Checkrail - I owe you an apology!

[HCA]

Some weeks back, you were having a disastrous time with your valve timing. I asked why you would even consider turning one cam independently of the other:

I remembered that you were following a book by a Miles Wilkins, that I confess to never have read but knew that many here genuflected and fell prostrate on the floor at the mere mention of his name. I thought maybe, with all the hype, I should add the book to my Christmas reading.

I got as far as page 137 and gave up, realising at the same time why you might have got into a pickle reading this:

And this is where I owe you the apology! The chap may not fully understand hemispherical combustion chamber design, as it is just not possible to rotate one camshaft without the other when both are tightened down. When measuring tappet clearance on these engines with Hemi CCs, one tightens only one camshaft, then when done, loosen it completely and tighten down the other one... The only time to tighten both together is when the two are perfectly aligned and neither is rotated without the timing belt/chain connected...

I hope you are well into renewing the broken parts and that your engine will be running again soon.

[nmauduit]

IMG_4875.jpeg

And this is where I owe you the apology! The chap may not fully understand hemispherical combustion chamber design, as it is just not possible to rotate one camshaft without the other when both are tightened down. When measuring tappet clearance on these engines with Hemi CCs, one tightens only one camshaft, then when done, loosen it completely and tighten down the other one... The only time to tighten both together is when the two are perfectly aligned and neither is rotated without the timing belt/chain connected...

In what do the quoted piece make you understand or infer what you claim ? making sure boths cams turn freely doesn't imply what you denounce ("rotate one camshaft without the other when both are tightened down")...

I'm not here to side with Mike W. (esp. since he's been owing me a brand new dash for a long time now) but I seriously doubt that one can get a clear understanding of how things work from books when reading things that are not written in said book.

[HCA]

You need to know the passage prior to the clip. It starts with Mr Miles sequencing the of assembling the head - lap the valves, assemble valves with springs then lay the camshafts in the bearings...

This is what Checkrail followed and ended up in all sorts of trouble trying to turn, as instructed, the shafts independently of each other. Had I read the book I could have corrected that Mr Miles was incorrect instead of, in hindsight, being a bit unnecessarily harsh on him!

[2cams70]

What MW means is that you should gently rock the cams back and forth to see that they turn freely - not rotate them to the extent that the valves bash into each other!!

[Hawksfield]

2cams70
That how I interpreted the first time I had my TC in bits.

John

[englishmaninwales]

I’m with Hal on this.
The description is pretty clear, as Hal states, if read with full context of the preceding paragraph. I believe MW is clearly describing full rotation of the fitted camshafts, after both are fitted, to check for any binding.

Rocking the cams back and forth as described above will determine camshaft binding only over 180 degs, therefore an incomplete test.

MW’s book has another howler, see page 115. Centre photograph shows the crank thrust washer being fitted back to front.

Some parts of the book, from the historical perspective, are interesting (if one presumes accurate). But I think there will be better sources of information for engine assembly (and I can’t recommend speaking to MW for advice, for me a few years ago it was an unpleasant, never to be repeated experience!)
Malcolm

[nmauduit]

You need to know the passage prior to the clip. It starts with Mr Miles sequencing the of assembling the head - lap the valves, assemble valves with springs then lay the camshafts in the bearings...

This is what Checkrail followed and ended up in all sorts of trouble trying to turn, as instructed, the shafts independently of each other. Had I read the book I could have corrected that Mr Miles was incorrect instead of, in hindsight, being a bit unnecessarily harsh on him!

I just had a quick glance at the book (and p115 to find out on which I had written the caution about the thrust washer long ago): nothing struck me as inducing a potentially damaging mistake there. The book dates from the eighties, a time when manual did not specify that one should not put his cat in a microwave oven: it is eventually down to each individual to exercice his best thinking in understanding and following procedures so as not to do anything damaging. If unable to assess if some action may be damaging the responsibility goes down to the mechanics to proceed or to seek further advice on how to proceed.

Ignoring common rules like these is also a way to make progress quickly, though at some occasional cost... live and learn.

[englishmaninwales]

Nah, I disagree entirely, boiled cats in microwaves or not. Two pretty serious errors in what masquerades as an assembly guide. All in IMHO, of course.

Malcolm

[HCA]

2cams70
That how I interpreted the first time I had my TC in bits.

John

What MW means is that you should gently rock the cams back and forth to see that they turn freely - not rotate them to the extent that the valves bash into each other!!

mmm! I am due to step onto an airliner next week - I certainly hope the over night engine technicians definitely did not debate amongst themselves what Pratt and Witney might have meant or made any interpretations on the Procedures manual

As already said, Mr Wilkins' book is not the best for clear instructions. In my opinion after reading it some more, it is badly edited and is really only the written notes that might have been given to an observer in his workshop. It does not clearly define the checks and rectification that should be taken as a result of, say, the necessity of new valves being used and why these are important. He is not a teacher and the book should not be used by first time wanabees without a modicum of the ICE workings. hence my apology to Checkrail.

There is already a clearer manual on the TC available on the forum that just needs an edit to add in instructions for a novice. Now, if this were published...