10 replies to this topic

[Minladtom]

Hi I'm currently in the process of building a fast road/track day engine
I'm in no rush as I have to build this as my apprentice wage lets me.

This is the spec I was thinking of running and was interested as to what I could change or improve from others experience.

Kent cam 286 / or some say sw10?
Valves. 36 inlet. / 29 exhaust
Hif44 with a good inlet manifold plus an lcb manifold and I think 1.75 exhaust
Mega jolt or aldon distributor
Bored to 1330
Well gas flowed head and ported head
Cr raised 10.1?
Iight flywheel and clutch
Centre oil pickup
Vernier timing gears
Not sure on gearing at the moment

Things I'm unsure of.
Rockers?
Valve springs?

Thanks

Edited by Minladtom, 30 April 2014 - 06:52 PM.

[cal844]

Rockers... Keep them standard!
What you gain at the top end you lose low down!

[minilee94]

The bhp you loose down low you won't notice will be max 5bhp

1.3.1 roller rockers are better for low down but take abit more to set up

And compression ratio you have got down is a near enough standard ratio

Cr is mainly down to what head combustion chamber size , piston dish and the block

If it was me run 10.5

My 1380 runs 11.1 and with that you need to run the best fuel and fuel additive because my valves are too big ( same size valves as yours ) and you can't have unleaded seats fitted to a head with valves that big or you take the risk of them overlapping and has been know to become dislodged

Not trying to scare you off of building an engine but it's not cheap .. Far from it
I'm £3700 into my 1380 build and still going

Edited by minilee94, 30 April 2014 - 07:32 PM.

[minilee94]

Also what pistons you guna use

[Cooperman]

With a 286 it is best to run a straight-cut close ratio gearbox and a low ratio FDR in order to keep it 'on the cam'. The 286 delivers peak power at 6400 rpm, so you'll need pistons, balanced bottom end and a centre main strap to run those sort of revs a lot of the time.

Don't bother with 1.5:1 rockers. At best you'll gain about 2 bhp at 5700 and over, but lose a bit below that.

At those revs, i.e. a 286 cam, the usual 21253 pistons are not really up to it. I use Karl Schmidt pistons with my 286, but Omega also do a good product - both at a price and my Karl Schmidt cost me over £500 for the set of 4. I also use 11.1:1 with my 286 'S' engine, with twin H4 carbs.

But, when you get a 286 cammed car up to around 6000+ rpm in top it is flying, so long as the head and induction systems are on top form.

Expect to need to rebuilt it quite regularly.

[Minladtom]

What sorta bhp would I be looking at? And feedback spot on cheers

[minilee94]

Id say running at a 10.5 cr and the spec you listed I'd say about 90bhp

But it's hard to say really as iv seen a Minisport 1460 running 80bhp which is shocking

Edited by minilee94, 30 April 2014 - 09:14 PM.

[Cooperman]

With everything built very, very accurately, twin HS4's, etc., you could be looking at c.108 to 112 bhp at 6400 rpm.

It has to be stressed that with that sort of power re-building will be a regular thing, so it would be best to go to the next size up each time, rather than go straight to +0.060".

On my engine, which has the 286, I strip & re-build every 6 or 7 rallies, with a hone & piston ring change ever 15 rallies and a re-bore with new pistons and cam after 30 events.

To run an engine like this is not cheap, especially if used as intended, but you don't do a build which will probably cost around £5000+ just top drive it slowly.

Also, stronger drive shafts would be advised (I've snapped standard ones on dry tarmac rallies).

[Minladtom]

You recommend twin hs4s over hif44? Cheers cooperman. Don't think I could afford to be rebuilding that often bloody hell

[Cooperman]

With a hot cam like a 286 or similar, to get the power it is necessary to use a lot of serious revs. As the A-Series is a very long stroke engine , unlike a similar era Ford, that make for a lot of bore wear.

Reliable power is never cheap and with mega-revs being used wear rates are high.

Unless it is for 'against the clock' competition you might be advised to go for an engine which has better mid-range torque and thus not need over £1000 worth of transmission to go with it.

I built a 1990 Cooper 1275 Endurance rally car with an MG Metro cam, 'blueprinted' engine, standard transmission (as mandated by the regs) and a 3.44 FDR. It had about 85 bhp at 5700 and even after I sold it to buy a Rover 214Si rally car, the engine simply lasted forever. But it was fun to drive, handled superbly, was fairly competitive in its class and, overall, not expensive.

Actually it's not so much outright power which gives the Mini its unique performance, but the overall 'feel', handling and steering response. You are better spending £800 more on brakes and suspension then £1500 more on a full-on engine spec. The Mini is never going to be a quick car, so bring out its benefits of agility and friendly driving feel.

That endurance rally Cooper was quicker than a lot of modern cars on twisty tests because it did exactly what I wanted it to, when I wanted it to. I didn't keep putting it off the road or losing time with it 'bogged down' and 'off the cam'. Torque is more important then top end power and it doesn't keep wrecking the engine.

I hope this helps.

 

This is the 1990 Endurance Rally car, with its 85 bhp, in action: 

Edited by Cooperman, 30 April 2014 - 10:07 PM.

[Minladtom]

So if I was to keep that same spec and engine bore. Use maybe a 276 and a 3.44 Fdr . That's a nice little spec of a mini that endurance mini of yours. Was that 85bhp at fly?