Top end rebuild

[highlandmurf]

Hello,
I need to rebuild my the top end on my 2.0 early 76 engine. I have a sinking valve issue,and another cylinder with low very low compression that I am 95% sure is related to a valve issue.

I am trying to come up with a list of things to do and plan of attack, but after doing a lot of reading, my head is spinning!

I have a bunch of questions, forgive me if they are addresed elsewhere, but I am trying to figure out how all of this information fits into my situation. This will be the most involved job I have done on the Bus so far, and I am feeling a little overwhelmed.

I was going to ask what comes off the engine, but I guess the easier question is what is left on? Seems like a complete tear down to short block except for maybe the distributor right?

Ok, so I have these rebuilt heads, the lip where they will mate to the Cylinder is completely machined off.
Will they definitely need copper head gaskets, or only if the fins are touching before they mate?

Lapping the heads/ Cylinders, I get the concept, but how do you ensure that they remain parallel and don't get cocked?
When you start lapping are you pairing the cylinders to a particular head opening?

If I look at how the cylinder is shimmed up at it's base, then I only need to determine how the existing and new heads differ and adjust from there correct?

Can I use more than one shim below the cylinder, or do I need one the correct thickness?

I replaced the manifold gaskets last year, are they a one use item, that needs to be replaced, or can they be reused?

Lots of questions, I'm sure I'll have more.
Thanks for reading,

Joe

[Amskeptic]

1) what comes off the engine?

2) rebuilt heads the lip where they will mate to the Cylinder is completely machined off.
Will they definitely need copper head gaskets, or only if the fins are touching before they mate?

3) Lapping how do you ensure that they don't get cocked?
When you start lapping are you pairing the cylinders to a particular head opening?

4) If I look at how the cylinder is shimmed up at it's base, then I only need to determine how the existing and new heads differ and adjust from there correct?

5) Can I use more than one shim below the cylinder, or do I need one the correct thickness?

6) I replaced the manifold gaskets last year, are they a one use item, that needs to be replaced, or can they be reused?

1) strip it down to the long block, from there, restrain cylinders with wire and remove heads.

2) they will definitely need copper sealing rings (the thick ones from ACNet, not cheap-ass crap empi) only if:
fin casting area hits head surface
your compression ratio calculations require them and you are not keen on disrupting the rings by taking off the cylinders (people give the sealings an unnecessarily bad rap. They are only the canary in the coal mine.

3) lapping suggests that you are taking the cylinders off?

4) you measure, you do not "match". There are variables all over the place, the new heads may have different combustion chamber volumes that require a whole different set of base shims and/or copper sealing rings up top depending on the fin-to-head clearance, etc.

5) I recommend one correctly sized shim installed with Permatex Aviation. Any more than that and the possibility of leaks increases as well as loss of clamping force as all these stacked parts bed in.

6) you can reuse them if they pass your smoothness test. Please check your intake manifold surfaces for straight as well, they commonly need to be filed or milled flap.

7) Cleanliness is paramount.
Colin

[highlandmurf]

Thanks for the quick reply Colin!

Lapping the heads is not mentioned in Tom Wilson's book, but it has been discussed online enough that there must be some merit to it in certain situations, not quite sure yet what they would be other than a scratched head. Mine have slight marks from the flycutting, not sure if that qualifies.

Also wondering as I am into it so far at that point if I should just go ahead and replace the rings.
If the measurements deem that the cylinder heads need to be shimmed, they will have to come off anyway.
If I remember correctly my compression was running in the high 80's to low 100s last fall.

Would love to get you down for another day, but not sure if my finances will allow. Gotta see how the next couple of weeks go.
I see you are not really on the road until June, is that by choice?

Thanks
"VW Mechanic in training"

[Amskeptic]

Thanks for the quick reply Colin!

Lapping the heads is not mentioned in Tom Wilson's book, but it has been discussed online enough that there must be some merit to it in certain situations, not quite sure yet what they would be other than a scratched head. Mine have slight marks from the flycutting, not sure if that qualifies.

Machining marks are absolutely your friends as far as improving sealing performance if they are in the direction of the circle.

Also wondering as I am into it so far at that point if I should just go ahead and replace the rings.
If the measurements deem that the cylinder heads need to be shimmed, they will have to come off anyway.
If I remember correctly my compression was running in the high 80's to low 100s last fall.

If I had oil wet pistons or cylinders, I would take them off and do very good work with re-ringing if pistons passed all measurement tests. A novice builder is actually ahead if he just replaces them.

Would love to get you down for another day, but not sure if my finances will allow. Gotta see how the next couple of weeks go.
I see you are not really on the road until June, is that by choice?

Thanks
"VW Mechanic in training"

It could be fun or it could pay for your new pistons and cylinders . . .

[highlandmurf]

Ok, So I dove in and have a lot of parts and a few questions.

First are these deep or shallow dish pistons? How many CC's of space.



All of my plugs had a lot of carbon except # 1.
What do you think about how they look?

# 1,#2


#3,#4


I had a chipped Intake valve on Cylinder #1 and Sunk Intake valves on #2 and #3.
#2 intake in particular was not holding an adjustment for more than 100 miles.

Are there any problems/ issues that may arise with the FI system for having some exhaust forced through an open intake valve?

Lastly, How many CC's were in an original 2.0 head?

Thanks

[Amskeptic]

deep or shallow dish pistons? How many CC's of space.

plugs how they look?

I had a chipped Intake valve on Cylinder #1 and Sunk Intake valves on #2 and #3.
#2 intake in particular was not holding an adjustment for more than 100 miles.

Deep are 15cc, shallow are 7cc. Yours look deep.
Head volumes are too variable to just spew a number.
"Chipped valve"? Explain.

Sunk valves, do you see insert migration in head aluminum, or just erosion of the seat contact surface?
Colin

[highlandmurf]

#1 cylinder with chipped intake,
#2 cylinder with sunken intake.

[Bleyseng]

You must be running a carb(s).....

[highlandmurf]

Nope, fuel injected.

[Bleyseng]

usually you see a chipped intake on a carb motor as a nut or something falls in the intake to do that.

[Gypsie]

Dang, looks like something was playing around in the CC.

You must cc your own pistons, and heads, calculate deck height. you will find the nirvana you seek in each petal of the lotus...


or some such like that.

If you don't want to do it, have yer local shop do it. But your really need to do it.

get the heads either rebuilt or deemed 'gone'.

You will thank yourself later for your thoroughness now.




And don't ask how I know....


really.

[Amskeptic]

That "chip" looks like a burn, like a carbon chunk prevented the valve from seating and exhaust gas just eroded the seat like a collapsing dirt dam. Your combustion chambers all look too cool, which exacerbates carbon build-up, which increases the risk for carbon-based valve seating issues.
Your photographs tell me nothing about this valve seat recession/seat surface failure/which is it? A machine shop might be able to tell you more.
Colin