8 replies to this topic

[Dugman]

Hi there,

First post. I have a 1965 1275 Cooper S, LHD originally from France (I’m in US). The engine was very nicely rebuilt and I have pictures, it was bored out to 1310, received a cam and roller followers. It has great top-end and needs revs but the rebuild also put a short final drive so it’s easy to keep the engine on boil. It has a performance exhaust and twin HS2’s.

I have had some trouble with starting and flat spots at 3K and have found my timing curve is way off. I have Pertronix in the Lucas distributor. The distributor has “100AR” pin-etched into it so I assume this is an old Aldon Red. There is no vacuum advance.

I want to buy a new distributor but without knowing the cam and compression (the prior owner can’t remember).

Seems my choices are:
- another Aldon Red
- an Aldon Yellow since I don’t race it, maybe with Vac
- the “Evolution” distributors on minispares/minimania/minisport, and I’m assuming I’d get the one for 285/286 cam given the car seems pretty spicy.

I don’t need the very very best total power, would like something that it safe and gives the engine long life and is fun to drive on the back roads of northern CA and the occasional track day.

I have dug through the internet and can’t find anything other than old opinions on Aldon. I’d rather not do a 123 given the whole engine bay looks nice and stock. Any advice? I so appreciate having this community to look to.

[Cooperman]

If it’s still on HS2’s it’s unlikely that it has a high-overlap cam. An Aldon Yellow should be fine without vac advance.
You might need to change the needles, but experiment a bit first as the ones you have might be fine.
If original, the final drive ratio will be 3.44:1, which is a great road ratio.

[Spider]

The 100AR is indeed an Aldon Red. These were supposedly curved to suit 'full Race' cam profiles, but IMO, I can't see a use for it anywhere.

 

Respectfully, any distributor choice without knowing what Cam is in it is a guess and it could end up being a bad guess that results in engine damage.

 

I would strongly suggest you measure the Cam to see what it is and obtain a distributor to suit, you'll avoid engine damage and get the best performance from it.

You can measure the Cam with the engine in reasonably easily. Remove the Radiator, that gives you access to the Front Engine Damper / Pulley on to which you'd fit a degree wheel (blue tac is good here) and remove the Rocker Cover to set up a DTI to a Valve Spring Top Cap.

[Earwax]

As Spider suggests - it is all a bit of a guess without good data/knowledge.

 

To get a tune, you would be best advised to know the actual timing curve - and an idea of a reasonable starting point curve for a 1275. The other data is AFR - knowing when running rich etc.

 

other things to ponder:

 

Measure your final drive ratio- (chalk and pushing the car)

 

Do you have choke to only one Carb?

 

Is the flat spot related to the linkages ( twins set up)

 

and in more room for thought

 

A 1310 with a mild cam and a 3.44 ratio is highly capable of running twin HS4s - and there are lots of examples of which needles to start at ( eg CP4, 6,- both work in my 1310 running a 260 cam at 3.44)

 

Sounds like a great little machine - enjoy

[Dugman]

Thanks very much. I need to get her up and running and have a starting point. I would like to take it to a place that can identify the cam and do some dyno work but folks that know minis are not very common in the states.

From what I can tell a yellow would be a safer choice to start with, or I suppose I could do a CSI and have a few options as I learn more. I can’t find any of the CSI curves online though.

Thanks for the suggestions!

[Dugman]

Oh and to answer the questions.

The linkage is good and the carbs well balanced. The choke works on both carbs together.

[bpirie1000]

Have you sought the assistance from rolling Road or just going with how it feels and change and check as you see fit?,

A good old school Rolling Road operator will be able to tweak and advise with power delivery and work out where you are potentially going to gain any advance in power from.

[Coalhod]

Another option is to have the diz curved to suit your engine and knowing the camshaft spec will help.  I had Jeff at Advanced Distributors in Minnesota https://www.advanceddistributors.com rebuild the diz for my 1965 1275 S and it's night and day with the way it drives and can operate on pump gas!  Cost is $200-250 USD but it saved me a lot of guessing on how to set up the distributor.

[Dugman]

Thanks for more great suggestions. I will just need some help from a mechanic getting in there and understanding the cam, figuring out compression ratio. I can figure out the final drive ratio myself. I’m definitely up for custom tuning the advance with someone on a dyno (I assume that’s the same thing as what folks on here call a “running road”.

Thinking back to the flat spot at 3K: when climbing a hill at that speed I pulled the choke out a bit to see if it was mixture and got either better or worse. No change. But playing around with the distributor further I think the small spring is stretched out, and I’m getting all of its advance at 1K RPM. Then the car gets to a spot where it needs more advance. When I get past this point the larger spring comes into effect and the ignition starts advancing again and runs great. So while the distributor will give 20 degrees of advance I’m only actually getting the second half of that…