This is a fairly long post and explanation. Any good mechanics...please
take the time to read - I REALLY need your expertise and experiences. I
have two days before I have to get this on the road for a 10 hour trip, and
am running out of time. As much as I hate to even think about it, if I
can't get this solved, I am seriously thinking about selling the truck. I
just spent almost $900 to rebuild the new engine, and am now where closer to
fixing it than before. I can't afford to keep throwing money at a problem
that doesn't seem to me to be solvable.
Well, I am absolutely and totally at a loss as to what is wrong. During the
breakin, I followed the advice I've always heard as to how to break in an
engine, ie. to run it up to around 2000 rpms, and let it sit there for 15-20
minutes. So I did that. Everything seemed to go pretty normal. The temp
gradually got up to 190 or so (no thermostat yet installed), and held there.
I didn't see any small bubbles during this time and just before the end of
the 20 minutes, I put the radiator cap on. BUT, as I reached the end of the
break in, and as I reduced the rpms to idle, all of a sudden the water from
the radiator started spewing (with sufficient force to shoot to the fender)
out under pressure out of the overflow tube at the filler neck (cap is a
zero pressure cap). I immediately shut down the engine, and looked inside
the radiator and saw nothing of concern. I started the engine again and
gradually added water so it wouldn't be hit with a large volume of cold
water at once. That went fine, but at idle, I am seeing the same damn small
bubbles!
As some may recall, I originally rebuilt the 235 because of bubbles in the
radiator and pressure getting into the water system (I had a thermostat
installed and when it hit opening temperature, a rush of water and air
caused the radiator to volcano. I had originally suspected a blown head
gasket was allowing air to enter the system, causing it to not only
overheat, but was the source of the air getting into the system which, when
the thermostat opened, allowed this air to rapidly escape and cause the
volcano effect. So I put on a new head gasket, but the same problem was
there. So, suspecting I may have messed up the head gasket somehow when I
put on the head (I did it myself and thought I might have somehow scored the
gasket while setting the head on), I tried again with a new head gasket, but
before that, I took the head and had it magnafluxed and surfaced...but after
putting on the head and new gasket...same thing, same bubbles and air
getting into the water jacket. So, suspecting a cracked head (as 235 heads
are prone to do) and that was missed by the machine shop, I found a
replacement engine (thanks again Skip) to use the head. I took that head
and had it pressure tested and the surface checked...it checked out ok. So,
now the third new gasket went on with the second head. Same problem. That
pretty much, at least in my mind, left only the block as being the
cause....so out with the engine, and I began rebuilding the engine I got
with the replacement head.
The "new" block was able to be bored to .040...I also had the crank turned
to .010. Anyway, I put in new pistons, bearings, timing set, cam, lifters,
and everything was within specs. I mic'd everything, and also used
plastigauge to be sure. All clearances (bearing and rings) were perfect.
So, I don't think anything was wrong with the machine work. I am getting
good compression on all cylinders and all within acceptable range.
So, I have now rebuilt the engine with new everything at least internally,
and am still at the same point I was at in the beginning, ie. with small
bubbles getting into the water system, and judging by the way the water shot
out when I dropped the RPMs after the breakin, I suspect the system is
building up pressure somehow. The water pump is the original pump, and all
hoses are the ones from the old engine.
I have to believe my rebuild was done accurately. I followed torque specs
to the letter, and torqued the head following the torque pattern in the
manual, and did it in 3 stages. I took my time and was always careful and
thorough. The last time I rebuilt a 235, it was able to do two crosscountry
trips and all was good (until this saga with the bubbles and overheating
began), and have never had any other engine rebuild go bad. I consider
myself a pretty good mechanic, and follow the manual to the letter. This
problem has me totally stumped.
Assuming then that all the machine work was done correctly (block boring and
head checking), and my rebuild done correctly, where else might air be
entering the system? Could it be coming in from the water pump even though
the pump is showing no signs of an external leak? Could it be coming in one
of the hoses and not show any external signs of a leak?
The system is a zero pressure system...so, my thinking is that maybe somehow
air is able to be sucked into the system, but since the system itself
doesn't build up pressure, it is not "squeezing" water to the outside...just
sucking air. Does this make any sense to anyone? If so, how do I determine
what is behind this if not the head or head gasket? Can the system be
pressurized to see if the reverse occurs, in other words, if air can get
into the water jacket, if the system is pressurized, could it cause water to
follow the air path?
ANY thoughts are VERY much appreciated. If anyone wants to discuss this in
person, my phone number (cell) is 360-551-2490.
Thanks for your patience with this long post and in advance for any help you
can offer.
P.S. I am thinking of going ahead and replacing the water pump and all
hoses, but know I need a shortshaft water pump, which is not generally
available at the local auto parts but has to be ordered from one of the
truck vendors, but unfortuantely, I don't have time now to wait for it to be
shipped. SO....if I buy a long shaft at one of the local stores, can't I
simply have the plate that the fan and pulley mount to, pressed down the
shaft and then have the excess cut off? If so, as I suspect I can, can
anyone tell me how far down to have the plate pressed (ie. when to stop so
that the pulley would line up).
Rob
----- Original Message -----
From: "Rob J." <robertjacobs@ureach.com>
To: <old-chevy-truck@yahoogroups.com>; "_Oletrucks"
<oletrucks@autox.team.net>
Sent: Saturday, August 24, 2002 1:39 PM
Subject: [oletrucks] Engine troubles
> Got the 235 rebuilt...build went just fine. I got it dropped in just
fine,
> but am having trouble firing it off. I am getting spark, good
> compression...checked all cylinders and they range from a low of 105, to a
> high of 113. I suspect it is either a timing issue, or carburation. I
have
> the rotor set at dead TDC for the #1 cylinder...checked and rechecked my
> valve lash, but it just won't fire...actually, I am getting combustion,
but
> I just can't seem to get it to sustain and run on its own. As long as I
am
> pumping the gas, and using the foot starter, it is hitting, but as soon as
I
> let off either, it dies.
>
> The previous engine was a 235 overbored to .060 and was running dual
> rochester 1 bbl carbs. This new engine is only a .040 overbore, and set
up
> with the same carb set up. I suspect it may be running a bit rich since
> there is less total displacement, but should that be enough to cause it to
> just not run at all?
>
> How can I check various items to see what it needs to run right?
>
> I have a single intake I could put on, and could put points in instead of
> the Pertronix I am currently using (forgot to mention I was using a
> Pertronix dist on the last engine and it has moved to the new engine.
>
> Any thoughts or what I can try to maybe lean out the carbs without
resorting
> to changing out the jets (ie. just to see if that is the problem?).
>
> I put new spark plugs in (correctly gapped) and the rotor and dist. cap
are
> nearly new.
>
> I have to get this running as I am due to drive to Idaho from Seattle next
> Wednesday.
>
> TIA,
> Rob
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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