123 Dizzy for 1300 race car?

[Richard_M]

I'm suspect of the Lucas dizzy on my Spitfire 1300 race car - and am wondering whether to have it reconditioned and setup professionally, or to go with a more electronic method.

Background : This is a small crank 1300 engine, bored to +60 with a Kent 264 race cam and high flow head.
I've just finished fitting new twin Dell'orto DHLA40E carbs - with a good choke and jetting setup. Before starting for the first time, I checked the ancillaries and noticed a fair degree of crud (some from dry powder fire extingusihers - long story) inside the dizzy. This is a standard Lucas unit with the vernier and vacuum unit removed, and a '15 degree' arm. It also has Pirhanna optical electronic points.
So I disassembled to about halfway and cleaned up the obvious crud - but overall it looks pretty tired in there.

Reassembled and got the car started, but lumpy and reluctant to rev. This worried me - I know it will need a good rolling road session to setup the carbs finally, but I'm confident they should be in the ballpark up to about 8000rpm.
Checking the timing using a strobe, the car was at 30+ degrees advance at idle - yikes!

So, being a stranger to the way of the dizzy, I did some research last night on what to look for in a sorted dizzy. Well, this obviously isn't. With the cap off, the rotor can be turned ACW approx 30 degrees, but doesn't return to static - there's about 10 degrees of play. Taking the plate off reveals that the springs aren't pulling the arm back sufficiently.

I'm about to test some shorter springs from an old, gash Lucas dizzy off the shelf - these do seem to return the arm, but it clearly needs sorting properly really.

So - do I send it to somewhere wonderful and have it reconned then setup for the characteristics of the race engine, or could I go for a programmable 123? Getting a 123 gives me a new dizzy that can be programmed for the advance curve I need, and avoids the recon cost - but will it stand up to race use and work happily up to circa 8000RPM?

Thoughts gentlemen?

Richard

[Clive]

Are you allowed electronic ignition like 123 on the race car?
I was under the impression that when race cars are running(ie above 3000rpm), the dizzy is always at max advance so the condition isn't too important, they are just set to give 32 degress or whatever and that is good enough.
Otherwise the dizzy doctor should be able to set one up for you with a suitable advance curve. Other specialists too.

[CRAJ]

I'm guessing you are considering the distributor doctor Richard? Seems to have a very good reputation and can build to suit your engine.........alledgedly. Surely a rolling road is the only place to tune a component to suit the engine. Also after having one rebuilt you are still at the mercy of the service items you fit to it.

I have heard it said that the 123 has a curve to suit everything , except the engine that you have just fitted it to, if you know what I mean ;)

Had you considered a megajolt jobby?

Colin.

[Richard_M]

Hi Clive

Yes - electronic ignition is allowed within CSCC regulations - I could even go MegaJolt if I thought it would help but my understanding is that its a case of staying at 32 most of the time too.

However, the engine is behaving pretty strangely, and I don't want to damage it by being too advanced at low revs.

Richard

[James]

If you can go for a megajolt then don't waste money on a 123 — you want the megajolt no without a doubt.

[Richard_M]

MJ eh?

Well, it's possible - I even have a kit here. The only significant work to do is adding a trigger wheel to the aluminium crank pulley, something I'm a little loathe to do because of how much money's been spent on balancing the bottom end...

But - it it overkill for a race engine that lives at 4000RPM plus apart from idling..?

R

[thebrookster]

1819 wrote:

But - it it overkill for a race engine that lives at 4000RPM plus apart from idling..?

R

I would say no, purely from a point of view of absolutely no experience here!!

Reasoning:

If you look at everyone else's MJ conversions on here etc, they all seem to make decent sizeable gains from fitting this, and actually being able to tune the ignition properly, so to speak. So I cannot see any reason why this would not also apply to your race engine? OK, different use, but surely there must be an improvement in having a tunable 'map' over simply slapping a static 32 degrees in place??

Cheers,

Phil

[Richard_M]

Thanks for the thoughts chaps.

With a chance of getting the car RR'd and to the Blyton Park track day next Friday - I'm resisting the MJ idea, but it sounds like a possible over Winter for next season.

In the meantime, I've tried my stiffer springs in the Lucas Dizzy AND an entirely different Aldo dizzy from my mk3 road car.

In all cases, the engine idles happiest at what is indicated on the pulley as +30 degrees. So maybe the dizzy isn't the fundamental problem here. Or maybe the timing mark is out significantly? I did a TDC test with a straw through the spark plug hole earlier and it seemed roughly correct - maybe I'll try a more accurate measurement, but fundamentally I don't get it - why would it want to idle at +30 degrees? Is it the 'bonkers' cam?

(think)

R

[Nick Jones]

If you are allowed programmable ignition then it's a no-brainer.  MJL is king.  However, the mappable 123 (not the one with switchable curves) does much the same thing.  Costs more, but easier to install.  My only caveat on the 123 is that with a big cam and webers you might do better to use a throttle position sensor rather than manifold pressure to sense engine load.

I disagree with the common racer (and race tuner) opinion that 3D timing (ie with engine load input) is of no benefit on a racecar.

Are you sure you TDC mark is in the right place?  Having said that, an engine with a wild cam will have v poor cylinder filling at idle and will thus want lots of advance (though 30º does seem like quite a bit!).  Wouldn't have thought it will start with that much advance though as it will tend to try and run backwards, which makes the starter unhappy!  An big advantage of programmable ignition is that you can accommodate these odd timing needs, which can go a long way to making a wild cam more civilised and tractable low down.

Nick

[Richard_M]

Hello Nick

And so we meet on the other side... :)

Thanks for your input. I'll establish the accuracy of the indicated TDC tomorrow but in the meantime have a decision to make on MJ. I too would prefer to use TPS in a race situation.

My immediate problem is compounded by the very rough way the engine runs as fuel is added - lumpy, backfiring through the carbs and reluctant to get above 4500ish revs.  Of course this could be down to the new carbs. This is their first use since acquisition and gentle refurb by a mutual friend. The lump runs so badly that I've gone down the precautionary route of checking timing first to avoid damage by detonation etc.

R

[James]

The other negative point of the 123 (or any dizzy) is that the timing comes off a chain from the crank and then sent through a cam.

MJ takes it direct from source.

[piman]

Hello Richard,

although it's a bit of a catch 22, you do need your fuelling to be reasonably good or all the timing tuning will be wasted if you correct the fuelling afterwards.

Alec

[Richard_M]

Well, TDC is pretty much TDC. I've done a more accurate check today and the timing cover pointer is perhaps 1 degree out.
Checking my timing light is next - thanks for the offer Colin - and then it really is decision time...

Richard

[Richard_M]

.... or not.

Good friend Pete (Yorkshire Triumphs) brought me round his timing light tonight (sorry Colin).

All it cost was tea, and he was dropping by anyway. Gives exactly the same results as mine - only happy idling (circa 1250RPM) at 30 degrees advanced.

But, what with him knowing a thing or two about the way of the Triumph, he immediately said 'that's fuelling'. His opinion was that the stuttering and popping back through the carbs was simply too much air/not enough fuel. So we got it idling relatively happily at +30, then flicked some fuel into the Dell'ortos' trumpets. Result? Idle picked up and the advance dropped to approx +10. Seemed happier to pick up on the throttle too.

Conclusion (so far) - the carbs are set up way off, even on the idle jets.
I'll talk to the person that specified/did the setup and see what he thinks - think there might be a long story to develop there; we'll see.

Richard

[Nick Jones]

Check for inlet air leaks before condemning carb setup?

Nick

[Richard_M]

Good thinking, will do....

[RRR]

I have run a 1300 with a similar build to yours, and would not expect it to tick over cleanly with this cam.
In terms of timing, a smoother idle can be achieved by advancing the ignition, as you have found. However with a conventional Dizzy this will still advance the timing with an increase in RPM.
The Lucas is generally timed ~10deg BTDC, and gives a timing advance of ~22deg at full advance, giving a total of 32deg achieved by 4000rpm.
Therefore if your static timing is at 30deg BTDC the motor is trying to work with 52deg 4000rpm  and so you find the engine cannot maintain proper combustion at higher revs.(Engine will not rev over 4500rpm)
I assume the engine is running a compression of something in the region of 11:1 or higher being a race engine, and the danger here is with pre-ignition, which can quickly damage the rings or melt a piston. With this sort of C.R. I would start with a maximum advance of 30deg before properly setting this on a rolling road.
The 123 Dizzy whilst it would provide a more consistent timing, it would not address the basic issue,s as the pre-sets offer the same basicadvance characteristics, only tuneable at tickover, 2500rpm, and 4000rpm.
As you have discovered, I think you will get a better result by increasing the idle jet, rather than running excessive advance in order to smooth out the combustion at low rpm.
A conventional dizzy(which the std 123 distributer is) will not give youthis functionality of tune-ability like a map-able ignition, and beware of pre-ignition.

[Nick Jones]

Generally agree with above except to note that there are now two versions of the 123 dizzy.  The original, with switchable curves, which do indeed suffer from the same limitations and newer one, which is supposed to be fully mappable which should make it nearly the equal of the dizzyless systems.

Nick

[piman]

Hello RRR,

if 32 degrees is the maximum required then essentially a distributor with about 2 degrees advance is required, unless the static timing needs to be closer to 10 or 15 degrees to be able to crank the engine and start it? If it starts easily at 30 degrees advance then a simple sleeve stop on the distributor cam stop will limit the advance.

Alec

[Richard_M]

Thanks RRR, Nick and Piman.

I'm on the hunt for air leaks today.

In terms of overall advance, I can get the engine to idle fairly happily at circa 1250RPM, which is when it shows +30deg advance. Applying throttle from there does increase the advance, but only marginally - maybe to +35deg - its a little hard to tell.

So I tend to believe the dizzy is operating properly, and I have it out of position to force a stable idle - instability being caused by a bad air/fuel ratio. This could be the jetting OR an air leak, so I'll check for leaks today and report back.

Nick - it was the programmable version of the 123 I was considering as it gives much of the flexibility offered by MJ - but I do hear James' comment on the inherent instability of the dizzy pedestal when compared to a crank sensor, especially at 8000RPM...

R

[James]

Add to that the direct nature of the spark from the coil to the plug — after that the whole idea of a thing spinning around distributing sparks through a dizzy cap and then through the leads all feels a bit antiquated.

:)

[Richard_M]

Hmmmm.

Spent some time today checking for leaks with WD40 and carb cleaner. Nothing obvious, but there did seem to be rev fluctuations at times, so I removed the carbs on their manifolds, prepped the surfaces, adjusted the lugs for equal height on inlet and exhaust manifolds, applied some Stag sealant and refitted, torquing up the nuts proper tight.

The car is now happy to tickover at 1750RMP with +15deg advance - so an improvement.
Blip the throttle though and it dies in a number of ways, and there's still much popping through the carbs.

So jetting seems the most likely issue. I've booked a session with Dennie Vessey and his rolling road for next Wednesday - we'll see what the real problem is and how far off the proposed jetting is. All this may avoid the need for MJ or 123 - but it's still something I'll consider over the Winter for next season.

Richard

[CRAJ]

So the Gulf spitfire may still be blasting around Blyton this time next week Richard? Let's hope so, I think my internal organs might be able to withstand a couple of laps crashing around my rib cage in a full harness! Not use to the extreme Gs of a well setup race car, more the extreme lean of a 70s 'luxobarge'. ;)
Not long now.

Colin.

[Richard_M]

We'll find out tomorrow AM - Rolling Road sess with Mr Vessey, should be interesting (meaning exciting or disappointing, delete as appropriate)...

Hoping to get her to Blyton on Friday - even with her battle scarred bonnet - we'll see.... :)

[Richard_M]

4 hours well spent with Mr Vessey and his tuning gang.

Idle jets and holders were well off. Sorting these allowed a good idle at about 1500 and better pick up. That allowed the ignition timing to be set properly at about 4000. Still popping through the carbs at this stage, and mains and aide were next. Dennis suggested putting a bung in the exhaust for a lambda sensor so he could tune more accurately, and with this done mains/airs were played with on a series of power runs, trying to make it more lean at lower revs put keeping it fully-fuelled at full revs.

End result? 100bhp at the wheels and 127 at the flywheel at 7000rpm.
There may have been a tad more in the head if valve bounce hadn't come in at 7500 - a mechanical rev limiter!
Will try to stay sub-7500 on Friday at Blyton. Lots to do now refreshing suspension etc tomorrow.

All in all a good day, and a genuine 100bhp/litre. Nice.

Richard