Head assembly question

[BDA]

A half a thou tight isn't terrible. I'd rather it be a half a thou loose - especially on the exhaust but I wouldn't sweat it. I might still "introduce" the shim to some wet/dry since it is now known to be tight but if I couldn't measure that close (and I can't) I'd be happily ignorant!

[Bryan Boyle]

A half a thou tight isn't terrible. I'd rather it be a half a thou loose - especially on the exhaust but I wouldn't sweat it. I might still "introduce" the shim to some wet/dry since it is now known to be tight but if I couldn't measure that close (and I can't) I'd be happily ignorant!

At some point...it's really splitting hairs.  if it was outside the range entirely (and it's not...it's within spec, this is not a blueprinted engine by any stretch) then it might be cause to pull out the wet/dry and some cutting oil and having at it...and there is noise on the FB page about the clearances changing when the head gets torqued down.  I'm not going to worry about it; Wilkins doesn't mention any issues in his book, neither does the factory manual, and except for my OCD following of both manuals while I'm doing this, pretty sure I would have caught that warning.  I'm set at the maximum of the limits published; if anything, I'm thinking that even if it does move, it's not going to change enough to worry about; I'll be more concerned with valve seat wear closing it up over time as the valve receeds in. 

Pretty sure that Miles (considering the number of engines he built over his career) and other folks I've talked to (Ralph at RS, Ray, Banks, and a fellow lister here (and on FB) who has a lot of experience with the twink) would have mentioned it when I discussed the job and my approach with them.  No one mentioned it.  Worst that happens is that I pull the VCG, d-plugs, remove the sprockets, tie up the chain, and re-shim.  Going to have to pull the VCG anyway to retorque in 500 miles anyway, so I'll spot check then (or if any strange noises emanate from the thing when I start it.)

[BDA]

I think you misunderstood me. At a half a thou within spec you don’t need to do anything nor is there anything to apologize for (I know you’re not apologizing but I think you get my drift). I was only describing my OCD. If I knew I was only half a thou off, I might be tempted to rub off that half thou regardless how useless it would be.

You’re golden, obviously! I can’t wait to hear your first report that it made noise! 

[jbcollier]

I read that comment on FB as and thought BS.  Done some Twinks, lots of Jags and others, and the clearances don't change when you torque down the head.  Heck, I've done Aston Martins.  You have to remove the head to adjust valves on them!

[Bryan Boyle]

***DELETIA***

You’re golden, obviously! I can’t wait to hear your first report that it made noise! 

Yeah, that will be a good day (assuming, of course...realized that I had not replaced the butterfly shaft seals in the Strombergs when I freshened them up earlier (found the little bag with the seals and brass keepers when I was looking in my parts drawers for something)...that it all goes back properly and tighter in terms of fluid retention.  Give me a chance to clean off the block and repaint it (trying to find the right color Ford grey...I think it's the same color they painted tractor engines with...) and generally freshen up/clean the back end...along with a new clutch.

Figure it's a good month of sporadic pulling apart, cleaning up, reassembly, etc. after the Real Work(tm) is done.  Pretty sure I have all the bits and pieces on the shelf...if not, it's a couple days for the bits to get here from our PA friend....