An update on the timing light purchase and the vacuum advance unit on Minnie.

First up, I bought a hand held vacuum pump to see if the vacuum unit was working as I couldn't see any movement when sucking by mouth. When I connected the hand pump, I found there was a leak where I had the plastic hose pushed over the threaded part of the vacuum unit (where the metal pipe connects to the unit, not the later push on types) so no wonder I didn't get any movement before. I ended up reconnecting the screw on metal pipe which has the fuel trap in it and connecting the hand pump to the piece of rubber tube I had fitted on the end of the pipe to block it off and keep it clean. No leaks in the system and the vacuum advance unit stated to operate at about 8" and was fully open at around 13". According to the book I have, the unit should start at 7" and be fully open at 10".

I put a small squirt of oil onto under the points plate in the dissy as I reckon the movement of the vacuum advance was a bit tight. Seems to work fine now, albeit a maybe a higher vacuum than in the book. The diaphragm is no doubt quite stiff as I reckon it might be the original.

However, now that 68 + 86 Auto has provided the info about stampings on the unit, I'll go and see if I can find any markings on my unit to determine actual settings.

On the timing light front, I couldn't get one from any stores within 100km of home so I ordered one online from a major online auto parts supplier, not an ebay seller.

The light was advertised as an Innova 5568 and cost $172 delivered. Got it yesterday and initially disappointed that it's not an Innova but an Equus 590-518. After checking it out, it looks and works exactly the same as the Innova unit, however it shouldn't have been sold as an Innova when it clearly isn't. From what I've read, Equus bought out Innova years ago and the unit sold under the Toolpro name looks to be the same. Misleading advertising I reckon and given that it looks the same thing, not worth the hassle of returning it.

When I was playing around with the vacuum unit, I noticed that the little spring that holds the vernier adjuster wheel on the end of the vacuum advance unit is missing and the wheel moves quite freely with no spring notch to keep it from turning, and hence altering the timing. I rang a bloke who has a shed full of spare parts and I'll get a spring from him.

In the meantime though, I checked how the timing light works and it's terrific. It does look like the timing is slightly advanced with 12 degrees at 800 revs running through to 32 degrees at 3000rpm. Across the rev range, it was about 2 or 3 degrees more advanced than the top range figure quoted in the book. For example, if I'm reading the book correctly, it should be 21 - 25 degrees at 2000rpm. I've got 27 degrees.

I haven't altered anything yet as I'll fit the vernier wheel spring first to prevent any movement there and then see how I go with adjusting the timing.

Thanks for everyone's help and info. I really appreciate it and allows me to work on Minnie rather than take it to a workshop all the time.

Cheers Rocky

I find a lot of cheap gauges are very inaccurate. Those values you got are probably close enough especially with the quality of many gauges.

The Innova branding issue is annoying but I'm sure there's zero difference. Mine had three different brands across it, the packaging and what I ordered.

The advance values in the manual are based on the timing being at 0° static which is hard to set accurately. If you record the values you can still work it out without setting the timing at 0°. You just can't confirm what happens below idle, it could advance a lot due to wear. The distributor being noisy is a sign of wear which effects idle.


Here is some vacuum advance testing information.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

An update on progress so far. I've got hold of another vacuum advance unit of an old dissy and according to the hand held vacuum pump, it starts to work at around 7" so the diaphragm in that one seems to be a bit more flexible than the one on Minnie now so swap them over. Also got hold of of the little spring that keeps the vernier wheel adjuster on the end of the vacuum advance unit form turning and I'll put that on as well.

Before changing anything, I thought it best to see what numbers I have already so if all else fails, I can go back to them.

A sanity check first though on how I'm using the timing light please. No vacuum advance connected.

With the engine at 600rpm, when I use the timing light in 'normal' mode, the timing is at around 7 degrees - need to guess a bit as it's somewhere between 5 and 10.

Putting the timing light into 'advance' mode and adjusting the advance button on the timing light to show when the timing mark on the clutch cover lines up with the 1/4 mark on the flywheel, I get a reading of 7 degrees.

Next I did all my timing measurements by adjusting the advance button on the timing light to show when the 1/4 mark lined up with the timing mark on the clutch cover.

The results were:
At 600rpm - 7 degrees
At 800rpm - 13 degrees
At 1000rpm - 17 degrees
At 2000rpm - 26 degrees
At 2500rpm - 29 degrees
At 3000rpm - 34 degrees
At 3500rpm- 36 degrees
At 4000 rpm - 36 degrees

My initial thoughts when I first checked the timing was that it's a bit too far advanced and if I'm using the timing light correctly, the above results indicate the same thing.

Do you blokes reckon I'm using the timing light correctly by adjusting the advance button on the light to align each measurement at different revs with the 1/4 mark?

Thanks Rocky

By the looks of it, your timing light is reporting engine degrees since you get 7 btdc in manual mode and in advance mode. The distributor specifications in the workshop manual are distributor degrees/rpm which are half that of engine degrees/rpm. However, you have to treat that workshop manual data with some caution since I have found that sometimes these tables can report engine data even though the labels say differently. I realise you may already know this, but your data looks OK to me for an 850. A couple of degrees here or there is within specifications.

Edit: I checked the specs. All your data is on the upper end of the allowed specifications for mechanical advance which is probably a good place to be. You can always wind back on the thumbwheel if there is any pinging evident.

That sounds like you’ve used it correctly.

The 1968 manual says an 850 (premium fuel) should be:
3 degrees at 600rpm
Total 30-34 degrees

If you retard the timing 3-4 degrees you’ll be in the ball park. You should be able to get that much adjustment with the vernier wheel

_________________

You are doing everything correctly.

_________________
1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

Thanks Timmy and 68+86 auto for your replies.

I've hooked up the replacement vacuum unit and adjusted the timing to back off the advance a bit.

With the vacuum unit not connected (and carby tit blocked off still), here's the results after my adjustment:
At 600rpm - 3 degrees (was 7)
At 800rpm - 8 degrees (was 13)
At 1000rpm - 16 degrees (was 17)
At 2000rpm - 23 degrees (was 26)
At 2500rpm - 25 degrees (was 29)
At 3000rpm - 29 degrees (was 34)
At 3500rpm- 31 degrees (was 36)
At 4000 rpm - 31 degrees (was 36)

I then hooked up the vacuum unit and after backing revs off to 800rpm, timing was 12 degrees so it looks like at those revs, the vacuum unit added 4 degrees.

I took Minnie for a run and while it accelerated ok, it seemed maybe a bit slower than before. More noticeable on slight uphills where it seemed to bog down a bit. Mind you, it's only an 850 so power machine but I've driven the same roads heaps of times and it just felt a bit different. Quite noticeable when turning up my road to home. Normally, I can drop it down to 3rd and it will pull away ok. While it would have today, it was happier going back to 2nd.

While out on a test run, I advanced the vernier wheel 3 turns and it seems to run a bit better. I did a quick check of the timing when I got back home and it looks like I've added about 2 degrees (with vac adv unhooked) but will check again tomorrow when I've got more time.

For years now I've been running 95 petrol. Now running 98 as the local servo stop selling 95. From what I've read, the higher the octane, the longer it takes to burn so maybe that's why it seems to run better with a bit more advance?

Out of interest, the distributor is a 25D model 40768A.

If I have time tomorrow, I'll double check the numbers and take it for another run.

Thanks Rocky

Do we know anything about your engine ... other than its probably a pretty stock 850???

More advance usually = more power ..but more than optimum will reduce power ... and can destroy your engine (won't hurt if it doesn't ping but will affect performance). Does it ping under load? if not, the extra octane you're buying is a waste of money. Stock compression is about 8.3:1 ..and your driver's manual would probably have specified standard fuel (87ish octane). Octane is a measure of how well the fuel resists detonation.. Required level is determined pretty much by your (dynamic) compression ratio..

As I've said before; vac advance will not affect your cars power under load (ie won't buy you anything with regard to top speed or acceleration ... or ability to climb hills). You fit it to improve your fuel consumption at cruise.

Timing is always set with the VA disconnected.

IMHO?? Disconnect the advance. Find some hills that you can go up at a stable speed in second gear flat out. Does it ping? No?.. add some advance. Rinse and repeat until is does. Now back of the advance a couple of degrees (and reconnect the VA .

Or, spend some money, get it on a dyno (run by someone who knows what they're doing) and get the timing and fuel (needle) optimised.

Cheers, Ian

Thanks Ian,

Yep - it's a pretty stock 850. Since it's been on the road, I've used mostly 95 but sometimes 91 if 95 not available. Local servo no longer has 95, now 98. My original thinking was that 95 was more aligned to the old Super petrol and wouldn't hurt to run it. I don't have a drivers handbook but all the workshop manuals mention standard or premium fuels in the ignition sections and timing specs and I initially thought they were referring to the actual fuel used but if I'm correct, the reference to the fuels is about the actual distributor installed, not the fuel in the tank.

The dizzy in Minnie is a 47068A for standard fuels and I believe the 47068F was for premium fuels. Totally different timing specs as the pic posted by Timmy shows. Strobe timing at 600rpm is either 3 deg or 10 deg depending on which column you take.

Before changing anything, the timing at 600rpm was 7 deg with max timing of 36 deg from 3500rpm. The 36 deg number appeared to be a tad high so I backed off the timing at 600rpm to 3 deg which gave 31 deg from 3500rpm.

At the new numbers, the car didn't feel quite as zippy . Not much different around town but out on the road it seemed to lack a bit of punch when under load so I'm thinking that the timing is either a bit too much backed off on advance or maybe the recently hooked up vacuum advance unit is playing up. I did advance it by about 2 deg and it felt better.

I'm going to check what the numbers are today and out of interest, will try it out on the road with the VA connected and disconnected and see if there's any difference. When checking the timing, I do have VA disconnected and carby plugged off.

I haven't noticed any pinging but do remember the sound quite well when we were younger and working on cars with no timing lights and just adjusting the timing by ear. I thought I'd get with the times and lash out and buy a proper timing light and have a go myself, and with the help of blokes on this forum. I've done most of the work I could on the restoration and like many here, get a real satisfaction by working on the car. If all else fails, I will take it to the workshop I had it initially tuned at although that's a good 2 hour run each way on a trailer and would need 2 trips as he doesn't necessarily get the work done in one day, depending on what other jobs come in on the day or other jobs that take longer than expected.

Cheers Rocky

With the specs you have mentioned, yours is the one in the “premium” fuel category.

The “commercial” one listed there only advances from 10 degrees at 600rpm to 22-26 degrees full in.

If it runs better with the 36 degrees and you don’t have any pinging or hot running then your engine may well just want a little more timing than the spec from the factory

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Gee Timmy - I've been looking at those numbers in the table you posted as they're the same as in the workshop manual I have and it's only after reading your reply, I noticed the maximum advance numbers for the 2 different "fuels" and the penny dropped about which one I have.

Thanks for pointing that out. I did reset the timing to 3 deg at 600rpm which gave around 31 at 3500rpm, which is at the bottom end of the range stated. I'll take it for another run to warm it up and see what I have now. My guess is that it will be closer to 34 now that I've advanced it a bit while on the road yesterday.

I've never heard any pinging and the engine doesn't run hot at all. As you say, maybe it just likes a bit more timing than the standard specs.

Cheers Rocky

Hi Rocky,

"....My original thinking was that 95 was more aligned to the old Super petrol and wouldn't hurt to run it...."

Wouldn't hurt... but costs more for no benefit... And back in the 60s when those specs were written we had standard and super but in the UK they sold 2, 3, 4 and 5 star fuel. I don't remember what the octane readings were but my S was definitely happier on 5 star.

IMHO part of the issue is that you seem to have things backwards.... The type of fuel you can get drives the type of distributor you can use .. not the other way around... Similarly, a timing light tells you what you have ... but not what you need.

Specifications are fine. If you're dealing with what the specs refer to .... ie a new engine (and fuels) just like they were 60 years ago .... they make a good starting point. I'll bet your car is no longer an 850, rather something more following a rebuild (or two??).

Some years ago I had a dizzy built by Aldon (a top UK tuning firm at the time). Their promise was that If I gave them the engine spec they would build a dizzy to suit. Didn't quite work out. Once the engine was built it all worked ... OK ... but a few hours on the dyno and a rebuilt (even though brand new) dizzy really made a significant difference.

Seat of the pants home build is fine, however, it amazing what a difference an expert with the proper tools can make.

Cheers, Ian