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Valve Shims


Sir Paolo

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Gents, a quick question, please.

When it comes to valve shimming, does any Lotus outlet offer a selection on a sale or return basis?

If as I understand, it could take a couple of attempts to get it right, could you not order a number of combinations (based on measured requirements), then just pay for what you use.

I know the shims are only a £1 or so, but it would speed up the process if you had a number of similar sizes to hand.

I'd appreciate your thoughts/advise.

Apologies if this is a stupid question (as you can probably tell, I've always had the luxury of someone else doing this in the past).

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I just went through this myself. The cam follower shims are the same size (15.5mm - 15.75mm diameter) as found on other engines. Including the Saab 99 and the Triumph TR7.

A Saab mechanic might have the box of shims for the 99. It's an older engine and you can probably take it off their hands fairly inexpensively. That should give you everything you need.

I was unable to source the Saab shims and ended up making 3 separate orders from JAE here in the US. I should be able to return my unused shims to them.

I'll admit it was a painful process that should have taken a few days that stretched more then four weeks, especially because one of my orders I accidentally subtracted rather than added the change so I had a whole order that was completely useless to me.

1997 Jeep XJ | 1983 Lotus Turbo Esprit

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I used plain washers. Careful measuring of the resulting clearances and washer thicknesses enabled the shim sizes to be calculated...then I used whatever correct shims I had to hand and ordered the others. And.....it worked!! No, I'm not suggesting you run the engine with washers as shims....but it did help to get rid of the iterative part of the procedure.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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I used plain washers. Careful measuring of the resulting clearances and washer thicknesses enabled the shim sizes to be calculated...then I used whatever correct shims I had to hand and ordered the others. And.....it worked!! No, I'm not suggesting you run the engine with washers as shims....but it did help to get rid of the iterative part of the procedure.

I did something similar because the old shims were all too tall. I ordered some thin steel and cut my own "spacers" to get me started. It worked ok, but I swear I felt like I was chasing ghosts half the time. I don't know how you'd use washers unless the center hole was very small. That said, I bet the the washer idea probably worked better than my idea.

I was even trying to figure out a way I could engineer a way to grind down the original shims, but in the end I just couldn't think of a way that I could be absolutely sure that they were flat.

That's one task I'm glad to be done with. I think I bolted that cam carrier down 15 times for each side.

Speaking of which, I HIGHLY recommend cleaning the threads of your bolts each time before securing the carriers. I had one bolt that must have had something on it, and I wrecked the bolt hole trying to torque it down. Luckily it's not horrible to drill, tap and helicoil a fix, but what a pain.

Edited by DrieStone

1997 Jeep XJ | 1983 Lotus Turbo Esprit

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Thanks, Gents.

Looks like which ever way you cut it, it's going to be a time consuming trial and error PITA.

But I do like the idea of trial fitting with washers - it might save a lot of ordering and re-ordering to get the sizes right.

I did manage to pick up some NOS Hillman Imp shims.

I must admit, I've been very careful about cleaning all threads, especially the captive ones in the alloy housings! I've used literally hundreds of cotton buds to clean out swarf.

If I'm in for the long haul, at least the engine is on a stand - I wouldn't fancy doing it in situ!

BTW - does anyone know if Sparky has a selection of shims?

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I ordered the steel cam followers from JAE to replace my cracking cast iron original tappets. The new cam followers are thinner, so I had to get all new shims. I made cast iron ones to enable me to get accurate measurements so I could order the correct shims on the first try.

My cast iron temporary shims (just used to get accurate measurements)

IMG_2652.JPG

Be careful with washers, they may be a bit cupped and give varying results...

Travis

Vulcan Grey 89SE

 

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Washers work well...but check they are flat first, and use sizes where the holes aren't too big....also make sure that there is no edge to the holes where they are punched through...some careful work on an oilstone can take care of this. Worn proper shims get dips in the middle, too, where they impinge on the top of the valve stem...this can make fools of us all (!) so a micrometer is a better tool for measuring than a digital caliper, as the micrometer will fit down the dip and give you the true measurement.

Don't you just love iterative adjustments? Thankfully zero thickness sealants have taken some of the inspired guesswork away....

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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I purchased new shims from a Lotus parts supplier in the States, after making my measurements with the cast iron shims that I made.

In my experience, none of the hardened shims have worn down from their original nominal thickness at all... zero wear! That is measured with a micrometer on the centers, and compared to measuring with calipers across the whole face. And comparing that to the etched thickness specified on the shims. My engine has 80,000 miles.

Travis

Vulcan Grey 89SE

 

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Worn proper shims get dips in the middle, too, where they impinge on the top of the valve stem...this can make fools of us all (!)

But also bear in mind that this dip can get you an extra 1 -2 thou either way by turning the shim over so that the dip is either eliminated or makes the actual thickness of the shim smaller than when measured with a vernier / caliper gauge.

i.e. you measure the gap and its too large. The shim you have taken out has the dip (facing the top of the valve stem) you take it out and turn it over and voila the gap is correct.

Or again you are re-using a shim with a dip on a different valve, with the dip facing the cam follower the gap is too small turn it over and you hit the right number.

two thicknesses of shim for the price of one :thumbsup:

John

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In my experience, none of the hardened shims have worn down from their original nominal thickness at all... zero wear! That is measured with a micrometer on the centers, and compared to measuring with calipers across the whole face. And comparing that to the etched thickness specified on the shims. My engine has 80,000 miles.

No doubt about it, a micrometer is a vital tool here. I started with calipers and didn't trust the tool enough. I picked up a used micrometer for US$40 and couldn't be happier. Always good to have an excuse to buy new tools right?

My existing shims did have visible indentations in them from use. I have to imagine flipping them over would work, but I don't know if I'd trust them that way.

1997 Jeep XJ | 1983 Lotus Turbo Esprit

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Speaking of which, I HIGHLY recommend cleaning the threads of your bolts each time before securing the carriers. I had one bolt that must have had something on it, and I wrecked the bolt hole trying to torque it down. Luckily it's not horrible to drill, tap and helicoil a fix, but what a pain.

I'm pretty sure that the factory recommend using new bolts, but I don't have my manual handy to check this. In any case, JAE carry a nice set of bolts made by ARP which are great because they have a smaller head than the original bolts, making them much easier to get tools onto in close proximity to the cam-lobes. I found that they made the re-assembly job a bit easier.

"If you can't fix it with a hammer, it's electrical." -somebody's dad

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I had endless hours playing around with shims when my head came off. Measured exactly the correct thickness purchased the shims and when they arrived measurements were not as I expected. Scratched my thinning scalp for a while and then decided to measure the thickness of the shims. They were a few thou out so even if you have done all your measurements correctly remember the shims have tolerences. Purchased more shims and with a bit of playing around got it right but remember dont rely on the number stamped on the shim.

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Mike is dead right. Just because the shim says it's a certain thickness, doesn't mean it is....always measure it before fitting. Don't forget that micrometers wear, too...especially if they've been used to measure diameters on things rotating in a lathe(!) A known standard is useful for calibration purposes. Just persevere until you have the right clearances....

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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  • 4 weeks later...

I was also wondering how accurate this 'gap' has to be.

Especially as the manufacturers (Kent) list the clearance on my L14's as 0.008 inlet and exhaust, yet my experienced 'head builder states 0.010 inlet and 0.012 exhaust.

Any advice would be appreciated - many thanks

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Especially as the manufacturers (Kent) list the clearance on my L14's as 0.008 inlet and exhaust,

The exhaust tappets should always be greater than the inlets because the exhaust valves get so much hotter than the inlets.

Cheers,

John W

http://jonwatkins.co.uk

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  • 8 years later...
On 07/08/2012 at 23:30, molemot said:

Washers work well...but check they are flat first, and use sizes where the holes aren't too big....also make sure that there is no edge to the holes where they are punched through...some careful work on an oilstone can take care of this. Worn proper shims get dips in the middle, too, where they impinge on the top of the valve stem...this can make fools of us all (!) so a micrometer is a better tool for measuring than a digital caliper, as the micrometer will fit down the dip and give you the true measurement.

 

Don't you just love iterative adjustments? Thankfully zero thickness sealants have taken some of the inspired guesswork away....

Hi mr molemot. What zero thickness gasket goo do you recommend

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1 hour ago, PrecisionMike said:

Hi mr molemot. What zero thickness gasket goo do you recommend

Unfortunately Molemot passed away 

In terms of which zero thickness sealant, I believe Loctite 518 is suitable (think it may be the recommended one) but there will be other brands, just match the characteristics https://www.henkel-adhesives.com/uk/en/product/flexible-sealants/loctite_518.html

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  • 2 months later...
  • Gold FFM

Yes, they can.  Be careful not to drop any shims as you lift the towers.  Magnets are useful.

  • Like 1

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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