19 replies to this topic

[blakie]

Good evening all,

After a few weeks of searching the internet and viewing old posts on the forum I have drawn up an engine spec to build for a 998 to ready for my MK2 project.

I’m not looking for anything to set the world alight or something that needs stupid rpm to get anywhere. I’m hoping the following will be nippy off the line and be good for driving around country lanes.

-998cc +0.080” (1060cc)
-12g295 cylinder head
-Kent 256 camshaft
-10:1 compression ratio
-Hiff 38 Carburettor
-Mini spares Alloy inlet
-Maniflow exhaust manifold
-Facet gold-flow fuel pump
-123 electronic ignition distributor

General thoughts on this would be much appreciated plus any advise on what pistons to use. Also which final drive would be advisable.

Thanks in advance

Blakie

[cal844]

I would get the block measured and go next size, going 80 thou over bore means it's scrap at the end of that bores life...

Id go for a 266 cam profile and a 3.44 (DAM5626 box) diff, also get the head unleaded converted.

My 998 is a little revvy at 60mph with a 3.76 but it'll pull from 30 mph in 4th gear

Edited by cal844, 18 January 2022 - 05:46 PM.

[Gilles1000]

DAM5626 is an A+ Box, can you fit a 3,44 diff in it? AFAIK there is no 3,44 diff with A+ gears.

Interested to know more about that as I plan to have similar setup

[timmy850]

I liked the 3.76 diff in my 998 engine. It was good off the line and it needed the RPM to get up big hills on the highway

You’ll need to match your pistons to the desired compression ratio. Flat top pistons will mean you don’t have to skim so much off the head to get the right CR.

You can also get a 12G202 head modified to 295 specs or even better for a 998.

Another option is a 1098 crank and pistons and get more displacement for about the same outlay as a 998

[Shooter63]

Good evening all,

After a few weeks of searching the internet and viewing old posts on the forum I have drawn up an engine spec to build for a 998 to ready for my MK2 project.

I’m not looking for anything to set the world alight or something that needs stupid rpm to get anywhere. I’m hoping the following will be nippy off the line and be good for driving around country lanes.

-998cc +0.080” (1060cc)
-12g295 cylinder head
-Kent 256 camshaft
-10:1 compression ratio
-Hiff 38 Carburettor
-Mini spares Alloy inlet
-Maniflow exhaust manifold
-Facet gold-flow fuel pump
-123 electronic ignition distributor

General thoughts on this would be much appreciated plus any advise on what pistons to use. Also which final drive would be advisable.

Thanks in advance

Blakie

I think your pretty much spot on, it should make a great road engine, diff wise I'd go for a 3.44 if you don't go on many fast A roads, the only thing I might change is the pump those Facets can be a bit noisy

Shooter

[blakie]

Thanks for the input guys.

One thing I haven’t put any thought into is rockers, would it be worth changing to roller rockers as well?

[DomCr250]

I've had a number very similar spec 998's over the years, I'd personally save your cash on the Facet pump, the mechanical one will be fine, or even the cheap eBay pumps if you want pump immobilisation for security reasons.

 

Unless you are very lucky the majority of 12G295's will be skimmed to use with dished pistons already (they are all 50 years plus old now), check the depth using either the total head face depth or the oil feed measurement. If it has had a chunk taken off just use the standard 998 oversize pistons, as mentioned above don't over bore it anymore than is necessary. You wont need to do much with the head as standard, they seem to work well with only light mods.

 

3.44 diff on 10's is a good compromise.

 

​Once it's done you'll enjoy the benefits of thrashing the little thing to death at every opportunity and knowing you wont have an expensive rebuild every few thousand miles.  Moving from big bores to 998's was a revelation to me, so much fun and reliability.

 

Look forward to seeing it down at the H café when its built and running.

Edited by DomCr250, 20 January 2022 - 10:01 AM.

[humph]

Good evening all,

After a few weeks of searching the internet and viewing old posts on the forum I have drawn up an engine spec to build for a 998 to ready for my MK2 project.

I’m not looking for anything to set the world alight or something that needs stupid rpm to get anywhere. I’m hoping the following will be nippy off the line and be good for driving around country lanes.

-998cc +0.080” (1060cc)
-12g295 cylinder head
-Kent 256 camshaft
-10:1 compression ratio
-Hiff 38 Carburettor
-Mini spares Alloy inlet
-Maniflow exhaust manifold
-Facet gold-flow fuel pump
-123 electronic ignition distributor

General thoughts on this would be much appreciated plus any advise on what pistons to use. Also which final drive would be advisable.

Thanks in advance

Blakie

 

I have pretty much the same spec 998 in my Elf, the differences being;

 

Bored 60 thou

Minispares EVOLUTION001 cam

Distributor - C-27H7701 - This is A Plus only

Electric fuel pump AUF214MS

K&N filter in standard box drilled as per Vizard

Lightened flywheel - Road spec 4.48kg from MS

Final drive 3.44

 

Not driven the car yet, few weeks away, but it sounds great.

Edited by humph, 20 January 2022 - 01:13 PM.

[blakie]

I've had a number very similar spec 998's over the years, I'd personally save your cash on the Facet pump, the mechanical one will be fine, or even the cheap eBay pumps if you want pump immobilisation for security reasons.

Unless you are very lucky the majority of 12G295's will be skimmed to use with dished pistons already (they are all 50 years plus old now), check the depth using either the total head face depth or the oil feed measurement. If it has had a chunk taken off just use the standard 998 oversize pistons, as mentioned above don't over bore it anymore than is necessary. You wont need to do much with the head as standard, they seem to work well with only light mods.

3.44 diff on 10's is a good compromise.

​Once it's done you'll enjoy the benefits of thrashing the little thing to death at every opportunity and knowing you wont have an expensive rebuild every few thousand miles. Moving from big bores to 998's was a revelation to me, so much fun and reliability.

Look forward to seeing it down at the H café when its built and running.

I already have the facet pump as it came with the carb I brought, but may stick to a standard mechanical for ease.

I’ve just checked the thickness of the head 2.750” so it’s never been skimmed. That’s a result.

So bore wise, if the block is fine and just needs a hone you’d say just stick with a 998cc?

Cheers

Blakie

Edited by blakie, 20 January 2022 - 05:22 PM.

[eric67]

I would suggest using an electric fuel pump as the mechanical pump will otherwise be close to your exhaust manifold. A standard SU or Hardi pump on the rear subframe would do the job.

You'll also need to be careful with fitting the HIF 38 as it will be perilously close to the bulkhead. I needed to cut down the carb spacer on mine so that the accelerator quadrant barely cleared the manifold.

Otherwise all looks good to me although a CR of 9.5:1 may be a safer bet for 95 RON unleaded. 

[Turbo Phil]

If you’re fitting a 295 head you need to calculate your compression ratio. If it’s unskimmed they have a 28.3cc chamber. Even with flat top pistons on a standard bore 998 this puts the compression around 8.5-1 iirc.

Phil.

[blakie]

If you’re fitting a 295 head you need to calculate your compression ratio. If it’s unskimmed they have a 28.3cc chamber. Even with flat top pistons on a standard bore 998 this puts the compression around 8.5-1 iirc.

Phil.

Thanks……….. please see original post. This has been thought of. 👍🏻

[Earwax]

Hi Blakie

 

Your spec seems well sorted and thought out.

  I see you have already 'accounted' for the CR. change required ( as pointed out by Turbo Phil). When this mentioned , I wondered how much of a skim required.  ( think there is a rule of thumb type guesstimate but cant recall it)... and found this similar post on a separate forum    https://www.pistonheads.com/gassing/topic.asp?h=0&f=90&t=474554   - 295 cylinder head related and worries about hitting oil galleries. Again i am not familiar with the standard 998 block heights , but do know 1275s can benefit from small block height reduction for piston to deck heights  albeit small difference to CR.

 

A third possibility for you,  sell the 295 to the turbo set ( low CR is ideal) , sell the 12940 and look for a suitable 202 or 206.  With a couple of port mods by well known cylinder head specialists you will still have a sweet build without excessive skimming.   Good luck with your build.

[timmy850]

By my quick calculations the 295 won’t need much skimming with flat top pistons, with the overbore to 1060cc I’ve got above 9.5:1 with a stock unskimmed head.

[blakie]

By my quick calculations the 295 won’t need much skimming with flat top pistons, with the overbore to 1060cc I’ve got above 9.5:1 with a stock unskimmed head.

Without sounding to much like a school teacher could you please show your workings? 🙄

It will help ensure I’m doing it correctly 👍🏻

Blakie