Funning Head Gaskets
Turbo Mini Forums

I'm not sure what I'm doing wrong. The original failures were not det related, and definately head gasket (the black ones); although others seem to be fine with this gasket.

I have now changed to the copper type and since had a further 2 failures, but this time det related between 3 and 4 cylinders.

The first one was because the boost was a bit high for some reason following the RR day. But this time I have been running a maximum of 9psi and 20 deg advance, fuelling is around 12:1 on boost, and it still went after 500 miles.

I'll check that the advance is what the MS is telling me with a strobe whe it's back together, but any thiughts would be nice.

I'm going to double check the CR too, but it's around 9:1

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Are the head and block faces both flat?

wil

i have a few pre problem bk450's do you want me to send one over to try with the TB

The BK450 don't fit with the 295 head. On the hillclimber we use a BK450 with lots more boost and revs than the Sprint's engine, and have no head gasket issues.

Cheers for the offer though.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Wil, double check the block surface, I had issues with a 1275 years ago that kept blowing gaskets, this was what it was in the end.

If it's not the block, then it will be the MS setting for the trigger wheel.

Depends what version of the MS code you are using, but the more recent code needs different offset angles from earlier versions. Tooth No. 1 Angle should be set to 80 Degrees BTDC with a 36-1 wheel.

EDIT: that is if you have the sensor in the usual place.

Edited by Paul S on 1st Nov, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I agree with Paul. This is what killed Mike's engine at Avon.

Well and the fact that the trigger bracked I gave him was a mile out!

If something is worth doing, it's worth doing half of.

i killed 3 copper gaskets within 500 miles on an na mg lump, changed to a bk450, it never blew again maybe its half down to the gaskets?

Yes i moved to the darkside

Instagram @jdm_brett

Not something daft like a streched head bolt?

torque wrench?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Yes i moved to the darkside

Instagram @jdm_brett

The problem is the BK450 is not an option. I use the BK450 on the hillclimber with no issues.

I callibrated the wrench (specifically at 70 Nm) only the other month.

Streached bolts could be an issue, but it's not the failure I'd expect. This is a det issue and only evident on cylinder No.4. The car never runs hot, but I guess No.4 could be the hottest and potentially lean for some reason.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

water pump not pushing coolant. Inlet temp higher than you think?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

fucked crank damper?

If something is worth doing, it's worth doing half of.

yep, or may have just moved,

Just a thought, which I'm guessing Will has thought of already from the strobe comment,

I have now retarded the indicated (as in on the laptop) advance to 15 deg max on boost until I can check with my strobe.

The strobe is at my bro's with the hillclimber 'til the end of the month.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

I can post you my timing light up if you like. It's got the adjustable bit for checking advance.

Right, back to this. I'm not sure I've found the problem yet.

I've remeasured everything to check the CR, it's 9:1.

I've change the carb and fitted the wideband.

What seems to happen is that the AFR is 12:1 on boost at 5psi and stays there if you up the boost while already boosting.

But when you try the higher boost making it from say 2.5k it leans out and then pinks. However it only leans to 14.5:1.

Timing is currently set at 15deg on boost. This is Still need to check, but the trigger wheel is where it should be, so can't see it being any different to when I fitted it. Changing it on the laptop definately makes a differance (i.e. changes rpm at tickover)

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

hi will, as above also........ i assume your using top grade fuel...............

"But when you try the higher boost making it from say 2.5k it leans out and then pinks. However it only leans to 14.5:1."

the above wil is your problem it pinks it only takes a mili second to do this and take the head gasket out on HI Boost!
richen the needle profile up on hi boost, to 12.5:1 we know that it would be a tad rich on WOT on low boost but theres you problem

could you get a larger intercooler in the air stream in there ? to help things ?

what about me lowering the CR some more ? PM me wil

I have considered lowering the CR further, but I think the head is about as far as it'll go. the only way is bigger dishes in the pistons.

The problem is why is it leaning out? it never used to up to 12psi.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

The 14.5 AFR is an average. I found the spread between inner and outer cylinders on the carb to be quite high at lowish revs. Reality is that you are probably on 16:1 on the outer cylinders.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

That makes sense Paul as it's obviously No 4 that is the only one with signs of det

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

This is the thread with all the datalogs with a carb.

There was always the lean off spike on a gearchange. If your small turbo is spooling up very quick and boosting during the lean off spike then that may be the problem.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."