18 replies to this topic

[austinmini1963]

Hi,

I am currently running a 998 in my clubby and after much debate I have got a 1275 engine and gearbox to go in her from a 90's cooper. (quality beef!) and the engine from a 90's 1275cc auto (blergh!), with the view of combining the best bits to make one good one:



The engine and box I have bought needs rebuilding but while its apart I want to spice it up a bit, so the easiest way to do it is to get an uprated camshaft and roller rockers (I already have a meaty carb, lcb and metro electronic ignition).

But I am new to all this tuning stuff so what camshaft do I get? (I want the car to still be useable for round town use but more power)

Also whats the deal with these roller rockers, 1.3 to 1 and 1.5 to 1 stuff? how does it work?

Many thanks, Tom =

[smartie93]

What bits do you plan on using from the auto? just wondering why you bought two engines haha

As for roller tip rockers, unless you can get them cheap I wouldn't bother. the ratio is the difference between the distance from the roller tip and the centre of rotation, and the pushrod and the centre of rotation, the higher the ratio the higher the lift... I believe haha

[AndyMiniMad.]

Hi Tom...first thing to do is get the head off and have some porting done. then get a decent exhaust system for it. This will prepare the way for an uprated cam and rockers. In my opinion there is no point in fitting a high lift long duration cam or high lift rockers if the head cant flow the gases in and out properly, This is after all where the power comes from!!

Basicly a higher ratio set of rockers will open the valves a bit further which will increase the charge going into the bore, giving you a bigger bang and more power, but as I said above, if the gasses cant get in fast enough whats the point of the expensive rockers or cam?

[smartie93]

Head work is the way to go, i'm not sure what a 90s cooper head is like, i imagine slightly better than a standard 1275. so depends on how far you want to go.

the valves are the most restrictive part of any engine, so i'd look at bigger ones with better seats before porting

[Cooperman]

The head is the key to releasing the power from an A-series engine.
Then an MG Metro or Kent 266 cam will be super. They are virtually identical.
If you have the head ported & flowed and use 35.6 mm inlet valves a set of 1.5 rockers might give a few extra bhp at the top end, but mid-range you'll not notice the difference despite spending a large sum on them. A0's Cooper wil probably only have 33.5 mm inlet valves so you'll need to get bigger ones fitted when the head is being flowed.
The Cooper carb should be an HIF44 on an alloy manifold, so clean out the manifold a bit by removing the casting 'flash'.
It'll go well when finished.

[austinmini1963]

Hi everyone!

Cheers for the help, by the sounds of things I will start with tinkering with the head. The head itself looked like it had quite big in and out ports but that may just be my untrained eyes, also the last engine I rebuilt was an 850 sooooo no comparison I suppose. Is the head modifying something that can be easily be done I me or is it a job for a professional?

Also, do I need a bypass hose on the waterpump? My 1275 doesn't have one, is this a good thing?

Oh the other 1275 auto came out the car because I changed it to manual when the gearbox became just an empty box. Kept it to play about with u see :)

Cheers, Tom

[tiger99]

If your engine is assembled from all the correct parts, i.e.head and water pump, which seems likely, and there is no bypass hose, you do not need one, which I am sure you will be relieved to hear. It would only be if the head had come from one engine and the water pump from another that you might have a mismatch, which could cause problems. However, there are ways round that.

[racingbob]

dont bother with 1.5 rockers save your money

for something else like a MED substack with the IG filter

with a mg metro cam or 266 cam not needed you will have plenty

of punch with nice head

[R1minimagic]

Rollers rockers can be very beneficial so worth the money if you can afford them IMO

[Cooperman]

The biggest advantage of roller rockers is that with them there is no side load on the valves so the valve guid wear is reduced.
I terms of power they don't seem to do too much when considering how much they cost. You might gain 2 to 4 bhp at the top end, but lose a bit lower down.

[Mrpeanut]

I agree with Cooperman and racingbob. I fitted 1.5 rockers to a 1275 engine with a worked head. I lost grunt below 2k revs and couldn't get the rockers off quick enough.

[Cooperman]

I have 1.5 roller-tip rockers on my 'S' which has a 286 cam, etc. I gained 2 bhp at the flywheel at over 5700 rpm, gained nothing below that and lost a bit at the bottom end. It's very 'cammy' below about 3000 rpm when hot.

[jaydee]

I have them and roller rockers are A VAST improvement over the poor sintered crap rockers.
Once you have an expensive freshly reworked head, i'd go for rollers, but in a 1.3 form, to keep it at its best conditions and get the best out of your camshaft, which is most likely profiled for a 1.3:1 lift ratio. Accurate adjustment of rocker geometry is vital.
Fitting of 1.5 rollers require precise calculation and evalutaion of valve size and camshaft options to get the best out of the combo. A wrong combination of ratio-lift-duration-valve size wont take you anywhere.
Theres always to add that the increased ratio and heavy poundage valves can really shorten followers and camshaft lobes life. An high revving engine has a short life itself so i wouldnt worry bout it, but if you're building a reliable unit then i'd start to think about it.
If youre' fitting them just looking for power improvement, then you're wasting money.

[AndyMiniMad.]

Lots of good advice here!! I have 1.5 roller rockers on my 1380 and they made a bit of difference at the top end..by which I mean over 6000 revs!! below that there was no power improvement...but they helped to even out my lumpy idle a wee bit. Your cam and head are way more important than your rockers though. If you get the right cam and your head is right then they will work well together, If you go for a big overlap on the cam, Once the scavenging effect comes into play at high revs you will appreciate a decent good flowing head!!

Edited by AndyMiniMad., 15 October 2012 - 10:11 PM.

[rock1day]

I recently replaced the exhaust on my standard 1275 (carburettor) Cooper with a twin box RC40 (cat deleted) linked to the original (LCB pattern) manifold/downpipe.

 

No idea how much power this gave, but the performance has noticeably improved, which interested me in fitting a modified head with "S" sized intakes and having the car set-up on a rolling road.

 

I`m only looking at bolt-on`s, and the head guy (Peter Burgess) suggested 1.5 ratio rockers, which he felt would suit the short timing/ low lift of the standard cam and add about 4 bhp at the top-end without losing anything at the bottom end. 

 

Has anyone tried this?