Yesterday things got out of hand and many questions were still not answered.

A point I want to make VERY clear is that my project was for my own use. I am not doing this for a income [I go to sea for that] and with all my projects I will assist anyone who wants to try it. If they cannot do one then I will do it but I charge for it.

What I propose is to set-up a discussion on the conversions purely on the technical aspects , the benifits for and against. At the same time use the wealth of information that people on Ausmini have to help others understand the dynamics of engines.

Most of my experince is with marine diesels however the same principles of an internal comb eng still apply to the engs that I build.
I DO NOT know a lot about the BMW conversion so the guys who are involved with them hopefully will supply info.

I have only used a Honda cbr 600 F4 race F4, and F3 heads onto a 1100 block for testing. The reason is that I wanted to concerntrate on the small bore engines as a cheaper alternative.

A bit of tech info on the 600 heads and the basic bike they are off.
F2 and F3 engs 65mm boreX45.2 stroke. 110H.P at 12,000 rpm torque 46 ft/lbs
F4, F4i, F4 race 67mm bore X 42.5 stroke Hp range 120 to 150 [race]

when looking at at air flow [N/A at 1 bar or 14.7.lbs/sq"] the maximum volume of air the eng can take is 1/2 total swept volume X rpm.[4 stroke]
The limiting factor in the air flow is the inside diameter of the v/v seat. Ports can be larger but it's the amount of air flow thru this area. The hondas have seat I.D.[per v/v] of 22.5mm & 18.5mm F3, 24.5mm& 20.5mm F4. The V/Vs are set at 15 deg to vertical.

Inlet port base dia on F3 is 35mm F4 40mm at 45 deg. to v/v head. From carby to valve head is almost a straight line.

I have had failures with some of my engs for various reasons but this is all part of research. Learn from your mistakes!!!!!

So if anyone would like anymore info or input then I am happy to hold a discussion on this conversion and it's pro's and cons.

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

Hi David,
Now before I make my comments, I want everyone to know that I have spoken to David in regards to posting on this via PM and he has warmly welcomed comments. I am not trying to be a PIA, I for am out for more info.

If it is ok with you David I might start with one thing at a time so we can go thru it thoroughly and I can be more certain of what I am saying.

Starting with Capacity and most importantly in my mind Stroke.



A mini 1100 has a bore and stroke of 65mm and 84mm.

looking at the stroke on each of the motor's or 45.2mm and 84mm the distance the piston has to travel is almost 40mm more on the mini to the bike motor.
Now taking that into consideration, how does that effect the performance of the motor when the piston/ring speed is going to remarkably higher at any paticular rev speed.
So my questions are

1. Lets say at 6k (half of where the bikes motor's peak performance is) the motor isn;t going to react the same way with the bike head is it?
2. The cam(s) opening and closing durations would have to changed would they not to create a more efficient use of fuels would they not?

I am asking because i am testing my theory's in my head on heads. If i am way off the mark, then if you can point my in the right direction that would be great.

so yeah, thanks david for giving me the chance to go thru this and really fully understand.

Cheers
Aaron

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from an alternative angle



Wouldnt an A-Series head become asthmatic long before a bike head if you took it to say 10000rpm?

I think maybe we need to put a mini head in a bike heads position to fully understand the benifits.

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True. I'd say the bike head would be far more efficient in standard form especially at achieving rediculous rpms. But the main question is about the cams.

When is the bike head, with it's twin cams, "on cam"? For example, if the powerband of the bike engine is from 6000 to 10000 rpm would it not be fairly pointless on a Mini? Or, is the flow of the head and the cam timing OK at an rpm of say 6000 such that there is a remarkable increase in power anyways with plenty more potential at higher rpm again? (In this case you would use an rpm limiter to stop from killing the motor by sending it into orbit)

If the flow of the head, even though the cams aren't optimal for a Mini's rpm range is so great, then these setups would hugely benefit from a new cam grind. But my knowledge of camshafts and cam timing is very small so I could be way off the mark here.

<edit> Maybe I should word this differently... What I would like to know is at say, 6000 rpm which motor would be producing more HP, a Mini with a 5 port head, or a Mini with a 16valve bike head. Probably the bike head, but what about a Mini with a 5 port, a good cam and some light head mods?

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

What Aaron is talking about is the bike is only half the size, so:
- the 1100 A series has twice the stroke & the same bore
- therefore only needs to rev at half the speed to generate the same flow rates & same peak power.
- the standard bike cams may not be perfectly suited to the new application

As I see it:
- the standard bike cams will be suitable for the flow rate
- the standard bike cams will be close to ideal for a turbo application
- being twin cam, the exhaust cam timing can be dialled in easily to give a little more overlap for a high reving (race) naturally aspirated motor
- given the longer stroke, the A-series should generate more torque
- the efficiencies of a multi valve, non-pushrod, crossflow head with no siamesed ports offer so many other advantages including more efficient cooling eliminating hot spots, lighter mass, accurate valve timing, and the ability to effectively employ EFI makes it a winner.

Unfortunately I have too many projects, a temporary lack of funds & no license, otherwise I'd be building one now

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Too many cars, and too little time.

sounds like you have been stroking it a bit much

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busier than a 0ne legged man in a butt kicking competion

thanks Awd moke for your thoughts on that one. Looking forward to some other points of view as well.
One point on your post though, you say exhaust cam timing can be retimed, does this mean the inlet could be retimed to bring the curve back to "mini" levels or would that require a regrind. And if so, does that mean a billet custom Cam as generally a cam regrind of a cam is to increase power which normally means taking away from the low to give to the top. Where in this case we want more power at lower revs which are more suitable for the A sreies motor.
I think the turbo side of things is a bit non plus as a turbo can make any head work as essentially it "pushes" air in. If it doesn;t flow wind up the boost. But this is another part of the questions i have, and would like to clear up the first lot of questions first.

Mini Dunger - whats the point?
We know the heads work on a bike, otherwise these guys wouldn't have decided to try them. We know the A series 5 port is asthmaitc in std form, but it can be made to flow quite well, if your willing to spend the money. Or the alternate routes of a 8v 8 port design re adren, etc or even the westlake. or even the KAD 16v even though there is a massive cash reduction from your wallet to do it. Having said that some of the posts about how much it costs to build a bike headed a series come very close to buying a 8v 8 port.

Slinkey Inc, you mention a test at 6k with a bike head on a a-series. I personally would be more interested to see the torque curve from around 1800 thru to 5000-5500 as that is about all you will use 99% of the time in a road going mini.

I have more questions relating to this but i'd like to go thru this part of it first then I'll ask the next lot. I thiink it makes it easier to clear up one part then move to the next even though there will be cross overs in the answers.

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You just go and play with whatever you want to stroke elsewhere please Al and let these guy's have a serious discussion on this matter .

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ok but this tosser lost this forum a very knowledgable member

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busier than a 0ne legged man in a butt kicking competion

Al , please let this go , I know from seeing behind the scenes that Aaron has honestly apologised to Matt for the way that all panned out and is now asking the questions here that he wants to know about all the motorbike head conversions . I honestly believe Aaron is not trying anything malicious to Matt or David but is wanting to settle his own curiosity , please trust me on this one and leave it be .

Matt hasn't gone from the forum by the way , as he told me in a PM the other day he'll be back soon .

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I have been following this subject for a while purely from an interest point of view. One thing I am interested in is that the motorbike heads are made of a completely different metal to the cast iron A blocks their being put on. With the difference in expansion and contraction rates and differences in heat loss,this must make it critical for your gasket choices and head stud torque. This must also affect how you cool the system as these modified engines have the potential to rev to 10,000, I assume this would mean a race core radiator and a minimum of a 13 row oil cooler.

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I'm not sure that's as big a problem as you think. Ford put alloy heads on iron blocks for a long time, and I don't think they built a reputation for blowing gaskets...

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Simon

The adventures of an owner builder in the Tallarook Ranges

The difference in cooling should actually be in favor of the alloy head depending on the construction and design of the water galleries.

Lots of manufacturers have gone from an iron head to an alloy head without any problems with cooling capacity.

What we are talking about is L99 aluminium alloy which has been heat treated for stability at high temperatures mounted on a cast iron east-west block with a cooling system designed to pull heat out of the engine bay, this is a highly specialized after market modification and I am just interested in how in this application you would control heat and any twisting or warping.

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There have been aftermarket alloy heads available for Minis since the 60s. Alexander, Arden, Elder, Pierce, etc. Warping doesn't seem to be a problem.

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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.