Trust me, you will not get any worthwhile power out of a stock A series head, unless you port it. Shape is important too, but all the ports are just too bloody small in stock form.
Sources- Vizard's 2 books, also Des Hammill- how toPower Tune the BMC etc A series engine.

Bikes = 4V or 5V heads, twin OHC, injection, yada yada.. Mini is a tractor by comparison.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

but what about the run in ideas?
should u baby it for 3000 k's and only take it to full throttle and give it high load up hills but low revs?

OK its late and i will ramble on here.............

Break in of a modern engine, especially bike engines with much tighter tolerances than the average A-series might well be different. I know that most guys who race cars that are not registered, don't take it very easy when they first rebuild an engine. If the report was in a paper by a recognised metrology engineer, published in a recognised engineering journal it would have more credibility than a website and the is this true or not argument would not ensue......no offence to anyone here of course

as for the smaller port theory, all engine design is a compromise. If you have a certain rev range, and a certain volumetric efficiency, and a certain intake runner length, then at a particular point you might get more power from a smaller port. This is the case if you have a long inlet runner, and low revs. A smaller port will maintain the intake gas velocity such that the piston has to do less sucking to fill. think of the exhaust extractor theory in reverse But at some point as the revs rise and the volume of air demanded by the engine increases, that port just ain't gunna flow enough air so has to be enlarged. Classic example is the old T-VIS dual inlet runner system on toyota 4AGE engines. Do a google search, i'm too tired to explain how it works Suffice to say that when the butterflies are removed from teh T-VIS the dual inlet runners are just too big to maintain velocity at low revs and drivability goes out the window. When toyota ditched the T-VIS system for a single compromised length inlet runner, they reduced the inle port size and changed its shape to round instead of oval. To be honest, dyno results for race engines with the different ports show bugger all difference at the 6-7k rev area.

polishing is a bling thing really IMO. depending on the combustion chamber shape and the efficiency of the mixing of the fuel, it can actually be of benefit to have inlet ports with a helix cut into them to promote swirl. I have read elsewhere that it marginally helps with exhaust flow, but we are talking boundary layer stuff if the flow is subsonic. if the exhaust gas reaches near sonic velocities it may be of benefit to remove anything that will induce a shock wave, since that will kill the flow dramatically. Anyone know what speed and pressure the exhaust gas is at in a-series? Speed of sound is approx 300m/s at sea level in a standard atmosphere, and will be much lower at higher pressure.

The flowbench does not represent the variation in piston and gas velocity throughout the stroke, which when combined with the valve lift and the shape of everything in on the way, determines the actual fill of the cylinder. Plus the combustion chamber shape is a big factor that determines the efficiency of the burn. But the flow bench is a great standard measurement device that allows things to be compared with a degree of confidence.

There is only one way to increase the output from an engine, and that is to increase the mass flow of gas processed (done the maths from first principles, got the degree, not boasting really ). How you do that is up to you, since increasing revs, reducing inlet and exhaust restrictions, increasing cam duration, turbo or supercharging, or even simply increasing the density of the inlet charge (by cooling ) will increase the mass flow.

my $.02
michael

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the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

It's really coincidental that this thread has been posted up here, 'cause we were talking at work today about what some manufacturers do when the vehicles roll off the production line.

One guy at work has a mate who used to own a bike shop in Lithgow and he went to Japan and had a tour through the Honda factory. This guy reckons that Honda fire up every motor cycle after it's finished and rev the crap out of it.

I work for a company that manufactures front end loaders to fit onto agricultural tractors, and one of the guys involved in this discussion has been through a tractor manufacturing plant in Europe and says they do exactly the same thing. They put every tractor up on a set of rollers kinda like a dyno and run the thing flat out through every gear - straight off the assembly line.

We havin' a laugh 'cause then when the vehicle's sold, Joe Owner cotton wools it and won't run it past a couple of thousand revs for the first 500 miles.

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Who's MadMax?

Concerning the porting part of the articles....

I think we are all in violent agreement for the most part.

I don't think the fact that they are on the internet instantly means they're bullshit (hey, most of us are here taking advice from people we have never met).

Otherwise, with my limited knowledge (my engineering degree didn't delve too much into fluid dynamics I'm afraid) Mick I agree with all you said, and you pretty much match most of what the author of the articles says.

The bottom line is this: the jap bike manufacturers decided a some point that larger ports would increase their peak HP figures, affecting sales. But they overshot the mark making them too big. A race tuner has discovered by trial and error that by making the ports smaller, he actually increases HP across the rev range (go look at the graphs). My '60s model tractor... err... mini.. never had any such problem. It has the opposite problem, ports not big enough.

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"Life is not like a box of chocolates... it's more like a jar of jalapenos. Whatever you do today, may burn your arse tomorrow."

NOS?

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But he's thriving and striving and hugging the turns.

re the running in- I bought a new Fiat 124 Coupe (1438cc, DOHC) back in `69.
Running in schedule was on quarter window:
0-600 miles, 4,500rpm max
600-1200miles- 5,500 rpm max
1200-2400 miles- 6,500 rpm max.
BTW redline was only 6,800...

My motto-
Run 'em in fast, they stay fast
Run 'em in slow, they never go!

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Discuss running in with the engineer that built the motor as you will void any warrenty if running in instructions aren't followed to the letter. that is if you have had the motor professionally built. I Garuntee If professionally built you will receive running in instructions, along the lines of various speed and loads but not to exceed 80km/ph for 2000 kms, not to use full throttle. Change oil @ 250km, 500km, 1000km and 2000km. and attach MTA number of mechanic who installed motor.

But if motor is not built by qualified persons and flogged I wish you luck.

This is for rebuilt motor not reconditioned. Take advice of people with quailfications in the apprpriate field and you will enjoy your motor for years to come

Best of luck

Steve

I have always run my engines in by working them hard. not in terms of revs, but making them work really hard in their max torque range. (3-4K). I put them in 3rd, on long up-hill sections and open them up. (pretty much as per the article)

The only thing i do differently is that when i first fire it up i let it idle for 15 minutes without revving it at all. I have found that this is all that is necessary to run in bearings (particularly cam bearings) Strictly speaking engine bearings shouldn't need running in because there is a layer of oil between beaing and crankshaft, so in perfect conditions they will never wear at all. but just for good luck i give them 15 minutes.

I think that engine builders who tell you to take it easy, are probably just covering their bases. firstly they don't necessarily care if you get A grade performance out of your engine. Secondly, they may not know the customer, and what he's likely to do to the engine. If you go and thrash it recklessly you can damage it, so they need to cover themselves.

It also depends on what you're using the engine for. I was once told to run it in as you use it. if you want a really fast race engine, rev it from minute 1. but don't expect it to last too long. if you want a good performing road engine, do as the article says. it will serve you well IMO.

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anything is possible - if you don't know what you're talking about.

yep, forgot about that one It does a couple of things, first it increases the mass of oxygen in the inlet charge (NOS is a brand of Nitrous Oxide equipment, Nitous Oxide is the gas) , so you can increase the amount of fuel, hence increasing the mass flow of gas processed. second as it changes state from liquid to gas, it cools the inlet charge, increasing its density, thus increasing the mass flow of gas processed. Note the emphasis i place on the mass of gas processed, rather than volume. density of the inlet charge is a big factor that affects power output, as anyone who has a turbo will attest. ever wonder why george fury's qualifying lap record in the bluebird turbo at bathurst was set on a morning after it snowed?

michael

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the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

Interesting read for a newbie with an engine being re-built as I type.
I work as a test driver for a large Australian car manufacturere (dertails withheld because I probably shouldn't be telling you this) and we do a lot of run-ins on new engines. They are run in for 6400km.
The first 600 is at constant 75 for a km and 90 for a km (real fun to do......)
Up to 1500 is 90km for 5 k's, 105 for 5 k's.
Up to 3200 is 105 k/h with 1/2 k bursts as fast as it can go every 3 km,
The last 3200 is 5k's at 100 5k's at 120.
This seems to incorporate all of the ideas put forward in the other articles.
Who knows which is right but I think the engineers of this company have a good reason for what they are doing.
Hope this helps....
Two Mokes

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don't put your arms out the side or
this moke will take off