Ignition Timing

[spiderpete]

My 907 Elite is running reliably but does not want to rev, most likely retarded??
Noticed particularly with A road trip.
No advantage revving above 4000 - well short of red line
Pootling in town or Motorway below 3500 if fine
I would expect the engine to want to rev.

I have planned to change to some type of electronic ignition with engine out but think this needs to be done now.
Any tips on timing?
What electronic system do you suggest?
Is the practical way to remove the carbs for access to check points etc. first?

Thanks
Pete

[Pete Boole]

Have you also checked that the cam timing is OK?

Pete

[Alan_M]

Start with the basics first. Have you put a timing light on the car. Is timing set correctly? Is mechanical advance working correctly? Do you have vacuum advance or retard capsule? Is that working - can apply vacuum with mityvac or similar to test.
As Pete says - is cam timing correct - don’t assume this, even if last belt was replaced professionally. Mine was out when purchased and had recent belt change by Lotus specialist!
If you have points - check dwell angle.

Low power at high revs - ? Fuel starvation. Is float level correct? Blocked jets?

Good luck sorting

[spiderpete]

Good advice guys
Is it usual to remove carbs to work on dizzy?
I will discover exactly what is on the car as I strip
Could be it is already electronic
I am right that the engine should love to rev, with the power at top end?
Pete

[Hawaiis0]

Airbox removal should give plenty of room to get to dizzy.

Check your fuel filter bowl for sediment. Some guy just took his engine out because of a clogged filter!

[spiderpete]

Hi all
Airbox off - really lucky - one of the four screws inside the box holding to the carbs was undone by around 20mm and one was missing
It had dropped into the condensate drain hole.
I wonder who last worked on the carbs or ignition???
Nice to have a lucky engine.

1st purpose was to see if standard points and condenser were fitted - they are
Number on the dizzy is 41150 A which does not appear in the list.
Vacuum advance is blanked off

Any ideas?

I do find I am totally puzzled with the 9 types of distributer and 7 different timing options which do not match the number on the dizzy.

I am however looking to fit Accuspark, or other electronic system.
I have seen good and bad reports on Accuspark - comments or other options?

Maybe this takes away which type to set up but timing advice would be a help.
Not quite as critical as a turbo engine but pinking still a bad idea.

[Tanz]

I fitted the Aldon Ignitor in Aug 2014. 19,500 miles later still OK
https://www.aldonauto.co.uk/productlist.aspx?SID=53

[Alan_M]

Not cheap, but there is also the 123 ignition distributor. This is programmable and has an immobiliser built in. I have one fitted to one of mine - no problems with reliability as no moving parts for mechanical or vacuum advance.

[spiderpete]

I have ordered the Accuspark, I will report what I think of it
Pete

[DavidOliver]

Hi Pete.
First of all I assume you have an Elite engine, or at least original cams, carbs etc.
Then, have you always had this engine rev hesitation or is it a recent new feature.

The following data is from the Elite 1979 Workshop Manual:

Distributor Revision May 1978 Type 43D and all cars from engine number 14736.
Distributor should have vacuum advance fitted and working.
Note that the rotor arm had a speed limiter incorporated, check that it does not operate inadvertently.
Static Ignition timing 12º BTDC (Federal/North American for Zenith carbs is 8º)
Contact breaker gap .35/.40 mm.
Distributor advance from static 1000 revs none
1500 revs 3.0º
2000 revs 10.0º
2500 revs 16.0º No further advance.

Suggestions Before changeing anything diagnose the problem, if you fit electronic and the problem remains you are two stages behind solving.
Check spark strength, pull a plug lead and check spark length against engine body.
If spark is weak consider a new ignition coil.
Remove distributor cap, set crank to TDCentre with rotor arm pointing to no.1 cylinder contact, and remove distributor.
Remove points assembly for access to centrifugal weights and check for free working, spring loads, clean and regrease.
Preferably install new points, condenser and set gap acccurately. Inspect cam lobes ( thus a first checking of dwell angle).
Do not remove carbs but inspect flexibility of spacer plates and for air leaks. Replace 8no. Airbox fixing nuts with new selflock.
type.
Check carburettor fuel bowls for cleanliness, if not perfectly clean remove and inspect main and idle jets.
You can also check spark plug colours for fuel mix and cylinder condition, best done with a hot engine and correct engine cut.
I assume your throttle pedal fully opens the carbs.

Hope this helps.

Dave the cog.

[spiderpete]

Thanks to all for the advice, it has been a great help.

Accuspark on.
Straightforward fit.
Can't do static timing so set to 3-4 degrees on tickover
At 3500 the advance is around the 25 degrees given for most of the dizzy iterations.

Short test run - no bonnet or airbox
Transformed, loves to rev.
No sounds of pinking on high throttle low rpm.

Maybe mechanical advance jammed on old dizzy.
Should check but most likely dizzy will go into store if someone wants to put back to points and condenser.

Thanks again for help and advice
Sign off now until next issue!!!


Pete

[dancroft1984]

Start with the basics first. Have you put a timing light on the car. Is timing set correctly? Is mechanical advance working correctly? Do you have vacuum advance or retard capsule? Is that working - can apply vacuum with mityvac or similar to test.
As Pete says - is cam timing correct - don’t assume this, even if last belt was replaced professionally. Mine was out when purchased and had recent belt change by Lotus specialist!
If you have points - check dwell angle.

Low power at high revs - ? Fuel starvation. Is float level correct? Blocked jets?

Good luck sorting

Or fuel pump on the way out?