anthony1956

ok so I reduced the ignition timing to as close as I can estimate on the cam sprockets to 3 degrees (which is 1/3 of a "tooth" ; (where a tooth is one tooth plus its next gap)), i.e. 6 on the crank. To my pleasant surprise we now get almost the best emissions figures, the HC is higher than best I have had before, but CO2 and CO are better and lamda is nearly 0.9 . So i have arranged the gas test for tomorrow. That said i have the mixture screws turned almost all the way in. I started at zero and unscrewed instead of starting at 2.5 out and going in. I think tick-over needs a tweak faster. and the strobe RPM reading won't photo at all. The timing marks are hard to see/video (this is a screenshot from the video) in bright sunlight

It sounds like you’ve done a lot of detailed investigation, and you're spot on about the complexities of setting the timing via the cam sprockets rather than using the crankshaft markers. Let me try to untangle some of this: ### 1. **Timing Based on Cam Sprockets**: - You’re correct that since the camshaft rotates at half the speed of the crankshaft, **10 degrees on the cam sprockets** translates to **20 degrees on the crankshaft**. If the correct timing spec is **6 degrees BTDC (crank)**, this would indeed require only **3 degrees on the cam sprockets**. ### 2. **Understanding the Discrepancy**: - The **RS 1600 spec** being **12 degrees BTDC at 1500 RPM** is for that particular engine's design, but **Caterham's 6 degrees for the BDR** is more conservative, likely tuned for road use rather than performance. - Setting **10 degrees on the cam sprockets** (equating to 20 degrees on the crank) is likely **too advanced** for the engine based on the BDR's intended setting of 6 degrees crank timing. ### 3. **Crankshaft Pulley Marker Issue**: - If you're unable to reference the crank pulley markers due to positioning or potential refitting errors, it makes sense that you'd have to rely on the cam sprockets. Since the crank pulley might be inaccurately positioned, it could lead to confusion about actual crankshaft timing. - Refitting the pulley randomly, as you mentioned, could have caused the timing marks to be misaligned, making it nearly impossible to use the traditional crankshaft reference. ### 4. **HC as an Indicator of Timing**: - As you noted, **HC levels** (hydrocarbon emissions) are useful because they indicate how much unburnt fuel is leaving the combustion chamber. - If you're able to reduce HC levels by slightly retarding the timing (bringing it closer to 6 degrees BTDC on the crank, or 3 degrees on the cam), that suggests more complete combustion and proper timing. - If HC levels rise as you advance the timing, it could be a sign that the ignition is too advanced, resulting in incomplete combustion or pre-ignition. ### 5. **Next Steps**: - **Retard the timing** closer to **3 degrees on the cam sprockets** (equivalent to 6 degrees crank), as per the BDR spec. This should get the timing closer to what's optimal for your engine, and then observe both the engine's behavior and the HC readings. - **Test and adjust gradually**, observing how the engine responds, particularly under load. A slight improvement in performance coupled with reduced HC readings could confirm you’re heading in the right direction. ### Mental Rescue Summary: Yes, you’re working in an **unusual situation**, setting timing based on the camshaft sprockets rather than the crank. The key is to **halve the crankshaft timing spec** when working on the cam sprockets. Since you're at 10 degrees on the cam, reducing it to 3 degrees on the cam (which equates to 6 degrees on the crank) should bring you closer to spec. By adjusting and observing HC levels and engine response, you’ll be able to find the sweet spot for your engine. Let me know how it goes.

sorry got confused, here > https://www.caterhamlotus7.club/blogs/entry/1122-bdr-ignition-timing-crank-versus-cams-we-are-timing-on-the-cam-sprockets-not-the-crank/

Now that for the first time the timing is the same in the morning as it was the previous evening. (Dizzy clamp issue). I am now wondering if she is too far advanced, because on the cam sprockets I have her set to about 10 degrees (1 1/3 "teeth)". The RS 1600 s/be 12 degrees at 1500 rpm. CC says 6 degrees for BDR. Either way given the crank turns twice for every one turn of the cams sprockets, I think that should be half the advance on the sprockets so that 3 deg on the cams gives 6 deg on the crank. However, oddly this is doing my head in. Edit: ok the reason it is doing my head in is every single discussion (here and elsewhere) starts with respondents explaining that timing is ALWAYS based on the crank not the cams. However, we are setting the timing based on the cams NOT the crank, therefore compensation is (seems to be) required because the cams only turn half as fast as the crank. This is UNUSUAL and requires alternative thought. The reason for this is we have, after extensive searches, been unable to find any crank case markers to match the crank pulley markings. I am wondering if in 2012 when I knew nothing about such things I refitted the crank pulley randomly with a 33% chance of it being right and it is wrong. Also, access to view the crank pulley and any case mark is practically impossible. Also all the alleged timing markings in the book (Haynes RS 1600) are simply not present. So whereas I have 10 deg on the cams that's 20 deg on the crank, which is too much. I gather also that other things being optimised (mixture, air comp, tickover, carbs balance) the HC reading indicates degree of unburnt fuel so it can also indicate good or bad timing. Mental rescue welcome Anthony

So I did it tighter and today, for the first time, I got her started at the first attempt. It wasn't easy, but she started. I checked the timing and it has not changed from yesterday.

yes, I see you illustrated doubling. Holdens want £6 to deliver their £20 item. Not willing to be ripped off like that.

a bit bent but still working

I am clearly wrong about doubling the timing, but it's doing my head in:

@oldandrewe Yes exactly one of those. Yes it is looking a bit out of shapish. However, not closing up where it shouldn't. and @MIKER7 No can't turn it by hand, checked that, in fact always check that. It lost about 6 degrees, or 2/3 of a cam tooth. "A" tooth defined as one tooth AND one gap on the sprocket. Given a cam degree is half a crank degree that'll be 12 degrees on the cam I guess. I THINK what's going on is that I am not tightening it enough so that when driving it gradually loses its grip just a bit at a time. I did it up much tighter today and it hasn't budged. Also previously I was having to put a lot of force on to the dizzy to turn it to get enough advance. So I Moved all the HT leads one-to-the-left. I.e one contact clockwise given the rotor goes anti-clockwise, which retards the dizzy by 45 degrees, and then I can advance it to get my 6 degrees nice and easily. This has worked today so whether the fact it was forced top far and slipped back or was not tight enough or both is as maybe was. I picked up the 45 degree trick for a 2006 post of chevy owners, which I find remarkable. All the above is subject to my timing should be 6 degrees BTDC no 1 compression stroke. I am not at all certain the numbers I mention above stack up in the context given cam degrees are half crank degrees. If you could sort me out in that regard I could stop worrying about it 🙂 My cam sprocket has 40 teeth so 360/40 = 9 degrees, but do I then want 2/3 of a tooth (defined as above) or if this is only half, then 4/3 of a tooth i.e. 1 1/3 teeth? We do not have any crank markers that are capable of use. edit @OldAndrewE the one I found had two holes for bolts.. Have to admit I am very wary of replacing it as it looks like one has to lift the dizzy out completely and knowing me I would put it back a tooth different https://www.holden.co.uk/p/distributor_clamp Anthony

Covering the bases here. Probably my error when retightening it, but I do seem to keep finding the timing has changed. Nothing surprises me any more with this car being (nearly) 40 years old. Anthony

you have my total sympathy - been there for several weeks and compressors are cheap bits of kit and neverendingly useful once you have one - I have an electric one from Aldi, or I did til I broke it (literally) a couple of weeks ago; so bought another also not expensive. This sort of thing (but check details this is just a rough example of amazon.co.uk ) - reason I am pushing a tiny bit is I don't think youll get all that crud out without one at home, having tried blowing through myself, just doesn't cut it. Also good for cleaning grot traps....

ok so yesterday I finally got the emissions to legal requirements and it seemed to be stable, not moving much. She started fine, hot engine. Now, cold engine, she won't start. She tries, but can't. I guess it's the mixture; I've tried the choke, but no success. She's probably well flooded now so I have come away so she can dry out. Suggestions welcome - checked the plug leads are right and the dizzy is properly on. Yesterday I had the plugs out for the Colortune, cleaned plugs and refitted. I've refitted the Manometer vacuum take offs, the blanks - one was not sealed, might be that... Every time I think she's finished, she's not. I suppose too lean to cold start Anthony I suppose I could try a simple half turn out on all the mixture screws - did that, also went back to first principles which is 2.5 turns out, think I might just take the plugs out, clean, gap, refit just in case I screwed up something there.. and yes I checked the HT leads are in the right order on the dizzy, not that they have been off since yesterday, and no the dizzy cap is not wobbly or off kilter, and yes the rotor arm inside tab is not sheered off..

warmer weather today and I am using a trombone to hold the cable; first time out it fell off.(!!) Second time I sort of knotted it and it stayed on.

ah well now! I have bought the jets but not yet experimented. Des Hammill writes that the emulsion tubes will not need to be changed, which saves significant bucks. Buying jets etc is NOT cheap. Couple of things strike me you could try; good old guess work and lean the mixtures, given you are only passing by seems like the simplest. Beyond that are various AFR (not really sure I like that acronym as it suggests i know more than I do) so, Air Fuel Ratio, i.e. the mixture in my language, devices you could carry. Gas analyser (dead easy to fit), Carbtune Pro (mucking about with screws to fit), Gunson Colortune (changing spark plugs on a hot engine TWICE, did this today.. still reflecting.) Methinks none of all those are what anyone will want to carry and learning how to lean and re-richen the mixture is the way to go. Anthony (is it your old sixspeed I have? goes well.)

Thank you for even trying to engage when it seems you haven't seen much afoot.