Mini Spares 1.5 Ratio Rockers, any good?

I think what I’m about to say might cause disagreement amongst some of the Mini fraternity, but this is my ‘forum’ so there you go!

In a previous post referring to my engines performance, I wrote:
“There is a great big flat spot when accelerating of idle. It seems fine if I floor it, but hesitates and has a lot of induction noise, but not much go if I tread lightly on the gas. I’ll check the mixture as I still have the wideband O2 sensor installed, and maybe thicken up the oil in the SU damper, to give a richer mixture when accelerating. I currently have ATF in there, prior to that I had 3-in-1 oil which I believe is 20 SAE, the same as original specced ‘SU oil’. I’ll also re-visit the ignition advance curve, not that I can do much for it at the moment.”

Well I started to go down the air fuel ratio route as well as the type (viscosity) of damping oil in the SU carburettor, but it dawned on me last night that maybe it might be the 1.5:1 ratio rockers that I fitted well over 18 months ago. The other clue is the ‘reversion’ noise that it has in the lower rev range. When I had the ECU on I had a very unusual hump in the Volumetric Efficiency (VE) table.

VE table with large hump
VE table with large hump

If you where to research VE tables, then you would note that this one is far from ideal, in fact it’s plain wrong. The following table demonstrates what it should look like (this is not my VE table).

What a 'normal' VE table should look like
What a ‘normal’ VE table should look like

So what would cause the VE table go like this, that is increasing the VE which results in a richer mixture at the hump? My theory is that it is intake reversion i.e. where the intake valve is opening and some of the exhaust gases get pushed out of the intake diluting the intake charge and causing ‘standing waves’. It’s these standing waves that I believe cause the growling sound from the intake. People with a Weber or Dellorto carburettor would know what I mean!

So what caused this sudden increase in noise from the intake? From what I can remember, I put on a K&N air filter along with a stub stack  at the same time as some Mini Spares 1.5:1 ratio rockers. I have blamed the smaller air filter all along for the increased noise, which is understandable, but why the loss of torque down low?

So getting back to reality, it slowly dawned upon me (I know I’m a bit old/slow/stupid) that maybe it was the 1.5:1 ratio rockers. Since I never throw out anything, I put the old rockers back on, set the clearances and started her up.

The first thing I noticed was that she started a lot easier, required less choke and once warm idled smoother. I adjusted the mixture (slightly leaner) and then took it for a brief fang around the neighbourhood.

Chalk and cheese, 90% gone was the ‘reversion’ noise’ a heap more torque in the lower to middle RPM band, and would easily rev out to 6000 RPM. The car would easily accelerate away from 20 KPH in third gear with no pinging or hysterics. I later went for a drive down to the beach and surrounds with a friend, who remarked that it was a lot smoother and quieter.

So in summary, it appears my engine, intake, carburettor, camshaft (standard Mini Metro) and cylinder head combination just does not like the extra lift and increased overlap that these rockers give. It also could be a gas velocity problem, due to the valves opening ~ 20% wider and quicker. Who knows? I’m not a mechanical engineer, but my seat pants tell me that something has changed for the better! Regretfully I don’t have the ECU on, so I can’t see what effect it would have made to the VE table…. but you never know I might revisit it again!

The Brakes are a Braking

Just a little update for today. I spent most of the day cleaning the garage and whilst there I put the Peugeot on charge, as I will start looking at it shortly.

I had time this arvo to adjust the rear brakes on the Mini; the L/H drum was the worse. I also removed the ATF fluid from the SU damper using a piece of clear plastic tubing as a pipette. Don’t use non-clear tubing for obvious reasons! I then filled it up with 20-40W motor oil.

I haven’t had time to look at the Smiths instrument voltage regulator yet, maybe tomorrow. I’ll also road test for the flat spot in the carb as well as the brakes.

Mini and Pug back in garage after garage clean up
Mini and Pug back in garage after garage clean up


  • Adjusted rear brakes.
  • replaced SU damper oil with 20-40W motor oil.

To Do

  • Find out why instrument regulator is not working yet again!
  • Enjoy car!

Nice to do, but not required!

  • Fit the new heater. (Not doing until I have car on the road and tuned in… it is summer after all!)
  • Get a wheel balance and alignment.

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It Friken Lives Again!

Jeez I’m getting sick of working on this car! Anyway got it going (see the Done section below) just in time to take it over to my sons place some 42 km’s away to share pizza with him.

I have not completely finished it, in fact I still haven’t installed the under bonnet firewall sound deadening and also the internal dash cards along with some tidy up required of the wiring.

It drives very well, but the advance curve is not right, and I think it’s running a bit lean… I didn’t have time to adjust the mixture. The car sits better at the rear, the hydrolastic has evened out a bit better since I put a couple of washers in the front.

Very happy it’s back on the road though. Now to start looking at the Peugeot 306’s automatic transmission.


  • Removed blanking plate and installed mechanical fuel pump
  • Removed Rover SPI fuel tank and wiring, installed smaller Morris tank
  • Removed EFI filter from rear sub-frame
  • Installed Davies Craig thermatic fan controller as previously the fan was controlled via the MegaSquirt
  • Replaced a rear exhaust hanger and discovered that the previous company that had installed the exhaust system had done up the system under tension and all of the hangars were damaged (rubber breaking away from the steel). Fixed this after a lot of swearing.
  • Bleed the brakes again
  • Installed the HIF44 SU with new gaskets and connect accelerator and choke cables
  • Installed the Lucas 65dm4 electronic distributor and ignition coil and set distributor to roughly 8 degrees BTDC
  • Installed fuel pipes for fuel tank and carburetor along with a fuel filter
  • Filled radiator
  • Prayed
  • Turned ignition and it started once the fuel primed up
  • Set the timing so that I had no more than 32 degrees BTDC… this distributor’s advance curve is way wrong for this engine… so stay put for future developments on this matter
  • Drove it 42 km’s to my sons house, no problems! Hopefully return leg will be also!

Edit: It made it back!

To Do

  • Find out why both the fuel and temperature gauges are not working… most probably the +12v to the instrument regulator is missing
  • Adjust rear brakes and try to bed in the brakes
  • Put back the sound deadening on both sides of the firewall… it’s deafening without it!
  • Wire up the tachometer again
  • Enjoy car!

Nice to do, but not required!

  • Fit the new heater. (Not doing until I have car on the road and tuned in… it is summer after all!)
  • Get a wheel balance and alignment.

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No more EFI

I have done the unthinkable to some; I have removed all of the EFI related hardware. My EFI project is now dead. I’ll leave all previous post here for future readers to read, hopefully there is some value here for others.

You might be wondering why I’ve abandon the EFI installation on my Mini at this late stage. Firstly the reason is mainly a time related thing, I have found I’m spending more time on the car to find solutions to problems with the EFI setup, rather than driving it. My son Hamish who is in his last year of ‘L’ plates, is itching to get into it to build up his hours, plus to spend more time with me in enjoying this car.

Secondly, going to a TBI with a single injector, has issues as well. ‘A’ series engines, as well as ‘B’ series engines have siamesed inlet ports, this leads to an effect called “port robbing” where the inner cylinders steal the outer cylinders intake mixture, causing the outer cylinders to run lean. A very detailed explanation of the siamese port injection problem can be found here.

You might be wondering, like me, what I’ll be doing whilst not fiddling with the EFI. Well one thing I have always noticed from the onset of installing the MegaSquirt, was the increase in torque at low to mid RPM’s. This was because of the programmable nature of the ignition system replacing the distributors mechanical and vacuum advance. I have been looking at some of the commercial offerings, and at this stage have not found one I like. Maybe I’ll make my own, as some of you might know, I have backgrounds both in electronics as well as programming.


  • Removed all EFI related wiring and hardware except for the knock VR ignition and Temperature sensors… they might be needed for a new project 😉
  • Removed the MegaSquirt ECU
  • Removed the Injector from the carburettor
  • Removed the HIF44 carburettor so I can drill a new vacuum port on the carby side of the butterfly to suit the Lucas Electronic distributors vacuum advance. The advance curve of this distributor is really not suitable for this engines tune… but it will do until something better comes up.
  • Fitted the coil and bracket
  • Fitted the Lucas distributor  and drive gear. Checked that it was aligned correctly.
  • Purchased a Davies Craig Thermatic Fan Switch, since the MegaSquirt used to control my electric radiator fan, I need to control it somehow!

To Do

  • Install mechanical fuel pump
  • Install non-injection fuel tank
  • Remove EFI filter from rear sub-frame
  • Fit Davies Craig Thermatic Fan Switch
  • Enjoy car!

Nice to do, but not required!

  • Fit the new heater. (Not doing until I have car on the road and tuned in… it is summer after all!)
  • Get a wheel balance and alignment.

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