Setting Timing S/E engine with 40953 Distributor

[AHM]

Hi All,

I?m after some help setting the timing on the S3.

I know it isn?t difficult but I have now read too much ? books manuals the archive.

So here is the issue.
The engine was the 47th in the Mk2 sequence. As such appeared to have been in the Lotus ?use up what is on the shelf? methodology having ?A? type pistons and a 40953 distributor. It is original to the car and having only done 45k miles with one owner and it is still on the standard bore size.

Having been ?stored? for 28 years I rebuilt the engine as follows:
Nos ?C? type pistons (still on std bore size)
S/E cams (it is an S/E engine)
Weber 18?s to S/E spec (cleaned and rebuilt)
Rebuilt head with the lightest of skim ? assume std compression
Big Vale valves and seats ? but no porting work done.
Lumenition optronic ignition fitted.
Standard petrol

Gently run-in over 1000 miles ? I've changed all the fluids and done the checks except tappet clearance and setting the timing...... What to?
Miles Wilkins book states that the 40953 advance is not required and ?big vale must not have the 40953 fitted, otherwise severe pinking will occur?

For getting her running I set 10 deg static and that seems ok but I know it is a lot more scientific than that. From experience can anyone suggest a starting point?

[Quart Meg Miles]

You may have Big Balves but not the cam or porting so won't have the much greater torque of the full Big Valve engine. I would use the standad settings for the 40953. I didn't notice any changes with 'C' pistons in my last rebuild though I had to be careful with clearances.

[Mazzini]

In the 1980's I had a '66 S3, it had a 40953 distributor with S/E cams and chokes, it wasn't particularly happy in the mid range, but at higher revs it flew. I took it to a local rolling road, thinking it was a jetting problem, the guy there spotted the advance curve was out, a few quid later I was the happy owner of a 43 D4 distributor, which transformed the car, but then it went onto three cylinders because the dizzy cap rubbed on the inlet manifold causing a short... So the dizzy was pulled out and machined...

There must be a company out there that can overhaul your dizzy and give you an advance curve to match the S/E advance curve?

[AHM]

Thanks both for the replies.

Mazzini,
you got me thinking, as your description sounds similar to what I am experiencing.
I noticed that the tick-over was rather rich so probably masking something else.

Out with the strobe this afternoon .... Tickover advance 20 deg - loose clamp bolt I set it to 12 degrees.

Then checked the tickover with a meter - I rebuilt the Rev counter so didn't trust it - only 600 rpm wound that up to 850 rpm (rev counter accurate!) and went for a long drive - Much better

Meg,
I thought you had got your c-type cams and pistons mixed up... until I read the manual this afternoon! A type 12 deg C-type 10 deg so reset the timing to 10 deg advance - thanks for that!

I then had a go at the carbs - a noticeable improvement.

The car is much nicer to drive now and much smoother.

I have a bit of a stumble when I open the throttle from closed, and I din't think I am getting the nearly 30 deg advance at 2500 rpm so more work to do.

I'm probably now somewhere near where I thought I was!

[Mazzini]

What plugs are you running? I used to use BP7's on my old standard compression engines, but found that 6's were better for general driving.

I can remember reading somewhere (workshop manual?) that Lotus had alternative chokes and jets for the S/E - probably to compensate for the wrong distributor advance curve

You probably already know that the collar on the original distributor is hollow, so will crack if over tightened - it's an easy repair though.

Matching the distributor advance curve to what Lotus recommend will probably give you a nicer drive.

[AHM]

I have a set of both plugs - I think the 6's are in at the moment - will have to check.

The distributor was repaired in the rebuild.

After setting the carbs up yesterday I noticed black exhaust from the accelerator pump actuation - so when I read the manual after your comment I noticed the cure to the flat spot was changing the acc pump jet - Another thing to check.

I also noticed that the 40953 curve changes at 2000 revs which is where the flat spot occurs (according to the manual) so your comments about the wrong advance curve could be correct.

[billwill]

The 'curve' of a distributor is determined by the spring-rates of the centrifugal weights, so if alternative springs are available it should be easy to change the curve.

It was described in detail in a page linked to from this forum. Try a Google search for "Distributor Doctor"

[billwill]

Ah, I think this was the article.

http://www.google.com/url?sa=t&rct=j&q= ... ZX17FqDkRA

Distributor Doctor is a firm that services & recalibrates distributors and sell parts including the springs.

http://www.distributordoctor.com/process.html