14 replies to this topic

[spiguy]

I have a '92 SPi cooper. Happy enough with the car's performance, however at some point in the future I may want to try to get a bit more out of it. Just wondered - is there any point on fitting a  better head (eg stage 3 I think it's called) on the engine, but with the standard camshaft? or is this a waste of time and money?

[Steve220]

Anything to improve the flow of the standard head. It's a severe weak point on the a series.

[FlyingScot]

Same tuning as carbs so better head should be good. Cams is the only area of concern as due to the overlap on some too much unburnt fuel can mess with the lambda sensor. There are however specific cams which work well in an SPi.

FS

[spiguy]

Cool, so dropping a good head on the car without doing anything else (ie not taking the engine out...) could yield some results ?

[Nu2mini]

More information to digest here. Not sure what the head alone may give you v Head/Cam combination

 

http://www.theminifo...mini/?p=2363221

[IainStallard]

I gained 10bhp and 6lbs ft of torque when I bolted my ported cylinder head on, completely standard engine other than a stage one kit on my SPi

[spiguy]

Hmm that is very interesting Iain... can you tell a bit more about the head in question? Was it an off the shelf item or something you worked yourself?

[IainStallard]

Hmm that is very interesting Iain... can you tell a bit more about the head in question? Was it an off the shelf item or something you worked yourself?

 

I worked on it myself, did all the porting myself with tuition from my local engine builder (used to do some of minispeed's head before they moved in house). Could be better but it wasn't a bad job from a first attempt.

[Fast Ivan]

Hmm that is very interesting Iain... can you tell a bit more about the head in question? Was it an off the shelf item or something you worked yourself?

 
I worked on it myself, did all the porting myself with tuition from my local engine builder (used to do some of minispeed's head before they moved in house). Could be better but it wasn't a bad job from a first attempt.

That must be satisfying Iain, you must be pleased knowing you did that yourself

[spiguy]

Superb! As said, must be very satisfying. So in that case then I guess there is no reason why somebody fitting an off the shelf Stage 3 head (I keep calling it that, is that correct?) shouldn't see similar benefits?  Was it standard rockers too ?

[Fast Ivan]

Worth talking to Calver or Dodd about what might be best for your engine I would say mate

[IainStallard]

Superb! As said, must be very satisfying. So in that case then I guess there is no reason why somebody fitting an off the shelf Stage 3 head (I keep calling it that, is that correct?) shouldn't see similar benefits?  Was it standard rockers too ?

 

Standard rockers still. Just need to make sure you have the correct compression ratio by skimming it down the appropriate amount

[spiguy]

Thanks guys.

[brivinci]

John Coopers Garage only did heads and 1.5 lifters on their "Si" converted cars. Obviously, the more you do, the better but a head alone would certainly help things. If a cam is out of the question (assume you dont want pull the motor) then adding 1.5 rockers is sometimes said to be like adding a cam...though I'm not sure about that.

 

With these injected cars, its not about outright HP. You are never going to have a fire breathing monster unless you dont mind parting with piles of cash. Understanding that 85bhp is pretty much max, it really comes down to maximizing the power and delivery of it. Something with torque down low that lasts all the way through the rev range makes for a good time. 

 

Also, you are not completely off by calling it a "stage 3" head as it seems like what most companies sell them as. To me, its just such a generic name. As suggested, give Keith Calver or Dodd a call and have a chat. You would be amazing at how much info these guys can give you. Tell them what you are after and they can tailor a head that will fit your needs perfectly.

[Blatherskite]

Cool, so dropping a good head on the car without doing anything else (ie not taking the engine out...) could yield some results ?

We went with stage 3 head only on SPi and got a significant bhp rise to 73 on the rolling road. Quite happy with that!