Supercharged cylinder head torque figure
Turbo Mini Forums

I have been using 68NM / 50 ft lbs on my cylinder head torque as specified for stock 1275cc heads.

But, I recently blew a head gasket on my super charged 1380 engine and was wondering if I needed to torque the head to a higher # since I am running about 10#s boost with the SC.

Thanks

raising the torque will just compromise the fire ring,

use a BK450 and th std torque, and check the flatness of the head and block.

As above, more torque will be pointless. How has the gasket failed? photos would help.

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

Thanks very much, I will stay with the specified 5o' lbs.....I'am not experienced in this area.....

I forgot to state that I am using a decompression plate sandwiched between two BK 450 head gaskets. Required because I had 10.5 :1 CR and needed to reduce it to 8.5:1. The gasket on # 4 cylinder blew into the coolant gally, but we may have screwed up because we never re-torqued the head.....

Decompression plates are not highly regarded by the majority.....

But as they require the use of two gaskets, re-checking the torque is doubly important as two could have relaxed slightly, not just one.

Can't you just get the chambers in the head enlarged ???

The other often overlooked question is..... are you sure your torque wrench reads correctly - the internal spring(s) tend to relax over a period of time giving you false low settings.

Schrödinger's cat - so which one am I ???

Failures into the water chamber as you describe are usually caused by under-torquing. Is there any evidence of similar failures beginning on other pistons?

As Rod says, checking the callibration of the wrench is a worthwhile execise. I was caught out by this a few years ago.

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

The wrench is calibrated. No other cylinders were compromized. We will retorque the head to 50 ft spec today after an hour of hot run time. Thanks

good washers under the bolts and oiled threads before re-torquing?

When I got my new set of bolts and nuts from minispares the instructions stated that I had to re-torque them a number of times before to "bed" them in for want of a better term. They instructions also stated to replace the nuts after a number of times.

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

Just a note, but the Metro Turbo figure given in the Haynes is 55 ft/lb. :)

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