This is a cut and paste from something I wrote to a mailing list that I'm on....Figured I'd share it here too.



There are MANY factors that go into the condition we call "Head leakage". Many of these are misunderstood and simply overlooked until you get as deep as we are into these engines like we are and try to make 50+ HP per cylinder.

The Type IV faced a challenge right off the designers drafting desk... Below I will go over the most important ones and will sum it all up with a few tricks that we use to seal heads off with no problems.

First off, keep in mind that proper engine temperatures play a huge role in head leaks. Engines that run hotter suffer from higher degrees of expansion and contraction. This expansion and contraction will do their best to warp heads and cylinders and START a small leak. When the leak starts it doesn’t take long to grow into a hissing, popping sound that eventually means a burnt cylinder or head or both.

Keeping your engine at operating temperatures and head leaks won’t be near as much of an issue. Even VWs engineering flaws aren’t too bad unless the engine is overheated.

Dis-similar materials
You have a full does of them with a TIV engine, and they cause more issues than anything else! The selection of materials that VW chose was all over the place, and they tried to make them as compatible as possible. When you have a die cast ALUMINUM engine case, cast iron cylinders, sand cast ALUMINUM cylinder heads and sometimes (hopefully not) a head gasket there are a lot of things growing at way different rates. This is why when one installs an aluminum cylinder (see www.lnengineering.com) all the normal problems go away- its all in the expansion rates and the way its all designed to work. When other things enter into the problem, its gets really tricky.


Offset head stud pattern
The engineers designed the engine with an offset, non square bore spacing that places the lower, outside head stud on each bore "out of square" .. This really complicates things as this stud effects the tension and torque that the cylinder head clamps onto the cylinder. This in its self is not a huge deal, but when placed with the other deficiencies with the engine made the challenge of correcting it difficult, as it requires a multitude of procedures to correct.. After other modifications this bit of mis-engineering is not as big of a player in head leaks.. However- The bigger the bore size you go with, the more apparent these problems become and the harder they are to whip. This can be noted simply by the fact that the 1.7 engines had much better success with sealing off the heads, and seldom ever have these issues. Their small 90mm bore

Unequal head stud lengths (this is where you can see Porsche didn’t design this engine)

Look at even the earliest Porsche 356 engines, the 547 4 Cam Carrera and all the way up to the 911 and even piston engined aircooled aircraft engines- you will see a trend. All these engines had all head studs made the same length! The cylinder heads were designed to accommodate this so the studs would all expand and contract at like rates due to the same amount of elasticity and stretch. The VW TI and TIV do NOT incorporate this, and that’s one reason why we have head leakage. The upper studs are shorter than the lower and expand less! Also the upper studs are in the cooling air charge on the upper side of the plenums and are cooled more than the lowers, this also worsens the issue by keeping those studs not as expanded also… I have went so far as to use sleeves to insulate these studs from the cooling air trying to lessen these effects. There is nothing we can easily do to remedy this issue, it just adds a challenge to the equation and makes the offset bore spacing more of an issue. With proper procedures we can still have good results even with this design flaw that was undoubtedly a corner that was cut by VW to keep costs down.

Stud material (damn its wild stuff)

Who knows what this stuff is, but it is definitely odd! Some of the worst head leaks I have seen were on engines with aftermarket head studs that have weird expansion. VW did their homework on these studs and produced something that is damn near indestructible! When you break one off the only thing that will touch it is a cobalt tipped ball nose end mill, and even that has a tough time.

When the stud material is changed the effects of the off center cylinder head pattern, and the unequal lengths of top and bottom studs are multiplied and made much worse than ever before.

As with any stud, if these studs do not expand correctly they exert MORE CLAMPING PRESSURE on the cylinder heads and do so in an uneven method. This warps the head and causes leaks.. The hotter the engine gets the worse it becomes! Stick with stock studs or a set of specially engineered studs from www.lnengineering.com and you’ll have the best chances of success.


Cylinder head gaskets (what a mistake by vw!)

Perhaps my second biggest gripe with VW was these damn gaskets!! They are comprised of 3 layers of aluminum of .008 thickness and then pressed together and formed into a gasket. In the early 80s VW realized their problems and sent out a bulletin stating that these gaskets should be removed, and the compression ratio adjusted with a .030 cylinder bas shim at the first rebuild.

These shims are soft and thin and have a tendency to shrink with heat. As soon as they shrink a small leak is started, and then the soft material blows out making a huge leak. These gaskets kill TIV engines, and I never reuse them. We always remove the gaskets and do our procedures to seal the heads off. We use no gasket of any type and never have leaks. Our procedures promote a “Carbon seal” between the cylinder and head and require some machine work to complete.

ONCE AGAIN, THESE ISSUES ARE ALL MADE WORSE BY OVERHEATING THE ENGINE! MOST OVERHEATING IS DUE TO POOR ENGINE CONFIGURATION BUT MORE SO BY TUNING!!!!!!!!

How to remedy these issues

Its really not that hard. I will start with parts selection and go further into the procedures that we do to keep heads sealed off in our applications.

Parts-

Cylinders
Since you cannot change the composition of your case or cylinder heads, you must make do with what you can. The easiet part to change is the cylinders and many people do. Most cases they go the wrong way and cheap out! The OEM cylinders have different cast iron composition than the aftermarket kits and they wear less, warp less and create leaks because they are really crappy made. Their machine work is not flat, especially on their sealing surfaces. This is even more true with big bore kits of around 96mm. The 96s we use in our best engines use a VW OEM cylinder that has been re-bored to 96mm, and then plateau finished with our skirt clearance for the application. They also get both ends resurfaced and are indicated in the bed of a mill to check for flatness. If you replace your cylinders use OEM Mahle’s or step up to a set of LN engineering Nickies. Stepping up to the Nickies is a big step, but they are worth every dime they cost! Using Mexican made and Chinese made cylinders is the first big “no –No” one can make.

Head studs
This one is easy, keep them stock or if you go to Nickies, use the ones that were designed in the kit. No variations and no questions! VW knew what they were doing on stud material for the stock arrangement, just like the engineers did that designed the Nickies.

Head gaskets
Throw the stockers away that come in the gasket set and don’t use ANY gasket between the cylinder/head… It gives ANOTHER expansion rate and point and starts issues, and makes others worse! This includes copper gaskets, they also have another different expansion rate and cause issues- they are advertised to be the best thing since sliced bread, but they are not for a TIV.

Cylinder base shims
Measure them closely. If they vary .002 or more don’t use them on the same side of the engine as they create uneven cylinder heights and create leaks just like anything else. When possible use the VW factory shims to get the proper deck height. If they say “Taiwan” on them, get a mike and start measuring!

Machine work

This separates the “men from the boys” fellows! Almost all the issues that VW created can be killed with the right machining procedures and checks. Here I will go over them.

cylinders

Before assembling your engine, use valve lapping compound on the base of the cylinder where it seals into case. I prefer to use the very fine clover brand. Rotate the cylinder into the case and then clean off the compound. Look for a very fine grey line to be consistent both on the case register and the cylinder. This will tell you if the base of your cylinder is true or warped and will also check the case register at the same time. Check each cylinder in its own register and marke them for future assembly in their respective positions. If the cylinder is warped all 4 will need to be chucked into a lathe and resurfaced. If the case is not flat it will need to be surfaced as well. Either of these can cause a problem and will be checked by a builder that has attention to detail.

The sealing surface of the cylinder into the head is the most important area of concern with the cylinder. Over time this surface will warp with heat, and on new cylinders sometimes they are warped out of the box. Grab some Dykem machininst dye (either blue or red) and a piece of 400 grit sandpaper. You will also need a piece of glass or a mirror, or a “lapping table” to create a totally flat surface to be the basis of your checks.

Using the flat surface and the 400 grit sandpaper as a tool, coat the head sealing surfaces of the cylinder with dye and allow it to dry. Hold the cylinder perfectly flat and move it across the sandpaper evenly and firmly, do this two times and then lift up the cylinder and look for dye remaining. If dye remains in some areas those areas are low and the cylinder is warped or has suffered from erosion. It is sometimes possible to complete this procedure a few times and remove the high spots, but you run risk of making uneven cylinder decks and creating a leak due to uneven sealing of the head.

The machinist way of checking this is to indicate the cylinder into the bed of a mill and use a indicator to rotate across the top of the cylinder and show inaccuracies in increments of .0005” This is what I do and it takes forever, but works well. We end up with a solid days work into a set of cylinder for many of our engines. (Nickies don’t need any of this, they are CNC machined and are spot on)

If your cylinders suffer from this, take them to a machine shop and have them turned .005 on all 4 and even out the cylinder heights at the same time.

Cylinder heads I swear I’m almost done
We machine a step in the top of our cylinder heads that is the same OD as the cylinder as well as the same ID as the cylinder. Basically the cylinder sits on top of this step and when we design the engine this step is used instead of “Deck height” to create our CR settings. Most steps are .060 deep and create a .060 deck height when the cylinder is set very closely at “ZERO” deck. We sometimes add a tad bit of room for error and give a cylinder deck height of .005.

By doing this is promotes strength under the cylinder as well as a “Carbon seal” to start at the head/cylinder mating point. This also increases efficiency and burn rates and makes more power as well as sealing things of well. The key is a proper combination and having the proper chamber volume for your bore and stroke and desired target static compression ratio.

I cannot really explain this process, but I will have pictures of it up when I re do my site in the next couple of months. This step is the trickiest and most important key to keeping things sealed off!

Conclusion:
Once again, keep your engine at operating temperature and do not overheat it and you may never see issues with head sealing… Use good parts to do the job and couple them with a bit of attention to detail during assembly.. and last but not least really look at the cylinder and head design and try to figure it out in your own mind as you assemble the engine.

I hope this explanation of these issues has helped you to understand how to “fix” the issues and how to prevent them. I hope I was able to word it so it could be understood by those who don’t do this everyday.

Now you see one reason why what we do seldom breaks, doesn’t leak and benefits from efficiency. (some people think I charge too much, now you see why this isn’t a cheap process)

I wish you luck and happy days of driving- keeping your combustion where it belongs- In the chamber making power

thanks for sharing

Thanks Jake.......

cool, your welcome!

I could write many, many more pages on the subject--

Jake,
Thank You, I saved it for future referance...

Wow, thanks Jake.

I knew that I didn't have the experience, knowledge, tools, patience to correctly build a TIV engine, you just helped confirm my feelings.

Thanks again for sharing the wealth of knowledge that you have.

Nope... you just need good parts with the special work already done to them...

Those might be available "soon"

Good info! I read this a couple times and am still a bit confused If youre machining a 'step' in the cylinder head (essentially adding volume in the head) and run a 0 piston deck, wont you run a risk of piston/valve interference (the piston is the same distance from the valve with or without the step cut)

The step cut is carefully made... The step is actually the new deck height..

The piston runs within a few thou of the top of the cylinder and the deck is achieved by the plunge cut of the chamber...

works like a dream.. One key to unlocking power!

so ideally, you'd want new pushrods for any engine that you do that "carbon seal" on correct??

if I am thinking correct, the old pushrods are going to be too long?????

as soon as the heads are touched with a flycutter, the valve train geometry is wasted...

The rocker pads would need to be reshimmed. or length could be adjusted with a different length pushrod..

Is this step similar to how some of the German Type 1 heads are done?

Good info Jake.

very similar, just more precise and not done for smog reasons...

Jake,

i thought i read that in order to promote the "carbon" buildup process, you are using Permatex Copper coat, still using that?

yep, along with the procedures....

Thanks again Jake.
Should this be moved to classics location?
L. McC