45 replies to this topic

[TR7]

Everyone drives in a different manner, be it on road or track. So the engine characteristics to suit an individual will be different for different drivers.

Some drivers love good mid-range torque and value it over sheer top-end power, so they will choose a mild cam.

It is not the cam choice which determines the rate at which a car can be driven down a road, it's how well the driver used the available torque & power to carry the speed smoothly through the corners. 

I come from a serious rallying background and the successful drivers were not necessarily in the most powerful cars. Success was from driving very smoothly, carrying the speed through the corners and having the car set up to give best road-holding combined with superb handling. If you can exit a corner 5 mph faster, then you will carry that speed up to the next corner where your better brakes and car balance will enable later braking and, again, faster speed through the corner.

I used to tell people who wanted to modify their cars to start with the suspension & brakes, then move on to gearing and, finally, to engine modifications.

Then learn to drive very, very smoothly and to carry the speed through the corners.

I know this doesn't answer the cam question but, in a way, it leans towards saying that final cam choice is not critical and a well set-up car will always be quick in relative terms over a given piece of road.

I well remember the 'works' rally Minis which were not really highly tuned and, for some events, had standard 510 cams. They were so torquey that they got good results combined with reliability and ease of driving. 

So, in terms of which cam for road use, I would say whichever gives the best torque at 3500 rpm. Check the cam graphs for the answer to this. Then build the engine very carefully and accurately. I think that, except for racing or hill-climbing, cam choice is a bit irrelevant.

I hope this helps

thanks I have done the brakes and suspension and had it set up just got the engine to do now

[Cooperman]

Yes, cam choice is often a 'big issue' for owners and it is often unnecessarily so. In the end it is the quality of the engine build and, especially, the gas-flowing of the head which is most important.

Unless, that is, the car is for out-and-out competition where a few tenths of a second per lap are critical. On the public roads it is more important to have a car which gives smooth power, good torque and is easy to drive well.

My choice is usually a 266 or MG Metro cam as I've used these for Endurance Rallying with good results. In my rally Cooper 'S' I run a 286, but that really is not a good road car and it has a 3.9:1 FDR. I can never see the point of very high-revving engines with 'hot' cams for use on the public roads.

Of course, those making & selling their own cams will always tell you that their cam will outperform any other cam, but it is largely 'turd polishing' IMHO.

Don't get too stressed out about cam choice. Any good mid-range cam will give good results in an otherwise well-built engine.

[PandO]

Thank you. I have decided to marry my MG Metro cam to the engine being prepared. Your extremely valid points add up and I'll have the peace of mind when finished that it was the right decision and I'll have no regrets. I.e I didn't mess too much with one factor (the cam) when the sum of the whole is what's important.

Build summary.

Austin 1300GT base - crank is perfect - never ground so just new shells

+40 bore to give 1310cc

21253 pistons

MG Metro Cam

MED 1.3 roller tipped rockers

Unleaded 36/29 self Vizarded 12G940 (CR 10.25)

Aldon Amethyst mappable Ignition

Vernier

Twin 1 1//14 (HS2s)

Leyland inlet - Vizarded

Maniflow LCB (Medium)

Twin box RC40 

NGKs

To make it stop - part two of the equation I'll use the standard 1275GT brakes except some Green stuff pads and Minispares posh grooved discs.

To make it handle it's Yoko 165/60/12 on Compomotive rims

Redspots, Adjustable front/rear with Hilos and adjustable arms and rear brackets. (Minispares kit with correct bushes)

Spax Krypton adjustable shocks - standard height.

 

Have I forgotten anything I wonder - a tank of super unleaded excepted. Thanks again for the post.  Cheers, Pete

[PandO]

I did forget one thing in my spec - rebuilt close ratio (standard 1275GT) box with 3.4 final drive.

Hopefully this will give a true 100 mph capability with the stubby front - when standard this was never achievable.

It will be RRd to get the Aldon and needles fettled when run in. I'm hoping for approx 80bhp, is my estimate of HP about right - it's only a figure I know but if I don't hit 72 I'll blame my Vizarding skills - not you guys.

No addition of a centre steel strap or central pickup as is usual - I don't expect to thrash it too hard with any regularity and bear this in mind when driving.

[Mrpeanut]

80 ought to be achievable. My rover carb Cooper hit 78 with a stock cam. That looks a really nice set up.

[Cooperman]

With careful assembly I would have thought 85+ bhp would be easily on. You need 80 bhp to reach 100 mph, a bit more, maybe 85 to 87 bhp, if you have wheel arch extensions and the later big mirrors and it needs to be geared to be pulling about 5600 to 5800 rpm at 100 mph, which means a 3.44:1 is about spot on.

 

I built a 1330 cc with a spec not far from yours. It had 10.5:1 C.R., an Aldon 'Red' distributor, a single HIF44 on a slightly cleaned-up manifold, MG Metro cam and a mildly improved head in terms of flow (the engine was supposed to be 'standard'). It gave 84 bhp at 5700 rpm at the flywheel and with a standard gearbox with a 3.44:1 FDR it drove very well. It would be well worth lightening the flywheel as this improves acceleration and the standard flywheel is a bit on the heavy side. Your choice of transmission is excellent.

 

If you are running 10" wheels and 7.5" discs you can save some cash by fitting standard good quality solid discs and the Carbon-Metallic pads as supplied by Mini Spares. I've used these for years in my 1964 rally Cooper 'S' and they are without a doubt the finest Mini brakes I've ever experienced. 'Green Stuff' are nothing special. Mintex 1144 are a good alternative pad.

[Orange-Phantom]

I second Cooperman's views on the brake pads!

 

I had the EBC Greenstuff on my Mini  (KAD 4 Pot 7.9" Discs with 10" wheels).

 

They didn't have any particular feel and were inconsistent in their performance.

 

I swapped to the Mintex 1144 (fast road pad) and was a-lot happier.  They have proper feel to the brakes and good consistent performance (which is kind of important with the brakes).

[PandO]

Interesting comments on the GreenStuff pads - sorry if I took this topic away from the initial discussion on Cam suitability but any potential brake issues are worthy of mention. If you make a car go faster it's obvious that making it stop and handle well has to be borne in mind.  I chose the GS pads as it has been mentioned elsewhere in this forum that they produce less dust with no adverse comments on their braking performance. (That I've seen). I plan to be very protective of my period 12" Compmotive wheels so this was the prime reason. These have just been refurbished and they look stunning with a blackgloss powdercoat and diamond cut to the rims and spokes. (Cost more than a new set of wheels to do but I could of bought a new car with the whole project spend) "Built not Bought" as has been said . "Old and too good to be sold" will do for me.

I don't think it'll make this years IMM - the shell is being painted next week so a 400 mile round trip after a rushed re build is not a sensible idea  My cam choice made (MG Metro N/A) I'll leave you in peace and I'll update  my 1275GT to be reborn posting as soon as the car hits the road.   

[carbon]

AC Dodd has made some really good points about comparing cams. He should be in a very good position to comment here as unlike most of us he actually builds a lot of engines and can see what really works well in practice based on hard facts.

 

AC Dodd also has a range of his own cam specs, to give him credit he has not mentioned this in his replies to this thread. He also has made a lot of properly measured cam data available to everyone as well as a series of rolling road power curve data - and these are not just 'peak power output' numbers he has made available. Would be great to see more of this transparency.

 

It would be really useful to see some good back-to-back tests carried out, this might help to dispel a few myths. Maybe a good topic for one of the Mini magazines to cover in the future? Maybe a series of tests :

 

For 'mild road' looks like the choice is between SW5, ACD-RT, MD256, Evo 1

 

For 'fast road' you have SW8, 731, MG Metro, ACD-RS, MD266/MD276, Piper 270

 

For 'ultimate road' you have SW10, 643, MD286, RE13, ACD-RS+, Piper 285

 

So much choice, so few hard facts. No wonder this always raises a lot of discussion about 'what is the best cam?'...

[Mrpeanut]

AC Dodd has made some really good points about comparing cams. He should be in a very good position to comment here as unlike most of us he actually builds a lot of engines and can see what really works well in practice based on hard facts.
 
AC Dodd also has a range of his own cam specs, to give him credit he has not mentioned this in his replies to this thread. He also has made a lot of properly measured cam data available to everyone as well as a series of rolling road power curve data - and these are not just 'peak power output' numbers he has made available. Would be great to see more of this transparency.
 
It would be really useful to see some good back-to-back tests carried out, this might help to dispel a few myths. Maybe a good topic for one of the Mini magazines to cover in the future? Maybe a series of tests :
 
For 'mild road' looks like the choice is between SW5, ACD-RT, MD256, Evo 1
 
For 'fast road' you have SW8, 731, MG Metro, ACD-RS, MD266/MD276, Piper 270
 
For 'ultimate road' you have SW10, 643, MD286, RE13, ACD-RS+, Piper 285
 
So much choice, so few hard facts. No wonder this always raises a lot of discussion about 'what is the best cam?'...

I'd put mg metro and possibly 266 in the mild list. Evo 1 arguably in fast road - it has the same duration as the 266 and loads more lift. 276 & 266 shouldn't be listed as the same, they're different animals.

[ACDodd]

Its not as easy as just testing. You need money and a lot of it. Dyno time is not cheap. What you propose here would take consideable time. Not to mention the need to optimise CR and cAm timimg after a cam change. You also need a dyno engine to be built first.

AC

[ACDodd]

The thing is camshafts are mathematical science, if you know how to read cams, you don't need to test them. I can draw up on paper a cam spec to deliver power and torque where you need it. The engine will deliver if built and run in correctly. Its just (complex) math!

AC

[gkmini]

So did we ever determine if the SW8 was a better option than the SW5 for everyday road use?

If so, would anyone be interested in trading my new 286 Scatter straight across for either one? Partly joking of course... haha

[Vegard]

Does anyone have the spec sheet, where it says where the SW8 should be timed in at?

[Arthy]

Does anyone have the spec sheet, where it says where the SW8 should be timed in at?

 

It's the same as the SW5, between 106-108 degrees to my knowledge! 

 

If you're not sure, give Swiftune a ring!