<VV> Looking for some advice on low compression
efki at verizon.net
Thu Dec 28 02:37:58 EST 2017
Head de-flashing is something that would be an extra. If the owner didn't want to pay for it you shouldn't blame the shop that worked on it.
Having de-flashed the heads you know how long it takes. A shop will not do it for free.
There is a great shop here in the Los Angeles area. If you want to ship your head let me know and I will get you the info.
The carb issue is a different story.
From: Larry Forman via VirtualVairs <virtualvairs at corvair.org>
To: virtualvairs <virtualvairs at corvair.org>; Ultravan Group <ultravan at yahoogroups.com>
Sent: Tue, Dec 26, 2017 9:59 pm
Subject: <VV> Looking for some advice on low compression
I recently purchased a nice 65 Monza Vert PG at Hot August Nights car
auction with about 80 K miles on the odometer. It was claimed to have
had a recent engine rebuilt about 5K miles ago (now about 7K miles). I
measured the cylinder compression and got the following readings:
cyl 1: 100 and w/ oil at 115 cyl 2: 120
cyl 3: 125 cyl 4: 90 and w/ oil at 95
cyl 5: 125 cyl 6: 125
As luck would have it, it just dropped an exhaust valve seat on #2, but
fortunately the valve seat remained whole but wallowed out the valve
seat mounting area and gouged the piston top. I will smooth out the
piston top so there are no sharp edges where it was gouged.
The cylinders show the cross hatching evidence of a recent rebuild. I
have not yet measured the cylinders on the driver's side for taper. I
have only removed the driver's side cylinder head and am not planning on
removing the passenger side since the engine is still in the car.
I am not too impressed with whatever Reno area shop did the rebuild
since they did not do ANY head deflashing, which likely contributed to
the dropped valve seat. That same shop also rebuilt the carbs and left
out one power enrichment needle, which explains why I had trouble
getting the carbs balanced until I redid the carbs and found that
problem. I have now done a proper head deflashing on both heads so
hopefully once the engine is back together it should be more reliable.
I am now looking for a Sacramento area air cooled engine shop who can do
a proper valve seat repair and check the head out for any other issues
or possible loose valve seats.
My question is: What are the recommendations for determining why the #4
cylinder compression is low? And what should I do to make the best of
the current situation?
I assume I should check cylinder taper, ring conditions and orientation,
and look for any valve issues on #4. Any other recommendations? I
have not yet determined if the pistons have been replaced from the stock
ones that can lose their tops. I certainly hope so.
Any recommendations would be very welcome.
Thanks in advance and have a Happy New Year,
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