35 replies to this topic

[welshdan]

my brother got 102 bhp at the flywheel last week. not sure of exact spec, its 1380, standard crank, 286 cam, minisport stage 3 head, CR id guess of around 11-12:1. running on twin 1.5 SUs, straight through exhaust with a 3into1 manifold.

it all depends on timing of the cam and engine build, how accurate the rolling road is, how good the guy there is at setting up the engine.

as said its how it drives that counts. BHP figures are usually much exagerated. just look at the mini magazines at the ads to see what some builders claim will make certain powers. it doesnt happen

[Sprocket]

Nothing mentioned about what type of ignition you are running?

[twign]

sorry you've lost me?

[bmcecosse]

As above - the 'stage 4' head means nothing! And - are you SURE it's a 286 cam ?? Has the HIF 44 been 'Vizardised' - and what needle is in there ? Did the RR people optimise the mixture by trying different needles - and did they modify/optimise the dizzy advance curve ??

[twign]

As I've said, I purchased the car built so I don't know the ins-and-outs of everything.

It's definitely got a 286 cam. The carb is 2000miles old, but I wouldn't know if it's been vizardised. Why 'stage 4' means nothing I don't know, but that's what it's got, so that's what I said it had. I really don't question the spec, it's been in at several garages, they've all seen the list, and none have had suspicions.

The RR people said the needle was fine, but I can't remember which one they said it was. HBL? BDL? Something like that. They said they advanced the timing slightly, and agreed with me that it's quite flat pre-cam but other than that they said all was well, and that they wouldn't expect all that much more with this spec.

Who knows. A million and one different opinions lol.

[bmcecosse]

You would need to see the head off - and measure the valve sizes. Can you get a compression test done and report back with the figures ? How can you be SURE it has a 286 cam - have you measured the valve events ? BDL needle is the standard MG Metro needle -I doubt it will be right for this engine spec! Did the RR people actually have the slightest idea what they were doing ? Or did they just empty your wallet ??

Edited by bmcecosse, 09 November 2009 - 11:07 PM.

[liirge]

As I've said, I purchased the car built so I don't know the ins-and-outs of everything.

It's definitely got a 286 cam. The carb is 2000miles old, but I wouldn't know if it's been vizardised. Why 'stage 4' means nothing I don't know, but that's what it's got, so that's what I said it had. I really don't question the spec, it's been in at several garages, they've all seen the list, and none have had suspicions.

The RR people said the needle was fine, but I can't remember which one they said it was. HBL? BDL? Something like that. They said they advanced the timing slightly, and agreed with me that it's quite flat pre-cam but other than that they said all was well, and that they wouldn't expect all that much more with this spec.

Who knows. A million and one different opinions lol.

The stage 4 thing to clear up for you is:
Stage 4 is not a set standard between everyone, so some "stage 4" heads are better than others, bits that some companies would include in their "stage 4" head does not mean that others will, e.g
Company A sells a stage 4 head,
Company B sells a stage 4 head,
When company A looks at Company B's Stage 4, they find its equivalent to Company A's Stage 2 head.
You see, so your head may not be as worked as you might think you need to find the exact spec of the head from an engineer or the company that produced it originally.

Edited by liirge, 10 November 2009 - 12:27 AM.

[GraemeC]

You have a receipt for the head - where was it bought from? That will at least give the guys on here some idea as to how well it will have been modified.

[Sprocket]

sorry you've lost me?

Is the distributor the standard item? Has it been 'tailored' the the engine spec? is it an Aldon performance distributor?

I suspect you dont know which is fair enough, but what we are all trying to get at here is that you cannot just expect to throw parts together and expect to get the results. I know you didnt build the engine, but you are either going to have to put up with the fact that the engine is capeble of a little more, or set about fixing it

The standard distributor will be no good for an engine of that suggested spec.

Edited by Sprocket, 10 November 2009 - 10:42 AM.

[Ethel]

The dyno graphs would give us a better idea. What rpm was it turning to give that 90bhp - what did it give at the wheels?

[Cooperman]

It may have a Stage 'whatever' head, but were the compression ratio calculations done correctly and do you have them? If the calculations and subsequent machining have not been done, then you could be running a very low compression ratio.
The distributor issue has been covered above, as has the issue with the needle. You would probably gain a bit with twin 1.5" SU's on a properly modified inlet manifold.
Has the cam just been 'installed' dot-to-dot, or was it properly timed-in using a DTI, a crank protractor and offset-keys?
What exhaust system is fitted? It may be that it has a huge diameter exhaust pipe which will lose quite a bit of power, or even an extra-large diameter end pipe which will also lose you power. An oversize exhaust can lose as much as 5 to 6 bhp, possibly more. The diameter should be 1.75" internal from end of exhaust manifold to end of final exit pipe.
As a matter of interest, the Cooper 'S' does not have 90 bhp, it had 75 bhp (on a good day). The later John Cooper 'S-Works' cars had a claimed 90 bhp, but having stripped and re-built a couple of those engines, I reckon they would be lucky to have had 80 to 85. A bit of 'salesman's licence' there for sure.
Think it through. A standard 1275 Mini like yours was originally would have had about 63 bhp. In combination with all the other correct parts, assembled properly, you could expect to gain:

12 bhp from the overbore and big-valve flowed head
8 bhp from the cam at higher revs only if timed in accurately
5 bhp from the inlet manifold and larger improved carb
5 bhp from a decent exhaust system

That's about plus 30 bhp, which is what you've got

Those are fairly general figures and all the above must be fitted, you can't just bore it out and gain 12 bhp just by adding a big-valve head, or just fit a 286 cam and gain 8 bhp.

90 bhp, if combined with an improved mid-range torque improvement is not bad at all and shopuld make the car drive very well. If, however, you want to race it, then that's a different matter.

[1430 Mk1]

That sounds a bit thin.

I had a 1360 with a 286 cam on. There were 2 carbs with the head, both allegedly set up right. A 40DCOE and a HIF44 with a highly modded and dowelled inlet. The dizzy had been curved. I fitted the HIF44 as I didn't want to go hacking my bulkhead up. The previous engine was an MG 1275 which was good fun. I was expecting a lot more than I got. It was pretty lame. It wasn't as fluffy as I'd expect down low but just wouldn't breathe fully. I thought the HIF44 was choking it too much. The head was a work of art, the valves were 36/31, the CR 11:1. It was fun, but nothing electric.

NOW. 1380/286 with a head with S valves and holes is a pretty standard hillclimb spec. It's a good combination of welly and drivability. They always always always use 45DCOE's though. The couple I've seen running HIF44's have been slower.

I see 1430's and even bigger on a single SU and the reported performance is less. You've got a big cam, big capacity and you're expecting it to suck through a single SU? There is your problem.

Whack a 45 on it and it will become more bad mannered, but it'll at least rev out.

For a 1380 with a 286, I'd expect it to be pretty rapid.

You're not trying to drag it around with a 3.1 FD or similar? That would account for it being lame.......

Get a 3.7 in there.

[mars red mike]

Why is everyone jumping on this guys engine, could it not be that the rolling road itself isn't calibrated properly? Never understand why people are obsessed with HP figures. BHP is just ammo for pub talks. Driveability is what its all about. No point in having 100 odd BHP under your right foot if the car is a pain in the arse to drive.

[twign]

I have the graph in my hand, it's 87.3bhp @ 6168rpm and 82.1lbs/ft @ 4672rpm. bhp goes from 19 at 2086 to about 23 at 2500, back to 19 at 2750 and then back to 23 at 3000. It steadily increases from there. Torque follows a similar pattern. 48 at 2086, 50 at 2400, 36 at 2800, back to 50 at 3400 and then increasing to peak at 4600 before tailing off. Obviously that's VERY roughly.

I'm not obsessed with bhp... I took my car for a RR and the bhp was less than I expected... so I opened it for discussion. I completely agree, driveability is what it's all about... and it doesn't accelerate as I'd expect it to either, and I think the figures from the RR are a reasonable reflection of this. It seems to leap from the mark, then it bogs, and then come 3500rpm it comes good again.

J max 73.5 mm pistons running a 10.8:1 compression ratio, again, this information has come from the guy that built it and it hasn't been tested or inspected.

When I had a new crown wheel and pinion, the guy at my local mini specialist offered me a choice of diff, a 31 and a 34. He said the 31 was what it had in it, which would give more low down, and the 34 was what he could put in it for more top end, so I had the 31.

Not sure what distributor it has on it, I'm going to my local tomorrow so I'll ask them to identify it for me, and then I'll post it.

I'm no mechanic so I just trust what people tell me. Not dead impressed with the RR service though I must admit.

Thanks

Twign

[1380rich]

the 3.1 would give you more top end