Cylinder head bolts

[David M]

I am currently refitting the cylinder head to my '61 super major.
The head has been off for many months following a head gasket failure and lack of time to sort it.
As I tighten down the head bolts one of them goes tight before the bolt head even gets near its seating surface.
I have swapped bolts around and it is the hole that is tight rather than the bolt.
I was thinking of running a tap down the hole just to clean it a bit.
Can anyone tell me if this is a bad idea?
If not what size are the head bolts?

Thanks.

[cwayne]

David, that is a good practice, however it will most likely be necessary to first run a 27/64 drill bit in the hole till it bottoms out. You do not want to remove any metal, just clean the crud out , then the tap. The head bolt threads are 1/2 x 13 NC.
I did this on mine and found about 1/2 inch of crud in the bottom of a couple holes.

[David M]

Thanks Wayne.

That gives me a bit more confidence as I was afraid of damaging the block.
I've got a drill bit and I'll borrow a tap from work this week.

Regards,
David

[Roadless63]

Hi, it is definately a good idea to clean out all bolt holes, run a tap down the holes too (UNC but cant quite remember the size offhand) also wire brush off bolt threads but dont use lubricant as it will throw the torque figures out. Follow the sequence in the handbook for torqueing, it pays to go round just adding a bit 0f torque each time to get an even clamping load. Once tractor has been run up and cooled down I always recheck torques again (along with tappet clearances)

[JohnnyBoy]

Thanks Wayne.

That gives me a bit more confidence as I was afraid of damaging the block.
I've got a drill bit and I'll borrow a tap from work this week.

Regards,
David

Dave, if you smear the tap with grease before you re-tap the thread then any swarf or debris that the tap cuts will stick in the grease in the flutes of the tap rather than drop into the bottom of the hole.

[Kim]

If you magnetize a skinny screwdriver blade, you can retrieve metal cuttings from the bottom of a hole without greasing the threads. Grease will cause problems with accurate torque wrench readings. Clean and dry is the way torqing should be done as any lubricant in the threads will cause false readings.

[JC]

Sorry to disagree with you guys, but head bolts are meant to be torqued when the threads are lubricated with engine oil. If you torque them dry, more of the torque is used to overcome the friction between the threads, and less is used to clamp the gasket.

Here's an interesting article about head bolt torque.
http://www.enginebuildermag.com/Article ... t_use.aspx

[henk]

I agree with you JC.

[Dandy Dave]

I also always lube the threads. Been doing it that way for 40 years, and I have put on more heads than I care to remember. Never has been a problem. Dandy Dave!

[David M]

Thanks for everybodys advise and input. Interesting article JC.

The workshop manual doesn't state whether the torque values given are dry or lubricated but the general consensus on the internet seems to be to lubricate (although of course each case should be investigated individually).
I also sought advise from my friend, (a "master technician" no less), who advises lubrication.

Dry threads increasing friction and giving the wrong torque could explain my other problem.
See one of my previous posts which I haven't solved yet;
http://www.fordsontractorpages.nl/phpbb ... ?f=2&t=524

I've now got a tap from work so will give the holes a clean out this weekend.
I think I'll lightly oil the bolts and carry on from there.

Thanks again guys.

[Nick]

reading this, i reckon because i didnt clean any of the holes out on my first major was the reason it leaked water out the head gasket the first time i put the head on. Second time around i cleaned the holes and threads out and put a tiny bit of oil on the bolt threads and shes been fine since.

[henk]

Nick,
I've been there, done that and made the same mistake.

But expertise is the sum of our mistakes.