12 replies to this topic

[The Portly Knaresbruffian]

Hi, I'd like to know a definitive timing degree BTDC for the following.

A+ 1293
10:1 CR
Stage 2 head
1.5 roller rockers
Minispares C-27H7701 electronic ignition dizzy
Hif44, BDL needle, K&N standard filter.
Running 95ron unleaded

I've seen lots of claims from 5 to 15 BTDC @ 1500 rpm with vac adv removed.

All suggestions considered. Thanks.

[alex-95]

I have a similar spec and was told by Ac Dodd that it should be set at 10 degrees BTDC at 900Rpm with the vacuum disconnected.

[ACDodd]

What cam is fitted?

It’s not as easy as what I he timing setting, the setting needs to take into account the advance curve that your particular dizzy has.

Ac

Edited by ACDodd, 13 April 2021 - 05:14 PM.

[The Portly Knaresbruffian]

I believe it's the standard fitted to a 1275 A+ MG metro.

[ACDodd]

Measure the advance curve of what you have fitted and post back the results.

Ac

[dotmatrix]

some of those dizzys have a lot of centrifugal advance i have found. some have something like 50 degrees. try to get some one to measure it. chances are you could benefit from limiting the amount of Advance, but guy like ac is probably able to help you change it

[The Portly Knaresbruffian]

Measure the advance curve of what you have fitted and post back the results.

Sorry it took a while.

1000rpm - 8 deg
1500rpm - 10
2000 - 12
2500 - 16
3000 - 18
3500 - 20
4000 - 22
4500 - 23

All with vacuum disconnected and plugged

Ac

[The Portly Knaresbruffian]

Sorry it took a while.

1000rpm - 8 deg
1500rpm - 10
2000 - 12
2500 - 16
3000 - 18
3500 - 20
4000 - 22
4500 - 23

All with vacuum disconnected and plugged

[ACDodd]

With that advance curve set it at 12degrees at 1000rpm with the vacuum disconnected.

Ideally this needs a recurved dizzy to get the best from the engine the advance curve it has now is too short. Did you not check the advance after 4500rpm, I am assuming with my recommendation that the advance is maxed out at that point.

Ac

[The Portly Knaresbruffian]

I was advised by minispares to set static at 8 degrees ,and that it topped out at 4500 and 20 degrees, so didn't go any further than that.

Thanks for your take on it, it's much appreciated. I'll change to 12 tomorrow.

[ACDodd]

It’s not just short at full advance but still off by about 4 degrees at 2000rpm. This will cause a lack of punch through the low and mid range, even with the timing set at 12degrees.

Ac

Edited by ACDodd, 16 April 2021 - 08:44 PM.

[The Portly Knaresbruffian]

Update:

Running very nicely now thank you, with a slight hesitation at 2000rpm as predicted.

I'm a little annoyed that MSpares own distributor is lacking in advance as you observed, considering their sales blurb about poor quality alternatives, but it's fine for now.

[The Portly Knaresbruffian]

Update:

Running very nicely now thank you, with a slight hesitation at 2000rpm as predicted.

I'm a little annoyed that MSpares own distributor is lacking in advance as you observed, considering their sales blurb about poor quality alternatives, but it's fine for now.