35 replies to this topic

[mrmeds]

Electronic ignition won't give you any more horsepower

i think the suggestion was that maybe i was getting a weak spark, and by upgrading to electronic ignition i might manage the full ptential of my stage 3 head etc rather than increase bhp. He was a bit perplexed as to why it wasnt  reaching 60bhp ish with the set up.

[Cooperman]

Can we assume that you have a standard cam and has the cam been accurately timed in using offset keys?
Are the pistons flat-top or dished?
What is the comp ratio?
What exhaust system is fitted, what is the diameter of the main pipe and the tail pipe.
'Stage 3' means very little. A standard head at 'Stage xx' is unlikely to be any better than a mildly 'cleaned up' 22g295.

[Spider]

There can be a whole host of reasons for the apparent low numbers.

 

Were the numbers corrected to allow for environmental conditions of the day and for that matter, when the 'base engine' that it was modeled off was tested, were those numbers corrected ?

 

How's the front wheels tracking ?

 

What condition are the front wheel bearings ?

 

Was there good air pressure in the tyres ?

 

What condition is the Gearbox in ?

 

Also, The way that so many of these blocks (in particular) were machined in the factory is ~ OK ~ to down right poor. I had an early totally stock and unopened A+ 1275 years ago that wouldn't pull the skin off a rice pudding, 998's would leave it standing. On stripping it down and going over everything, the machining accuracy and set up was very poor. The biggest killer of the power from that engine was that the bores were all crooked, but there were many other issues. Once corrected, it became a whole new engine all together.

The way that many machine shops set up and machine engines for reconditioning (and even for performance), any errors, like crooked bores or out of phase cranks, will only be replaced when items are fresh machined, one often has to ask to have issues like firstly found and then sorted on the machining process, not all shops are prepared or set up to do them in such a way.

 

So, what I'm getting at with that long winded piece is - how good was the machining accuracy ?

[Ethel]

 

That doesn't look unreasonable for a 998, there's a colossal amount of guesswork in estimating what makes it through the transmission, tyres & rollers to be recorded on the dial.

 

It looks like they've done a sensible job of setting it up too, setting the timing for peak torque where you actually use it rather than squeezing out the last HP for pub bragging. The electronic ignition might've been suggested if they saw some timing scatter: removing the points means there's nothing to bounce or drag on the dizzy spindle.

[Sam76]

And let’s be honest - it’s a bloody big improvement over the standard output of a 998!
I always used the electronic ignition for reliability and durability over the points and condenser set up, always felt the engine pulled better after swapping out the old bits!
As previously said, pub figures are great, but if it’s set up well and you feel a smile each time you open the loud pedal - it’s all good!!

[mrmeds]

driving around today, and i'd say its performing really well, to be fair its probably got more pressing issues still than a few missing horses !  Very stiff clutch despite being new ! Lots of condensation ( leaking matrix i think- though could be the new windscreen seal !). Ill leave those horses until the block needs attention.

[mrmeds]

had the engine rebuilt last this time last year, and have put on around 2500 miles since-  over the last few tankfuls of petrol ( so 800 miles ish ) i have noticed the fuel economy go down from 34 mpg to 28 mph and she's lost her oomph a bit. 

So back to the rolling road and the max bhp is now 54 bhp !!!

 

Had a compression test done and it seems like each cylinder is losing about 20%  and there is evidence of a  leaking head gasket !

 

Not very impressed with this considering the age  of engine ! 

I ran it in as per minisports advice - just hoping  getting head gasket changed  will help get some of my missing horses back, and its not something going on in the lump

[Clip]

Leaking head gasket will do it every time. You’ll also get the chance to check the bores too. Did you use the same shop as last time for the test?

[whistler]

You don't say what high lift rockers you are using but I'll assume they're 1.5. Have a read of this article from Keith Calver. https://calverst.com...al-compendium/.

Personally I'd remove the high lift rockers and change the cam for Minispares EVO001 or similar.

 

[mrmeds]

Leaking head gasket will do it every time. You’ll also get the chance to check the bores too. Did you use the same shop as last time for the test?

yes, slark race engineering

[mrmeds]

You don't say what high lift rockers you are using but I'll assume they're 1.5. Have a read of this article from Keith Calver. https://calverst.com...al-compendium/.

Personally I'd remove the high lift rockers and change the cam for Minispares EVO001 or similar.

1.3:1 roller tip rockers. and has a CA 2 cam

[coopertaz]

while head is off you can also check for any damage on block or head faces

[mrmeds]

well it got checked over at the engine refurbishers - they told be the compression is fine. around 185 lb/in but told be valve clearnces were out , 030'' rather than 015''

 

- would this result in massive loss of power and bad emissions ?

[timmy850]

More valve clearance means less valve opening time and lift. It’s similar to having a more mild cam

[mrmeds]

okay -tried checking my valve cleances - as not been done for over a year - jacked up car -put on axle stands left in gear , turned wheel to try and see valves opening and closing - ( no flat ground to push bck and forth at home ) - but o sign of movement from valves ?

 how many turns of the whee in forth do you need to get movement from the  valves  ? or am I missing something ?