117 replies to this topic

[ollydc5]

Lovely build

[evoderby]

The engine from the head gasket down is a standard 1275 as fitted to GTs straight from the Austin 1300 range. To be honest an increase of about 8 MPH and maybe 10 BHP doesn`t exactly elate me but the tuner said the fault may lie with the 1.5 ratio roller rockers so they are coming off - takers anyone? £80, only done 20 miles. It still looks lovely when the bonnet is open but the bottom line is - was it worth it? Err.......................................no (said very quietly).

Sorry to see you disappointed after spending a significant amount of money & energy on your 7-port conversion. On a £/HP level a 10HP increase towards 70HP overall is indeed a bit of a joke since a standard MG metro head, cam and Hif44 carb gives the same overall performance.

Before being too disappointed however please consider that the Pierce 7-port head is just a piece of the puzzle towards performance. A rather demanding piece to get the most performance out of, since it features enormous inlet port volumes allowing the direct fitment of a 45mm carb per port. To effectively use the flow potential (and achieve workable port velocity) requires the engine to actually suck in large enough volumes of air. This can be achieved by ( a combination of) two things, engine displacement and revs (as dictated by cam).

Accordingly, I feel you'd best consider a 1380cc bottom end fitted with a cam peaking above at least 6800Rpm, but rather 7500Rpm. Building a bottom end to last such revs requires a detailed build, with 7500rpm best requiring all steel components. This should get you into 120HP territory. If lower end driveability is more your thing I'd consider selling your current head and swapping it for a specialist components 7-port head which features much smaller port volumes (still good for up to 135HP in standard form though!) and something like a SW5 cam for around 100HP on your current 1275 CC.

Best talk to a few of the engine builders, MED does the Pierce head and can advice on what overall combination of cam and displacement works best...and how much to expect from it. SC does so for their own head. Both companies have spent a lot for going through the learning curve you're now experiencing...why not make use of it?

Good luck, let us know when you're above 100HP!!!

Edited by evoderby, 16 September 2015 - 04:11 PM.

[Mini-Hazel-Nut]

Well thanks for that. You obviously know more about these things than I do. I`ll have a think about things. There is a 1340 lump for sale on oilbay at the moment that I`m considering buying. It`s in bits - lots of bits and may be worth mating with said head. But talking of heads mine is in a bit of a spin at the moment so I need to calm down and have a good cogitate. No, that ain`t rude! 

[phil hill]

Don't fall into the trap of comparing the "book" figure of 72bhp from an MG Metro/Rover Cooper with the "measured" figure of 70bhp on a rolling-road, they are quite, quite different.  The manufacturers figure is generally an "at the flywheel" figure and is the minimum pass-off test for the engines as they come down the production line.  Some may be better, none should be worse.

 

A standard MG Metro in my experience "measures" about 52-56bhp at the wheels on a rolling-road.  I'm of course assuming the the "70bhp" you quoted is in fact an "at the wheels" value rather than some calculated/estimated "at the flywheel" value from the rolling-road test.

 

If the car has 70bhp at the wheels then that's not too shabby at all.  I can't see any mention of what cam the engine has, or what compression ratio, so if that is 70bhp on a more-or-less standard bottom end then that's pretty good to be honest.  

 

I guess the key question is : Are you happy with the performance ??  

 

If yes, then happy days.  Stop worrying about the actual bhp figure and enjoy the experience of (to quote CooperMan) a "not so slow" Mini.

 

If no, then look into a different cam, maybe some more displacement etc.  As already mentioned perhaps speak to someone who has more experience of this type of head.  Often it's more about the combination of parts and experience of these combinations, of what works and what doesn't, which makes or breaks a certain build.

 

Phil.

 

Edited to add : I've just re-read the above and if the engine underneath is a standard 1275GT/Austin 1300 unit, with a conservative standard cam and pretty low compression then imagine what it will do with 10.5:1 compression and a better cam in it !!

Edited by phil hill, 17 September 2015 - 01:29 PM.

[mini13]

what phil said,

 

 

these heads neally need a big cam and high CR as they ports are quite large, you need the hiogh lift to get enough port flow,

 

somthing liker a 286 SW10 or RE13

[Mini-Hazel-Nut]

Thanks you 2. The 72 bhp is at the flywheel with 47.8 at the wheels. I`m really tempted with a MG Metro Turbo engine at the moment in which case I`ll sell the head and carbs as a unit. The engine would have to come out for a cam change anyway...............oh, I don`t know what to do, where`s me gun? 

[The Principal]

Consider taking the head off and taking it to someone like Neil Slark, the standard Pierce heads are fairly basic the gas flowing can be improved and you can have larger valves fitted but not too large as the heads are known to crack between the valve seats also the hardened exhaust seats can only go so large. Combine that with the correct Compression ratio and a decent cam and you'll see some improvement. Sounds like you have plenty of potential i wouldn't give up just yet. 

[phil hill]

Thanks you 2. The 72 bhp is at the flywheel with 47.8 at the wheels. I`m really tempted with a MG Metro Turbo engine at the moment in which case I`ll sell the head and carbs as a unit. The engine would have to come out for a cam change anyway...............oh, I don`t know what to do, where`s me gun? 

Ok so 48bhp at the wheels isn't quite so impressive, it seems like the combination of parts just are not working together very well.

 

If you are resigned to taking the motor out why not build something up to suit the head ??  Take some advice from a reputable builder and see if you can get the power you desire that way.

 

A second hand MG Metro Turbo unit (or any second hand engine to be honest) is always going to be a bit of a gamble unless you are absolutely certain of it's history or strip and inspect it.  If you're going to those lengths why not rebuild the engine you know ??

 

Phil.

[evoderby]

..............oh, I don`t know what to do, where`s me gun? 

Let's start with what you want out of an engine. Do you want a peaky street screamer well in excess of 100HP, or rather a very torquey tractable engine with between 90-100HP??

[nicklouse]

Reads as the engine us just not up to the head.

Whip it off and skip a 5 port on with a single su and go have fun.

Then let's get some parts put together to give you a motor that you want.

Don't sell the high lift rockers you will need then for the new build.

[coopdog]

Could always add the turbo to this engine, would work well with that head

[minipete]

After reading this you've put me off investing such a lump of cash for a cylinder head.Think i'll stay with 5ports and my bike carbs. Its a shame as they look the dogs danglies when the bonnet is open.
Maybe what you'll have to do is put a standard head back on and build a good bottom end to suit.
Whoever said making minis go fast was easy was a liar.

[Mini-Hazel-Nut]

Yes the WOW factor is deffo there for eyes an ears but after that it`s a case of the "hmmmm" factor, lol.

[sonikk4]

For me i would find another lump, modify the bottom end, decent cam etc then swap the 7 port head over. However before that check to see what else can be done to the head first to help improve it. Not going to be cheap but ultimately worth it.

[Mini-Hazel-Nut]

The problem for me is that my workshop, garage etc is a strip of tarmac by my front door. If I had otherwise the head would most definitely gone onto a tweaked bottom end. As for paying someone else to do the same there`s no-one within miles who would know what they are looking at even, It`s all curry and pizza round here