Hello,
I had leaking pushrod tube seals and dropped the engine to make the job easier.
I decided to pull the heads to check condition. I’ve done quite a bit of reading about whether or not gaskets should be used between the cylinder and case and between the cylinder and head. Some posters point to a service bulletin stating not to use gaskets.

I have metal spacers/gaskets between the heads and cylinders. I think this engine has been rebuilt once before I got it. It runs well but it’s not as quick as another 914 2.0 I had years ago. Maybe the other car had higher compression and no gasket? I’m wondering if this metal gasket should be there. I haven’t checked for a gasket between the cylinder and case. My 356 has a thin copper gasket between the cylinder and case.

Can anyone shed some light in this?

Thanks in advance,

Jack

You have opened a can of worms with that question.

Lots of people say to leave the gaskets out because of a technical bulletin issued around 78 or 79 that says to. But the bulletin never mentions the 914 at all. They say to lap them like you would do for valves.

I don't do that. I use the head gaskets. I cannot see how anyone other than a professional engine builder would be able to lap the cylinders into the heads and get the deck height to within .001. You certainly can't do it in a home garage. So one cylinder will be tighter than the other when that side is assembled.

I have never had an issue in the 35 years I have been working on these cars.

Clay

...and the shims between the cylinders and the case are primarily for setting/adjusting the deck height...

Thanks Clay. I understand what you mean about deck height. Regarding the cylinder to case, is there a gasket in that location? I’m seeing some oil weeping from all four barrels. If no gasket, would it be appropriate to seal the barrels with a narrow bead of Ultra Gray or Curil T?

OK, Cuddy. I haven’t pulled a barrel yet but on my 356 I used Curil T on both sides of the copper shims. That should stop the weeping on this car.

I always use a thin bead of Drei-Bond on both sides of the bottom cylinder gasket to make sure it doesn't leak oil.

@ClayPerrine ' date='Apr 9 2020, 12:31 PM' post='2802542']
[quote name='jack20' post='2802528' date='Apr 9 2020, 02:14 PM']
OK, Cuddy. I haven’t pulled a barrel yet but on my 356 I used Curil T on both sides of the copper shims. That should stop the weeping on this car.
[/quote]

I always use a thin bead of Drei-Bond on both sides of the bottom cylinder gasket to make sure it doesn't leak oil.
[/quote]

I hear your argument Clay. But the last two 1.8L engines I torn down had original gaskets that got sucked in at a small area and created a leak. Wish I saved them and look pictures.

Bruce

On any type 4 engine don't use the freaking cylinder to head metal gaskets as they leak. VW who actually built these engines came out later and said "No".

Leave out the headgaskets.

They are made of laminated steel. Over time many will delaminate. This leads to the gaskets getting sucked in, as BD reported.

I have seen countless T4 heads over the years, Bus and 914, that did this and the leak was ignored long enough to burn a trough in the head you could stick a finger in. This almost always ruins the jug, too.

Lapping is not needed if the surface finish of the heads is smooth.

Lapping doesn't hurt anything if it's done very carefully with fine grit compound, but the idea of lapping originated in the days of the proliferation of bolt on flycutter's, which in good hands did a fine job, but in the typical hands out there left chatter marks or streaks. These imperfections needed to be lapped down.

Heads that leave our shop do not need to be lapped and we advise our customers not to.

You all have been very helpful. I appreciate it.
So VW put those metal gaskets in to reduce the possibility of oil leaks but cause a potentially bigger problem.
Clay, you were correct about opening a can of worms. I researched many old posts before asking the questions. I wondered what the current thinking is.
Obviously I’m no journeyman mechanic but have done a little of the type of work on other air cooled engines.
If I leave the head gaskets out, will deck height be effected to a point where I will have problems with too high compression or any other problem?

Thanks to all.
Jack

You will need to make sure you have adequate deck ht. No less than 1mm

The headgaskets are ~.8mm thick and do count as deck ht.

If you don't use the headgaskets you may need to put a shim at the base of the jugs to achieve the proper deck ht.

Thanks Len. I do have a shim at the base. Would it be correct to assume that the base shim and the head gasket created a 1mm or less deck height on a stock engine? If so, I will need to calculate how thick the base gasket should be to be under 1mm at the head. Have you been through this? If so what shim thickness did you choose? I’ve read that stacking shims is not the best way to create the needed space.
Thanks for your help.
Jack

Don't stack jug base shims.

A single .8mm shim should get you the 1mm deck minimum since usually you will have at least .2mm without one.

Determining what base shim you need is easy. Just measure what you have without any shim at TDC. Subtract that number from 1mm and that's what you need.

If you need more than 1mm to hit your target CR subtract what you have from what the required deck ht is.

I understand that the laminated metal gasket can be problematic but what is so unique about VW Type 4 heads that makes them fail? Laminated metal gasket is commonly used on water cooled engines all the time.

Maybe the fact that heads run so much hotter than a water pumper?

Then I wonder, why not use a different material like copper? Norton Commando's use a copper head gasket and they are air cooled. I think some other Brit bikes used copper as well.

I suspect that in the end the aluminum head is soft enough vs. the steel jug to deform and basically form it's own seal and account for a 0.0005" - 0.001" inconsistency between any of the mating surfaces. Sort of odd that air cooled 911 heads use a head seal though?

Like other's I haven't used laminated gaskets but as I read this thread I'm wondering what the real development history behind it was.

Len,
I just want to run this by you. I checked out some YouTube videos on measuring deck height on a VW engine. What I saw looks nothing like the deck height I appear to have. I just took a photo of my #1 cylinder which shows the extent of piston travel at the head.
I show roughly 6mm of unused surface. Does this look normal to you?Click to view attachment

If you read the tech order from VW, it does NOT mention any type IV motor before 78 or 79. I actually worked for VW in the early 80, and confirmed this tech order does not apply to the older Type IV motors.

I have always run the head gaskets in all of the 914-4 engines I build. Betty's engine has 413,000 miles on it, and I have never had any issues with the head gaskets.


Almost all of the people on this thread are experienced in working on the 914 engines. But we all have different experiences, which gives us each different opinions on what to do. So read the responses, and base your decision on what you think is best.

Do you base your opinion on what "everyone" says to do, or do you base your opinion on personal experience? How many Type IV motors have you built? Have you ever seen any issues with the head gaskets? Have you seen any issues because the head gaskets were left out?

My personal experience is I have seen more leaks in the sealing surface because the gaskets were left out. And I have probably built around 200 or so Type IV motors.

Thanks Clay. I certainly intend to do that. Right now I’m looking at what was done when this engine was rebuilt sometime in its life. I just posted a photo that leads me to believe that I could have excess deck height so I need to solve that before putting everything back together.
Jack

You should measure the combustion chamber volume as well as the deck height and calculate your compression ratio.

Deck height is not measured based on the wear marks in the cylinder wall.
Measure to the top of the piston to the top of the cylinder.
The wear marks in the cylinder are normally created by the piston rings not the piston.

I don't use the head gaskets and in my 20 years as a mechanic I never had a leak without the gaskets. The expansion and contraction cycles as the engine heats and cools cause the gaskets to squirm around and sometimes fail.
The AMC heads I put on my 78 bus said not to use head gaskets with their heads. I don't recall an explanation for the instructions.

Good luck with the engine!

Take care
Jim

Very helpful, Jim!
Thanks very much.

10 engines and I follow Raby’s and Len’s advice on this as they have plenty of experience too besides VW coming out with that service notice not to use them as they leak

I don't use head gaskets and I always measure CR

My 102mm nickies T4 and all the 96mm performance engines I build have no head gaskets. I've been at this 30 years and I haven't used head gaskets in the last 20 years. But every set of heads I use is a fresh fly cut.
BTW Every head gasket solution that you can think of including copper gaskets has been tried.

Excellent question, and the answer hits at the heart of the problem.

For the laminated gaskets to stay laminated they have to have even crush, all the way around. For that to happen the case spigots have to be deadnuts level and exactly on the same plane, the jugs have to be deadnuts the same ht., and the heads have to have the same level of precision as the case. Having decked over 150 cases over the years and seen how wildly uneven the spigots have been all but one (a low mileage 911 case) I can tell you the likelyhood of success of all 4 laminated gaskets on an old, undecked case (or an improperly decked case) is bleak.

Next, at operating temps the clamping has to be perfectly even and the expansion of of both chambers in each head has to be the same for that to happen. This is rarely the case.
Shuffling of the heads on the jugs frets the gaskets.

Frankly I consider it a miracle that any of them make it. I feel like Clay's success probably stems from careful builds, good tuning and frankly speaking some luck, unless he did all his machine work, too.

@HAM Inc

Thank you for taking the time to post the explanation. That helps satisfy the engineer in me.

When you think of all the tolerance stacks in VW/Porsche motors it seems like a bit of miracle that they work so well and have proven to be so durable.

I just wanted to thank everyone for responding to my post on whether or not to use head gaskets when I put my heads back on.

The consensus is not to use the gaskets. I don’t know how many miles the existing gaskets have on them and since I now know they’re laminated I would want to replace them. I would rather just buy new base gaskets and eliminate a potential problem.

I’ve done some measurements and determined that my engine is totally stock. Bore and stroke match the engine specs found on the Pelican site.
The German pistons are dished.
The head gasket is ~ .8 and the base gasket is .2mm equaling 1mm of total deck height.

So my choices are to replace the laminated gaskets and substitute a 1mm base shim for the .2mm shim or to buy new .8mm laminated gaskets and re-use the .2mm shim.

Some of you suggested I measure the volume of the combustion chamber to determine the compression ratio. If I do that I will also need to pull a piston to get the dish volume. The heads are stock and the pistons are stock. I can’t imagine I would find much deviation from the stock comp ratio of 7:6 if I do either of the suggested options.

I believe I’m down to these two choices but I tend to over-think things that are new to me.

Please let me know if my logic is flawed. In the meantime, thanks again for all your input. I really appreciate it.

Jack

I know I'm going to get blasted for having said this but if you can't measure CR and you're staying stock and have very near to stock deck height, you will be fine.

Is it best practice to CC the heads and even things out. Absolutely. All manufactured componets have nominal tolerances that were designed to yield a perfectly functional engine regarless of how the parts intermixed at the time of assembly. Did some engines come with a litle higher CR and/or a bit more Horsepower than the next one? Yup. Did some come with a little lower CR and maybe down a smidge on power. Yup.

Did the factory build them without CC'ing heads and perfectly matching CR cylinder to cylinder. You betcha.

Depending on the dish of the pistons, if they are stock pistons as you mention someone can post the standard CC volume. You could use that and still CC the heads if you were curious.

CC'ing and equalizing CR is all part of the game if you're trying to build the best possible engine you can with the parts you have. Basically working in the vain of "blueprinting" the engine. However, that is not the way mass production assembly lines work.

As a side note, I should mention that deck height is important for for other reasons beyond Compression Ratio. You don't want to go too tight on deck height. If I couldn't measure all components and do CR calculation, I'd make sure to err on having just a bit more deck and a slightly lower compression ratio.

You won’t get blasted by me. I appreciate the perspective you laid out.
I could go to the trouble of buying the components to CC the heads and frankly I’d like to do it but given what I’m trying to accomplish, I don’t think I’d really gain anything. This project started out as a pushrod tube seal replacement. I pulled the heads to check the carbon buildup on the pistons and combustion chamber on this ~50,000 mile engine. That’s when I noticed the head gaskets. My 356 doesn’t have head gaskets and that’s why I asked the question about the need for them. My research before posting caused me to think they should be eliminated. This engine runs well so all I want to do is de-carbon, lap the valves, change the tube seals, either replace the head gaskets or eliminate them by creating 1mm of deck height at the base.
Everyone has weighed in with very valuable info and I have learned a lot.
This forum is superior to any car or motorcycle forum I’ve experienced.