12 replies to this topic

[BillyBoy1993]

I wanted to know if these are are worth buying to put on my standard 1275 Mpi engine ? What sort of difference would it make to performace and what not ? I know it would be better to spend the money on a new cam but i dont really want to have to take the engine out to fit one :)

Edited by BillyBoy1993, 09 February 2012 - 01:01 AM.

[liam1288]

on your standard engine, i would say not to bother spending the money...i fell into the trap of the impression that they are a bolt on mod for performance but i noticed no power increace...if anything a power loss at low end...didnt have as much umph getting to say 40 as before...plus its not really as simple as a bolt on mod...the head gasket should be changed once you take the current rockers off as the rear head nuts have to be removed to get the shaft off and i had to grind a little off my (high lift) rocker cover as they were tapping on the back at one end. if i could be bothered with the hassle, id put my standard ones back on lol however mine are 1.5.1 roller rockers, not sure if theres any difference to non roller high lift but just thought id say...
they may be ok performance wise on a more modified engine so the new cam, modified head, manifold and rockers work in harmony but i cant say when it comes to that...

Edited by liam1288, 09 February 2012 - 01:45 AM.

[BillyBoy1993]

Thanks for the help mate pretty confused reading all the other threads loads of people say there good others say there bad lol well for some reason my mini only revs to about 4500 and ive seen another post that said it makes it smoother and rev to about 6000? and still kinda toying with the idea though if they go for the right price on ebay lol any idea of what i should go up to if i do decide to buy them ?

[Sam Walters]

I would say there is an issue elsewhere then.

[BillyBoy1993]

Any ideas what it could be ?

[Spherix]

Ignition timing & fueling.

[Bungle]

stage 1 kit first then you will need a good modified head

any more than that and you will find the standard ECU can't cope

[Magic jason]

ECU's

[JonnyBMX]

<sup>Well i looked into all this on my SPI, and ive now brought a new SC ecu and have the maniflow exzaust system and air filter(stage 1) and am now going to put these rockers onto my car (altough mine is allready cammed aswell) and before i put them on im going to put a new head on! as previously said it would be unlikely for the standard ECUS to be able to cope with to many extensive engine mods as far as im aware they are not re programmable!

there might just be a bit of a dodgey sensor or something if you car isnt running properly as standard!</sup>

Edited by JonnyBMX, 09 February 2012 - 08:42 AM.

[BillyBoy1993]

Thanks for the replies people and the car runs fine as standard just seems to not rev very high ?

[racingbob]

as far as i am aware the single valve springs seem to reach a peak 5200 5500 and some

valve spring bounce occurs so 6000 as you say you heard with these 1.5 rockers probably wont happen

your propably better off staying as you are they only make 2 -3 hp anyway and more likley top endish

with loosing some lower end, they work well on race engines for that extra bit

[ministar]

You will loose power low down, but may gain a little top end, as it basically increases the valve lift in correlation to the cam shaft. Putting a 1.5:1 on a more high performance engine would be more beneficial as extends the valve open/close time.

As said above, there is something wrong if you cant get above 4.5k. Most likely need a tune up on a mini friendly rolling road. After that you might realise you dont need more power after all

Im chucking out 77 horses with a 276cam and dont have high lift rockers, as the benefit wouldnt be worth it for the cost involved. If it was a 286/296+ i might be more interested!

[Ethel]

Hi-lift rockers also improve the lever rate for the valve springs so they will help extend the rev range - or wear your cam out if you fit beefy springs to do the same job.

The issue many fall foul of is that they do increase the effective duration, and overlap because the valves lift of their seats quicker to the point where there's some meaningful flow. If your cam is already "wild" to the limit of drivabilty they'll overcook the pudding.