Head, barrels, gaskets ....

Previously paul_reynolds wrote:

Previously david_henshaw wrote:

This follows on from my last posting asking for suggestions in curing oil leak from the cylinder head on my 1965 650SS ......

After fitting a composite head gasket the problem still remains and after further investigation it seems that the head has been skimmed and when torqued down it does not have sufficient clearance between the head and cylinder spigots, consequently the head is tightening down on the cylinder spigots, probably by only a few thou' but sufficient to not allow compression of the head gasket.

As I see it I have perhaps two options (a) Replace the cylinder head (b) skim the top of the cylinder spigots to reduce the height and allow the head to close in a lower position.

Option (a) - expensive but perhaps inevitable

Option (b) - Would this affect the gas flow, would the stroke of the pistons be affected on TDC and the valve faces strike the tip of the pistons - get the skim wrong and new barrels don't come cheap either

Someone has suggested an old fashioned idea was to use two head gaskets, one solid copper and one composite thus increasing the gap between head and barrels to allow the correct torque procedure.

If anyone has a life line of ideas I would be pleased to hear from you.

Best regards

David

Hi David, If it were me I would re-machine the recess deeper on my Milling Machine. Try RGM or Steve Maney for a thicker head gasket. Head gaskets do vary if you look on the Service notes. I have seeen a 2mm thick Copper gasket advertised. Two copper head gakets will do you for thickness up to 0.040 skim. You would need to check pushrod lenghts as well. Watch the valve clearances to piston. I believe Paul Dunstals tuning notes cover this problem. ATB . Paul

Many thanks for taking the time to reply but I am limited to engineering services here in Menorca so I will bear this in mind.Best regardsDavid

Previously gordon_johnston wrote:

Skimming the spigots won't do any harm. Plenty of laterNortons have spigotless barrels in any case. Considerably easierthan machining a recess in the head. Otherwise the head gasket arrangement suggested by Paul will do the job.

Hi Gordon,Many thanks for your thoughts and a possible otion I can get done here in MenorcaBest regardsDavid

Previously frank_kateley wrote:

Previously david_henshaw wrote:

This follows on from my last posting asking for suggestions in curing oil leak from the cylinder head on my 1965 650SS ......

After fitting a composite head gasket the problem still remains and after further investigation it seems that the head has been skimmed and when torqued down it does not have sufficient clearance between the head and cylinder spigots, consequently the head is tightening down on the cylinder spigots, probably by only a few thou' but sufficient to not allow compression of the head gasket.

As I see it I have perhaps two options (a) Replace the cylinder head (b) skim the top of the cylinder spigots to reduce the height and allow the head to close in a lower position.

Option (a) - expensive but perhaps inevitable

Option (b) - Would this affect the gas flow, would the stroke of the pistons be affected on TDC and the valve faces strike the tip of the pistons - get the skim wrong and new barrels don't come cheap either

Someone has suggested an old fashioned idea was to use two head gaskets, one solid copper and one composite thus increasing the gap between head and barrels to allow the correct torque procedure.

If anyone has a life line of ideas I would be pleased to hear from you.

Best regards

David

Hi David,

If I was confronted with this problem, which I have been, I would try the following :-

Measure the the height of the barrel spigot.

Measure the depth of the recesses in the head and note the difference in the two.

Get yourself a solid copper head gasket from RGM (which is the only one available which I have found to be any good) and measure this. I have several of these and they are about 39/1000 ".

About 15/1000" nip should do the job, and I doubt if what you have is too far out but if you find that you need a little more clearance to achieve this I would carefully take a file to it. It is only cast Iron and is easy to work. Check your work as you go with the depth gauge until you get a suitable clearance.

Coat the head gasket with clear silicon (thin layer) the day before fitting.

I hope this will sort your problem.

Take care

Frank Kateley

Hi Frank,Seems to be a common problem ......I am skimming the spigots to make a better fit into the head and try again .....Thanks for your response - much appreciated.David

Previously phil_hannam wrote:

Skim the Head.....skim the spigots...........alarm bells ringing here very loudly.

If some care is not taken, then at some point, the valve heads are going to start bouncing off the piston tops.

From very bitter experience of a similar head gasket blowingproblem, I would recommend going down a thicker head gasket route as the best option.

Hi Phil,

I am well aware that it's entering dangerous territory and will be using composite gaskect when I get the head back from the machine shop - fingers crossed ........

David