8 replies to this topic

[Spherix]

Hi there,

I'm in the process of uprating my engine, which will eventually be tuned at a rolling road. To prevent any damage to the engine whilst driving from my home to the rolling road, I was wondering if there are any known figures to set the timing at with the following specs, as I can imagine timing will have to be adjusted in comparison to the standard engine.

Specs as of now;
1275cc block coming from a '91 Mainstream Cooper
Richard Longman GT6 12G940 head (35.7mm inlet, 29mm exhaust valves; bronze bullet-shaped valve guides, Longman valves, double valve springs)
1:5 MiniSport rollertip rockers
Duplex timing chain
HIF44 with K&N Cone filter (with substack) tuned according to Vizard.
Fletcher big bore LCB
PlayMini 2.5" linkpipe, 3" center exit damper

Cam is the standard cam out of the mainstream cooper block; didn't touch it.

Thanks in advance.

[Cooperman]

Set static timing to 5 degs BTDC and it will be safe to start.
Your specification looks like it'll be a great car, but it's a pity that exhaust will lose you maybe around 4 bhp. Ideally you should have a 1.75" internal diameter exhaust pipe from exhaust manifold end to final exit point. To gain the power you are losing fit either a 1.75" Maniflow 2-box or 1.75" RC40 2-box.

[racingbob]

mines at 10 deg at 1000 revs modified mg metro engine

[Spherix]

Cheers!
Regarding the exhaust, I assume you are speaking of a lack of backpressure? I'm known to the fact, but since this is mostly a town car and the occasional trackday car, i'm loving the exhaust sound over the 4bhp at the moment But it's in the back of my head, if the rolling road measurements dissapoint me, I might as well swap.

Annoying sidenote: was in the process of swapping the head today, and whilst attempting to do the first run of tightning the head nuts to 35nm, the first thread snapped. I'm assuming my new torque-wrench is off, since it felt stronger than 35nm, but the thread might have been bad as well. O well, it's fixable.

[bmcecosse]

Great shame to not change the cam! You are seriously hampering the engine - would have been a MUCH better option rather than the high lift rockers....... MG Metro or 266 cam will make a worthwhile difference if you don't want a 'revvy' engine - if you do - go for a 544 cam (~286 modern equiv). The dizzy will need the advance curve optimising - check the vacuum and mechanical advances are working as they should be. Just start off at ~ 5 advance - then move the advance up in small steps till you hear some pinking - then take it back slightly so it's 'not quite pinking'. But the best curve will be found at the rolling road - IF they know how to do that.......?? Ask before you go.......

[Spherix]

I'm going to a rolling road specialized in older sportscars, mostly british and so on, they do have years of experience with Mini's, so no problem there.

Reason why the cam isn't changed at the moment is that the engine is not coming out. In a later stage I'm fitting a lightened flywheel, changing the diff to 3.2 and possibly changing the cam at that point as well. Thanks for the advice nonetheless.

[racingbob]

if you have the engine out i urge you to change the cam
to as others have said to a mg metro like mine or 266
if not am sure you will be dissapointed

[govig]

Or a SW5 which I've been told works well with 1.5 rockers.

Edited by govig, 13 February 2012 - 09:17 AM.

[Spherix]

This engine has been in and out several times before, so far I am not disappointed with the car. Thanks for cam advices though, but this was not my initial question.