distributor cam

[les]

Any ideas as to the correct fitment for 1098 distributor cam/centrifugal timing plate, mine has 10 degrees stamped on it.
presume there is a difference between low and high compression engines? Thought this detail would be in the manual, but I can't find it.

[bmcecosse]

10 degrees is the maximum mechanical advance that dizzy will give - in dizzy degrees. So that's = 20 degrees of engine advance. A good A series wants ~ 34/36 degrees total advance - so to get that you would need 14/16 degrees of static advance - which is FAR too much. So - you need to remove some metal from the 'tip' of that cam with the 10 stamped on it. To get an idea of how much - assemble up the bob weights and springs - then measure (as best you can) the distance that tip will move as the dizzy advances until the tip hits the stop. Let's say that is 10mm - so each 1mm is one (dizzy) degree. You need ~ another 5 dizzy degrees of advance - so in this case - remove 5mm from the tip, and you will now have 30 degrees advance available, which will allow a much more reasonable 4 to 6 degrees of static advance to get the best from the engine. The actual measurements will vary slightly from these 'example' figures I used above - but I'm sure you get the idea!

[les]

Thanks Roy, I'll work on it, although maybe better to get another cam.

[les]

I've found a 15degree cam and a 17degree cam?

[bmcecosse]

15 sounds good to me!

[les]

Now installed, a bit puzzled about the small springs though, both were quite thick whereas I thought one should be lighter than the other. Any thoughts on this please?

[MarkyB]

That;s what I would expect too, Roy will be along shortly to give chapter and verse.

[bmcecosse]

Yes - I've always seen a thin one and a thick one...... That 10 degree bob-weight is a bit unusual - and the springs may be matched to that. Do you not have any others ???

[les]

Yes I have fitted different ones, ie one thick, one thin. It would be interesting to know how many variations there are/were.
Also nice to know the factory setting regarding the standard cam advance, ( the number stamped on the base) If it didn't involve removing the points plate for inspection it would be handy to run a sort of survey of what is fitted to others cars, as since I've changed to a 15 degree cam my pick-up flies. The new springs might also contribute to this.

[bmcecosse]

Glad to hear it 'flies'! Great success!! Advance it till it pinks - then back it off very slightly do it's 'not quite' pinking. It's the best you can do without spending hours on a rolling road or an engine dyno.

[les]

Great success yes but I must have been running that 10 degree cam for the last 11 years! Have been thinking of selling shortly, but to get the benefit, looks like I'll have to keep it for another 11.

[bmcecosse]

One question - why do have a Mini on show? It's VERY like my original Mini - mine was dark (Brunswick?) green with orange roof.

[les]

Minis have been very special to me, the one on my post was my first, an 850 which I 'did-up' as you see, I fitted a cooper remote and diff housing, made the arches from glass fibre and moulded them on, then chose a crazy colour scheme, well it was at the time! I eventually gave a guy £150 plus the car for my first 'S'. Memories-----I'm welling up now

[bmcecosse]

Excellent - similar to my Mini experience - so -what colour scheme was it ?

[les]

Ford aubergine and mustard yellow.--Plus the obligatory matt black bonnet!!

[bmcecosse]

Excellent -happy days!