62 replies to this topic

[stardude]

i will be building up my new engine soon, as soon as i have taken it out of my car. i plan on doing something different with it.

here is the spec i am looking at:

i am toying between these ideas -

Block

998 bored to +80 or +120
OR
998 bored to +60 with 1100 crank and +60 1100 pistons


Head

Worked 12g295
OR
Worked or standard 1275 head


Cam

Morspeed Phase 3 cam


Timing

Second hand belt drive kit
OR
Vernier Duplex chain drive


Transmission

Standard Gearbox - Rebuilt
Straight cut drop gears 1:1


Crank

lightened
wedged
hardened
balanced

Rods

lightened
balanced

Flywheel

ultralight flywheel


what do you all think?? any problems that you can see? any advice?

many thanks

adam

Edited by stardude, 21 April 2009 - 07:42 PM.

[stardude]

bump

[Shifty]

Looks ok, I can give you the spec of my recent build

998+20
Sw5 cam
Vernier pulley
12g 295 head
Ultralite flywheel
Lightened backing plate
Maniflow and an rc40
hs4 carb

That gave me 50bhp at the wheels and about 68 at the flywheel.

It goes well, I will say the SW5 is a bit tame, you can't really tell its there. I looked at the morspeed ph3 and was told that its a bit hardcore for a 998, however some people do like it(from morspeed themselves)

They recommended the PH3 for a daily.

If I were doing it all again I may look at a wilder cam. However he does drive well and still gives good MPG

I'm running a standard box and a 3.4 diff on 10" rims

Have you looked at the cost?

I spent about £1200 on mine for parts and machining

[Racer_Pete]

Looks a good spec, along the same lines as mine, If you choose the 1100 crank it won't rev as well as a 998 will though due to the longer stroke (think it had the largest stroke out of them all) but will give you more torque.
I'd advise using a orange spec diaghram with it though, what carb you going to be using?

[mike.]

Only thing i'd bear in mind is that the 'lairyness' of cams is much worse in small bore engines. The morspeed phase 3 cam is pretty lairy in a large bore engine with power coming in at 2krpm. In a small bore, all low down power will be gone and power won't come until pretty high in the revs; but when it does come in, you'll know about it and it'll just rev and rev.

It depends what your building it for but that cam with an excessivley light flywheel will idle pretty bad and drive pretty bad at low speeds.

[stardude]

currently my costings are looking like this:

Pistons and rings - £115-120 shipped from australia
Gearbox - £310 GW
12g295 head - £100 max
Cam kit - unsure of cost estimating around £130
Vernier Duplex - £85
Crank work - dont fancy spending any more than £200
Flywheel - £120
back plate - £80
Rally clutch - £50

block machining - unsure of cost.

and all of the other little bits that ned buying.

so that comes to £1190 without the block machining. so not far off

and if i can find an extra £270 i will be getting a nice set of drop gears for it too

[stardude]

i will be using a HIF38 with it. and yeah, orange diaphragm too

i was wondering if it would be too lairy for the 998. the thing is i do stupid amounts of motorway driving, so will be at high revs most of the time anyway.

but on the other hand i do a fair bit of town driving too.

what would be a mildly lumpy cam for a 998 then??

i dont want to go the flat route with the sw5, i want to know there is something different in there.

[stardude]

i am realy torn between the 998 +120 route and the 1100 +60 route.

less volume but much more 'revvyness'

VS

greater volume and much greater torque

i realy cant decide

[Darkscamp]

torque anyday of the week

[mini7boy]

why don't you run your plan past AC Dodd either on his Ask Doddy forum, or ML Motorsport forum or on Minifintity.

The Ph3 cam combined with a 1275 head on a small bore engine may be a bit rough for road driving.

It might be OK with the 1100 crank, but AC will know for sure.

[Wil_h]

I have a few comments:

1) don't bother with straight cut drops, not needed for the kind of power you'll make, and they're really noisy. Use the money to buy a mini spared crosspin diff instead.

2) Don't bother with a belt drive, chains are much more reliable for a road car.

3) The 998 +120 is the better option IMO.

4) 276 cam is great in a small bore.

5) fit a mapped ignition system such as megajolt to get the most out of your engine.

[stardude]

I have a few comments:

1) don't bother with straight cut drops, not needed for the kind of power you'll make, and they're really noisy. Use the money to buy a mini spared crosspin diff instead.

2) Don't bother with a belt drive, chains are much more reliable for a road car.

3) The 998 +120 is the better option IMO.

4) 276 cam is great in a small bore.

5) fit a mapped ignition system such as megajolt to get the most out of your engine.

hiya

thanks for your reply, can you expand on why you think the +120 is the better route? i just want all the information i can, and good advise from people who know their stuff.

and i know you know your stuff

i will look at magejolt in the future, but i wont be able to afford it just at the minute.

[liirge]

Few questions here mate,
Where are you getting +120 Pistons from? also what will that make the bore? it must be nearly square?
Also where are you getting the Straight cut drops from?
im thinking of doing something excessivly similar..

[stardude]

minisport AU in australia. they sell 998 pistons all the way to +120.
you can buy straight cut drop gears for 998 from MRA minis.

im not sure what bore it makes it. cant work it out

anyone know??

[Cooperman]

I built a sort-of development 998 a couple of years ago with the following spec:

Bored to +0.080", i.e. 1061 cc
Flat-top Hastings pistons from Mini Spares (excellent quality and price)
12G295 head with slightly larger inlet valves, gas flowed and chambered with 10.4:1 comp ratio
HS4 carb on flowed and matched Howley inlet manifold.
Standard 998 crank
Original Cooper 'S' 510 cam (2nd hand out of one of my rally engines)
Original 3-branch Cooper 998 nexhaust manifold with single RC40 box
Slightly lightened flywheel, but still the Verto clutch (I will fit a pre-verto clutch when I get around to it)
Aldon 'Yellow' distributor
Duplex timing chain with Mini Spares 'budget' sprockets timed in with offset key.

This gives 68 bhp at 6000 rpm (at the flywheel). With a 998 it is important not to go too 'wild' with the specification if the car is to be used on the road.

The gearbox is standard and the final drive ratio is 3.2:1 although I think a 3.44 might be just a little better.

It is a very nice car to drive.
One thing I would not do is to fit straight drop gears or even straight cut gears in the box. S.C. gears are fine for competition, but not really for the road. With S.C. gears and drops you do really need ear plugs for driving any distance. They are fine for competition when the crash helmet kills off a bit of the noise, but not for a road journey of any length.