Head torques
- Thread starter Naz-b23
- Start date
pollyp
Club Member
getting a HG to seal properly requires alot of careful attention to detail & precision.
first, is the head & block surface absolutely flat? especially check for flatness if the HG previously failed from overheating. use a steel straight edge & feeler gauges.
is the head & block surface smooth? especially where it seals near the cylinder fire rings. every last speck of old HG material should be carefully removed off the machined face, no bumps or dimples.
is the mating surface clean, oil/grease free & dry?
clear any residue oil out the oil drainage ports in the engine head, otherwise when fitting the head, old oil will simply trickle out onto the mating surfaces that u just carefully cleaned and ruined the HG seal.
next carefully wipe down the surfaces absolutely clean n dry with clean lint-free cloth or kitchen roll soaked with carb cleaner. need to remove all grease & fibres & debris.
are the head bolts clean? clean all male/female head bolt threads with m10x1.25 tap & die to ensure a smooth uninterrupted accurate torqueing sequence.
suck all trapped fluids out the head bolt holes so it doesn't hydrolock.
only apply a light dab of engine oil to the head bolt threads and a light dab of general grease between the bolts head and washer. too much oil on the threads will again pool & hydrolock in the hole during torquing.
follow haynes diagonal torquing sequence & torque values to the letter to ensure the head & HG doesn't warp.
when torquing, swing the torque wrench to achieve the target torque in one single, non-stop, smooth, gradual, confident movement.
it's important not to let the head bolt threads stop or "grab" briefly which'll stutter/creak and ruin the torque accuracy.
stage1: 39nm
stage2: 78nm, leave afew hrs or overnight for HG metal to creep/mould/stabilise to the new surfaces.
loosen bolts in reverse sequence 1/2 turn each until they're all slack.
stage3: 35nm
stage4: Angle-Tighten to 60deg
first, is the head & block surface absolutely flat? especially check for flatness if the HG previously failed from overheating. use a steel straight edge & feeler gauges.
is the head & block surface smooth? especially where it seals near the cylinder fire rings. every last speck of old HG material should be carefully removed off the machined face, no bumps or dimples.
is the mating surface clean, oil/grease free & dry?
clear any residue oil out the oil drainage ports in the engine head, otherwise when fitting the head, old oil will simply trickle out onto the mating surfaces that u just carefully cleaned and ruined the HG seal.
next carefully wipe down the surfaces absolutely clean n dry with clean lint-free cloth or kitchen roll soaked with carb cleaner. need to remove all grease & fibres & debris.
are the head bolts clean? clean all male/female head bolt threads with m10x1.25 tap & die to ensure a smooth uninterrupted accurate torqueing sequence.
suck all trapped fluids out the head bolt holes so it doesn't hydrolock.
only apply a light dab of engine oil to the head bolt threads and a light dab of general grease between the bolts head and washer. too much oil on the threads will again pool & hydrolock in the hole during torquing.
follow haynes diagonal torquing sequence & torque values to the letter to ensure the head & HG doesn't warp.
when torquing, swing the torque wrench to achieve the target torque in one single, non-stop, smooth, gradual, confident movement.
it's important not to let the head bolt threads stop or "grab" briefly which'll stutter/creak and ruin the torque accuracy.
stage1: 39nm
stage2: 78nm, leave afew hrs or overnight for HG metal to creep/mould/stabilise to the new surfaces.
loosen bolts in reverse sequence 1/2 turn each until they're all slack.
stage3: 35nm
stage4: Angle-Tighten to 60deg
