I have finally upgraded the 3 dwell/tachometers that are all stuffed and a 40 year old timing light that only works sometimes and bought myself a proper digital timing light. http://innova.com/en-US/Product/Detail/5568 .
Here are my current settings.
9deg @ 1000rpm, 12deg @ 1500rpm, 14deg @ 2000rpm, 17deg @ 2500rpm, 19deg @ 3000rpm, 23deg @ 3500rpm , 27deg @ 4000rpm, 30deg @ 4500, Max 32deg @ 5000rpm.

I think my curve is to slow and I may need to back off my springs to speed it up a bit. Maybe a curve similar to this.
10deg @ 1000rpm, 15deg @ 1500rpm, 20deg @ 2000rpm, 24deg @ 2500rpm, 28deg @ 3000rpm, 30deg @ 3500rpm, 32deg max @ 4000rpm

The engine is 1275 auto block 1330cc,Hepolite Pistons. Cooper S crank and rods, lightened flywheel, all balanced. Road/Rally cam, 12G940 head, 1.5 roller tip rockers, LCB extractors, Crane Cams Fireball electronic Ign, 45 DCOE with 36 chokes ( Unknown cam, Unknown compression ratio.)

In the past I have just bent the spring posts willy-nilly but I would like to hear from people that are in the know and have done a few dizzys. Do you use different springs or bend the posts? I am thinking of bending the primary and secondary springs posts a couple of thou to give a little less tension.

Thanks Brad

Brad,

For altering dizzy advance curve I have just changed springs. I have never adjusted by bending the spring posts, you normally find that the two pairs of posts have slightly different spacing and this is normally enough to get the right 'take-up' point on the secondary spring (the heavier of the two, and is normally slack on the posts).
- to get quicker initial advance use a lighter primary
- to get more mid-range advance use a slacker secondary
- for slower mid-top range advance use a heavier secondary

The two factors which really affect ignition timing are CR and fuel octane.

Here's a plot of mine, most points copied from the Pulsar dizzy I was running. I used my Innova timing light to get them.
Note- I've modded the bottom few points to avoid kickback, as the Pulsar dizzy had a 9deg plate in, it had 20deg static and 38deg total BTDC.
That used to break starter pinions until I fitted a kill switch to the coil so I could spin er up then throw the switch.

You would need to take 8-10deg off all these numbers, my 1360 motor needs all this advance because it has a bathtubbed head (no chamber beak).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks carbon, I have been lazy in the past and just bent the posts, I do have a couple of old dizzys DM2 and 29D so I can take the springs from them and give it a go. I haven't had the luxury of a dial back timing light before so it should be fun.



Hi Doc, I have plotted my current settings against your curve -10 degrees. Big difference in the mid range. My curve goes the wrong way and doesn't hit max advance until 5000rpm.



If anyone else has a worked 1275 and details of their timing advance curve I would love to see it to compare.

Thanks Brad

I have played around with dizzy's and the best results where are all of the timing needs to be in about 3000-3500 rpm on a mini engine. Yours is coming way to late.

To achieve this try only one spring or two light springs and aim for 34-36 degrees total advance.

I fitted a 10 degree 25d4 dizzy to my standard 998 Mini Moke dialed it in at 10 degress and the improvement in starting and HP was noticeable. It had a 17 degree cam in the old dizzy too much advance.

The reason they used so much advance in the 60's was the pertol was low octane and poor quality. You need more advance with low octance fuel.

better still do what Kevin has done is invest in a programable dizzy. You can only go so far with a mechanically dizzy.

Cheers, I am happy with the top end advance it doesn't ping at 32degrees. Advanced it to 36 and she started to rattle a little.
Just need a few different curves to compare to. Can't really use Docs engine as a good reference.
The programmable ones are the way to go. But I want to have a play with the dizzy I have.

As Kiwi said you need more midrange advance.
I'd remove 1 or change both springs to get the advance all in by 3500 or maybe sooner.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Brad,

The set-up I have is using 25D4 based on 1275GT UK spec 41257, 10 degrees centrifugal advance (ie 20 at crank). The primary spring is replaced by the lightest available primary spring (from 41238 or similar), and the secondary spring kicks in just after half way on the centrifugal advance. Running with about 12 degrees static advance, and even with these lighter springs I don't think the advance is coming in fast enough at mid rpm.

Motor is a 1293, MD266 cam, 9.75:1 CR with balanced chambers and cleaned up head. Twin HS2s and RC40.

Thanks mate,
I have had the car nearly 3 months now and I have been trying to track down a dead spot in my engine. I noticed my dizzy curve was a bit flat and still advancing later in the rev range. Not a lot happens until I hit 4000rpm then wheel spin.
Already found heaps of things wrong. The accelerator pump return valve needed to be blocked off in the bottom of the fuel bowl. Carb jets were a bit lean as well. The electronic ignition was running non ballast and burning out the coil. The GT40 coil measured 0.2 ohms when it should be more like 3ohms. Some loose and some tight rockers. Still a work in progress but having fun tracking down the faults.

I now stock the Stealth Boxes. Which allows you to map your own advance curve from your lap top. You will need to lock the mechanical advance plate and remove springs.

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Brad,

For reference here's the approximate advance curve I am using in my 1293. Only approximate as I have never had the kit to check...
12 deg @ 400 (no mech advance)
17 deg @ 800
22 deg @ 1200
27 deg @ 2400
32 deg @ 3600

All of above are total timings as deg at the crank and for crankshaft rpm, using 12 deg static timing. I'm also using vacuum advance on this unit with a 4-11-7 can from 1300GT.

Yes, this is a lot faster advance curve than the original 1300GT spec. The MD266 is only a fast road cam, so very surprising that it needed such a different advance curve. Also I noticed was when I swapped from A+ sintered rockers to slightly higher lift forged rockers (about 1.35 using offset bushes) a couple of years back the engine went totally flat at low-mid rpm until I used this much quicker advance curve.

you can also have a look at the csi programmable dizzy curves for mini,as examples but the steep early advance as in Docs and Carbons plots is a common character trait ..... and it works, whether you max out at 28 or 32 etc is probably a function of fuel and chamber shape/size but being 'in' early is crucial.... carbon sure does know his springs and vacuum, so if staying with traditional heed his words..

Excellent carbon. That gives me enough info to start off. Thanks for the replies everyone. I really was just chasing examples of advance curves that would match a similar engine to mine and whether or not you bend the posts or replace springs. I have enough info now to go and play. Cheers

How much are they from you (with postage to NSW 2761)?

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PM Sent

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DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"