Grubbster Posted February 6, 2007 Share Posted February 6, 2007 A friend of mine has a pretty standard 1.6 K with about 13,000 on the clock. Last summer he did his first trackday (at Keevil on Avon ZV1's) and this highlighted a potential problem that is making him less keen to get back on track, so I'd like to try and sort it. He was new to trackdays so short sessions, not massive cornering forces but he did frequently rev close to the limiter so the engine got a reasonable work-out. He noticed that the engine developed quite a loud knocking noise - seemingly from the head - a bit like a diesel. This continued in the pit area even at low revs. Once switched off and cooled a bit then all was OK again and has been during use on the road since. Oil level seemed OK, and oil is fairly new, no massive temperatures noticed, no obvious other symptoms. So we have been thinking. If it were head gasket then we'd probably see other signs? Any temporary loss of oil pressure would have been easily spotted and noise continued when back in the pits and pressure was certainly fine. So, could it be air in the oil? Possibly caused by slight over-filling (although we don't think it is over filled but is this a possible symptom?)? Or could it be to do with the hydraulic followers - hence my question about how do they work? Any ideas greatly appreciated, Ta Roadsport build photo's here Le Mans 2004 photo's here Link to comment Share on other sites More sharing options...
CageyH Posted February 6, 2007 Share Posted February 6, 2007 They fill up with oil when the engine is running, to take up the slack between the cam lobes and valves. When the air get aireated, they don't pump up, so the top end sounds tappetty. Has he got an Apollo? Only dead fish go with the flow.... Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted February 6, 2007 Leadership Team Share Posted February 6, 2007 Put simplisticly - whilst being driven hard the oil wants to stay in the block and not return to the sump - this causes the pickup pipe to draw air causing a air/oil mix to be pumped around the system to the bearings etc, including the hydraulic followers. Because air is more easily compressed than oil, the oil/air mix is more easily compressed than a pure oil mix, taking the followers outside their normal operating tolerences and hence the rattles. Seems to be more of a problem with some followers than others. Stu. Must type faster! Edited by - sforshaw on 6 Feb 2007 22:01:39 Link to comment Share on other sites More sharing options...
F355GTS Posted February 6, 2007 Share Posted February 6, 2007 Off the wall but when the Manifolds fail on an F355 (common problem) it sounds like a failed Tappet, got me going for a while I can tell you . Always worse when Hot as the crack expands, worth a check of the Manifolds, Exhaust Gasket etc Mark Link to comment Share on other sites More sharing options...
Grubbster Posted February 6, 2007 Author Share Posted February 6, 2007 Ok thanks guys Exhaust manifold worth a check, but I think a 4-2-1 is on the way soon so that will sort it for sure. I am tending to think of air in the oil - no Apollo yet (on the way) so we'll see how it goes. Roadsport build photo's here Le Mans 2004 photo's here Link to comment Share on other sites More sharing options...
oilyhands Posted February 6, 2007 Share Posted February 6, 2007 Classic oil aeration symptoms, if the air is becoming aerated, just think what could be happening to your bearings... oily Link to comment Share on other sites More sharing options...
DaveMorris Posted February 6, 2007 Share Posted February 6, 2007 Subtle hint from Oily there .. .. trackdays with no apollo or dry sump could get expensive with high-revs and high-g on corners ! Dave X-flow(er) powered Link to comment Share on other sites More sharing options...
Grubbster Posted February 6, 2007 Author Share Posted February 6, 2007 😳As I suspected, seems to be a bit of 'luck of the draw' as I did a few trackdays on A048s pretty mercilessly before I got my Apollo - so either I have damage that I don't know or I was lucky (never any symptoms like this). This was Daves first time on track (unsure of the history prior to this) and on fairly poor rubber so didn't expect any cornering forces sufficient to cause a problem. Live and learn . . . Cheers for the comments Roadsport build photo's here Le Mans 2004 photo's here Link to comment Share on other sites More sharing options...
Frying Pan Posted February 7, 2007 Share Posted February 7, 2007 Steve Apollo for sale here Guy See some pictures of the build here. 11000 miles completed! Link to comment Share on other sites More sharing options...
Beelzebub Posted February 7, 2007 Share Posted February 7, 2007 Do hyd tappets have any flow & return, or do they simply pump up to ambient oil pressure 🤔 Once they're at pressure are there any means by wiich the pressure is trapped inside 🤔 Link to comment Share on other sites More sharing options...
Sheds Moderator Posted February 7, 2007 Share Posted February 7, 2007 I think they have a drilling with a simple valve mechanism. Once pumped up they "sort of" stay there but obviously oil will leak out under pressure in a mechanism like an engine where forces and speeds are rather high. I don't think they have an "in" and an "out" pipe hence why they get gummed up if you don't change the oil and the top end gets rattly on startup. Link to comment Share on other sites More sharing options...
old captain slow Posted February 7, 2007 Share Posted February 7, 2007 If your friend is doing track days without at least an Apollo tank fitted he's going to run into expensive trouble as others have posted above. Just to re-emphasise - one good surge will wipe all the bearings and (speaking from experience) could also lead to more expensive damage. We had a K that wiped it's bearing to the extent that the pistons hit the valves. Ouch 😳 C7 CDW Link to comment Share on other sites More sharing options...
Englishmaninwales Posted February 7, 2007 Share Posted February 7, 2007 Thank you 7heavensoon *thumbup* Link to comment Share on other sites More sharing options...
Pelico Posted February 7, 2007 Share Posted February 7, 2007 I have an apollo kit that is just missing the sandwich plate (can get them from Think Auto for £20-30 ish) if anyone else is looking for one. I keep on meaning to put it on for sale Link to comment Share on other sites More sharing options...
oilyhands Posted February 7, 2007 Share Posted February 7, 2007 The followers have an internal spring in the central hydraulic plunger which keeps them in contact with the cam and valve tip, oil is fed through a one way valve to the hydraulic plunger. The plunger allows a certain amount of oil to bleed out during each lift cycle and this is recharged during the latent period of the cam followers movement. This way the follower can properly adjust to changes in the required clearances due to changes in termperature and resulting expansion and contraction fo components. oily Link to comment Share on other sites More sharing options...
Beelzebub Posted February 7, 2007 Share Posted February 7, 2007 Thank you Link to comment Share on other sites More sharing options...
wag Posted February 8, 2007 Share Posted February 8, 2007 I have noticed similar symptoms after extended running at about 5000rpm but no hefty g forces. Goes away after a couple of minutes of slow running. Oh dear. Link to comment Share on other sites More sharing options...
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