounded like a diesel idling ). Valve clearances were all correct. I was forced to drive it with the noise until one day the engine died just as I pulled into my parking space at the apartment complex. Less competent then than I am now, I had it towed to a repair shop to be fixed. The cam sprocket bolts had sheared. While the mechanic was reassembling the engine he noticed the rocker shaft was very worn. I got a replacement from a junkyard for $10. It solved the knock. Cheers, Tom Iain, Might it be the cam sprocket moving slightly?- would fit I think wihe tappith tng going away when the throttle is blipped, the clearance taken up by chain tesion. Peter Edited January 2, 2017 by Peter Cobbold Quote Link to post Share on other sites
Ian Vincent Posted January 2, 2017 Report Share Posted January 2, 2017 Could it be one of the springs getting coil bound when it gets hot? Check if you can slide a 4 thou feeler gauge between the coils at max compression. Rgds Ian Quote Link to post Share on other sites
iain Posted January 2, 2017 Author Report Share Posted January 2, 2017 Iain, Might it be the cam sprocket moving slightly?- would fit I think wihe tappith tng going away when the throttle is blipped, the clearance taken up by chain tesion. Peter Hi Peter I had the self same thought.....Timing chain area is very quiet.....Again using the stethoscope. Quote Link to post Share on other sites
iain Posted January 2, 2017 Author Report Share Posted January 2, 2017 Could it be one of the springs getting coil bound when it gets hot? Check if you can slide a 4 thou feeler gauge between the coils at max compression. Rgds Ian Umh....But why the tap at cam level as opposed to rocker height? We had coil binding on the Sprite...But that had a very silly Cam :-) Iain Quote Link to post Share on other sites
Peter Cobbold Posted January 2, 2017 Report Share Posted January 2, 2017 (edited) Hi Peter I had the self same thought.....Timing chain area is very quiet.....Again using the stethoscope. Hi Iain, The sound might travel along the camshaft and not be heard on t/c cover.....maybe. I wonder if you might pick up more spark timing spread when its hot and tapping compared with cold? Strobe light- easier than dismantling anything. Peter Edited January 2, 2017 by Peter Cobbold Quote Link to post Share on other sites
iain Posted January 2, 2017 Author Report Share Posted January 2, 2017 Hi Iain, The sound might travel along the camshaft and not be heard on t/c cover.....maybe. I wonder if you might pick up more spark timing spread when its hot and tapping compared with cold? Strobe light- easier than dismantling anything. Peter Peter I'll give that a try,easy enough as you say. Iain Quote Link to post Share on other sites
LGFromage Posted January 4, 2017 Report Share Posted January 4, 2017 Hi Iain, Maybe there is too much end float on the distributor drive gear causing it to rattle up and down at idle. Tim Quote Link to post Share on other sites
iain Posted January 4, 2017 Author Report Share Posted January 4, 2017 Hi Tim Good thought but this has been ruled out already, all within factory tolerances..... Cheers Iain Quote Link to post Share on other sites
GT6M Posted January 4, 2017 Report Share Posted January 4, 2017 Did ye check lift on cam,!! as if cams onits way oot, or ramps gon awol, then it,ll rattle on take up. as follower is bangin into cam, no riding up it, follow,!! failing that, yee,ve got thee,s wee things, orrible little buggers at times https://www.google.co.uk/search?q=engine+gremlins&client=firefox-b&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiGysjKvKnRAhWpCsAKHdL_AroQ_AUICCgB&biw=970&bih=558#imgdii=EMimyFpLvsFTiM%3A%3BEMimyFpLvsFTiM%3A%3Bd7-WyD5iziEQNM%3A&imgrc=EMimyFpLvsFTiM%3A M Quote Link to post Share on other sites
iain Posted January 4, 2017 Author Report Share Posted January 4, 2017 Good point Marcus I will check the cam lobes again. I hope it's not those orrible little buggers tho! Iain Quote Link to post Share on other sites
GT6M Posted January 4, 2017 Report Share Posted January 4, 2017 Ohh, forgot t,mention, check t,see if yer push rods are turning if not, then it cud well be a follower gon hollow in direction of cam Have ye had to adjust this end rockers moer than the others If so, it shows that summats wearin away if constant adjustment is needed Ye can get one of thee,s wee thingys, an bung it inside the engin, an look at the cam followers frae underneath http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1311.R4.TR12.TRC2.A0.H1.Xendoscope.TRS0&_nkw=endoscope+camera&_sacat=0 M Quote Link to post Share on other sites
Revolution Posted January 4, 2017 Report Share Posted January 4, 2017 Iain I'm intrigued as to what could be the cause of the tapping noise............have I missed it or could you post a video so we can all see the engine and hear the noise? Cheers, Nick Quote Link to post Share on other sites
Lebro Posted January 5, 2017 Report Share Posted January 5, 2017 One thought - I had this on one of my original (solid steel) pushrods Check the top end, I discovered that the hollow cup had a crack in it, which was closed when static (setting up the gap), but opened up a little when running, resulting in a loud tap. Bob. Quote Link to post Share on other sites
iain Posted January 5, 2017 Author Report Share Posted January 5, 2017 (edited) Iain I'm intrigued as to what could be the cause of the tapping noise............have I missed it or could you post a video so we can all see the engine and hear the noise? Cheers, Nick Hi Nick, no video posted think I would need an external mic for that...... One thought - I had this on one of my original (solid steel) pushrods Check the top end, I discovered that the hollow cup had a crack in it, which was closed when static (setting up the gap), but opened up a little when running, resulting in a loud tap. Bob. Bob, not looked that hard at the push rods other than for straightness........they are hollow steel rods with fitted ends...... Will report back when I get a chance to have another play Many thanks Iain Edited January 5, 2017 by iain Quote Link to post Share on other sites
Revolution Posted January 5, 2017 Report Share Posted January 5, 2017 Hi Iain I think your mobile phone should have sound when you shoot a video I'm pretty sure if you post a clip, there will be someone on this Forum who will recognise the "tapping" ! Best wishes, Nick Quote Link to post Share on other sites
Paul J Posted January 5, 2017 Report Share Posted January 5, 2017 I recently carried out a cylinder head service on a Austin Shearline, the push rods had spring loaded tappet ends such a simple easy idea keeps the rod in light constant contact with the follower and creates the quietest engine on tickover I've ever heard. Would be really easy to do, surprised other engine manufacturers have not used the idea, or have they. Paul Quote Link to post Share on other sites
RogerH Posted January 5, 2017 Report Share Posted January 5, 2017 Hi Paul, modern cars have hydraulic tappets etc. These work well. Roger Quote Link to post Share on other sites
iain Posted January 7, 2017 Author Report Share Posted January 7, 2017 Update Not coil bound good 0.004" clearance on all springs (Ian) No timing wander with strobe at tickeover ( Peter) Ran with cover off and inserted 0.010" feeler gauge to reduce valve clearance, makes no difference to tapping. (Chris) Will load videos later if they ever load to photobucket.....they have been uploading for 3 hrs already.......the joys of living in the country! Cheers Iain Quote Link to post Share on other sites
GT6M Posted January 7, 2017 Report Share Posted January 7, 2017 Ohh, forgot t,mention, check t,see if yer push rods are turning if not, then it cud well be a follower gon hollow in direction of cam Ian, did ye doo as above, they gotta rotate wen engines running M Quote Link to post Share on other sites
ChrisR-4A Posted January 7, 2017 Report Share Posted January 7, 2017 Hi Ian, have you checked the advance/retard weights in the dist. When engine is cold tick over is faster so springs are tensioned on weights. When hot and tickover slows down A/R weights if fitted with standard springs are loose and could make a noise, either try another dist or fit one tighter spring on one weight to take up the slack. If this fixes problem then contact Distributor Doctor to get dist rebuilt to suit engine. Regards Chris Quote Link to post Share on other sites
iain Posted January 7, 2017 Author Report Share Posted January 7, 2017 Marcus....I forgot, but I did check with a scope down inside each cam follower and couldn't see anything a miss. All pushrods straight, no loose ends or splits in the cups. Chris the dizzy is a fully rebuilt re calibrated to engine spec Distributor Dr unit, which has been back to Martin for checking as I thought it had a bit too much end float. Its absolutely on the money and the noise is not coming from the dizzy. Also its end float on the drive shaft has been check and rechecked, its within spec. More tomorrow Thanks guys Quote Link to post Share on other sites
iain Posted January 7, 2017 Author Report Share Posted January 7, 2017 (edited) Here we go..What a performance getting a video or two sorted. First, Engine just warm enough not to need choke. Oil pressure 70psi.Temp about 160F Second. Engine thoroughly warm, Oil pressure 55psi at tick over, Temp 185F Removing a plug lead in sequence makes no difference. Still puzzled Edited January 7, 2017 by iain Quote Link to post Share on other sites
Guest ntc Posted January 7, 2017 Report Share Posted January 7, 2017 Still say a tooth on the cam or one shot rocker. Quote Link to post Share on other sites
iain Posted January 7, 2017 Author Report Share Posted January 7, 2017 Hi Neil its not the Rockers. Tooth on the cam? Not sure I understand? Cheers Iain Quote Link to post Share on other sites
Guest ntc Posted January 7, 2017 Report Share Posted January 7, 2017 Hi Neil its not the Rockers. Tooth on the cam? Not sure I understand? Cheers Iain Iain If I hear it right on the second vid you can hear just one tap,listen just under the dizzy Quote Link to post Share on other sites
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