24 replies to this topic

[James_1]

I'm going to be rebuilding a 998 to fast road spec over the next few weeks as I have the parts laying around and the engine has to come out of my daily Mini-Metro because 2nd gear syncro has gone completely.

I've got a 'rebuilt' gearbox which I'm going to strip down and check over, it looks fine from a glance and everything is clean so I'm going to be optomistic. Apparently the bearings and syncros only have a few hundred miles on them but we shall see.

The engine is going to be built around the 998 A+ block currently in the car with just under 40k on the clock. It doesn't use much oil and is quiet so I'm not planning on touching the bores, pistons or rings unless they turn out to be ruined.

I've got a very good 10/10 balanced crank and bearings with no wear which I'm planning on dropping in, along with some lightenened and balanced rods along with a 2 bolt Mini Spares CMS.

The cam is a good MG Metro N/A and I've got a duplex timing gear set to go with it and I've ordered some Mini Spares 'performance' followers.

The head is a 12G940 late MG Metro with the smaller exhaust valves but big inlets. The exhaust valves have been cut back into the head to give clearance as the block isn't pocketed. I've done some CFD testing to investigate how much this effects the flow and the results suggest that recessing the valves actually gives better flow than pocketing the block. I'm sure I've seen some bench flow tests that say the same somewhere too. Either way, I've got the head and it's in very good condition so that'll be going on.

The exhaust is standard at the moment with the cast type LCB manifold and HIF38. I've got a Cooper Freeflow manifold and an LCB as well and a choice of carbs, a Nikki which has been jetted for a 1275 A-Series, twin HS2s, a Webber 40DCOE on a Maniflow manifold and an MG Metro Turbo HIF44 and manifold. If the Webber will fit without cutting the baulkhead then I'd like to go with it but I'm not sure which of the others would be best.

Ignition wise I've got a choice between the standard Lucus with Accuspark ignition and Megajolt. I'd be interested to know how much more power and drivability can be gained from the Megajolt if setup on a rolling road and if it would be worth fitting to this engine or keeping it for a racier engine that will be on the way.

I'm hoping to get similar power to the original 998 Cooper, so about 55bhp.

James

Edited by James_1, 12 June 2012 - 03:19 PM.

[coopdog]

sounds good!,
you should get around the bhp your hoping for,
probably get a bit more with the a better exhaust and manifold to get the most from the head,
i have a similar build going on, check it out
http://www.theminifo...8-my-998-turbo/

[Sam Walters]

Have you chucked the head through a scanner or modeled it? It would be intesresting to have a look at that file.

[James_1]

I've done a fairly basic model as an evenings experiment. I can send you the files if you are interested, they are SolidWorks 2011. The chamber is fairly accurate but the ports aren't yet.

I'll get some photos up of the crankshaft and conrods later.

[dan187]

Have you thought about fitting a turbo? Use that setup with the HIF and get yourself a small turbo (i got a 2nd hand T2 for £50) and you'll turbo 55 bhp into 110 bhp no problems.
The N/A mg metro cam with the 12G940 head would give you good performance.

I have a turbo 998 and it is great for the road.

[James_1]

The conrods are standard 998 A Plus which I have started work on. I am using a powerfile followed by wet and dry to polish them trying to remove metal 'lengthwise' as much as possible. I am waiting on a set of digital scales but hope to have lost a few grams total. I'll then balance them end to end.

Is it worth shot peaning or going as far as using metal polish on the rods?







James

[James_1]

Stop giving me expensive ideas Dan! That does sound very interesting though. Sadly the engine has flat top pistons though so the CR will be right up at around 10.5:1.

I have all the turbo bits in the garage on a 1300 inline block with proper low comp. dished pistons and a turbo head with the special valves. If I can afford to keep that (I'm going to have to sell it as I can't find a job at the moment) then those bits may well find their way onto this engine in the future with some nice dished pistons. I'll be keeping an eye on eBay.

What are the best turbo 998 pistons to go for? Are the factory dished ones up to it assuming I'm not running silly boost?

James

[coopdog]

All standard pistons are pretty much up to the job unless your running stupid boost,
You could just work the chambers to lower the CR enough, 10psi will give you around 100bhp and the CR only needs to be around 9:3:1 to run this

[dan187]

I've run mine in 2 configurations.
9:1 comp, 13 psi, 110 bhp (megajolt)
9.4:1 comp, 8 psi, 80 bhp (dizzy)

always used the standard flat top pistons.

I imagine (as suggested above) that at 9.4:1 I could have gotten nearer the 100 mark but if I'd had the megajolt to give correct timing.

If you could bring comp down to 10:1 and run an intercooler you should be ok for at least 4 psi. Should give you a nice bit of power topping.

I'm currently building a 1275 turbo injected motor using an MPi block which will be my daily. Going for 10:1 and at least 4 psi.

[James_1]

This could get expensive...I think I'll stick to building a N/A engine for the time being with the potential to turbocharge at a later date.

James

[coopdog]

This could get expensive...I think I'll stick to building a N/A engine for the time being with the potential to turbocharge at a later date.

James

turboing doesnt have to be expensive if you do it right

[James_1]

My entire build is being done strictly for under £120 so at the moment it is too expensive for me, but I know that it's totatly feasable in the not to distant future for sensible money.

I've been reading up on shot peening and it seems to make sense when most places seem to be charging around £5/rod according to forums but I can't find anyone actually advertising that they do it in the UK. Does anyone know of a half decent company that isn't going to wreck my rods, ideally in the south east?

James

[dan187]

Yeah fair enough. My turbo conversion cost £600 which is cheap compared to the same power from an N/A.
Sorry don't know about a shot peener

[mymini007]

Yeah fair enough. My turbo conversion cost £600 which is cheap compared to the same power from an N/A.
Sorry don't know about a shot peener

Have you got a breakdown of the parts and costs, and what you did as this is something I would like to do in the future.

Sorry to Hijack the thread

[dan187]

http://www.turbomini...p=vt&tid=326421

...is my build thread. Have a search on the forum there are lots of guides and advice. There is a pdf put together by another chap wil_h) which i based my build on.