17 replies to this topic

[booton]

my 998 mini engine pipe 270 cam is a bit flat under 2500 rpm

i know the cams kick in later than standard but is there any way of improving the performance lower down the rev range.

theres plently of power above 3000 rpm,

just wondering if i could do anything to improve this,

Currently ruining a standard 1"1/2 carb soon changing to a 1"3/4 that will be modified as the vizards guide.

anything else i could do. any need, jet.

[Cooperman]

That is exactly what you should expect with a 270 degree cam in a 998. Peak power will probably be at about 5800 rpm in a 998 with very little below 3000 rpm.
The only way to obtain better performance at lower revs is to fit a more suitable cam. With a 270 cam you should expect to be keeping the revs at over around 3000 rpm at all times. In a 998 a 270 is quite an aggressive cam.

[booton]

i thought it that was. i was just wondering if there was anything i could do to improve it slightly that all. hard to keep it over 3000 around town and at junction with out looking like a right tit having it idelling really high.

from my rolling road chart it goes up from 1to 2 thou then drop then shoots up.
i just don't like the drop. love when it kick in and the lush noise it makes just before 3000.
 img017.jpg   901.98K   55 downloads

just wondering if i could reduce the drop.

[Cooperman]

In a 1275 a 270 degree cam will pull from around 2500 rpm, but cams are always a bit more 'cammy' in the 998 engine. A 270 cam is great overall in a 1275, but in a 998 you will have to accept the need to 'keep the revs up'. After all, you don't fit a hot cam to drive around slowly.
You'll have to accept it as it is or change the cam for a 'softer' one.

[booton]

no prob thanks for the advice.
just thought i would ask. see if there anything i could do.
i do have a veneer pully could i alter the valve timing with that.
just an idea.

if you don't ask you don't learn.

thanks for the advise. steve

[Cooperman]

Altering the cam timing won't help and could make it worse.
As it's a 998 you can change the cam without taking the engine out.
A really good cam for a 998 is the early Cooper 'S' 510 profile and that will pull from 2000 rpm, be strong from about 3200 and peak at about 5600 rpm.

[booton]

no don't want to change the cam,

just thought i would ask. thanks for the advise, still learning.
i like the cam and the power it delivers.
with a few more tweeks it should be good for a few more BHP.
i think i got the bug lol.

[R1minimagic]

Change the diff for a higher ratio, it will help it rev a little bit quicker...

[Cooperman]

Altering the cam timing won't help and could make it worse.
As it's a 998 you can change the cam without taking the engine out.
A really good cam for a 998 is the early Cooper 'S' 510 profile and that will pull from 2000 rpm, be strong from about 3200 and peak at about 5600 rpm.

Who said anything about altering the cam timing...........

If you what to give up on this cam even before trying to get it working right, a better choice would be the MG cam. Pulls from 2000 but doesn't stop until well over 6000............

He did, he said he has a Vernier Pulley and could alter the valve timing (= cam timing). Please read before replying with implied criticism.

[R1minimagic]

A piper 270 is a perfectly good cam for a 998 engine as long as you have a good head (I built one myself many years ago). Looking at the power curve it looks very respectable so assuming the head is good

[booton]

head is a good one.
 WP_000025.jpg   1.21MB   21 downloads
i was just wondering if the dip could be fuelling due to only having a 1"1/2

changing the diff would be a good idea.
what ratio would u recommed.

currently i have a 3.1 diff.

[booton]

also would a lighter flywheel. help keep the revs up.
the head was skimmed and check by a cylinder head specialised.

[booton]

don;t think so he said to ruin the engine in and bring it back.
will ring him tomz and find out.

[andymini12]

Also megajolt would properly make it less 'cammy' and have a little more power down low.

[nafnaforiginal12]

mine's a 1293 with a piper 270i cam, it does nothing below 2500-3000 rpm but then just takes off.
I also have a lightened flywheel but i've noticed that if i let the revs drop suddenly from a high rpm with the clutch in, it stalls, don't whether this is because of the flywheel or whether i just can't drive. lol