<VV> Looking for some advice on low compression

hugo at aruncoaches.co.uk hugo at aruncoaches.co.uk
Wed Dec 27 21:16:53 EST 2017


Forgive my ignorance but what is 'flashing'? I'm from the UK originally 
& I'm not familiar with this term!

On 2017-12-27 14:05, dan petz via VirtualVairs wrote:
> if you lost one seat you will loose the rest of you seats  !!!
> cylinder head flashing is costly & extra $ where you do heads . Use
> Total Seal rings  And  G.I. the ring lands ... Your compression is
> very low  & more than likely a bad valve job   Tdan   Air Cooled
> Research
>
>
>     On Tuesday, December 26, 2017 9:59 PM, Larry Forman via
> VirtualVairs <virtualvairs at corvair.org> wrote:
>
>
>  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
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