<VV> backfiring out carbs and exhaust (long)

[Keith Hammett]

Background:

This is the 110 hp motor that I attempted my first rebuild on (car motor
drilled for FC dipstick).  I have taken plenty of time on things
following the '65 shop manual as my guide.  Installed the engine into
the rampside and fired it up to have it race away (that problem was
solved).  Next was a very rough running engine, not all cylinders were
firing.  A check of the ignition system indicated that all plugs were
gaped right, plug wires (new) ohmed out good, static timed the
distributor again (right back were I had it the first time), replaced
the plug wires and found that the number four sparkplug end is really
hard to get to seat on the plug.  Fired the motor up and it ran better
(still not right but better).  Let the engine warm up (medium rpm) and
it smoothed out for a really short time, then it started backfiring
through the carbs and exhaust.  I also rebuilt the carbs (first time for
that as well) and do not suspect them to be the cause.

 

Suspect cause:

I am leaning toward valves not being adjusted properly.  When I built
the engine I used the cold method out of the shop manual, first time
doing this I was unsure and everything seamed to go to easy (must be
something there as nothing goes easy).  Could I have the valves adjusted
to tight allowing them to remain open some and causing this problem? My
thinking is that when the engine got warm the lifters started to pump up
causing the engine to smooth out briefly, then once pumped up the valves
were forced open causing a backfire condition (never got lifter noise).
This is my theory, what say the wise ones am I on the right track?  If
so should I replace the valve cover gaskets or will they reseal and not
leak (A leak will anger the financial advisor and possibly cut funding)?

 

Further work:

Once the engine is up and running good then I can move on to rebuilding
the rear suspension, packing rear bearings, gas tank installation,
direct heater rebuild, and finally putting it on the road and removing
it from group red.  Actually it has been out of group red for some time,
but I don't consider it to be until I can drive it on the roads.

 

Thanks in Advance,

Keith (learning the hard way) Hammett