20 replies to this topic

[Dan]

Why does nearly everyone say Roller Rockers are bad for Minis???

Err, they don't and that's not the point of this. The point is that the increased ratio of 1.5 rockers doesn't really work well in many 998 builds, it's nothing to do with the rollers. Whether rollers have any advantage is a different question and depends on how well shaped the original rockers are. Just because everyone automatically applies a certain upgrade to an engine doesn't mean it actually does anything, you use a cold air intake as an example but in many well designed cars it would be a waste of time and money to fit one.

I have to say that this stage 2 kit sounds like a load of parts that Mini Sport have decided to throw into a box because they think it will sound attractive to people who maybe don't know enough to develop their own engine. Examples of this would be:

As said above, high ratio rockers are not usually considered worthwhile on 998s unless they spend all their time at high revs (race engines)
LCB manifolds on 998 engines usually follow the same rules as the high ratio rockers.
Cone air filters are not the best choice for a Mini.
Your carb has a red dashpot spring already, most Mini HS carbs do.
Uprated head gasket?

This really doesn't seem to be a properly developed kit to me.

[Team Loxley Racing]

Why does nearly everyone say Roller Rockers are bad for Minis???

Err, they don't and that's not the point of this. The point is that the increased ratio of 1.5 rockers doesn't really work well in many 998 builds, it's nothing to do with the rollers.

So would it be advisable to swap the 1.5s to 1.3?

[Trail of Dead]

Why does nearly everyone say Roller Rockers are bad for Minis???

Err, they don't and that's not the point of this. The point is that the increased ratio of 1.5 rockers doesn't really work well in many 998 builds, it's nothing to do with the rollers. Whether rollers have any advantage is a different question and depends on how well shaped the original rockers are. Just because everyone automatically applies a certain upgrade to an engine doesn't mean it actually does anything, you use a cold air intake as an example but in many well designed cars it would be a waste of time and money to fit one.

I have to say that this stage 2 kit sounds like a load of parts that Mini Sport have decided to throw into a box because they think it will sound attractive to people who maybe don't know enough to develop their own engine. Examples of this would be:

As said above, high ratio rockers are not usually considered worthwhile on 998s unless they spend all their time at high revs (race engines)
LCB manifolds on 998 engines usually follow the same rules as the high ratio rockers.
Cone air filters are not the best choice for a Mini.
Your carb has a red dashpot spring already, most Mini HS carbs do.
Uprated head gasket?

This really doesn't seem to be a properly developed kit to me.

In my experience lots of people are saying Roller Rockers are no good for the Mini. I am simply wondering why....what is the science involved. I have read "Calvers Corner" regarding Roller Rockers and I just don't get it.

As far as "Just because everyone automatically applies a certain upgrade to an engine doesn't mean it actually does anything" is kind of a strongly opinionated perspective. Most people apply the same upgrades cause they WORK. Sure, a cold air intake probably wouldn't be suitable for the Classic Mini. I know, I know I keep raving about SN95 Mustangs (New Edges too) but on a standard 1999 Mustang GT a CAI can net you 12-20RWHP. On a 2003 Cobra you can gain around 30RWHP with simply a cold air intake swap. The factory piece is restrictive and makes the air tumble. My GT perked up nicely when I installed the BBK CAI on it. Sounded mean too! I know your an Admin and your making the point by saying we are talking about 998's here. I respect that, great. What I am saying is why do people say Roller Rockers are bad for Minis? The OP is planning on running them on his 998, someone replied to him telling him not to bother running them. I simply would like to know why. I am planning on running a set of 1.5 Rollers on my MPi1275 so I am kind of in the same boat as the OP. I am planning on installing a stage 1 kit that I already have on the 1275, many of the components are the same.

Edited by Trail of Dead, 27 January 2010 - 04:19 PM.

[Dan]

No, you still mis-understand. Maybe many people do debate the use of roller rockers but in this case the issue is with the ratio. 1.3:1 rockers are all a road going 998 needs. There are many threads debating the use of roller rockers with lots of useful information but that's not what's going on here.

As for my perspective being strongly opinionated, I'm afraid its actually based on bitter experience of 6 years on this forum. Most people apply modifications to their engine because they see them advertised in magazines or are advised by their friends. Not because they are actually any good for their specific need.

[minimender]

I tried 1.5 cast rockers on a 998 once or twice.
The one time I tested straight away without doing anything else to the motor it lost power.
Spec.
998cc with 12g940 head
MG metro inlet with HIF38 S.U. carb.
Cast LCB type exhaust manifold with single box straight through silencer.
Standard cam
Standard rockers
Lightened Flywheel and backplate
3.76 to 1 Diff on standard Metro gearbox
MG metro dizzy, tweaked a bit
10 " wheels
Called this my late yellow engine as it was the second all yellow motor and I painted my engines in different colours so I knew what bit was used on which motor after testing.
This was at the time my every day car and I used to rag it round everywhere changing bits on an almost weekly basis.

Anyway, it went up our measured quarter mile in 18.5 to 19 secs depending on the direction.
Took it home and changed the rocker shaft to one with the 1.5 to 1 cast rockers on and went back to the quarter mile.
Did two or three runs and it was slower, couldn't even make the low 20 secs, altered the dizzy and it went a bit better but overall it was worse so put the standard rockers back on, it seemed to go ok top end but not as lively getting up there hence the slower time.
Could be ok on race track where it's reving all the time with close gears but I didn't rate the rockers at low to med revs with out serious tweaking of the timing, that could just be my engine though as it was a bitsa (they all were)...

So there you are, pays yer money and takes yer choice, if you are messing about on not much cash then the above engine is probably near to what you've got so I wouldn't bother. The money is better spent on keeping the sparks bang on and the carb in tune to get the best out of it.
If you have loads of dosh to throw at it then you probably will gain a few bhp and so do it if it makes you feel better but bear in mind you cant just bolt something on to a standard 998 and expect miracles, it takes time and effort to make things work when non standard bits are being put together.

Now on a different spec engine they may work but I was stuck with what I had on the shelf in the garage and was on a very tight budget.

[minimender]

Why does nearly everyone say Roller Rockers are bad for Minis???

As said above, high ratio rockers are not usually considered worthwhile on 998s unless they spend all their time at high revs (race engines)
LCB manifolds on 998 engines usually follow the same rules as the high ratio rockers.
Cone air filters are not the best choice for a Mini.
Your carb has a red dashpot spring already, most Mini HS carbs do.
Uprated head gasket?

This really doesn't seem to be a properly developed kit to me.

I agree I'm afraid,
although in my experience the cast LCB exhaust manifold does help with the power a bit and it does sound nice as well.
I'm with you on the carb, experiment with needles or profile one yourself
uprated head gasket is probably a copper one.
I've blown many an expensive motor away with a cheapo conversion.