Alex Wong1697456877 Posted August 3, 2000 Share Posted August 3, 2000 As those following the Le Sept thread in chitchat will know, my blew my engine whilst doing my best AJ Foyt impression on the banked oval at CERAM. The engine has been disassembled with a huge amount of help from Roger Swift. The pistons are now out. The worst one is 3. A photo can be seen here Funnily enough, the rings are intact but the piston itself has crumbled around the top part. The other side of the piston shows similar but milder wear. I'd say that detonation rather than lube failure was the cause of this seeing as the rings are intact. Any comments? Piston 4 showed a simiar failure at an earlier phase. Also, the head is showing signs of detonation in 3 and 4. There's some definite wear around the valves. Roger Swift has done some sterling work honing the two bores to get rid of the scoring and I'm much more optimistic now that I'm sure the big ends and crank are all fine. The next step is going to be looking more closely at the valves and the top end. Curiously, when the engine was disassembled, 2,3 & 4 were damp with a bit of oil but 1 is bone dry with some crusty stuff on the valves. Any ideas? Alex Alex Wong alex.wong@lotus7club.co.uk www.alexwong.net Home : 44-(0)121-440 6972 Fax : 44-(0)121-440 4601 Edited by - Alex Wong on 4 Aug 2000 00:38:21 Edited by - Alex Wong on 4 Aug 2000 00:42:42 Link to comment Share on other sites More sharing options...
Andrew Russell Posted August 4, 2000 Share Posted August 4, 2000 Alex, Goes without saying but bad luck on your misfortune, you certainly seem to have caused some damage to your pistons! What pistons were/are they? Until I hear from you, I'm going to wind back my rev-limiter which was set at 7800 like yours.....how does 4500 sound? At least with the 2.0 XE, we can rely on good torque. Seriously though, I hope 7X is back on track and flying low soon. Best wishes, Andrew. Link to comment Share on other sites More sharing options...
Andrew Russell Posted August 4, 2000 Share Posted August 4, 2000 Alex, Goes without saying but bad luck on your misfortune, you certainly seem to have caused some damage to your pistons! What pistons were/are they? Until I hear from you, I'm going to wind back my rev-limiter which was set at 7800 like yours.....how does 4500 sound? At least with the 2.0 XE, we can rely on good torque. Seriously though, I hope 7X is back on track and flying low soon. Best wishes, Andrew. Link to comment Share on other sites More sharing options...
Andrew Russell Posted August 4, 2000 Share Posted August 4, 2000 Damn my sticky mouse! Link to comment Share on other sites More sharing options...
Simos Posted August 4, 2000 Share Posted August 4, 2000 Hi Alex, I saw exactly the same last week, except it was a round of cheese I was grating onto my lasgna. Sorry couldn't resist, the comparison is striking :-) On a serious note though I used to see a similar kind of thing on a fairly regular basis when racing two stroke engines. Straight forward lack of lubrication seizes were pretty horrifically scarred the whole length of the pistons as the oil film was broken (on lift-off) and the piston expanded due to the increased frictional heat. But, over-rev seizes looked somewhat similar with one distinction. On the two strokes, running at high revs (<20-22,000rpm) too many times used to crack the piston skirts, which used to then fall off (and rattle a bit) with the piston crown looking not dissimilar to yours (if it survived at all). Now your skirt (the piston's) looks fine but it does look like it's been rattling round.... Now can the engine guru's please tell us what's really been happening here ? Cheers, Simon. Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted August 4, 2000 Author Share Posted August 4, 2000 Thanks for the replies. The cams are QED Q420's The pistons are Omega flat tops (86mm bore)from QED These cost 90 quid before vat each which wasn't too bad but by the time I added all the bolts, gaskets, new leads, rings for the other 2 pistons and circlips etc, it came to over 600 quid! At least Roger doesn't charge for labour! Opinions differ on the cause. Either detonation due to too much advance or a hot spot, or picking up due to an oiling problem. QED want 300 quid plus vat to dyno the engine after the rebuild. This might be a good investment I suppose. Still, as has been suggested, I have 2 new ashtrays or cheese sculptures! Cheers, Alex Wong alex.wong@lotus7club.co.uk www.alexwong.net Home : 44-(0)121-440 6972 Fax : 44-(0)121-440 4601 Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted August 4, 2000 Share Posted August 4, 2000 I was sorry to hear the news, but looks like you're well on the way to a 'new' engine. Great photo (in the photographic sense!). Best of luck----Chris Link to comment Share on other sites More sharing options...
Rory McLeod Posted August 5, 2000 Share Posted August 5, 2000 That looks horrendous. Link to comment Share on other sites More sharing options...
Rory McLeod Posted August 5, 2000 Share Posted August 5, 2000 Re: deposits. May not be applicable in your case, but from my Triumph Bonny rebuild days... Light coating of grey/brown deposits is OK, Heavy crusty coating of greyish coral was a call for me to redo the head(again) too much oil through valve guides. Black and oily coating was WAY too much lube due to ring and also probably guide wear. This was generally balanced against - the carb tuning, black is rich, white is weak, and the ignition timing, early is black late is white. However I havent rebuilt anything more sophisticated. Link to comment Share on other sites More sharing options...
Rory McLeod Posted August 5, 2000 Share Posted August 5, 2000 Oh, and the ones I did rebuild blew up twice.. wink.gif Link to comment Share on other sites More sharing options...
StewartG Posted August 5, 2000 Share Posted August 5, 2000 Alex, Who was it that mapped your fuel injection - maybe the mixture was set too lean? No wonder the fuel consumption improved so much! Link to comment Share on other sites More sharing options...
Roger King Posted August 5, 2000 Share Posted August 5, 2000 Alex, Difficult to tell from the pic, but on the face of it, it doesn't seem like classic detonation. Photos of the crown and the piston skirts (both sides of piston) would help. I am a little suspicious of localised overheating or lubrication breakdown. Detonation tends to appear as a grey, grainy surface on the edge of the crown and running down the side of the piston. It often busts the rings. Also, what state were the spark plugs in? rkingeng@aol.com Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted August 5, 2000 Author Share Posted August 5, 2000 The top surface does have some grainyness but also, the head shows some damage above 3 and 4. It's only superficial but you can feel a step from the bit over the cylinders to the rest of the head. This isn't evident in 1 and 2. The sparkplugs - standard NGK's - had oil on them in 2,3 and 4. 3 was coated in a black metalicky layer, 1,2 and 4 were browny grey. I'll take the digital camera when I'm next at Roger Swift's place and try to photograph as much as possible. It's fascinating to see all the different opinions. With respect to temperature and oiling, 2 things spring to mind. The oil was at 125 degC when the engine blew. The engine was wet sumped and there was no oil cooler. Oil pressure was normal when it blew. Oil levels were ok after the incident. The engine has a foam baffle disintegrate before. It was cleaned out as much as possible but it is possible that some foam bits have blocked an oil channel. Thanks for all the opinions. I'm kind of enjoying the experience in a perverse sort of way, although the cost is fixing it is depressing! Cheers Alex Wong alex.wong@lotus7club.co.uk www.alexwong.net Home : 44-(0)121-440 6972 Fax : 44-(0)121-440 4601 Link to comment Share on other sites More sharing options...
Anna Rexia Posted August 6, 2000 Share Posted August 6, 2000 Hey Alex - did you know you can now join the piston broke club and have a badge for your overalls? (small compensation I know!) Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted August 6, 2000 Author Share Posted August 6, 2000 Great! Where can I get one of these badges? Maybe it should read pissed 'n broke instead though! smile.gif Alex Wong alex.wong@lotus7club.co.uk www.alexwong.net Home : 44-(0)121-440 6972 Fax : 44-(0)121-440 4601 Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted August 6, 2000 Author Share Posted August 6, 2000 Anna, I see you are now a fully fledged deity (God no. 3 by my reckoning). Welcome to Godliness and strike down a blasphemor when you're bored. It keeps me amused! God no. 1 (I am not a number, I am a free Deity!) (I think I'll be the first one struck down! I suppose it's better than struck off!) Edited by - Alex Wong on 7 Aug 2000 00:14:38 Link to comment Share on other sites More sharing options...
gareth Posted August 7, 2000 Share Posted August 7, 2000 Alex I have a tuned Vauxhal by QED and had an engine detonate just like the pictures, I now run Super Unleaded Petrol with an Octane booster being Manganese. Some very naughty people when they compete put 110 Octane petrol from Nascar 76 in. I never would !!!!!! Edited by - gareth on 7 Aug 2000 07:19:10 Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted August 7, 2000 Author Share Posted August 7, 2000 Gareth, Surely if the engine is mapped correctly for 95 octane unleaded, it should be ok with that. I try to use superunleaded for track driving but it's difficult to find. No performance benefit but I assume it makes it less likely to detonate. Running SUL and an octane booster sounds expensive! I do 10,000 miles a year in my 7. Incidentally, who mapped your engine? Mail offline if you prefer. I was just wondering before I part with more dosh to get it dyno'd. Alex Wong alex.wong@lotus7club.co.uk www.alexwong.net Home : 44-(0)121-440 6972 Fax : 44-(0)121-440 4601 Link to comment Share on other sites More sharing options...
Mike Bees Posted August 8, 2000 Share Posted August 8, 2000 Alex - what do you mean when you say the plugs are "standard NGKs"? I would have thought you should be running a colder-than-standard plug given that the engine is producing rather more power than standard. Mike Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted August 8, 2000 Author Share Posted August 8, 2000 Mike, I've read the same, but where do I get colder plugs from and how do I know they are colder? Alex Alex Wong alex.wong@lotus7club.co.uk www.alexwong.net Home : 44-(0)121-440 6972 Fax : 44-(0)121-440 4601 Link to comment Share on other sites More sharing options...
Roger King Posted August 8, 2000 Share Posted August 8, 2000 Alex, It's easy with NGK. The higher the number the colder the plug and as a general rule the more highly tuned an engine is, the colder the plug you should run. Note though, that this rule will only apply for any particular engine type, i.e. just because a heavily modified Vauxhall might need an 8, this doesn't mean that an equivalent Crossflow will also need an 8 (in fact, with it's less efficient combustion chamber, a Crossflow may need to go even colder on plug grade). The other letters in the plug type refer to all sorts of factors:- thread diameter and length, electrode design, hexagon size, resistor type or not, etc, etc. Throughout all this, the heat number remains consistent so that an 8 grade is the same heat range even if every other factor in the plug designation is different. At a guess, a good general plug for an engine of your type would be BCR8ES, but, IT IS IMPORTANT TO REALISE THAT THIS MAY BE WRONG AND THE ONLY PERSON WHO CAN DEFINITELY GIVE THIS INFORMATION IS THE ENGINE BUILDER. Certainly, a plug that is too hot might melt, leading to poor combustion and possible detonation problems Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted August 10, 2000 Author Share Posted August 10, 2000 Thanks Roger. I think I'll try some 8's though your disclaimer is noted! Engine update The bottom end has been complete disassembled and reassembled. I had a foam baffle disintegrate about 10,000 miles ago and whilst it was apart, we found some foam in one of the oil channels from the head to the crank case. When the crank came out, about 6x4 inches of foam was found behind the timing wheel and the case, blocking 2 of the channels! No wonder it breathed so much oil out all the time! Other engine build faults have been corrected as well, & hopefully, VDU7X will fire up next week. Fingers crossed. Alex Wong alex.wong@lotus7club.co.uk www.alexwong.net Home : 44-(0)121-440 6972 Fax : 44-(0)121-440 4601 Link to comment Share on other sites More sharing options...
Michael Peterson Posted August 11, 2000 Share Posted August 11, 2000 Shame about the engine Alex; On this side of the "pond" we have had some experiences with detonation of smokeless or "modern" rifle powder in large capacity cartrages like the 270 Winchester. When the powder charge is decreased in search of lower recoil (ouch!) the wrong mix of propellant and oxigen result in a flash burn as opposed to the desired normal burn rate. The resulting bang, and spike in pressure causes havoc inside the bore, litteraly hammering it. A lean fule mixture can produce the same conditions. Link to comment Share on other sites More sharing options...
Simos Posted August 11, 2000 Share Posted August 11, 2000 Hells Donkeys Alex, what are you running your car on !?! I mean octane booster is one thing but this sounds like your adding Semtex ! Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted August 14, 2000 Author Share Posted August 14, 2000 It's alive!!!!!!!!!!!! I need to run it in but up to 4000 rpm on partial throttle, it feels as good as ever. Good oil pressure and no blue smoke. Lots of photos so hopefully if I get some more webspace, I'll put it all on a page. (hence no updates on the links page for a while!) I can't thank Roger Swift enough for his help, and Barbara for feeding me for the two weeks when I practically moved in!! 2 weeks to run it in, an oil change, bolt check, stick the ACB's back on and Curborough here we come. All you SLR's in class 5 - Gordan and I (Team VDU7X) are coming after ya! cool.gif teeth.gif wink.gif cool.gif tongue.gif biggrin.gif smile.gif www.alexwong.net Home : 44-(0)121-440 6972 Fax : 44-(0)121-440 4601 Edited by - Alex Wong on 14 Aug 2000 20:04:01 Link to comment Share on other sites More sharing options...
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