Replacing 401 head gasket

[jhmidgley]

i managed to overheat my Bristol 401 with an 85C engine. i now need to replace the head gasket.
is there any documentation as to how to go about this process, and what pitfalls are there?
Do i need to take the engine out?

[jhmidgley]

Hi Geoff,
thanks so much for your reply & information.
Some questions if that is OK?

The manual specifies tool TFN.5030, is there an alternative?
I have undone all 14 head nuts but head still firmly attached to block, is there something else to undo?Replacing Head gasket

[Geoff Kingston]

What has caught me out in the past has been forgetting to remove the oil transfer pipe at the back of the head to the block, otherwise when everything else is off or out of the way some heads will lift easily others need a bit of persuasion, the last one we did moved after a bit of pressure with a small pry bar against a wood block between the water pump and timing cover, once it started to lift we pushed it down and and pulled at the back of the head when that started to lift we again pushed it back into place and then lifted from both ends and it came off without a struggle, I never use a pry bar between the head and block face but have needed to use small wooden wedges in the past to help things along.
Regarding the exhaust nut removal tool a friend if mine made me up one years ago out of a piece of flat bar, he bent one end to the shape of the clamping ring or nut, drilled a hole in it for a small piece of metal bar of the same size as the hole in the nut welded that to the bar and then welded a strengthening rib along the back forming a shallow T section. I still have it and it does the job fine, BODA in the UK have had two versions of the Bristol tool made and may have some left, I think they have an arrangement with the BOCA for exchange of parts so you might be able to get one through them.
Geoff.

[Stefan]

No , dont take the engine out.
Youll need to bribe someone to lend you the special, hen's teeth head spanner and copy the instructions from their manual. And a gasket set (from BCL )

Remove carbs, plug leads, fuel banjo pipe.
Remove carb bases.
Drain rad and remove water pipes
Undo head nuts.
Remove exhaust manifolds.
Lift the head off, and take it to a reputable motor engineering workshop to check for distortion, leaks,pinholes and damage. They will then need to planish it removing the absolute minimum of metal; it will probably be scorched between the 2 cylinders where the gasket has gone.
Consider fitting lead free valve seats and having it resin sealed. Look at the oil cross tubes for leaks, they are buggers to keep leakproof.

New heads can be bought from INskip Racing, but they cost THOUSANDS so cherish the one you've got.
Check that coolant is draining freely from the bottom block tap. If not the block is scaled up and you should take advice about having the block's water jacket chemically descaled and derusted, otherwise it could well overheat again.
Check head nuts and studs for damage, corrosion, and replace if necessary with new.
Reassemble , tightening the nuts in correct order as per manual, using the special spanner on the ones you cannot reach with your socket set. Tighten these ones (as you cant get to them with your torque wrench) " just right".
Reassemble carbs etc, insert coolant, drive it - some say 50 miles, others 500,, then take the carbs off again and retighten the head nuts.
Have I forgotten anything?
My record is 90 minutes to get the head off, and 3 weeks to get it back on....
Good luck! Take great care, and it will be repaid with good results.

[Stefan]

er, yes, I forgot to mention the oil transfer pipe...