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Crossflow missing at top revs, where to start?


dikko

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Recent carb p pump plugs old electronic ignition, missing at 7,000rpm

How and where should I start?

I'm thinking I should take it straight away to a rolling road to track it down rather than hunt it down...?

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There is every chance that something is failing/breaking down... 😬...but the question is do I use a lot of time guessing or hoping to find it.

I can't go and check it easily and it ain't road legal...

 

Rolling road and a big bag of bits mebbe...

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when I had the same sort of problem I decided to go straight to the rolling road .. it was a good decision, as it happened I would have ended up spending a month of sundays and a lot of money trying to track it down, purchasing a lot of unnecessary bits along the way - the RR nailed it immediately
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If you haven't replace the Distrubtor cap, rotor arm, plug caps (only use NGK or well known make), plug leads then change them all, the Distrubtor Doctor (google search will find him) is a good supplier of rotor arms the Lucas replacement ones are rubbish short between rivit and retaining clip, Auto Electrical Supplies are usefull and Lucas cheap coils etc, I dought if it is the coil unless its very old easy to swop over from 61?

( my misfires have been plug caps /dist caps/ rotor arms , I alway keep a spare set of everything now makes hunting the missfire easier!!)

 

Low battery volts will cause a missfire if you have electronic ignition

Brian

 

Edited by - Brian Soper on 22 May 2012 13:11:48

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Cheers guys, fortified by johnv... no rev limiter. will check springs Rog. Brian, thanks for contacts.

Silverstone was fun but short-changing due to miss lost me 10-12th... Spectators tell me it was freezing tho...

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Thanks elie but it's all-matching set of V12 Lucas..converted that is..was bomb-proof..might be it so Sun tuner might do the trick too except it works OK but not under load...

 

New baby next door so I have to plan garage noise well....

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I recently had a similar problem as the engine got hot. It was the electronic ignition (Aldon Ignitor) failing as it got hot.

 

As the enginge got hotter the misfire got earier - started at 6k rpm then gradually moved down the rev range to 4k rpm.

 

Rebuild at Aldon wasn't too expensive, proper advance curve now for my supersprint and it runs really well.

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Strongy! Beware!

Eugene may be along at some point to explain how an Aldon unit can electronically 'fight' a Rev counter AND LOSE...

He and I had one on our Sevens, they can take 2-5 years to break down..and down they went.

 

For a good unit that may be described as Bombproof go to Bestek (ebay on line) sells out of a workshop near Gatwick at the rear of a B&B that only accommodates airline stewardesses!!!!!!!!!!!!!!!!!!!!! *smokin* *cool*

 

A very attractive business.......

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Valve springs all OK as are tappet clearances. Carefully checking as I wait for rolling road appointment....
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Had a recent issue with my xflow - missing through the rev range when hot, so not quite the same as your issue, however after changing and checking various parts it turned out to be spark plugs breaking down when hot. The plugs were new last year and only done 2000 miles. As I said not quite the same issue but only a few quid to try to elliminate.
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Here we go. Rolling road two days ago........................prep was to look at fuel filter and check plugs and dizzy cap - clean and replace.

 

Started missing straight away (at top revs) ignition system working fine, fuel read-outs good. By the end of the run-up it had cleared. "Do you use Millers CVL Octane booster" "Yup" say I........"That'll be it then, it's a regular occurence...." and it was...it seems.

 

When the fault occured it was winter (3 weeks ago) practice was partially wet and the car didn't get up to temp. Come the race a build up of Brown - rust like colouring film on Spark plug electrode (noticed when plugs removed for check) effected the insulation and caused the misfire.

Now, Mr King. I have followed your instructions diligently all these years and religiously fitted your recommended plugs (until 3 years ago when I realised I'd got the Seven and the Formula Ford plugs mixed the wrong way round - after 17 years racing) then fitted the right ones... B8ECS instead of B7ECS...

Anyway,

I was told BP6ES was the way to go to keep the CVL bugs at bay. Ran it up and got extra BHP! (I think the operator can get an extra 100 bhp if he wanted to actually).

 

T'was Peter Baldwins RR I was on and he 'phoned Formula Ford engine builder and racer Simon Davey who recommended the plugs.

A bit of an odd one that, would have had me guessing a lot. Saying that, It's not been out yet (until Snetterton 9th June) if it turns out it's still doing it and be fuel surge I'll feel daft for saying all this....However, if I win I'll buy everyone in the club a drink!

 

Peter is a top man and is at Wilshers Garage, between Cambridge and Royston, Herts.

 

Oh, added to say, I used TOTAL petrol for Silverstone from a garage that was running stocks low as it was about to be bought out by Esso. There may have been a quality issue there too.

 

Edited by - dikko on 31 May 2012 09:18:46

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Hey hang on! I did mean 8's....

 

in 2010 SOMEONE said this.........

 

"The 8s are colder and would be recommended for track use over the 7s. But that assumes these grades are suitable for that particular engine spec in the first place and on that I can't comment without knowing a lot more about the engine such as compression ratio, etc.

 

Generally though an 8 is a safe choice in a Crossflow."

 

Now, who was that?

 

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Blimey - so a general comment (aimed at Caterham installations which have a much higher compression ratio than a FF1600) has been extrapolated into into a definite recommendation for FF1600's.

 

The point was that most (but not all) Crossflows in a Caterham will be safe on 8's for track use. If the plug is a little too cold, you might get a bit of fouling, but it it's too hot you might get melted pistons - which do you prefer?

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You did actually tell me to run those 20 years ago (8's in the 7 & 7's in the FF) but I'd got it the wrong way round I thought when you pointed it out 2 years ago. Seemed to go well enough...

so then, are the BP6ES a hot plug and maybe too hot?

 

I've also got a technical question on FF Engine cam scrutineering for you if you have 5 minutes thinking time...

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