18 replies to this topic

[gottamini]

Picked up my current mini about 6 months ago. Dont know what all has been done with the motor. Here is what I do know:
1275 that has been bored but I dont know to what. assuming 1380
cooper S head dont know what has been done to it.
No idea what cam
HIF 44
LCB with single box exhaust
straight cut gearbox and drops
3.1 diff
lightened flywheel
Dont know the compresion ratio but the compression is 205 on all 4 cylinders
10 inch wheels
At some point the car was being built for road racing.

the car has almost no power until 3500-4000 RPM. Still pulling strong at 7000. took it to 7500 once with no problems. Have had it to 105 mph on a closed road. Can drop the clutch at 4000rpm and it doesnt even chirp the tires, rpm drops, car starts going and then take off once the rpm gets back above 3500 or so. No fun in city traffic. A blast on country roads and the expressway. Around town I spend most of my time revving around in 2nd gear to avoid constantly shifting everytime I want to accelerate.

Here is what I want:
MORE TORQUE!
Would like more of the power to be in the lower RPMs. More torque. I want more of a punchy hot rod feel. no matter what RPM your at the way it is set up now it never has that "pin you in your seat" feeling.

What do I need to change to get where I want to be? I am assuming the cam is the first thing? If so which one? Regular weight flywheel? What else???

I am guessing that even if I change the final drive and just deal with the high RPM instead of messing with the motor I still wont really get the results I want. would rather keep my current final drive or at least not change it by much so I can keep my top end speed. To keep up with the crazy expressway traffic here I need to be able to cruise comfortably at 85mph.

What would you all recommend I do to get the results I want or at least happy compromise between what I have and what I want and why?

Thanks
Jon

[Ethel]

200+ psi is good; suggests the cam isn't too wild, but little more than a hunch really. I could just be the ignition timing is far from perfect

[gottamini]

200+ psi is good; suggests the cam isn't too wild, but little more than a hunch really. I could just be the ignition timing is far from perfect

Not trying to argue because I'm not much of a mechanic but several people that have driven the car seem to think it is some sort of race cam.

As far as timing, this is how I did it: Set idle at 4000, set timing at 32 degrees. the curve could be way off tho.

by the way I dont have a vac. advance.
Jon

Edited by gottamini, 19 September 2012 - 01:38 AM.

[jaydee]

Sound like you have something like a kent 286 camshaft. Also the 3.1 diff doesnt help with an hot camshaft, really.
You can cure it giving it more fuel at needle stations 3-4-5 but only at a proper mini friendly rolling road could actually work it out. Dont know if there are in Ohio.
If you want a torquey cam that pulls from low down, go for a kent 266 or a swiftune SW05.

[MiniLandy]

Sounds like it has a pretty racey cam in, or the timing's miiiles out.

If you don't think it has enough power up top as it is, and you want more torque low down, then I think you have two options:

Turbo A series, or a bigger engine conversion (Redtop, K series, VTEC).

Both are difficult and expensive (to do properly), but there you go.

[jaydee]

As far as timing, this is how I did it: Set idle at 4000, set timing at 32 degrees. the curve could be way off tho.

Can you plot the ingition curve through the rev range, in 500 rpm increase from 1500 up to 4000rpm?

[gottamini]

As far as timing, this is how I did it: Set idle at 4000, set timing at 32 degrees. the curve could be way off tho.

Can you plot the ingition curve through the rev range, in 500 rpm increase from 1500 up to 4000rpm?

I will try to do that this weekend. ( I love my adjustable timing light) Need to find an assistant first. will post when I get it done.

What would be some good cams to look at for an over-bored 1275 with a 3.1 fd to get the most torque/power at lower rpm's as opposed to the one I have now (no idea what my current cam is) that seems to make all its power between 4000 and 7500?

[jaydee]

Either the Kent 266 and the Swiftune SW05 will have a wider power band, something like 2500-6000 rpm.
Mind you swapping the cam in a big bore A series is an engine out job and i'd say try to see if you can iron out the lumpiness with some clever tune up.

[gottamini]

Engine is coming out this winter for a TO bearing and clutch while the car gets painted this winter anyway so that would be the time to do it if I decide to change the cam.

Should I keep the lightened flywheel or go back to stock?

And another question: How do I tell if I have a straight cut gearbox or just drop gears without opening anything up? The guy I bought it from said it had a straight cut gearbox but he didn't build it and didn't know much about it. I know it has straight somethings because the transmission whine is louder than the exhaust.

Jon

Edited by gottamini, 21 September 2012 - 04:32 AM.

[Cooperman]

The cam is quite obviously too 'hot' for a road car. The FDR at 3.1:1 is also far too high for the engine and gearbox configuration. With that sort of power band and the SC CR gears you probably need a 3.76:1 or even a 3.9:1 FDR to pull away cleanly. Basically it is not a road car, more a competition car. Why anyone would put a SC CR gearbox in and fit a 3.1:1 FDR is beyone comprehension.
You have two alternatives really:
Re-gear the FDR to be appropriate for the engine spec, or,
Change to a milder cam, like a Kent 266 or MG Metro and fit standard ratio gears with the 3.1 FDR to keep the cruising speed revs sensible.

[Ethel]

I suggested the cam may not be that wild because wild cams close the valves later leaving less air in the cylinder to compress. Of course the longer induction stroke adds more than you lose at higher rpm, but not when cranking it on the starter. It can only be a hunch since we don't know the compression ratio. It will be a lot cheaper & easier to rule out ignition and fuelling first (all you really know is it lacks power at certain rpm), and also worth assessing what you have if you intend reusing it after the strip down. If the gearbox is full of trick, straight cut, bits you'd know - it'd sound like 1st armored division at the charge

[Tinkerbelle]

I have had both a 286 and an SW05 cam in my 1310. The 286 was cammy but not like you are saying. I would agree and say fueling and ignition are probably out.

When I changed cam from 286 and single HIF44 carb engine was making about 85hp at the flywheel, with SW05 twin HS2 SUs and matching exhaust manifold (header) I am down to 70 at a push, but it pulls like a turbo diesel but bottoms out at about 4500rpm, I changed from a 3.44 diff to a 3.1 diff and that allowed for the lower rev power band and it is soooo good to drive around town now and very comfortable at 50-80mph (apart from the bleeding ears from the intake noise). I would say it could even go a little bit further down on final drive to use the torque.

I see you have 10 inch wheels (if picture is of the subject min), this affects the overall gearing also remember, cannot remember how off the top of my head.

Matt

[Cooperman]

10" wheels have 70 profile tyres so 10", 12" or 13" wheels don't really affect the overall gearing by more than about 3%.
There is no point in having a 286 cam unless you are going to rev it to about 6700 rpm. If you have a 286 and don't rev it to that figure you won't get the best power but you will lose out lower down when compared to, say, a 266 cam.

It sounds as though the OP has a mmis-matched engine and transmission for road driving and that it was built as a competition car, but with the wrong FDR.

[gottamini]

I'm going to play with the timing this weekend and next week sometime I will take it to the dyno just to see where the fueling is at. if anything it runs a little rich.

How do I tell if I have a straight cut gearbox or just drop gears without opening anything up? The guy I bought it from said it had a straight cut gearbox but he didn't build it and didn't know much about it. I know it has straight somethings because the transmission whine is louder than the exhaust. is there some thing I can do as a test? Say drive in Xgear at XXXXrpm at XX speed and the shift to the next gear and stay at the same speed and see what the rpm is?

I determined the final drive by driving side by side with another mini that has a 3.1 and we were both at the same rpm. if I do in fact have a sccr box would that have throw that calculation off? the other car had a standard gearbox.

Jon

Edited by gottamini, 21 September 2012 - 03:33 PM.

[Yoda]

Just a thought, but it might be worth fitting a vac advance until you get more into swapping stuff out on the engine. this may give you slightly more driveability for a while. I have a high spec engine and ran with no vac for a while on the road ( It was originally built for track ) but found it more tractable with the dizzy swap. the difference in spec was mainly the diff. I ran with a 4.1 and kept it in the higher rev range.

You can get dizzy,s with changeable curves apparrantly so mught be worth trying.

But As the others have said, you seem to have an engine built for track, fitted with the wrong diff ( for god knows what reason ) and just stuffed into a road car.

As Ethel has said, might be worth going down ign and fuel route first to get it driveable, then when the engine comes out, rework the spec to suit the road use.

It is definitely essential to get a full spec of what you have, then speak to Cooperman to work out the best combination of parts and tuning to get what you want.