<VV> Looking for some advice on low compression

Eric Kirven 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. 

Best Regards,

-----Original Message-----
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

Hi All,

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,

Larry Forman
This message was sent by the VirtualVairs mailing list, all copyrights are the property
of the writer, please attribute properly. For help, mailto:vv-help at corvair.org
This list sponsored by the Corvair Society of America, http://www.corvair.org/
Post messages to: VirtualVairs at corvair.org
Change your options: http://www.vv.corvair.org/mailman/options/virtualvairs
Archives: http://www.vv.corvair.org/archive.htm

More information about the VirtualVairs mailing list