Head assembly question

[TurboFource]

I left the front alignment stud out then swung the head into position while holding away from the block, then screwed the front alignment stud in and lowered the head. Great fun all by yourself, I would recommend help!

[Bryan Boyle]

I left the front alignment stud out then swung the head into position while holding away from the block, then screwed the front alignment stud in and lowered the head. Great fun all by yourself, I would recommend help!

There are a couple guys at the non-profit I am on the board of directors for who are 1) gear (petrol) heads, and 2) offered to help...so, thinking this would be a good test to see if they are willing to step up (and there is an adult beverage refrigerator in the garage, so...) when it gets to that.  I can tell you that when I've driven the buggy down to the building we're restoring...there is a lot of parking lot banter and popping engine room lids...

[Bryan Boyle]

Getting things lined up to set my valve clearances.  There is a range in the book, thinking that setting the clearances at the wider end of the spec is preferable to account for bedding in of the valves.  I don't think (and am ok with being proven wrong) that any wear on the lobes, bucket, and shim is minimal and most of the wear will occur at the valve head due to the pounding on the seat as it closes rather than what should be constant contact of the bucket, shim, and top of the valve stem.

Thoughts? 

(photo of emptied out head ready for new bearings, graphogen, and cams for reference.)

[Pfreen]

An interesting issue I found is that you will get slightly different intake clearances with the alternator belt installed and tightened.  I think this difference will go away when the the cam is rotating on a bed of oil on the bearings.
However, it is puzzling when you first encounter it.

[cazman]

That is very interesting.

[TurboFource]

I would think spring pressure normally pushes the cam upwards in the caps leaving the bearing clearance at the bottom, tightening the belt overcomes that tension and pulls the cam downwards leaving the bearing clearance on the cap side 

[Fotog]

Bryan:  I vaguely recalled that somebody concluded that the consensus is to set the clearances somewhere other than exactly what the manual says. 

I now remember, it was Rob Siegel, and he wrote about it here: https://www.hagerty.com/media/maintenance-and-tech/laborious-process-of-valve-adjustment-in-a-shimmed-engine/

He's not really a Lotus aficionado, but he's a knowledgeable amateur mechanic (much more than I) and he asks questions.  Maybe he even asked about this topic here.  And he lives not too far from you in the Boston area.

Vince

[EuropaTC]

Bryan:  I vaguely recalled that somebody concluded that the consensus is to set the clearances somewhere other than exactly what the manual says. 

I now remember, it was Rob Siegel, and he wrote about it here: https://www.hagerty.com/media/maintenance-and-tech/laborious-process-of-valve-adjustment-in-a-shimmed-engine/

I think that clearance dimension in the article refers to the very early manual for the Elans where the inlets were 5-6 thou, exhausts 6-7 thou. But that was in '63 and the original 105bhp TC engine, not what was used in the Europa TC.

I don't know when they increased the clearances but by the time I got my first Lotus manual in the mid 70s the clearances had become the 5-7, 9-11 that we know today. In fact I only know about the earlier dimensions because I bought one of the original S1 Elan manuals (ex Len Street dealership) which ironically has far better detail than the later one I was/am using !

I've not found clearances altering with belt tension but given the spec on allowable cam bearing clearances I could see how a thou' of so difference could happen. With new bearings I doubt you'll have a problem, especially if you go for the upper end of the ranges.

Brian

[Bryan Boyle]

***DELETIA***

I've not found clearances altering with belt tension but given the spec on allowable cam bearing clearances I could see how a thou' of so difference could happen. With new bearings I doubt you'll have a problem, especially if you go for the upper end of the ranges.

Brian

That's what I was thinking, Brian.  I did manage to pull off (and keep track of) the buckets and shims last night and wrote down the thicknesses (of those I could see) etched on the shims.  I'm going to pull out my micrometer (it was 9PM last night when I was fiddling with it, if I'm honest) and check to make sure what's etched is what it is.

I'm waiting for a shipment of plain 5/16-24 nuts (as well as the 5/16-24 nylocs, and a bunch of other hardware to come in...the pleasures of stocking hardware in a second garage 290 miles from my other residence/hangar)  to come in so I can torque down and measure the clearances that were ostensibly done by the rebuilder...and decide what changes/new shims or not?/or just leave be as rebuilt. 

In the meantime...no snow or salt on the roads here in SE Massachusetts...supposed to be in the high 50s today...thinking getting the oil circulating and coolant up to temperature might not be the worst thing to happen on the last Friday of the year!  And, a week from tomorrow will be one year since I was introduced to 3291R: not running, split upholstery, no carpets, distributor out, leaking oil from the pan, and sitting in the air on a 4-post jack in Beverly MA.  She's not perfect, not even close, but she is on the road again, and has been, since april of this year.

[Fotog]

Brian-  Thanks for the clarification!
-Vince

[Bryan Boyle]

Well...assembled the intake side (copious amounts of Graphogen on all the rotating surfaces...per Wilkins).  Guess I need to get a set of shims; they are close, but not close enough for me.  Caps torqued to specified 9 ft/lbs, no binding when turning the intake cam.

Cylinder              Clearance          existing shim thickness change to give .007 (ie if existing is .085, then replace with .084 to increase)
 1                        .006                                 - .001
 2                        .005                                 - .002
 3                        .008                                 +.001
 4                        .008                                 +.001

Now to mic (going to be a messy job cleaning off the buckets so I can extract them...again, used copious amounts of Graphogen...lol) the existing shims, and give ray a call.  They are cheap enough, right?  Also need the special washers for the tensioner bolt and pivot pin.  Might as well have them in stock.

Was always trained my professional mechanics that getting things as close to their intended tolerances (I could live with #1 and 2 measurements, but if I can get it closer...why not...) pays dividends in the long run.  One or two thousandths doesn't seem like a lot, but if you can get it closer without splitting atomic structure distances and the supplies are available...why not if you're in the area?

 



Still to do, the exhaust side.  Do that tomorrow. 

[jbcollier]

Never go tight.  Never ever.  A thou loose, maybe.  Myself, I always take the time to get it right.  Lots of time spent with emory paper, flat glass and bleeding finger tips.

[Bryan Boyle]

Never go tight.  Never ever.  A thou loose, maybe.  Myself, I always take the time to get it right.  Lots of time spent with emory paper, flat glass and bleeding finger tips.

I'm aiming for the intakes at .007 and the exhaust at .011 so as the seats wear...I've got .002  to allow it to close up thus decreasing the clearance (I don't believe that there is measurable wear on the shim or bottom of the tappet; I'm happy to be disabused of that notion; all the clearance-dependent wear, I think, would be on the valve/seat face; not taking into account guide ovality or wear which shouldn't change the length of the stem.)  I'm aiming for loose, as you point out, but within spec.  I'm taking my time, and keeping things together in their respective positions. 

Three of the 8 shims have no markings as to the thickness; will pull out the digital mic tomorrow and get the thickness readings for the exhaust side after running through the feeler gauge routine.  I'll have a good handle on that, and post back the proposed shim solution for comment.

[GavinT]

My question without notice is this:

Presumably new shims come with some predetermined surface finish spec.
Do they wear in more than old shims?
How much are new shims expected to 'shrink' in, say, 10K miles after initial installation? . . imperceptible?
Just curious.

[EuropaTC]

My question without notice is this:

Presumably new shims come with some predetermined surface finish spec.
Do they wear in more than old shims?
How much are new shims expected to 'shrink' in, say, 10K miles after initial installation? . . imperceptible?
Just curious.

I've had both brand new and s/h shims over the years and can't say I've noticed any reduction in thickness regardless of how old they were.  Very often I've noticed a bright area where the valve stem contacts and at first glance this looked like wear, but when I checked with a mike it's just polished. In theory it should have some metal removal if it was polished but I couldn't measure it.

If you take the trouble to get them right using the tolerance for valve seat wear them it's been fit & forget. But I'll admit to being a nerd whenever I do the job. I'll fiddle for so long that you'll only have to show a spanner to the cam bearing studs and they'll start undoing themselves. And when I'm finally ok I'll walk away and come back the next morning to repeat the measurements, just in case the fairies have changed things overnight. 

Brian