Bad Compression on one side of the engine

[pernest]

Picked car up from engine rebuilder on June 29, 2021. Car had between 97868 and 97,000 miles on it when rebuilt (1600 DP). Now has 99,228. Don't drive much.

A few days ago, my Gene Berg lite came on while exiting the interstate. Never exceeded 55 on the interstate that day. When I slowed down exiting the interstate from 50 to 40, the lite went off. Stopped the car at the earliest opportunity and turned the motor off.

Tested temp and could not get a reading hotter than 191. The engine didn't feel or smell hot. Started it again and it started to run very poorly. Sounded like 1/2 of the engine was running. Shut the engine down and had the car hauled home. Checked points and cleaned carb but this did no good.

I did a cold compression test with the following values: (1) 100 (2) 115 (3) 55 (4) 55. Less than six months ago (Jan 2022) did a compression test when the engine was running poorly with all four cylinders reading 120. The current odometer reading is 99,228 (less than 1400 miles since it was rebuilt).

What do you think?

[mukluk]

Check for valve lash that's way out of spec or loose cylinder head nuts on the 3/4 side.
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1960 Ragtop w/Semaphores "Inga"

[pernest]

Thanks and will check that out. Hope that is the problem.

[vwoldbug]

How many times have you adjusted the valves since the rebuild.

[pernest]

Once.

[HurpMcDurp]

Beings its both of the same side, my first thought is the head? As it touches both cylinders. I assume the compression is leaking at the head for both, cant imagine what else in a tandem could cause that, imo
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I call it Patches - My 72 body with the heart of 68..driven by a 1991 animal

[Murmsk]

Sounds like head bolts are loose. We don’t know what case he has so over tight head bolts at rebuild could have pulled out of case if it is a case w/o casesavers
Check the torque on the. Head bolts

S
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1970 Convertible
1972 super
1946 Willys Jeep

[gwinters]

Check the head studs and where they screw into the case. Mine overheated (because the previous owner had forgotten the air baffles) and the head studs pulled out of the case. They may have been overtorqued and done the same thing. They make case savers for this type of scenario. Good luck!
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68 bug
71 ghia project
"If it's stupid and it works, then its not stupid."

[ashman40]

I don't know the specs on your engine so can’t tell you what your head bolt torque should be (different between 10mm and 8mm studs). Look up the torque spec and retorque the 4 head bolts you can see under the left valve cover. If any are very loose you can assume the 4 nuts you cannot see are also loose. You will need to pull the engine and remove the cylinder head tin to reach all 8 nuts. If some are loose all need to be retorqued.

If all 4 nuts under the valve cover are to spec the ones you can’t see are probably okay too.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[pernest]

Found that the rocker arm shaft assembly nuts had worked themselves loose causing the push rods to disconnect from the lifters. Doesn’t look like there’s any damage othe than when I reassembled the rocker arm incorrectly (shims on top rather thsan bottom) and one of the supports broke when disassembling. Won’t make that mistake again!

The support looks like it might work even though cracked —- what do you think? Who sells the “supports” only? Adjusted Nos. 1 and 2 and will try to finish the job soon. Thanks for all of your help.

[mukluk]

Yep, that'll put your lash way out of spec. Good to hear you found the problem.

It's not clear exactly what you're asking about concerning the "supports". I'm thinking you may be talking about the rocker shaft mount blocks, but posting up some pics would be helpful. Pics would also show whether we're dealing with stock style components or something else.
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1960 Ragtop w/Semaphores "Inga"

[pernest]

[pernest]

Sorry for the huge photo ---- I can't find d any description for all of the rocker arm shaft parts in Haynes or Bentley. I hope I'm right that the broken part might even work once it's tightened to spec.

Thanks for your help!

[mukluk]

Looks like you're running stock rocker assembly parts but with aftermarket adjusters.
http://vwparts.aircooled.net/Stock-Rocker-Shaft-Mounting-Block-EACH-p/rocker-block-ea.htm
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1960 Ragtop w/Semaphores "Inga"

[pernest]

I heard it snap after I attempted to get the rocker shaft off without the shims under the supports. Will order the shaft mounting blocks per your info. Thanks!

[pernest]

Got the rocker shaft arm block and reinstalled the arm shaft. Adjusted valves on both sides. Compression now 115 on cylinders 3 and 4. Cylinder 1 tests at 115 and 2 at 118. Thanks for all of your suggestions and help. Happy ending!