Compression Questions

[amikulics]

Today I decided to check the compression on my 72 1700 type 4. During the dry test it got 91 PSI in all cylinders. During the wet test it had 91 in cylinders 1 and 3 and 120 in cylinders 2 and 4. Are these number low enough to warrant replacing the rings? Also if I choose not to so the rings myself is there a reputable shop that could replace them for me in the San Diego area?

[KentABQ]

I can't help you with the question about compression...

But if you've read any of the threads in the Bay Window forum, you must have seen Aeromech. He can fix anything.
_________________
-Kent-
1976 Riviera, 1.8l FI chrome yellow VAN - "Chloe"

"I must say, how can you be in a bad mood driving this vehicle full of vibrant color.
Cars of today are so bland in comparison. It's like driving a celebration!" ---WildIdea

Bus ownership via emoticons:
---williamM

[Wildthings]

Has the engine been in daily service for a while? Was it warmed up for the test? Are your valves adjusted? Was the battery well charged and the throttle held open? An engine really needs to be prepped for a compression test.

[SGKent]

[amikulics]

It is clear to me now that I made many mistakes with my original compression test. I plan to warm up the engine and check the compression sometime soon.

In the meantime I have been looking into piston ring replacement and I have a few questions. I found out about the service bulletin that suggested getting rid of the sealing ring at the top of the cylinder and replacing it with a 1.6mm ring at the bottom. This bulletin made no reference to machining the head. My questions are does this bulletin affect my 1972 1700 or can I use rings on top and bottom like from the factory. If I can use rings at the top and bottom is there any specific size they have to be or can I use these from bus depot on all 4 cylinders?

for the top:
http://www.busdepot.com/021101343

for the bottom:
http://www.busdepot.com/021101341a

[scubaseas]

Covered in the link below.

https://www.thesamba.com/vw/forum/viewtopic.php?t=695322&highlight=
_________________
Al

08/1970 T2a Westphalia owned since 1980

ASE Master certification. 50 years pushing a wrench
Retired

[airschooled]

As per the VW Technical Service Buliten, only the 2.0L GD, GE, and CV two-liter Type 4 engines should delete the sealing rings and install a spacer. With stock parts, that's it. If an engine with sealing rings is consistently overheated, the sealing rings may leak compression. This commonly shows up as a "soot" on the cylinder heads around the cylinder spigot. Here is a T1 head for example:

Here is the TSB for those curious:
http://www.ratwell.com/mirror/www.dolphinsci.com/techbull.html

--

Your compression ratio is set very carefully using a combination of cylinder deck height, combustion chamber volume, piston dish/dome, bore, and stroke. If you change the deck height by removing a gasket shim you will need to add that much at the bottom of the cylinder to make up for the difference in deck height. If you instead use a new AMC head that has a "step" cast into the head, that step takes up the deck height of the gasket shim instead of needing a shim at the base of the cylinder.

Clear as mud?

Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
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[Wildthings]

[amikulics]

Thanks a ton Robbie that's exactly the answer I was looking for. I'm trying to make my engine as stock as possible so can I just use these on top and bottom of each cylinder:

http://www.busdepot.com/021101341a

http://www.busdepot.com/021101343

Also I've seen mixed opinions on whether to not use sealant on these gaskets. Is this a bad idea or would it help?

[raygreenwood]