GaryH Posted November 5, 2007 Share Posted November 5, 2007 You can certainly see why you need to twin plug with that shape of crown. Er- just to check my engine knowledge RB , do you need to twin plug because that shape of piston crown divides the combustion chamber into two halves, reducing the flame front and potentially causing detonation, the two plugs ensuring that both halves of the mixture are properly ignited ? Link to comment Share on other sites More sharing options...
Richard Bernau Posted November 5, 2007 Share Posted November 5, 2007 Er- just to check my engine knowledge RB , do you need to twin plug because that shape of piston crown divides the combustion chamber into two halves, reducing the flame front and potentially causing detonation, the two plugs ensuring that both halves of the mixture are properly ignited ? Exactly grasshopper ! Link to comment Share on other sites More sharing options...
bruceb Posted November 5, 2007 Author Share Posted November 5, 2007 Looks that way doesn't it. Does your engine builder deburr (or whatever the term is) the sharp edges? You can certainly see why you need to twin plug with that shape of crown. here are a few comparison photos of the different style of pistons A Max Moritz 3.2 single plug compatible piston, crown is high and flat although sloped towards the spark plug apparently A 9.5:1 JE showing a flat top crown but sloped again towards the single plug, Whose piston is this I wonder And here is an RSR style piston which has a really high domed crown that splits the combustion chamber in two and needs twin plugs And my JE's with flat crown but no slope, better off with twin plug for sure, but its not as peaked as an RSR style piston so single plug might be an option? I'm going to ask about the de burring Link to comment Share on other sites More sharing options...
johndglynn Posted November 5, 2007 Share Posted November 5, 2007 I'm pretty sure they would deburr, though the ones we saw looked well finshed to my eye. I think twin plug helps even flatter pistons, Henry recommends it on most stuff AFAIK. Link to comment Share on other sites More sharing options...
GaryH Posted November 5, 2007 Share Posted November 5, 2007 (edited) Exactly grasshopper ! Haha - I 'knew' you were going to say that A Max Moritz 3.2 single plug compatible piston, crown is high and flat although sloped towards the spark plug apparently I was assuming that since you're keeping the CIS (for now) you'd be going Max Moritz pistons Bruce ? Btw, what are you doing distributor-wise for your twin plug setup ? Edited November 5, 2007 by GaryH Link to comment Share on other sites More sharing options...
johndglynn Posted November 5, 2007 Share Posted November 5, 2007 Btw, what are you doing distributor-wise for your twin plug setup ? After mucho pondering of all the options, I decided to keep the engine in 3.o form with the rebuild spec like this:- Tuthill spec lightweight JE pistons Clewett crankfire twin plug Link to comment Share on other sites More sharing options...
MrPerkles Posted November 5, 2007 Share Posted November 5, 2007 I found this old thread whilst researching about the car i am buying,quite interesting Click Link to comment Share on other sites More sharing options...
GaryH Posted November 5, 2007 Share Posted November 5, 2007 I read that but was wondering whether Bruce was going to use a modified or 964 dual distributor with it or go for the complete Clewett distributorless setup ? Link to comment Share on other sites More sharing options...
bruceb Posted November 7, 2007 Author Share Posted November 7, 2007 The crankfire ignition has arrived in Greece but is now stuck in customs at Athens airport. I was hoping for VAT and duty free ride through customs and had a good plan to achieve it, worse case was VAT at 20% It looks like it has back fired badly. Greek customs want the following payments on a commercial invoice for $1900 VAT and taxes......................225 cutomes clearance ................100 Paper work fee......................40 handling charge.....................50 management fee....................50 other ....................................15 grand total to you Mr Englishman in a hurry .......480 euro's or 330 quid thats 35% of the purchase price, the robbing feckers Link to comment Share on other sites More sharing options...
johndglynn Posted November 7, 2007 Share Posted November 7, 2007 Forward it to my address and I will pay english duty on it. Link to comment Share on other sites More sharing options...
jevvy Posted November 7, 2007 Share Posted November 7, 2007 I was thinking the same John - there must be a way to dodge it somehow with a cheeky forward of some description. If not what a bummer - no doubt assigned to the "lets forget about it" part of your brain so the pain should be short lived Link to comment Share on other sites More sharing options...
bruceb Posted November 12, 2007 Author Share Posted November 12, 2007 Took the pain and paid up so now I have this: Here is the complete twin plug kit these are the coils, six in total and very heavy Here is the box of tricks that makes it all work this bit fits in the hole where the distributer went I chose Clewetts own ignition wires in "non bling black" for that sleeper look and finally some small brackets to stop the bottom spark plug caps from falling off the engine assembly is coming on fine and is on schedule for the end of the month, fingers crossed. Unexpectedly though there appears to be a bit of wear in the valve guides, more than would be considered usual after 5000 miles, so another new set of guides are going in as we dont want valve heads getting all hot and falling off! Link to comment Share on other sites More sharing options...
AirCooledExcellence Posted November 12, 2007 Share Posted November 12, 2007 Whens the ignition stuff going on then mate? Link to comment Share on other sites More sharing options...
johndglynn Posted November 12, 2007 Share Posted November 12, 2007 This board just gets sexier every day Link to comment Share on other sites More sharing options...
bruceb Posted November 12, 2007 Author Share Posted November 12, 2007 Whens the ignition stuff going on then mate? before the end of November ACE, I have just repacked it and it will be on its way to Essex tomorrow, Link to comment Share on other sites More sharing options...
johndglynn Posted November 12, 2007 Share Posted November 12, 2007 before the end of November ACE, I have just repacked it and it will be on its way to Essex tomorrow, You should have just sent it to Ace's house, he has a regular trailer service to Neil's place Kidding Ace - any more news to put in your other thread? Link to comment Share on other sites More sharing options...
bruceb Posted December 7, 2007 Author Share Posted December 7, 2007 Well the end of November came and went, ACE did his queue jumping bit (surprised Carlo did not step in as well ) but finally the engine build is almost complete. It should be running late tomorrow with a bit of luck. I hope to collect the car monday morning, fingers crossed there are no problems over the weekend Link to comment Share on other sites More sharing options...
bruceb Posted December 13, 2007 Author Share Posted December 13, 2007 Finally the car is back in its garage in Guildford and running I had planned to collect the car on monday but a phone call late on sunday night delayed this a bit. My engine oil coiler had sprung a really bad leak. There was no option other than to replace it, so a new euorcarparts item ws fitted on monday. I tell ya you dont want one ot these things failing, talk about an arm and a leg! So pick up was arranged for tuesday, a nice clear day for a run up to Essex. The engine runs a treat, its very very smoothe and quiet, no problems at all with noisy JE pistons lurveerly. The exhaust makes a nice bark as well, and to my rusty IB ear did sound sharper than the old engine, I think this must be the twin plugging. The instalation of the pair of crankfire coils prooved a bit difficult with the bulky CIS injecgion system. One coil pack fits a treat on the engine bearer in the same position as the 993, but finding space for the other prooved tricky and it sort of sits where the old coil went. I'll move it later for sure but for now its works. The ignition brain is currently temporaraly installed inside the car on the rear quater. It is soon to be moved out of site under the rear speakers. The motor is going to get very carefuly run in, so far I have racked up 300 miles on a retared ignition setting but it feels eager enough. There is a slight problem with the clutch which wil be sorted later, other than that it needs more miles on it before setting up with power runs on the dyno. So I've left it in Guildford with plenty of petrol in it and told the old man to get cracking! Link to comment Share on other sites More sharing options...
Dr_Danger Posted December 13, 2007 Share Posted December 13, 2007 Great news Bruce! Looking forward to hearing your engine! Link to comment Share on other sites More sharing options...
AirCooledExcellence Posted December 16, 2007 Share Posted December 16, 2007 Glad it's all worked out for you mate, looking forward to some engine bay shots once you've got everything tidied up! See you at Snet in Feb then ? Link to comment Share on other sites More sharing options...
bruceb Posted January 7, 2008 Author Share Posted January 7, 2008 The engine has nearly a thousand miles on it now without incident. Should be over the 1500 mile mark soon with a nice weekend run up to the NEC autosport show on Saturday. The car is then off to the Harvey's for final setting up on the rolling road. So should all be ready by mid February ready for Snetterton. Link to comment Share on other sites More sharing options...
bruceb Posted February 10, 2008 Author Share Posted February 10, 2008 The engine now has 1500 miles on it, and its sounding good so yesterday I took it out for a bit of butt dyno testing in advance of a trip to the Harvey dyno this morning. The crankfire ignition timing had been set very safe for running in, to make sure there was no chance of detonation. So with a few tweaks of a screw diver on the ignition box I dialled in a bit more advance. The engine certainly picked up better but started to detonate around 4500rpm. A bit more tweaking and it the engine was running ok but was still way down on power. At this point I was a bit dissapointed as it seemed the engine would not take enough advance to make good power without detonating. Anyway an early start this morning and the car was on the dyno by 10.00. Very quickly it was apparent that the fuel mixture was very very weak, anywhere between 0% and 2% CO, it needs to be around 5%. So we called off any further runs today and the car is with Neil pending a modified WUR to get the mixture right. The car will go back on the dynop later his week. So with the mixture set right confidence is high that the engine will produce good power. The morning was rounded off in the local greasy spoon called broxborne Delight cafe with ACE, Carlo and Charlie(mini Carlo). Link to comment Share on other sites More sharing options...
johndglynn Posted February 10, 2008 Share Posted February 10, 2008 Bittersweet BB - good to know about the mixture though. Link to comment Share on other sites More sharing options...
carlbon Posted February 10, 2008 Share Posted February 10, 2008 Bittersweet BB - good to know about the mixture though. It sounded fantastic on the dyno though No mechanical noise, a nice growl, and the fan doing its thing... Link to comment Share on other sites More sharing options...
bruceb Posted February 10, 2008 Author Share Posted February 10, 2008 (edited) There is no doubt that the engine is very quiet, just fan noise and raspy exhaust as Casrlo said. There is zero mechanical noise from the JE pistons which seem to be working a treat. Any how a little bird tells me Dangers new engine, which is a very similar spec as mine, will be on the dyno tomorrow, should be useful to compare notes Edited February 10, 2008 by bruceb Link to comment Share on other sites More sharing options...
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