Valve timing 1979 Lotus Eclat

[TimHaydnJones]

I have a 1979 Eclat 521 which stood in the garage for many years but which I'm trying to get back into use.
Last year, after some work, which included a new cambelt and complete re-build of carbs, I found the
performance to be poor, there was a lot of induction noise (partially caused by the fact that the bloke who did the carbs couldn't get the mix right and ended up leaving the air box off).

On another forum, someone commented thus
"I had a lot induction noise, very poor performance, and mixture issues, which it transpired were because someone had set the cam timing incorrectly. Specifically, the exhaust timing was out"

I found this interesting, partly because the engine was non standard (Vegantune 200bhp in place of standard 160bhp)

I had difficulty cross-referencing because of difference in terminology
For Ignition Timing, the standard Lotus Workshop manual says
9° BTDC nominal static
25° BTDC @ 3500/4,000 rpm

but the paperwork from Vegantune says 21° strobe @ 1000 rpm
How do I compare these two figures? Are these the same or not?

Also, the Vegantune paperwork refers to Inlet and Exhaust valve timing of 104 full lift ATDC
The Lotus manual refers to 104° MOP
Are these the same or not?

It's not until I have ruled this out that I will revisit the carbs but can anyone recommend a top carbs bloke in the North East Wales/Chester area?

Thanks in anticipation

Tim

[lotus-types]

TimHaydnJones said:

I had difficulty cross-referencing because of difference in terminology
For Ignition Timing, the standard Lotus Workshop manual says
9° BTDC nominal static
25° BTDC @ 3500/4,000 rpm

but the paperwork from Vegantune says 21° strobe @ 1000 rpm
How do I compare these two figures? Are these the same or not?

Also, the Vegantune paperwork refers to Inlet and Exhaust valve timing of 104 full lift ATDC
The Lotus manual refers to 104° MOP
Are these the same or not? Tim

Yes, MOP (maximum opening point) is the same as FULL LIFT but both inlet & exhaust are not ATDC. The Exhaust is BTDC and the Inlet is ATDC.

Firstly I would set it to 9° static.
If it runs check with a strobe light and rev counter if is advancing to 25° @ 3500/4,000 which will be the maximum amount of advance. If incorrect adjust until you get this correct,the maximum amount is more important then the static setting, then check at 1000rpm, the chances are it will be correct but if not it may need a distributor overhaul.

[davepoth]

Assuming this motor is running Webers and someone has been "tuning" the carbs, I think you'll be best off getting it looked at by a specialist with a rolling road. It might be worth putting a post in the Lotus bit of the forums.

[droopsnoot]

I've heard good things about Mikeanics in Congleton, though I haven't used them myself. I'm trying to decide between messing around myself or dropping a couple of hundred quid on a rolling road session with them. The latter would be easier, but I don't learn anything and would need to do it again for the other car when it's running. Fortunately I have access to some space where I can run it into third to get a feel for what's going on.

I've been trying to get my head around where I should time the Firenza just recently. Reading the Sportpart manual (for the Vauxhall) they recommend disabling the vacuum advance for example, so that might lead to a higher static advance. The Dellorto tuning book suggests many engines would need increasing to a minimum of 12-15° with appropriate modifications to the distributor to limit overall advance. Right now it's on about 15°, which feels OK but still seems a bit high, others I know have it at the standard 9°.

Edited by droopsnoot on Monday 15th April 11:08

[droopsnoot]

Oh, one other thought. I had trouble getting a decent HC figure for the MOT, which turned out to be largley caused by a leak on the servo pipe that was letting air in.

[AllNines]

Yep, try Mikeanics. He is used to 900-series engines, having worked on Sunbeams a lot (a couple of my cars have been on his rolling road). A modified engine should be no problem. Oh, and who swore? Should be Dell'Ortos on these engines.