Lotus Elan

distributor woes

PostPost by: rdssdi » Thu Mar 19, 2009 8:35 pm

I have had intermittent problems with my TC since finishing the restoration. The latest problem, stuck zenith stromberg air piston, apparently is solved.

As part of a thorough "tune up" I attached a timing light and checked the timing. The timing mark was all over. Scattered within 30 or 40 degrees not staying in any one spot.

I have decided to send the distributor to be rebuilt. It will be interesting what is found and what the engine idle quality and running temperature will be once the rebuilt distributor is installed.

Anyone have distributor problems causing random varied engine difficulties?

Bob
1969 Elan +2
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PostPost by: hatman » Thu Mar 19, 2009 9:22 pm

[quote="rdssdi"

Anyone have distributor problems causing random varied engine difficulties?

[/quote]

Yes, me. My car started and ran fine but just wouldn't rev beyond five and a half thou - it started missing and running erratically. I assumed it was a wrongly set or malfunctioning rev limiter but had in any case booked it in for a rolling-road set up session. The rr man said the dizzy needed a re-build because spark scatter made it impossible for him to take accurate readings; he thought the bobweights were loose and sloppy in their action.

Sent it off to Aldon for a re-build and they reported back that the whole thing was scrap and couldn't be rebuilt so I bought a replacement from them, fitted with their igniter system. Been A1 ever since. Hope you have better luck with your original dizzy than I had with mine which, incidentally, had been supplied and subsequently 'maintained' by one of the long-established (but now no longer) Lotus restoring/servicing 'gurus' (this whilst with a previous owner, but I have the invoices). Caveat emptor.
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PostPost by: paddy » Thu Mar 19, 2009 9:27 pm

I had a similar issue with timing which was only partly due to the distributor, and partly down to a stretched and no-longer-adjustable timing chain. The most obvious problem was uneven idling, making it effectively impossible to do idling adjustments (at least by the traditional methods). At higher revs it was less obvious what the consequences were. If you have conventional points you may well also have dwell angle problems (weakening spark).

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PostPost by: worzel » Fri Mar 20, 2009 11:56 am

Hi

Had this problem years ago- couldn't get it to idle evenly.

Had Aldon rebuild the dizzy and that cured all of the problems. Cost was about ?60 if I remember correctly.

Regards

John
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PostPost by: tdafforn » Fri Mar 20, 2009 12:04 pm

have potentially got around all this by using ignition triggered by a toothed wheel on the crank (pruists look away)..
Interesting experiement if nothing else as it is the perfect solution compared to the dizzy and should give a baseline to measure dizzies against
result: car is V V smooth compared to with my 30 yo dizzy.
next job, play with the advance curve
Tim
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PostPost by: john.p.clegg » Fri Mar 20, 2009 12:39 pm

Tim

Yes,you've got no timing chain slapping around,no gears meshing on the layshaft,no play in the spindle,no bob-weights thrashing around,no rotor arm flailing etc,etc..

John :wink:

P.S. can you let me have a copy of your curve when you're done?

Thanks
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PostPost by: tdafforn » Fri Mar 20, 2009 2:26 pm

I was going to ask for yours !!!
(have been reading a "4 stroke Tuning" by A. Graham Bell (not the one famous for the telephone)) V good book, and much of the practice is demonstrated using a lotus twinc). Anyhow he has some thoughts on the pluses of ECU driven ignition, and like you, highlights the benefits.. However one thing he mentions (twisting of the camshaft driving the dissy at over 10K RPM ) isn't something I'm likely to see.. Made me smile though!
Cheers
tim
PS have the stock curve for the bigvalve + dellortos at the mo
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PostPost by: rdssdi » Fri Mar 20, 2009 2:47 pm

I did not anticipate such a large response. I had my engine rebuilt by a well regarded engine specialist here in the U.S.. That is why I was so reluctant to pull the distributor and send it out. I "assumed" that they would have rebuilt the distributor as part of the very expensive engine overhaul. They did install a pertronix ignition.

Of interest, I took the car back to them as we were having problems getting it to run properly. They moved the distributor a gear tooth and timed the engine. They also said the timing chain was fine. I again "assumed" they as experts were correct. They had the valve cover off and inspected the timing chain. When I got the car home, thankfully it was trailered, I discovered the timing chain was loose and hitting the valve cover. A fraction of a turn on the tensioner solved that issue. I also noticed they neglected to replace the half round rubber seal at the back of the valve cover. So much for the experts.

When the distributor is returned I will post what they say was wrong, if anything. After all they are the experts.

Bob
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PostPost by: gjz30075 » Fri Mar 20, 2009 4:27 pm

After all that, you let them have the distributor?? :(
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PostPost by: RotoFlexible » Fri Mar 20, 2009 5:21 pm

My distributor was worn in all respects and the timing (and idle) suffered as a result. At the start of my big rebuild project a couple of years ago, I sent it to a gentleman in Ohio. He rebuilt it to better-than-new condition, with a documented advance curve as requested by my engine builder, for a very reasonable price - about $150 including parts and return shipping. He discovered that my Pertronix was intermittent and installed points. The rebuilt distributor - along with a very thorough engine rebuild - allows a smooth idle at 800 rpm. Prior to the rebuild, that was out of the question.

I'll keep the points for the time being. I haven't had very good luck with the electronic alternatives.

As for the gentleman in Ohio - I think he was getting out of the business. Rebuilding distributors was a hobby for him, but he did beautiful work.
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PostPost by: frearther » Fri Mar 20, 2009 8:18 pm

Tim,
Can you give me any details on your ignition - including sources? Thanks.
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PostPost by: miked » Fri Mar 20, 2009 8:29 pm

I have a ZS Carb Elan and my mine showed scatter on the strobe. I pulled ths dizzy and went through it. Polished the sufaces of the bob weights & back plate ridges etc and lightly lubricated. Upon replacement I had a perfect scatter free line up. I found that the oil had made a brown sticky residue which I think prevented the weights from moving as they should.
I was going to go for a new one but it is going like stink.

Mike :D
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PostPost by: rdssdi » Fri Mar 20, 2009 10:21 pm

I was misunderstood. I sent the distributor to a distributor specialist not to the people who rebuilt the engine.

The distributor specialist called with his report. It appears that the luminition ignition that had been installed by the engine re-builder was done improperly. They neglected to add an internal ground wire. Apparently the plate that the ignition module is attached to is not an ideal ground. It tends to be intermittent. Further he reported once the distributor was rebuilt and put on the machine for testing it worked for a short period of time then began to scatter the timing and the luminition failed. He re-curved and installed a new Pertronix.

The distributor has been re-curved to emulate the pre emission zenith stromberg set up. and new weights and springs installed.

It was shipped back to me today and expect it by Tuesday. I will report on the rest of the story once I run the engine. Great rush service. Same day turn around.

Bob
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PostPost by: gjz30075 » Fri Mar 20, 2009 11:12 pm

Ah, now understand. Looking forward to the rest of the story.

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PostPost by: tdafforn » Sat Mar 21, 2009 10:03 am

Hi,
The system I am running is:

36-1 toothed crank pulley
VR sensor and bracket (attaches to the sump bolts at front of engine)

Both of these are available from QED for a reasonable price and are V easy to fit

Coil pack (from Ford Escort, ebay buy ?10, included plug leads that fitted and are much higher quality than the ones I had been using)

Megasquirt V2 Xtra (bought from EXTRAEFI)
you can use an earlier version of megasquirt and if you make it yourself it'll be cheaper.

Wiring was relatively simple. clean power and earth from battery, two wire + shield from sensor, power to coil and 2 trigger wires back from coil to ECU (add a relay or two and some fuses for safety)

Then you just need a laptop to burn the desired advance curve and off you go!

Once you have the ECU you can (if you like) add sensors for water temp/ air temp and throttle position sensor (TPS). this allows you to have the ignition altered for cold starting, air temp and pressure and with the TPS you can get the ignition working properly for cruising part throttle etc.

hope this helps
Cheers
Tim
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