14 replies to this topic

[MarkC123]

Hi all ,

Very torn as to how to proceed. I am about to purchase a stage 3 head off Keith calver, going for a fast road set up in my 96 sprite. It has an ecu off a 95 cooper so while I understand the limitations of the ecu generally, at least I have the ‘most capable’ set up besides getting into customizable ones.

Basically Keith has told me head and a new piper cross cam he provides (p255) and “you won’t believe the difference” plus it was designed to run with standard rockers which So I won’t need to invest in “expensive and often unreliable rockers”.

So that had me semi sold whereas my mechanic seems to think new head and either 1.4.1 rockers from calver or 1.5.1 MED racing rockers (270 quid mind you) would be as good.

I understand it’s a fairly massive job getting the cam out, new one in and dialed you but I have new clutch kit from MED - ultralight flywheel and heavy duty clutch and was planning on doing the gearbox / head and cam while engine is out. Not sure if it’s mere reluctance on the part of my mechanic or whether it really will make much of a difference.

Running 6x10s and opting for a 3.1 final drive along with a central oil pick up and 4 pin diff.

Have new suspension - doughnuts / hilos/ shocks all round and cooper s brakes on the front.

Also upgraded my rad to a performance two core / large impeller pump and replaced a few other bits so the ancillaries should be able to manage

HOWEVER any recommendations for things to change while engine is out would be massively appreciated. So far bar the head and gasket cam / followers etc for the engine modification haven’t thought of much else.

Thanks as always - about to blow some serious cash so want to move in the right direction.

Best,
Mark

[InnoCooperExport]

I would go new cam over new rockers, especially considering the trouble you´re going to elsewhere on the car. Increasing the rocker ratio is sometimes given to be equivalent to going up step in cam profile, however all you´re doing is increasing lift, not duration. To get the most out of your new stage 3 head I would go with Keith´s recommendation. 

[whistler]

I'm in the same situation with having a new head off Keith and have gone with his recommendation of a BP255 cam with standard/1.3:1 rockers. This keeps the torque well down and in the range of revs that I use for a road car. Not having to go to wide valve clearance is also a plus mark. Stick with what Keith recommends as he's the head designer.

[Cooperman]

I would always choose a better and appropriate cam over offset rockers.

A 255 cam sounds about ideal if you want to run with a 3.1:1 FDR. You might still find a 3.1:1 a bit on the high side for best acceleration. Many of us prefer a 3.44:1. I run a 3.44:1 on a 1990 Cooper 1330 with an MG Metro cam and improved head and it is super. It will cruise all day at 70 mph and gives very good acceleration.

[clem_c]

Hello,

 

My mini has got a similar spec to yours :

1995 spi non cooper

Minisport stage 3 head, Kent MD274 camshaft, high compression pistons

Running on 6x10 wheels with a 3.1FD, 4pin diff etc…

 

Before to buy the stage 3 cylinder head from Minisport, I was wondering why their “Stage 3 1275cc SPi cylinder head” has got 35mm inlet valve, while their “stage 3 1275cc Mini Cylinder Head” has got 37mm inlet valve.

 

Similar stage of tune, but different valve size for a carb or an injection? I know this is marketing, but there was probably an explanation.

 

I have asked their customer support, and they replied :

 

“With regard to the SPI cylinder head, the stage 3 version has 35mm inlet valves whereas the regular 1275 stage 3 has 37mm inlet valves,  the reason we don’t list a SPI with 37@S is because this spec’ of head would not work on the SPI engine and injection system due to reduction in velocity due to the oversize valves.”

 

Using high lift rockers will increase the flow section area at the inlet valve, thus reducing the flow velocity. (not good for the SPi injection management according to Minisport)

For this reason I believe that it is better to choose the cam (increase duration), over the 1.5 roller rocker (increasing lift).

 

My mini has got her own instagram profile : minimoon1310. There are a few pictures of the stage3 cylinder head. (ports and combustion chamber)

 

I think that the lower inlet flow velocity using high lift rockers also means that you would get the potential benefits at higher rpms.

 

Hope this helps.

[MarkC123]

Hi all - thanks a bunch , I think I’ll be picking up the cam instead of the rockers - sounds like a no brainer!

Any other ancillaries that would be recommended while engine is out ? Braided oil pipes or anything ?

Many thanks !

Edited by MarkC123, 03 March 2020 - 05:44 PM.

[clem_c]

Just take your time when closing the engine, be careful not to damage any gasket. You don’t want to have an oil leak. I found out that the gasket underneath the timing cover is quite fragile, I replaced it 2 times while tighting the timing cover bolts because I suspected it was damaged. Make sure the timing cover sitting face isn’t warped.

It is probably worth changing your timing chain for a good quality one, with a new chain tensionner. I am maybe stating the obvious, but make sure to time accurately your camshaft.

You could also rebuild the gearbox. I think it is worth doing it if you have the money. You can buy a rebuild kit with the essentials : bearings, layshaft and baulk ring. It only get very expensive if you have to replace gears. There are a lot of tutorials on YouTube, it’s no rocket science and quite interesting. My 2nd gear was sometime poping out while decelerating. I inspected each gear, and replaced the “synchro hub spring” and the “detend spring for rod box” (their names on the minispares website). That resolved the problem, the 2nd stays in place now. I think it is a common problem on minis, that you can sort out if you engine is out. (Preventive maintenance).

Be very careful with all the clearance you have to respect: diff side clearance, primary gear and idler gear. (It’s worth measuring them even if you don’t replace those elements).
If you rebuild the gearbox: layshaft end float and clearance under the retainer for roller bearing. (It’s all explained on YouTube)

I wouldn’t be worried about installing a breaded oil pipe, it is really easy to do with the engine in the car if you have an issue with the original pipe or the oil filter housing. You can do it later.

Edited by clem_c, 04 March 2020 - 07:50 AM.

[clem_c]

New oil pump too!

[clem_c]

And check the oil release valve. Mine was stucked, causing oil pressure problems.

[nicklouse]

i think you have decided correctly but to back this up.

 

the heart of an engine is the cam and everything else should be done to suit and maximise that.

 

so you may need to have the block decked as well to get the right CR.

 

throwing a set of rockers at it is not a fix really as they may not actually do much if not set correctly.

[MarkC123]

Great thanks guys.

 

Out of curiosity would rockers be worth doing down the line or am I best to just leave as standard if I plan to use the BP255 cam?

 

Thanks 

[postve]

Hey Mark,

I have been working with Keith for my build over the last 6 months and have a 1293/BP255/CST2001/1.4.1 rockers cylinder head and absolutely love the torque and top end thx to the rockers!!

My thoughts, absolutely get the rockers if in your budget and Nick is bang on with the starting point being the CAM and follow to the letter Keith's advise , I did and have been very happy as again I was crystal clear as to what I wanted - a lot of low end torque - 1500 a 5500 and runs out of breath at 6500 - trust me 95% of us never get past that RPM anyways!

I was pushing for a CST2002 and again Keith advised against it based on what I expecting the car to do and he was right!! He advised why waste the money and being more racier of a CAM introduces a host of other consideration and modifications I would have to do!

Only thing I would suggest and it has been amazing for me was a KAD quick shifter as greatly reduces the "slop" in shifting and make for a much better and quicker accelerating experience.

Keep us updated on when you are done and how it turned out - very interested.

[Tommymo]

Any update on this? Would be keen to know how it ended up

[PoolGuy]

Any update on this? Would be keen to know how it ended up

OP hasn’t been here for well over a year so I doubt you’ll get an update. Postve’s experiences are worth reading though.

[postve]

Hey guys, I was waiting for Mark to see where he was at and too bad he is no longer online as for mine, as follows and added to the power - lol:

 

• 2021
  • VMAX Super Charger – went from 90HP (wheels) to @140HP wheels) – 2021

 

• 2020
  • CST2001
  • BP255  - Absolutely agree with nick that CAM is the baseline and built everything around that
  • 1.4.1 rockers
  • Changed from 3:44 to 3:1 final gears (changed myself as just pulled engine and flipped on its side, no need to take off the box!!!!!)
    • I would highly recommend the 3:1 as I had 3:44 for 6 months and the RPM range is way too high for reasonable city and certainly highway use – at least in my experience as geared too low.  I found the 3.1, after months of testing was a relief as can get calm RPM levels on highway and not shifting from 1-3 by the time I go through an intersection just to stop the car from screaming.

If you are looking at adding a VMAX or any super charger, make damn sure you do a leak down, compression, check pistons and ultimate, check for any cracks in the gearbox.  My buddy missed the last one and gearbox split in (Torque) half after a heavy load run.

 

Anyone want my full speaks I can post.