18 replies to this topic

[Skinartnz]

Ok now i see there are plenty of threads on engine building but what the hell i'll do one too.

The plan is a reliable mildly fast 1098 engine.

A+998 block bored 40"
Cleaned and checked 1098 Crank
Hypatec pistons
Grant Rings
All ACL bearings
12g202 rocon head opened up a wee bit
Swiftune sw5-07 Cam
Duplex vernier timing gear
New Clutch kit
New oil pump (goes without saying)
Double valve springs
Alloy roller tip rockers, 1.3 ratio
Twin 1.25 SU carbs (may change to HIF44)

Will post pictures and fill in the blanks as i get things done.

 Photo0096.jpg   64.95K   23 downloads
All ready to start

 Photo0097.jpg   63.27K   31 downloads
Stripped and ready to go

[Cooperman]

That sounds like a good spec. With that cam it'll have good low-end torque and won't need more than around 5800 rpm, so no crankshaft breakage risk.
Make sure the head is well gas-flowed and set the compression ratio at between 9.5:1 & 10:1 for best results.

[Down&Out]

"Fast but not too fast" i like it! its nice to see someone not saying things such as "i want a 1380 with this and this and this and a turbo and rockets and fireworks" etc etc etc (you get my drift)

Should be just right, i'll be following this one for sure.

[Chance]

I want a similar engine spec :)

When I can afford to get a second car the mini is coming off the road and I want to rebuild the 998
Will be watching.

[Skinartnz]

Ok nothing much has been happening, been flat out at work, one development tho, My cank is from a 998 GRRRRRRRRRRR i have sourced a true 1098 for the rebuild but it means i have to wait for it.
Nothing can happen without that crank haha.

On a side note, i did manage to pick up a pair of mint condition hif44 carbs for $85nz.
Happy with that.

Will post again when i have the crank in hand.

[TimmyG]

That'll be lovely that will! :)

[Skinartnz]

That'll be lovely that will! :)

Thanks, spent a long time researching other peoples ideas. Mashed them all together and thats what i came up with.

[Sir Yun]

Excelent plan. I have helped with heads for exacly this setup a few times ( but 998). If you stick in a bigger intake valve and deshroud the chamber a tiny bit you can get a very nice engine. I have seen 68 BHP with a +80 overbore on a 998 (average 1275 does about 57 to 60 bhp there) but that was with a head that was fully ported. Sw5 is pretty rev happy when you have a balanced package.

As time allows I will be working on a 12G202 head and trying to do flowtests for each modification so you I figure out what is worthwhile and not.

maybe of interest (from wayback):

http://aseriesmodifi...limited-budget/

As a side note. If you bore it a bit bigger (hypatec do +80 and 100's) you can save on skimming the head. Bigger overbores are a little more expensive but you have to skim quite a bit off a 202 head to get the CR in the right region, so that is not free either. Upside is that you get a bit more displacement, and the bore /stroke ratio gets a bit squarer.

[Skinartnz]

Very interesting write up, will do some more talking with my head man, Thanks for that

[mk3 Cooper S]

^{Looks like a good spec but I would think again over the camshaft choise.}

[Skinartnz]

^{Looks like a good spec but I would think again over the camshaft choise.}

Bit late for that, its sitting on my work bench, whats your reason for this?

[mike.]

An SW5 will be a perfectly good cam in a small bore.

[mk3 Cooper S]

1100'S Dont rev so I would want as much torque as low down the rev range as I could get.
I would go for a 998 cooper CAM

[Sir Yun]

I don't agree and I'd go with either a SW5-07 or a Piper BP255 . Cam technology has advanced in the last 40 years and they are essentially updated 998 cooper cams. Beating a SW5 for torque is reaaaaly hard in my experience.. unless you go turbo. Duration wise it is actually quite short (244 isch !) but I think they did not name it after the duration because people are stuck on cam duration as the only parameter for cam performance.

I would budget for a good rolling road setup from the get go. ( check out the checklist from emerald3d to highten the chances that you are not trouble shooting instead of setting up while you are on the rollers

If you can stretch the budget a small bore ST3 head from (keith) www.calverst.com would be an excellent choice. Otherwise i'd just stick in the Minispares bigger valves and spend the money on the valve seat job and some minimal chamber work so the bigger valve can actually flow more.

If the budget is still too tight for that just get the seats recut (you can chase that for decades but in this case a two of three angle seat would work fine.. and even a super wide stock seat is not all that bad as long as you backcut the intake valves to 30 degrees so that the 45 degree part is about 1.6mm wide. That gains a relatively huge amount of flow for the work and cost involved. The exhaust valves don't need it really. A tiny bit of cutting to the chamber is not much work either

hope this helps a bit.

Edited by Sir Yun, 03 October 2012 - 05:38 PM.

[mk3 Cooper S]

Duration has an effect on the pumping losses. It is the lift and profile you should match to suit the peak torque area requirement for your spec