486 replies to this topic

[PhilipGCaldwell]

Thought its about time i did a thread

My plan is as follows: to build a 998 motor that is more than a match for a 1275

With th ridiculous price of 1275s I want to show people that the much maligned 998 is worth keeping and mod'ing, I own a 998 mini 30

Spec:
12g940 head, ported out as per Vizard's bible (converted to unleaded)
1.5 inch ram stacks with ITG filter
twin 1.25 carbs
standard 998 block (pocketed) and the original dished pistons (overboring is cheating)
Kent 276 canshaft
Megajolt
Ultralight flywheel
Ultralight backplate
Fletcher exhaust
modified intake manifold

Edited by PhilipGCaldwell, 29 March 2011 - 11:46 AM.

[PhilipGCaldwell]

Engine bought off ebay for the princley sum of £34




bores look great

[PhilipGCaldwell]

12g940 head


ported out

[PhilipGCaldwell]

i have done more work on the porting since this pic was taken, it doesnt look that rough now, nice and smooth

[PhilipGCaldwell]

[PhilipGCaldwell]

[MiniLandy]

Nice project!

I love fast small bores, and with a spec like that, should kick out more than enough power than a 1275.

There's a similar spec engine to that in the yellow bible (but with a 295 head, and 1 3/4" carb), and when they put it in a mini it'd beat a metro turbo on the quarter mile.

Good luck!

[PhilipGCaldwell]

There's a similar spec engine to that in the yellow bible (but with a 295 head, and 1 3/4" carb), and when they put it in a mini it'd beat a metro turbo on the quarter mile.

yeah, i have read that build page more than a few times! Im using the same cam as that build but different carbs aswell, think he used a hiff38 and overbore +20 with powermax pistons (i think)

I just want to show people that 998s are a really decent motor to modify rather than spending over the odds for a 2nd hand 1275 off ebay!

[benpopham]

Nice work

[PhilipGCaldwell]

block degreased and painted and on engine stand ready for honing


twins cleaned up and intake ported to Vizard's bible - new float needles installed

[PhilipGCaldwell]

Crank and flywheel assembly loosely assembled


Old pistons ready for another few thousand miles!cleaned up ready for new piston rings


some pitting on one of the pistons, not great but cant afford new ones


I honed 2 bores last night, got a 3 legged glaze breaker from machine mart for £25,
pictures to follow later

[mk3 Cooper S]

What sort of power are you expecting to make from it?

What size valves are in your 940 head?

[ministe]

Watching this with keen interest! Great work so far.

[WRLondon]

looking good!
some high lift rockers may help abit but other than that should be pretty nippy!
998s are very revvy
hmm maybe i shouldnt have sold both my 998s

[PhilipGCaldwell]

What sort of power are you expecting to make from it? What size valves are in your 940 head?

hoping for around 65-70 at the flywheel
Inlet - 36mm (I think from memory)
Exhaust - 29mm

some high lift rockers may help abit but other than that should be pretty nippy!

not on a 998, high lift rockers on small bore severly restrict the power and toque low-mid range revs, going with the Kent 276, lumpy idle but after 1500 revs should fly