Head assembly question

[jbcollier]

Shims and stems wear, absolutely.  In the Jag world it is very common to flip them which restores them to their original spec.  One to two thou wear is common and I have seen more, a lot more.  Make sure you lube the shim, both sides.  Oil really doesn’t get in there.

[jbcollier]

Shims do not shrink.  They do wear.

[Bryan Boyle]

As best I can tell, using a micrometer calibrated to 0.000 before each slug measured, and a sliding, yet somewhat firm feel on the feeler gauge...thinner shims increase clearance, thicker shims decrease clearance. 

Engine                Initial                    Existing           Projected                              Estimated
Cylinder           Clearance                  Shim                Change       New Shim        Clearance

Intake (.007 clearance)
 1                        .006                       .071                  - .001            .070                 .007
 2                        .005                       .083                   -.002            .081                 .007
 3                        .008                       .088                   +.001           .089                 .007
 4                        .008                       .076                   +.001           .077                 .007

Exhaust (.011 clearance)
 1                        .011                       .098                      ---               ---                   .011
 2                        .012                       .104                    +.001          .105                 .011
 3                        .013                       .106                    +.002          .108                 .011
 4                        .013                       .108                    +.002          .110                 .011

Caps torqued to 9 ft. lbs, existing shims mic'd to nearest thousandths.  Graphogen assembly lube, measured on heel of cam with lobe perpendicular to tappet face.

Anyone have thoughts?  Want to get this right!  Is my logic sound?

[BDA]

Looks right to me. IIRC, you have marked your followers for their position. It’s probably not an issue on the TC but I might mark the shims with their position and in your notebook note the size of the shim and where it goes for the next time. Check your clearances again after your caps are torqued to mark double dog sure it’s right. I suspect you were going to do those things anyway. 

[Kendo]

I wondered if the graphogen could be thick enough to affect the measurement? Would it be more accurate (but require an additional disassembly/reassembly) to measure it all dry?

[Bryan Boyle]

I wondered if the graphogen could be thick enough to affect the measurement? Would it be more accurate (but require an additional disassembly/reassembly) to measure it all dry?

I'd not want to rotate the lobes dry on the tappets.  I'd venture that pushing the feeler in, displaces enough of the assembly lube that it's not a significant issue. 

[Bryan Boyle]

Looks right to me. IIRC, you have marked your followers for their position. It’s probably not an issue on the TC but I might mark the shims with their position and in your notebook note the size of the shim and where it goes for the next time. Check your clearances again after your caps are torqued to mark double dog sure it’s right. I suspect you were going to do those things anyway. 

Everything is marked as to its position and bank.  Both on the top of the tappet (in sharpie) and inside the tappet itself.  Yeah, there are a bunch of notes stapled to the requisite shop manual pages as necessary; after 40+ years of fiddling with these little beasts and absorbing the manual like a sponge when I was the overnight transmission supervisor at ABC Radio, there isn't a lot I've not seen, but managed to avoid the TC formula until earlier this year...which is a new experience, at least on the engine side.

Probably overthinking the whole process and verbalizing it, but, if it clarifies, for future users, what goes into making these things last..why not?

[Kendo]

I was thinking more about any lube on the shims and inside the buckets

[BDA]

I thought my BDA might be easier to set the valve clearances on because the cams are housed in a cam carrier and taking that off the head takes cams, followers, and sometimes a shim or two. Boy was I wrong! Some shims stick to the followers, some stay in the valve spring retainer and some fall out onto the head or on the floor (and there are 16 of them)! Keeping track of stuff like what size shim goes where is critical! I don't think it's that big a deal with the TC but I think keeping track of what size shim goes where it's a good habit to get in. If nothing else, it will help you order the correct shims the next time.

Lotus Ltd. used to have a shim exchange back in the day but I doubt they still do. There are far more Loti that don't need those shims than do.

[GavinT]

Dunno if this is helpful, but attached is a spreadsheet written by Tim Engel which does the calculations for the shim job. He wrote it with a Lotus 907 type engine in mind, but I expect it could be used for an 8 valve engine, just fine. He even included Sealant Film Thickness (which is probably only relevant to the 907 engine cam trays).

Tim being the thorough gentleman he is, also includes instructions on how to use it.
I trust he's OK with my sharing this as it's posted in the files section of an Esprit group.

[Bryan Boyle]

***DELETIA***

I've known Tim for a long time; I modified the file to focus specifically on the TC engine and it jives with my manual calculations.  It's vastly simplified (we only have 1 intake and 1 exhaust valve per cylinder...) and I set up the formulas for the loose end of the intake and exhaust; if you speak excel, modifying it for the clearance values you prefer is left as an exercise.. 

What a way to spend new year's eve, right?

[GavinT]

It's New Years Day (afternoon) here, Bryan . . . 27°C (80.6°F) bright and sunny. 

Happy New Year to all and may your shims stick to your buckets.

[Bryan Boyle]

It's New Years Day (afternoon) here, Bryan . . . 27°C (80.6°F) bright and sunny. 

Happy New Year to all and may your shims stick to your buckets.

Well..being antipodal to us...it's just gone 7:30AM and 37 degrees F out here.  Happy new year, everyone.

[Bryan Boyle]

New shims in (and RD mic'd and marked them for me, so it saved me a step...but I checked just the same...) and the clearances all prove out to .007 for the intakes, and .011 for the exhaust (one exhaust is an RCH tighter than the rest, thinking it's a couple thou; I have some 400 grit carborundum paper...maybe a little cutting oil, and polish it a bit...but that's probably, at this point, being too OCD for even me).  Have to pull off the plain nuts and install the nylocs and washers.  Pull tappets off, put a little lube on the top of the valve stem, put tappets back in, torque 'em down (freshen up the graphogen since I have to clean off the tops of the tappets to get the valve lapping tool suction cap to stick...)

(Thanks Ray!)

On to putting the cam seal on (I have a supply of them brand new in sealed bags I found in my parts stash, but, I had acquired a fresh one from RD before I knew I had a few bags of them, so, thinking not knowing the age of the ones in my stash, using the fresh on the cam is probably the best path to take.

[Bryan Boyle]

Well...done...#4 exhaust is .0105 versus .011...oh well, .0005 tighter is well within tolerance, no?  Worked out pretty good.  Splitting hairs at this point, so, I could spend time buffing that shim down an RCH or just live with it.  Numbers on the outer flanges are the measured clearances; I rotated the cams a couple times to seat the tappets in the bore before measuring, then made sure the tip of the lobe was perpendicular to the tappet, slid the feeler gauge in...light resistance...and noted the size on the flange.  And, yes, the head is sitting on wood blocks to keep the valves happy...

Note: the big torque wrench was on the bench being used to set my wheel bolts...realized that some might get the wrong impression that I was using a 5-100 ft-lb wrench instead of a smaller one...they are not that accurate at the limits, so...actually used the inch-pound wrench (the shorter one; take ft-lbs and multiply by 12 to get the inch-pound setting...which in this case, 9 ft-lbs is 108 inch-pounds) to set the new nylocs.

Lots of graphogen, new nylocs and washers, new bearings, new inlet cam seal at the back (I used the fresh seal I had ordered from Ray; it seemed more flexible than the ones in the bag I had discovered),  warmed in hot water, single layer of tape over the snap ring, some grease...slipped right on nicely...in it's groove in the head with a touch of RTV in the channel to seal it up).

On to pulling the tranny, then the lump.  Progress, right?