valve clearance and shimming

[rocket]

Hi iv had my twincam a couple of years and guess i should check valve clearances.Is it an easy task and any special tools required? I havnt checked and adjusted car valves before but have done lots of bike engines ,i imagine its very similar.

Ian.

[Frank Howard]

Ian,

You'll need access to replacement shims. I went down to my local Saab dealer and they allowed me to help myself to their selection of shims used in the Saab 99. They told me that customers with Saabs that old never take them to the dealer for service so the shims don't get used anymore. Good luck.

[paddy]

To check, no special tools required apart from a feeler gauge.

To adjust, it's much less hit-and-miss if you have a micrometer to measure the existing shims so you know exactly which sizes to order.

You'll also need to remove the camshafts and sprockets, so you'll need the usual spanners/sockets/torque wrench, plus a means of measuring the timing chain deflection (eg steel rule).

You'll likely also need a new cam cover gasket.

Paddy

[reb53]

Ian,

Don't take any notice of etched numbers on shims as someone may have ground the shims in the past.
There are often small indentations in one side from where they have contacted the top of the valve stem. I've never regarded this as a problem but it must be taken it into consideration when measuring the thickness of the shim.
Ive found that even if a lot need correcting you can shuffle them around as long as you take good measurements, and I've usually only needed to actually replace/alter 2 or 3.

i.e. you find no. 1 exhaust has closed up and when you remove it and measure it it's 80 thou but should be 77. Number 3 inlet is wrong also but happens to be 77 thou.etc.

You wouldn't think this would happen often but bearing in mind that you're allowed a little lee-way it's surprising how well it works out.

Cheers
Ralph.

[curly type 26]

Make sure you take your time, the guys are spot on quite often shims are not as marked, also some shims are very rough round circumference & can catch on spring retainer particular culprits are hillman imp shims so please double check fit & grind if to close as it could cause you to drop a valve. Also if shim dimpled turn it face up as pad on follower larger & now back to true size. But Check & Re Check. Curly

[andyelan]

Hi Ian

An obvious comment but I assume you can read a micrometer and use a torque wrench. If you can then just take your time and you shouldn't have too much of a problem.

Good advice frome everyone here but here are a few additional tips.

I always work on one cam at a time. Before I remove a sprocket I cable tie it to the chain and hang it from my garage roof on a long piece of elastic. This prevents the chain falling off the crankshaft and jackshaft sprockets and avoids the need to re-time the ignition and cams afterwards (assuming they were correct to start with of course)

Check and record all the shims thickness used. Doing this means that when you next come to check the valve clearances, if any need adjustment, you can calculate and order up the correct thicknesses so they're to hand before you strip the engine

Finally can't really see the need to be going to Saab dealers. Paul Matty, Sue Miller, Burtons etc. all have shims in stock and can usually have them to you usually next day. Classic Lotus specialist should always be your first port of call for parts. If it's available, the'll have it. If they don't have it, almost certanly no one else will. I've never found much variation in price either.

Regards
Andy

[Esprit2]

Lotus valve shims for Twin Cam and 9XX engines are the same. So if you have a local Lotus-buddy with an 3rd Generation car (Elite, Eclat or Esprit), you can share shim collections.

Lotus shims are interchangeable with those used in the Triumph TR7 and older Jags (Moss, Victoria British, The Roadster Factory... etc), Saab 99 (local Saab dealer), Cosworth & Climax (motorsports shops) and the Hillman Imp (faux Climax FW_).

Lotus _______ .060"-.150", in 0.001" steps... 0.061, 0.062, 0.063...
Triumph TR-7, .070"-.120", in 0.002" steps... 0.070, 0.072, 0.074...
Saab 99 _____ .090"-.120"
also used on Cosworth, vintage Jaguar 6's (3.4, 3.8, 4.2), Hillman Imp and Coventry-Climax.

Many Saab dealers only service the newer cars these days, and even if they have a shim set from the old days, the parts counter guys may not know about it. I make a point of asking to speak with the Service Manager, or the most senior mechanic (the old guy), then ask him if they have a shop-collection of shims. It's usually a dusty bin the mechanics keep separate from the service parts inventory and it hasn't seen the light of day for quite some time. Most of the shims will be used, but that's okay, they work just as well.

If you re-use shims, note that the end of the valve stem has probably worn a depression in the center of the shim that can be anything from a polished bright spot to a pocket several thousandths deep... enough to frustrate your efforts to clearance the valves if you don't give it proper consideration.

It's important to measure used valve shims with a micrometer with it's anvil positioned in the center (ie, in the depression). That will give a true reading of the shim's thickness in the center working portion where the valve stem makes contact. If you use a vernier caliper, the jaws will bridge across the depression and produce a larger reading than the shim's true center thickness.

Then be certain to install used shims depression-side down against the valve stem. If the shim is installed flipped over, the inside of the tappet will bridge across the depression and the resulting clearance will be less than you calculated.

For a shim with a depression on both faces, neither a micrometer nor a caliper will give an accurate measurement of the shim?s functional thickness. You can make a mission out of measuring the shim?s working thickness, but is it really worth the effort. Time to trash that shim and move on.

Shim diameters vary. Not just between brands, but between sources and vintages. It seems not to have been treated as a critical dimension. The shim fits into a pocket on top of the upper spring seat, and there?s a corner radius/ fillet in the bottom of the pocket. A proper shim will be a loose diameter fit in the pocket, such that it?s sharp corner edge fit?s within the tangent point of the radius and doesn?t interfere with the fillet. Depending upon the valve stem's cut length, a shim that is a snug diameter fit, it may contact the fillet and not seat fully against the valve stem. In that case, the resulting clearance will be tighter than calculated.

If you have a large OD shim that interferes, just spend a couple of minutes at the grinding wheel and knock off the sharp corner. It doesn?t have to be pretty.

Inspect the tappets for cracks. They're getting old, and I've found a number of cracked ones in engines in the last couple of years. Stock tappets are chilled cast iron, and they will suffice for a street engine. However, steel tappets are available that are stronger and more durable... and more expensive.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)
Minnesota, USA

[Frank Howard]

can't really see the need to be going to Saab dealers. Paul Matty, Sue Miller, Burtons etc. all have shims in stock and can usually have them to you usually next day.

Andy,
The answer is simple. They're free and if you pick up a modest selection like I did, chances are the next time you adjust your valves, you'll have the correct shims on hand.

[Lincoln62]

My local engine machine shop had a tin full of shims the right diameter, mostly from the 60's/70's Morris/Austin OHC engines.

I told him how thick I needed them and he ground them to suit. Wasn't expensive.

Pete
66S2

[Esprit2]

Finally can't really see the need to be going to Saab dealers. Paul Matty, Sue Miller, Burtons etc. all have shims in stock and can usually have them to you usually next day.

For me, it's time. I'm 15 minutes from the local Saab dealer and a quick trip over there keeps the task down to a day job. No mail order vendor can deliver faster than that.

Classic Lotus specialist should always be your first port of call for parts. If it's available, the'll have it. If they don't have it, almost certanly no one else will. I've never found much variation in price either.

I agree. We need the support of the Lotus specialists as much as they need our business, and it's in our best intersts to support them. However, a handful of cheap shims isn't going to make their sales goal for the year, but a quick trip to the Saab dealer could save my day... or weekend.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)
Minnesota, USA

[612kiwi3333]

Frank, which saab dealer in mpls? a valve adjust is looming in very near future for me. Mike 70+2

[Esprit2]

Mike,

Morrie's Cadillac-Saab, on the north frontage road of I-394, just west of Louisiana Ave. They haven't serviced an old 8-valve Saab 99 in many years... at least not a customer car. But the owner, Morrie, has several old Saabs in his personal collection, so they keep the shims on hand.

The shims are kept in the Service Department (not the Parts Department), and not everyone there knows about them. I've visited the dealership since it moved, and had to ask three people before I found one who knew about the shims. And he wasn't sure where they were stored in the new building. Depending upon who you're dealing with, the shims are sometimes free on a 1 for 1 exchange basis, or for sale at a small fee. Most are used.

The only other Saab dealer in the area (Schmelz Countryside Saab in St Paul) no longer has their old shim collection. They dumped it 4 or 5 years ago. There are also independent Saab, Jaguar and Triumph TR-7 repair specialists in the area who, presumably, may have a stash of valve shims. Walk the Yellow Pages.

Where are you located? In the Twin Cities? Members of the local Lotus owners club to which I belong have a large combined shim collection (bigger than Morrie's). We routinely make shims available to members on an exchange basis, and we're open when Morrie's is not. PM me.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)
Wayzata, Minnesota, USA

[612kiwi3333]

Tim, I am in hopkins area. Please E-mail me with details of your clubs next get together. If it is soon enough maybe we can drive our cars. Weather has been quite nice this fall. I had a great road trip last weekend up in northern mn. Although it did snow a little. Thanks, Mike [email protected]

[CBUEB1771]

I always work on one cam at a time.

Andy,
I assume you mean that you only remove one cam at a time to change shims after you have measured the starting clearances with both cams connected by the timing chain and in correct phase relation. Rotating one cam with the other stationary can cause valve-to-valve interference.

[andyelan]

Hi Everyone

Of course Russ is quite right. I always check all the clearances fiirst and make a note of any which require changing. I then set the enging to it's TDC timing position before removing the first cam. For sure, on no account should the other cam be rotated once the cam chain has been removed and I usually put a blob of paint on the cam I'm working on, just as a double check, so I can be sure I'm replacing it in the correct orientation.

Sorry for any confusion

Regards
Andy