How to find the right size shim needed
 

Hello Everyone,

I have a 88 Volvo 740 GL non turbo. I need to change out the shims
and regain some compression.

The book reads that the clearance should be from .009-.064 that tells me that their is .055 of play allotted for and still be alright.

Where is the number if you dont want it set to where you can rev up the engine before it drops in. I just want the tightest compression for as much power as I can get. No kids play.

So I would like to know the number on the given scale from the book being .oo9-.064 is the number to try and shim for.

Also, after I take a gauge reading of the number one, do I add that reading to the corresponding shim that will add up to the magic number I seek.


Please mechanic god in the sky help me figure out what shims to order.

if the valves are fully closed at TDC, you get full compression. you need a certain amount of clearance on a totally cold valve so thermal expansion doesn't keep a valve from closing.... too much clearance means the valve won't be open long enough, but anywhere in the spec range is fine and will result in optimal engine performance. Note, I'm not double-checking your numbers, I'm assuming you got them from a good resource.

IPDUSA will ship you a whole shim kit of plenty of every possible shim for a hefty deposit, you use what you need, then return the kit, and just pay for what you used.

otherwise, you'd need to get in there, measure your clearance, pull the existing shim, measure it, and calculate the difference (if you measure 0.010, say, and the existing shim is a 0.050, and you want 0.030, you'd replace the 0.050 with a 0.070...)

Hello Pierce,

Thanks for the very informative reply. I got the specs from a Haynes manual at
.009 -.064 valve clearance.
Q: Your response read," (if you measure 0.010, say, and the existing shim is a 0.050, and you want 0.030, you'd replace the 0.050 with a 0.070...)

To me, I read it as the clearance is .010 and existing shim is 0.050 for a total of all space of lobe to valve is .060 & .070 wouldn't fit.
Now I need to know the way it goes. Thank you. What would be an Ideal range to shoot with on the specs of .009 to .064. I take it that .30 would be the target.

I will go measure the difference and post the results

https://volvoforums.com/forum/images...tons/quote.gif

hmm, you're right, a thinner shim would increase the clearance, I did that wrong.

given those specs, if its between 0.010 and 0.060, I wouldn't even touch it.

I will then just measure the gauge and not take out the shims if the gauge is between .010-.060

Thanks

How do the numbers work? the smaller the number the fatter the shim.


I just want to understand how would I get to a .030 if your example was my measurements. I need to know how to I calculate it.

Shims
 

Pls with sugar on top:)

the number is the thickness of the shim. a thicker shim raises the cam follower ('lifter') so reduces the clearance between the cam and said lifter/follower.

For the cost of a cam cover gasket I would measure all of the valves to see if any are out of the spec range. Usually as the mileage goes up the exhaust valves tend to pound in and the clearance will tighten up. Do the measurement with a warm engine and once you see the results it will determine if you need to adjust maybe one or two or more valves.

I thought valve clearance was ALWAYS supposed to be measured on a stone cold engine?

Hey Pierce and everyone who has commented.
 

I gauged the Valves and came out with .010 on the intake and exhaust.

on all. I will take out the shims tomorrow when there is more light.

But my question is how do I set it at .013. Alright, I know I will do the math. Maybe it's .016 that is the sweet spot. I just need to know do I add or subtract to get to the number I need. How do I come out with a number I want.

I will take any advice on what I should set it at. (13-16)

My reason for even doing this is because I have loss of compression and power when I go up a steep hill. (Texas street in San Diego).

Thanks.

your valves are well in range, I wouldn't touch them.

'loss of compression' ? ummmmm, i don't think so.

loss of power? maybe its a fuel delivery issue, like a weak in-tank pump. or a air leak in the intake path. or a bad MAF.

Adjusting your valves is not going to change your compression unless the clearance is too small. Have you performed a compression check? If so, was it low in one or all the cylinders?

Loss of power could be due any number of things. Blocked cat, timing belt off a notch, lack of fuel pressure, etc.

My '93 940 and '91 740, which have the same engine as yours, have a sticker on the inner, driver's side fender that says: Warm Engine - .016 to .018. I've also found other sources that say .014, for a cold engine. Either one will work. If yours are .010 cold then you need to reduce the thickness of the shim by .004 which will increase the gap by that amount and give you a total of .014. One tip: even though your gaps are all the same, the shim thicknesses of each valve will probably vary to achieve that .010. All engines are like that. Part sizes and tolerances are not identical from valve to valve. To save you some money measure all the shims and mark what valve they belong to and then mix and match. If exhaust #2 has a shim that's 4.4 mm, you need a 4.0 mm shim to gain that extra .004. See if any of the other shims already are 4.0 and just switch that to exhaust #2. I needed to readjust all my valves but by mixing and matching I was able to order just 5 shims. Also, if you're going to go to the trouble of doing this make sure you order some new "valve hushers", also called "valve absorbers", the little rubber boots that quiet the valves: https://www.eeuroparts.com/Parts/395...rber-21434432/
At 150,000 miles, all mine we're hard and split. Replacing them made quite a difference.