Club 80-90 Forums

You really should get the vacuum advance working, as suggested earlier...

Why do you think there is a problem with this?

7 degrees BTDC, but you won't get much in the way of economy from it I would have thought.

What is total advance of centrifugal advance dissy vs centrifugal and vacuum advance dissy? Used to always set for total advance at about 3000 rpm, not at spec for idle. Problem is I don't remember what that was.. something in the 32 degree range I think. Reason was because total advance on working/cruising engine is important, not the idle advance.

Assuming no vacuum retard..

7 deg BTDC static adv.
about 25 degrees centrifugal adv at 3400 rpm
= 30~34 degrees advance
10~12 deg vac adv at full vacuum

So on a light throttle or overrun advance can be over 40 degrees total

so

http://wiki.80-90.co.uk/index.php/Petro ... gnition_02

If you disagree or know better then let us know...

Sounds right. The problem with broken or blocked vacuum advance is total advance at rpm is not as high as it should be.... but if total is above 30ish at 3000+ under load/working hard engine builds more heat, ping, etc. and can destroy engine. Of course elevations above 3500 feet mean you can use a little more advance, etc., but only a little and if not adjusted when back when at lower elevation can cause problems. Leaner fuel mix is better at elevation too (thinner air means less oxygen), but again, need richened back up at lower elevation.. Used to live at 5300 feet base driving to 10000 - 12000. Rarely below 3000 feet. Jetted leaner and more advance, but when traveling to coast had to re-jet carbs and change timing accordingly.

FYI, at 10000 feet engine makes 68% of power it makes at sea level... unless you have it turboed or supercharged.

Some may find this link interesting:
http://www.slowgt.com/Calc2.htm#BasAltCal

Thanks for reply Harry. Can't find static timing quoted anywhere for 1600CT but assume 7deg BTDC right as engine basically same as 1600
DP.
Made new timing mark 12deg to right of standard one and set it to that. I had timed it with the strobe so was too advanced. Didn't realise vacuum retard had such an effect. There was me thinking poor starting was down to ICT carbs not having any chokes. Better now thanks.
Only done 20-30 mles with engine so advanced but didn't hear any pinking so be fine i'm sure.

Cheers, D.

Dekker, where are you located? My timing light has an advance on it and can check to see what full advance is when engine is revved up.

Didn't realise vacuum retard had such an effect.

Exactly! That is one of the important things to note I suppose, as timing to a position After TDC seems a bit strange, but with vac retard working, and using dynamic strobe timing, that's how it is.

So hope this thread has helped a bit in that direction. If any further info comes to light, particularly for the 1600, I will ensure it gets into the Wiki...

Thanks for the offer Lloyd but I'm in sunny (??) North Yorkshire.
I've timed it to 7deg BTDC with stobe and the thing starts easier and tickover went up.
Sounds sweeter and isn't quite as 'fluffy' at smaller throttle openings.
Setting of on a 500 mile round trip Thursday with the family. Engine will have done nearly 100 miles since complete rebuild by then. Nervous, er yeah. Trip involves a Festival that is the wifes birthday present.
Would have had timing over advanced if wasn't for this thread. Thanks again all.
Cheers, D

Forgot to add for Fingle. My previous van was a bay window with 1600DP engine. When I bought it dizzy was shot, lots of play in it and no vacuum advance. That and the fact plug leads were on wrong made PO think it needed a new engine.
Believed the hype and bought a screamer kit, blue coil, 009 dizzy, new leads etc. Ran lots better but had a HUGE flat spot at about 1500-2500 rpm. Messed about for ages but never sorted it. Eventually bought 2nd hand stock dizzy, it transformed the van. Much, much nicer to drive, no flat spot, better acceleration and about 2-3 mpg more.
Stick with the vacuum advance, worth the extra money.

Cheers, D