Deve,
I'd just leave it on it's not going to hurt anything. After sending the
reply I realized it could also be an aftermarket fix for low upper oil
pressure due to a worn rear cam bearing. The oil tube to the head runs
off the rear cam journal so a worn bearing could cause lower pressure.
I don't know on the 261, but the 400 had to have steam holes because the
cylinders were "siamesed" and water could not circulate between the
cylinders, so these holes let it circulate up the cusp were they met and
out into the head. They probably should have been called "steam
prevention holes" :-) It way be that some 261's had siamesed cylinders.
--
John Dorsey
Wauchula, FL
'49 Chevy Panel http://www.strato.net/~jrdorsey/truck.htm
'52 GMC Firetruck http://www.strato.net/~jrdorsey/fire/fire.htm
'51 Chevy suburban http://www.strato.net/~jrdorsey/burb/
Deve Krehbiel wrote:
>
> Thanks John! Great info. I will try to unclog the proper passage, but since
> this is setup for outside oiling, I wonder if there is any harm in having
> two paths running at once just in case the other gets clogged again? As I
> recall steam holes were so the thermostat would register the heat from the
> rear of the engine faster on those really cold mornings.. or something like
> that.
>
> Thanks again!
>
> Deve
>
> ----- Original Message -----
> From: "john dorsey" <jrdorsey@strato.net>
> Cc: "Ole Trucks" <oletrucks@autox.team.net>
> Sent: Sunday, December 03, 2000 11:00 PM
> Subject: Re: [oletrucks] 235/261 Heads
>
> > Ok,
> > To make the 235 head work on a 261 you have to drill the "steam holes"
> > into the water jacket of the head. The easiest way is to take the 261
> > gasket and mark the hole location on the 235 head. It's the same thing
> > you have to do to use 350 heads on a 400. Sometimes I think that Detroit
> > never comes up with anything new they just recycle old ideas! Lets
> > see... Chevys used to use center bolts on the valve covers, then they
> > went to edge bolts, now they are back to center bolts on the Vortecs :-)
> >
> > The outside oil line was an aftermarket accessory. I see them pop up
> > NORS on the un-named auction site about monthly. Awhile back a guy had a
> > whole box of them. I don't remember the brand, not GM but something
> > you'd get at a FLAPS. I gather it was a really common mod on the low
> > pressure dipper engines, probably when the passages were getting clogged
> > from that non-detergent oil :-)
> >
> > --
> > John Dorsey
> > Wauchula, FL
> > '49 Chevy Panel http://www.strato.net/~jrdorsey/truck.htm
> > '52 GMC Firetruck http://www.strato.net/~jrdorsey/fire/fire.htm
> > '51 Chevy suburban http://www.strato.net/~jrdorsey/burb/
> >
> >
> >
> > Deve Krehbiel wrote:
> > >
> > > I can accept that there is an oiler port for the rockers on the outside
> of
> > > this engine, but I dont see that on all 235's. This is a 261 (1959
> model) so
> > > maybe its normal. I am trying to ascertain whether or not the 261 motor
> has
> > > a 235 head on it. This might explain why the PO was having trouble
> getting
> > > oil to the rockers. When using a 235 head on a 261, there are two holes
> that
> > > need to be drilled in the head. I got that from Jim Carter. What I dont
> know
> > > is, what are those holes for? Maybe one of them is to provide an
> internal
> > > path for oil to get to the rockers? Since the manifolds are off, I
> figured
> > > now would be a good time to see if anyone here knows.
> > >
> > > Thanks again
> > >
> > > Deve
> > >
> > > ----- Original Message -----
> > > From: "R. Welch" <rwelch@ionet.net>
> > > To: "Ole Trucks" <oletrucks@autox.team.net>
> > > Sent: Sunday, December 03, 2000 4:23 PM
> > > Subject: Re: [oletrucks] In defense of the farmer
> > >
> > > > Well, I thought someone already posted to this issue. On an old 235 I
> > > had,
> > > > the rocker arm assembly wasn't getting any oil. I was told running
> the
> > > > tubing from the block up to the fitting in the head provided direct
> oiling
> > > > and was a quick fix short of tearing down the whole block and finding
> > > where
> > > > it was plugged. I don't think its any big deal - it seems to have
> been
> > > > commonplace. Now, why the hole is in the head to provide this relief
> to
> > > > begin with I don't know, but it obviously was put there by the factory
> so
> > > I
> > > > assume it was foreseen as a potential problem by GM.
> > > >
> > > > Bob Welch
> > > > '56 Cameo
> > > > '55 Belair
> > > > Bartlesville, OK
> > > >
> > > > ----- Original Message -----
> > > > From: "Deve Krehbiel" <dkrehbiel@kscable.com>
> > > > >... I am trying to figure out why my farmer
> > > > > friend decided he needed a different oil line going up to the rocker
> > > > > assembly.
> > > > > Deve
> > > > 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
> > 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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