Head Joint
Turbo Mini Forums

My gasket has failed (BK450) at about 13psi boost.

The head and block were both ground and I used the Minispares steel stud kit although only a 9 stud head.

I have read that 9 studs should be OK for higher boost levels than I am using (although I have a highish CR and close to boarderline knock so worst case for my boost level)

I would have thought that the small additional 2 studs don't provide much extra clamping load but please correct me if I am wrong.

Maybe there is a prefered nut lubrication and or/torque level and sequence.


What is the prefered best head joint on this forum?

Thanks for the help..

what's the CR?

Compression Ratio

Yes I think he knew it stood for compression ratio, he is asking what it is in numbers!!

lol, he means what CR does your engine have?

Sorry , read it quickly.
Its 9.2:1

Where did the gasket go? Between 3&4? If so extra studs at the outer ends of the head won't help with that.

It's possible that you had one of the bad batch of BK450s from early this year/late last year.

For me, 9.2:1 is a bit high. Might be worth getting some meet taken out of your head chambers while it's in bits.

This may be a personal thing but I dare say with mappable ignition a decent intercooler and good fuelling that 13psi at a CR 9.2:1 would be fine. It would also have decent off boost performance.

But as Andy says where did the gasket go? Any pictures?

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

IMO 9.2 is a bit close for comfort,

it should be ok as long as you have a good sized intercooler, but you'd probably only need a dose of low octane fuel or a warm day to push it over the edge.

I haven't taken it apart yet although I suspect its the clutch end as I could feel gas escaping at this end of the head as I reved it under no load.

I will have to check when its in bits.

I think 9.2 should be OK if its mapped properly.
WRC engines are at over 11:1 with 3bar boost!

I agree with Joe, I've found on the 205 that the octane of "super" unleaded varies greatly despite what it proclaims to be on the pump, a tank of Esso 97 recently had it detting like fcuk until I whacked a bottle of booster in it.

Ah yes but WRC lumps are a different animal, ally heads for a start, plus selected fuel,

also much longer cam durations IIRC which drops the dynamic CR right down... but we wont go there!

Assuming there was no detonation (which I can't at the moment), what is the best head joint in everybodies experience?

I stand correct on the CR bit then

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

Well, the BK450 is fine, loads of people using it at well over 200hp,

for your boost 9 studs should be fine, up around 20 psi a few people have spat the gasket out due to not having the 11 studs,

I always fit 11 std A+ studs and nuts and torque them all to 45lb.

Thanks for the info.
I will have a look at the gasket soon.

As regards to knock, I can say that I really have never hear it after I remapped it for my 266 cam (initially there was a hint at 3500rpm)
I use Shell V max and octane booster which should be over 100octane.
I don't want to compromise response by lowering CR as it is very good.

If I see it has been knocking I will retard a little.

I think the 11 stud route looks sensible.

Do you all retorque after it has run?

I used to, but haven't found that it screws up any more, so have given up.

What ignition advance?

In the 13's at last!.. Just

This is not the usual install:

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=216197

No comment.

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."

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

i see where paul is going with this (i think) any chance of a picture of the failed gasket and the piston crowns/head/sparkplugs?

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Impossible to diagnose without looking at the head gasket failure. All my head gaskets that have failed at the outer edges were owing to under torquing.

Paul. Please stop it.

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

Shell V Power is gauranteed to be 99 octane at the pump, unlike one said supermarket brand which could be up to one point less than advertised.

I you are using shell v power with a CR of 9.2 and boost of 10psi, you should not need octain booster. If the engine has suffered detonation, you need to look at the ignition timing, not the fuel octane.