17 replies to this topic

[SSCooperGT]

Hi,

I have recently dropped a 1275 GT A series in my mini Mayfair. Im trying to get a bit more power out of it and was looking into Roller tip rockers. In some of the mini mags they say that getting the higher ratio Rollers this can improve power on acceleration through the Cam.

Has anyone done this conversion and is it worth while?

Any other info on simple mods that can improve power would be greatly appreciated.

Im running a 1.75 ich SU Carb with performance air filter and a large bore exhaust.

Thanks

Sam =)

[glenboy]

hiya sam
they are weird things the roller rockers i investigated fitting them on mine for a few months , my mini already has a hi lift cam a 649 one and i was advised that the extra lift was not required, also really if you get roller rockers it really needs setting up on a rolling road as the fuelling etc is different which going to this expense plus the rockers in my view the money can be better spent on a performance cylinder head, as many people who love roller rockers as many people say they are a waste of time, personally in the end i left my normal rockers and fitted a maniflow stainless steel inlet manifold (mines on twin hs4 su's) and that gained me 6bhp, on yours you'd get a good power increase by buying a modified cylinder head like a stage 2 or 3 which is not a big job to get fitted or fit it yourself if your mechanical

Hi,

I have recently dropped a 1275 GT A series in my mini Mayfair. Im trying to get a bit more power out of it and was looking into Roller tip rockers. In some of the mini mags they say that getting the higher ratio Rollers this can improve power on acceleration through the Cam.

Has anyone done this conversion and is it worth while?

Any other info on simple mods that can improve power would be greatly appreciated.

Im running a 1.75 ich SU Carb with performance air filter and a large bore exhaust.

Thanks

Sam =)

Edited by glenboy, 08 June 2009 - 08:19 PM.

[Cooperman]

A rolling road test on my 1275 Cooper 'S' a few years ago confirmed what I suspected. The 1.5:1 roller tip rocker shaft only improved power above 5500 rpm, but caused a loss of torque lower down the rev range with no power increase. I gained 3 bhp at 6000+ with a 286 cam, but nothing measureable below that. Valve guide wear tends to increase as the valves are moving further in the guides each time they open, although side loads in the valves is decreased with the roller tips.
Unless you are running a 'hot' cam and intend using high revs, like over 6000 regularly, they are really not worth fitting. You can lose more than you gain.

Edited by Cooperman, 08 June 2009 - 08:35 PM.

[mini7boy]

sscooper,

Is the engine fresh or is it high mileage? No point in adding improved parts if it is worn out and in need of a rebuild.

you don't say which cam you are running. Am I to assume that it is the stock cam?

If you are running the stock 1275GT cam, 1.5 rockers are money wasted that could better be spent elsewhere.

There are several cams: SW-5-07, Morspeed Ph 2, Russell/Calver RE13 that would all be better than your cam, even without the 1.5 rockers. You don't have to run 1.5s with these cams.

You have plenty of carb in a 1.75 SU. No need to change that out.

If you want an expert opinion of which SU needle to run with this engine spec, click on the link at the bottom of this post
and scroll through the huge number of SU needle specs for all manner of engine builds.

Pardon me a minute or two while I get on the soapbox. I wouldn't do this if it wasn't true.

AC Dodd, a true A-series expert, has posted a LOT of information on various forums including his own Ask Doddy forum, the M&L Motorsports forum and the Minifinity forum.

His specialty is building serious torquer A-series engines by optimizing parts that get along well together and are tuned to produce useful "drivable" power at the RPMs that most people use most of the time.
He doesn't build engines that are useless below 3,000 RPM and need to be revved to 6000 to get anything done.

Everyone reading this forum would do very well to read Dodd's postings because they are full of common sense, no BS, effective engine building.
They provide a real education on A-series road engine building for those who want to get past the silly "road rocket" engines that require lots of shifting and wear out quickly.

On one of the forums, he posts the dyno(rollers) results of many engine builds of all types from mild 998s up to monster 1400s that he has built or tuned. Just by reading these listings,
you can quickly see what works and what doesn't. You can also decide which mix of components produces an engine performance profile that suits your driving requirements.

He is a true A-series specialist who spends a LOT of time on the rollers to test out his custom SU needles, distributor advance curves, cylinder heads and complete engine builds.

Once you decide what you are going to do with your engine from a cam standpoint, you would be well-advised to have Dodd tune it on the rollers so that you get
the very most out of your engine. He can provide a customized SU needle and advance curve tailored precisely to your engine's requirements

I know this sounds like an advert for Dodd, but the man is a real expert who has proven the quality of his work on loads of engines. Just look at the results he gets.

Here are some sample Dodd postings. This is just a tiny sampling of Dodd's understanding of how to build excellent A-series engines (mostly for road use.)
It may be necessary to register to use some of these forums, but it will be well worth the effort to do so.

here's an excellent thread that lists engines built or tuned by AC Dodd complete with dyno results and commentary
which provides a very good idea what kind of engines AC builds and what his tuning prorities are

http://www.mlmotorsp...i...r&Itemid=57
when you arrive at this webpage, search for a thread titled "Power figures verses engine specs, as Tested by ACDodd"

this next thread provides an excellent and very useful method of evaluating specific cams for their suitability

http://www.mlmotorsp...i...r&Itemid=57
when you arrive at this webpage, search for a thread titled "Camshaft selection made a little less difficult"


this next thread lists all of the relevant specs for a large number of cams used with the A-series:

http://specialistmin....com/topic/4389

this next thread details, with photos, just how Dodd goes about porting an A-series cylinder head:

http://specialistmin....com/topic/4576


this next thread lists Dodd's expert recommendations for SU needles and gives an idea of his level of SU expertise. In some cases, he recommends needle modifications performed by himself.
Please note that this subject has 20+ webpages detailing a HUGE number of needle specs for MANY different engine build specs. Search through them until you find one similar to your engine's spec.

http://specialistmin....com/topic/4131

Edited by mini7boy, 09 June 2009 - 04:42 AM.

[mini7boy]

here are some additional useful threads by AC Dodd,

this thread shows the dyno results for some really fine 1293s(on both webpages). Look at the flat torque curves !!!

http://www.minifinit...amp;hilit=65DM4

this one has details of a demon 1380 build by Dodd's "partner in crime" Andy who either owns or part owns M&L Motorsport

http://www.mlmotorsp...opic,323.0.html

this one is a great, concise piece that relates engine build type by using the RPM range where it produces peak horsepower.

http://miniclassic.yuku.com/topic/5262

Edited by mini7boy, 09 June 2009 - 05:32 AM.

[bigmotherwhale]

1.5 rockers go well with short duration camshafts i think, 286 is reasonably high, sw5 camshafts perform well with 1.5 rockers, i think because they are short duration, the good thing about this is they have little valve overlap and suffer less from reversion, its all in the vizzard manual

[Se7enS1ns]

I cant offer much in the way of advise, as i firmly beleive that a well adjusted set of stanard rockers is "good enough" however if we look at the £ per HP scale (parts which offer BHP increase and how much the cost), roller rockers come quite low down on the scale.

As a few have said above, they arent cheap, and any gain you achieve, if any at all, wont be much. The money could be spent wisely elsewhere - ie the cam etc

[mini7boy]

sscoopergt,

The links I included in my previous posts on this thread will provide information that you can use to select a cam and SU needle for your engine.

In the webpages that those links point to, AC Dodd had provided a wealth of information on the correct SU needles for specific engine builds.
He also has information on all of the popular cams for the A-series organized and analyzed so that you can compare cams and decide which cam is best for your engine.

He also includes a load of rolling road results for engines he has either built or tuned. This information is helpful in that it allows you to observe which combinations
of parts work well together to deliver the goods.

AC Dodd is about to make his second all-expenses paid trip to Italy to tune the Minis of a small group of Italian Mini enthusiasts.

To get to an excellent account of his trip to Italy and the tuning results obtained, click on:

http://www.mlmotorsp...i...r&Itemid=57
when you arrive at this webpage, search for a thread titled "very own Italian Job

Dodd is a very bright engineer who builds his engines using a logical approach and based on common sense. Luckily for the rest of us, he specializes in road engines and is very generous in sharing the information he has accumulated in many hours on the rollers. He also drives a Mini and has some very sensible ideas about what makes for a Mini engine that is pleasant to drive, rather than a short-lived, high-maintenance beast which requires a lot of RPMs and shifting to get the best out of it.

Edited by mini7boy, 09 June 2009 - 05:27 AM.

[Bungle]

i fitted a set of 1.5 rockers to my rover cooper and had good results

i think it all depends on what cam you have fitted, if its a standard cam without much lift you can get some good results

[mini7boy]

i fitted a set of 1.5 rockers to my rover cooper and had good results

i think it all depends on what cam you have fitted, if its a standard cam without much lift you can get some good results

Bungle,

it also depends, at least as much, on what your engine priorities are and what your budgetary constraints are.

1.5 roller rockers can be pretty damned expensive if you buy quality items. For those inclined to run reground cams,
it's possible to buy some cams with a hotter profile for less than the cost of some 1.5 rockers. In such a case, limited funds might be
better spent on a new cam rather than on the 1.5 rockers. 1.5 rockers also increase wear and as such should not be fitted gratuitously
without really looking at the bigger picture of what your engine needs, if anything, before it needs 1.5s.

Used properly, 1.5 rockers are fine and might be just the ticket for a given engine.

[glenboy]

mini7boy is right its an ongoing discussion roller tip rockers , there isn't a definitive answer either way i have a 649 cam which is hi lift and when i enquired about roller rockers was advised against them as the cam itself already had hi lift , as said i think look at other things before the roller rockers like inlet manifolds , stub stacks performance filters etc, i fitted a maniflow steel inlet manifold which gave an extra 5 bhp and cost less than fitting roller rockers

Edited by glenboy, 09 June 2009 - 06:48 PM.

[mini7boy]

mini7boy is right its an ongoing discussion roller tip rockers , there isn't a definitive answer either way i have a 649 cam which is hi lift and when i enquired about roller rockers was advised against them as the cam itself already had hi lift , as said i think look at other things before the roller rockers like inlet manifolds , stub stacks performance filters etc, i fitted a maniflow steel inlet manifold which gave an extra 5 bhp and cost less than fitting roller rockers

Glenboy,

I don't want to seem argumentative, but the 649 is not a high lift cam. If you read Vizard, he recommended using 1.5 rockers with it to make it work better.
The Mini Miglia race cars in England used to use 1.5 rockers with their required cam which was nearly the same as the 649. However, they had a lot of
problems breaking springs and causing other valvetrain problems, so their rules were changed to outlaw 1.5s. Funny thing, though, is that after they
started running the 1.25 rockers, they were eventually able to get nearly as much power from the engines. Not bad considering how many decades of
development the 1275 has undergone. The 649 is a cam that was originally a race cam and few people consider it a suitable road cam.

[Bungle]

i fitted a set of 1.5 rockers to my rover cooper and had good results

i think it all depends on what cam you have fitted, if its a standard cam without much lift you can get some good results

Bungle,

it also depends, at least as much, on what your engine priorities are and what your budgetary constraints are.

1.5 roller rockers can be pretty damned expensive if you buy quality items. For those inclined to run reground cams,
it's possible to buy some cams with a hotter profile for less than the cost of some 1.5 rockers. In such a case, limited funds might be
better spent on a new cam rather than on the 1.5 rockers. 1.5 rockers also increase wear and as such should not be fitted gratuitously
without really looking at the bigger picture of what your engine needs, if anything, before it needs 1.5s.

Used properly, 1.5 rockers are fine and might be just the ticket for a given engine.

i disagree you cost up the cost of buying a cam and the labour to fit in, especially in a non s 1275 engine compared to the cost of a set of 1.5 rockers and the labour involved

i would of thought the rockers worked out being 1/4 of the cost

[SSCooperGT]

Hey Guys,

Thank you all for the info much appreciated. Me and my uncle have just put the 1275 engine in already so im not sure im going to be able to change the cam without hauling the damn thing back out again. The engine and gearbox are sound it has 30,000 on the clock. im just researching how i can squeeze out a little more power. The last time i drove it, it had its original 998 so im hopin i will feel a difference with the 1275.

once again thanks for all the info, ill drop a few posts on when i get it running in the next few weeks and see what the rolling road brings out.

Sam

[jkjaxor]

ppersonaly, i would choose to save up a bit more money and change cam to somthing like a 286 and then get a better head,
id expect it to give better results over a wider rev range compared to fitting highlift rockers to the stock engine also will mean less wear on components as others have said.