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Mon Jul 30, 2007 8:24 pm

Hi. Im rebuilding a stock 1600 dp motor, and i noticed it came with two shims on each cylinder, for a total of 8. One is smaller that the other. One goes between the engine case and cylinder, and the other goes between the cylinder and the head. They are not copper, and appear to be steel. One thing i notice is that with out the shims, and with only one paper gasket on the cylinder to case, the piston goes level with the top of the cylinder, but with the shims the piston only gets to about 1/8th of an inch from the top of the cylinder, then goes back down. Is this 1/8th inch gap a problem? By 1/6th inch i mean that with the piston at TDC, or all the way up as far as it will go, It is almost at 1/6th inch from the top of the cylinder, and not level. the cylinder was bolted down with the head off, and that is how i noticed. The shims itself is about a 1/16th of an inch.

So the way its set up in order of parts starting from the block is:

Case, Paper gasket, Metal shim, Paper Gasket, Cylinder.

What is the purpose for these shims? Should i put them in? Should i only put one set in? Will they increase Power? Better MPG?

Mon Jul 30, 2007 10:01 pm

Thay are used to set the deck height/compression ratio. Can't say if you need them or not until you measure the deck height and CC the heads.

Tue Jul 31, 2007 2:20 am

Are you sure you don't have a stroker? Have you measured the stroke?
I've never seen a 1.6 that needed shims, then again some strokers don't need them if they are built that way either.

It could be that the case was decked a few times, and the shims are needed to make up the differance?

Tue Jul 31, 2007 7:45 am

Hi, im not sure if it is a stroker. I replaced the cylinders and pistons with stock 1600 Cylinders and pistons. With out the shims, the piston at TDC will come all the way up, even with the top of thew cylinder. With the shims, with the piston at TDC, it come to about an 1/8th of an inch from the top.

I'm not very knowledgeable with strokers, or measuring stuff (deck height, head CC'ing, Compression ratio's, etc) Im not sure how to do it, and i don't have a micrometer (probrobly need to get one :D ).

Also something with the heads are different. The ones the motor origionally had, the inside was level, like this

This is not my head, just a pic off the gallery. Mine have not been bored out. what i want you to see is the inside combustion chamber, on the outer edge, where you would put a shim. In this pic it is completely level. That is how the old heads were.

The new heads are raised up in this area. It looks like there is a shim in the head, but it's a part of the head. It is NOT flat like in the pic. Its like a permanent shim. Hope im not confusing anyone (because i think im confusing myself :lol:)

BTW, the old heads had very bad exhaust valve guides, so re-using them is not an option. The new heads came off another engine i had lying around, and they are in great shape (good valve guides, good valves). I also lapped/ grinded the valves, so they seat well.

Not sure if any of this info helps, just wanted to tell yall.

Also, hypothetically, Lets just say this is a completely stock 1600 dp engine. What would adding shims do to it? Would it lower compression?, if so what would that do? (less power, less MPG, etc?)

BTW, i have no time to take stuff to machine shops, as i need the car finished by monday morning (need to go to school).

Sorry for being so long-winded, just want to be as descriptive as possible.

Tue Jul 31, 2007 8:02 am

Difficult to give you advice without know more about the engine. However, it seems like whoever did the previous rebuild knew what he/she was doing. By far, the safest thing is to replace the shims. The worst that will happen is that you might lose some compression, but you won't hear expensive noises when you try to run the engine. Consensus around here is that you need at least .040 deck. I usually run a little more.

Tue Jul 31, 2007 8:18 am

TWD wrote: The worst that will happen is that you might lose some compression, but you won't hear expensive noises when you try to run the engine.

Expensive noises :shock: :shock: :shock: ??? Oh sh!t? I'm scared now. Will to much or too little compression damage my engine?

Tue Jul 31, 2007 8:41 am

FYI, deck height is the space between the top of the piston and the top edge of the cylinder at TDC.
If the pistons come all the way to the top edge they are a little too close
to the valve action.
Sounds like thats what those shims are for

Tue Jul 31, 2007 8:45 am

Last time my 1600 T3 was rebuilt by a shop, unleaded low octane gas was abound, so they shimmed it to lower the compression a little. Just one, though.

Tue Jul 31, 2007 10:36 am

BugMan114 wrote: Hi, im not sure if it is a stroker. I replaced the cylinders and pistons with stock 1600 Cylinders and pistons. With out the shims, the piston at TDC will come all the way up, even with the top of thew cylinder. With the shims, with the piston at TDC, it come to about an 1/8th of an inch from the top.

I'm not very knowledgeable with strokers, or measuring stuff (deck height, head CC'ing, Compression ratio's, etc) Im not sure how to do it, and i don't have a micrometer (probrobly need to get one :D ).

Also something with the heads are different. The ones the motor origionally had, the inside was level, like this

This is not my head, just a pic off the gallery. Mine have not been bored out. what i want you to see is the inside combustion chamber, on the outer edge, where you would put a shim. In this pic it is completely level. That is how the old heads were.

The new heads are raised up in this area. It looks like there is a shim in the head, but it's a part of the head. It is NOT flat like in the pic. Its like a permanent shim. Hope im not confusing anyone (because i think im confusing myself :lol:)

BTW, the old heads had very bad exhaust valve guides, so re-using them is not an option. The new heads came off another engine i had lying around, and they are in great shape (good valve guides, good valves). I also lapped/ grinded the valves, so they seat well.

Not sure if any of this info helps, just wanted to tell yall.

Also, hypothetically, Lets just say this is a completely stock 1600 dp engine. What would adding shims do to it? Would it lower compression?, if so what would that do? (less power, less MPG, etc?)

BTW, i have no time to take stuff to machine shops, as i need the car finished by monday morning (need to go to school).

Sorry for being so long-winded, just want to be as descriptive as possible.

This means you had no step on the original heads and you have a step on the new heads, nothing strange there, but you have to account correctly for it when assembling the engine. So, you HAVE to measure the combustion chamber on the new heads and you have to measure the deck height. It also wouldn't take more than a few minutes to measure the stroke(the distance from the piston being all the way down in the cylinder to when it is all the way up) Then and only then will you have the knowledge to put this engine back together. If you don't have time or money or interest in doing those things, you will just be guessing and we will not be able to give you any concrete answers, only worse guesses.

Tue Jul 31, 2007 11:09 am

Thanks for all of the responses so far.

Hi. How do i measure the combustion chambers on the heads. Not sure if this helps, but the new stepped heads came from a STOCK 1600 dp, AH engine, from a 71 standard beetle. I'll try to measure the stroke, but the most accutate measuring device i have is a tape measure. If the compression is too low, will it damage the engine?

I apologize for my ignorance :oops: , but as i've stated, all of this stuff is new to me :D. I've rebuilt engines in other cars, and i've rebuilt one VW engine before, but it didn't have these shims (and i didn't measure anything :oops: , but it runs good).

Tue Jul 31, 2007 11:57 am

Your descriptions have been good. As mentioned above, when the piston is at the top of its travel (that's TDC or top-dead center), there still should be at least 0.040" (or 1 mm) distance from the top edge of the piston to the top edge of the cylinder. That distance, whatever it turns out to be, is called your deck height. Measure around a few points of the piston so that you offset the effect of the off-center piston pin which can allow the piston top surface to be not entirely level.

You can get cylinder base shims of different thicknesses from various VW suppliers like CB Performance or aircooled.net.

When you do reassemble the cylinders, common practice is to not use the paper gaskets under the cylinders, but to use a THIN coating of RTV silicone. RTV comes in different colors for different heat ranges, and you really only need a THIN coat right on the thin edge where the cylinder sits on the engine case. Like a dab the size of a middle fingernail, spread all around the cylinder base, then wiping off the rest that smeared up on the cylinder edge that goes INTO the engine case's cylinder bore hole. Since you have already described and determined that you need "some" type of cylinder base shim, then you coat THAT with the RTV on both sides. Apply the shim with uncured RTV to the cylinder, then slip the cylinder into the engine case hole. Repeat for the other cylinder on that side of the engine, then install the head and snug it down per VW's specified torque spec's. Those torque specs are CRITICAL.

Now for the shim ABOVE the cylinder. You described that your new heads have that "ledge"; its thickness "could" do away with the need for a shim above the cylinder. It's really tough to accurately measure the depth of that ledge without a dial caliper; even a cheap plastic one for about $20 gives you a much better measurement than a tape measure.

But to really know your compression ratio (CR), you should try to measure the volume of the combustion chamber in the cylinder head. I've used a 50ml (same as cc) syringe for baby medicine that you can buy in a drug store, then use ATF as the fluid. The valves and spark plug must be installed in the head, and you have the head level with the combustion chambers facing upwards. Finally you need a plastic disc made of plexiglass that fits inside the edges of the combustion chamber. You could trace the cylinder edge onto the plexiglass then cut it out with a fine jig/coping saw to get the right size.

I'll venture to guess that the thickness of the shim you had above the cylinder is very close to the thickness/depth of the ledge on your new head. I also think there is a "sticky' above all these topics for figuring out your CR or to measure your CCs.

Tue Jul 31, 2007 1:25 pm

blacktruck wrote: FYI, deck height is the space between the top of the piston and the top edge of the cylinder at TDC.

not exactly...but that is what vw people have labeled it...

Tue Jul 31, 2007 8:17 pm

The shim appears to be exactly the same thickness as the head step. I have also put in the paper gaskets :oops: , oops. Would gasinact (not sure how to spell it), work. It supposed to be a sealer to seal the two case halves together. I happen to have a few can of that stuff laying around.

Also i don't have a syringe, what do you think i am, a junkie, lol just kidding :D :D :D. i'll buy one of those head CC'ing kits at Mid America Motorworks, or at CB performance if they have it.

I still need to know the answer to the above question. If i keep the shims in, and it lowers compression, could it be significant enough to make the engine run bad, or cause damage to it?

Wed Aug 01, 2007 7:34 am

"Gascacinch". I have personally not used it to seal the cylinder base to the case but others have; I think you'll be OK.

"syringe"? The type I mean does not have a needle end, just a "spout" hole for liquids like cough syrup that you measure per recommended dosages and give an infant into its mouth. It has graduations every 1 cc and labeled at each 10cc. Made of plastic. Have also seen larger ones for 100cc.

Low CR will not hurt the engine at all, but the engine will not make its most power.

The "CC" kit is a wise investment and will make your determination alot easier. Next time you're at a Sears, go to the HW section and try to find a cheap plastic sliding caliper for your deck height and cyl. head step measurements. Or one like this: http://www.sears.com/sr/javasr/product.do?cat=Hand...Cookie=Yes (item #00940703000)