9 replies to this topic

[HazleNut21]

Hi All,

Calling on the collective wisdom of those with more know-how than me. I've decided to keep the original 998 engine that came with the car I am restoring, but want to give it a little more pep for "spirited" road driving. The car will mainly be used as an enjoyable weekend toy, I am aware it's not going to be "fast" by modern standards but just something that has enough oomph to enjoy around country roads.

 

I understand that there are sooooo many options with engine building for the A series and after spending far too long reading forum posts about all the different pathways I have finally come to the conclusion that its best just to ask my own questions.

So my initial thoughts at piecing something together,

998 +60thou (flat top pistons)

Bottom end balanced

CST2004/05 head

SW05-07 Cam

1.3 ratio rockers

Stage one kit, exhaust

 

What would I need in terms of fueling and ignition? I would like to go electronic ignition, what kind of dizzy carb/needle should I be looking at etc etc. Should I also be aiming for around 10:1 comp?

Open to suggestions as relatively new to this stuff :)

[Dusky]

Sounds like a very good setup. I would add a lightened pre verto flywheel. Really brings engines to life.

[humph]

Sounds like a good spec.

I’ve just had this one Built by Jim @ r.a.c.e engineering;

998cc A+ block - Bored to 0.060" & skimmed to to get a C.R of 10.5:1
Crank - 998cc Re-ground
Head - 12G295 skimmed by 0.050"
Pistons - P-22463 +0.060" Flat Top
Cam - Minispares Evolution001 - recommended by many and cheaper than most.
Timing chain - 3H2127EVO timing chain (simplex)
Final Drive - 3.44
HIF38 Carb
RC40 exhaust
K&N filter in a modded original airbox

Being as it's a road car I was advised against a lightened flywheel, but we'll see how it goes when he's up and running. Seems there’s plenty of differing opinions on this.

Frustrating thing is it'll be next summer (at the earliest) before I'll be able to try it.

[Cooperman]

To get any meaningful improvement the head needs to have some work done on it. The head design is the biggest restriction to improved performance with the A-Series.

In particular the inlet and exhaust ports need to have the restrictions caused by the very intrusive valve guide bosses removed. If you can get hold of a copy of Vizard's 'bible', How to Modify the A-Series Engine' it shows how a relatively small amount of work will give a good improvement.

Then you need to flow the inlet manifold a bit to enable the induction mixture to flow in and fit a better exhaust manifold to get the old gases out.

Get the compression ratio to between 9.75:1 & 10:1. Accurate measuring and machining is needed to do this.

[unburntfuelinthemorning]

Modified 998s are great fun, it's what I have.  They aren't hugely fast but they are very enjoyable to drive. 

 

A 1.5" SU will be fine for that setup. 

 

With the ignition you can have your existing distributor advance curve altered to suit although it's always a bit of a compromise or you can go the whole hog with a fully programmable distributorless system.  Either will do, you'll get the best results with the latter but you'll spend a lot more. 

 

A 10:1 CR running super unleaded should work nicely.  Just get it set up properly. 

 

Think about the final drive ratio too, it makes a big difference.  A 3.76:1 ratio makes a 998 quite rapid if you don't mind 5000 rpm at 75 mph cruising in forth. 

[3VILC]

Watching opinions with interest as I'm thinking along the same lines for my 998, once I've finished cutting all the rust out

[OzOAP]

Done a few in the last couple of years.
1040cc,(+060), Mini 7 spec modified crank and rods, Steel flywheel/backplate, Piper 255 cam, 295 head with 33x29 valves, 10:1 cr, conical springs, 3.4 cwp.
2xHS2. Low 70s hp/ Mid 60s torque. Lovely fun, drivable, cars.

[Maccmike8]

Be worth having a chat with Calver if you are also buying their head.

If you are reboring then get the 2005 head as it has slightly bigger valves.

[whistler]

Be worth having a chat with Calver if you are also buying their head.

If you are reboring then get the 2005 head as it has slightly bigger valves.

As above, talk to Keith. he'll advise you what to put together with his head. 

[andyapanel]

Read Vizard and run any proposed mods past your insurance company.

I would eliminate ignition problems by fitting electronic ignition and put a fuel filter in keep the carb happy.

A lightened flywheel makes a great difference, as Dusky said.

Fit an RC40 or Manifold system plus a K+N.

Good luck and enjoy what you create.