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Re: [oletrucks] vacuum advance / lines

To: "Oletrucks" <oletrucks@autox.team.net>
Subject: Re: [oletrucks] vacuum advance / lines
From: "Allen Jones" <jonesal@u.washington.edu>
Date: Mon, 11 Dec 2000 10:57:59 -0800
The 848 head gives you the highest compression ratio using a stock set-up.
You can really boost up the compression with pop-up pistons, but that's
another story.  I decked the head a bit to get a little more.  I ported, it
may or may not have helped.  Carefully choose your cam, depending on how you
want to drive your ride.

Definitely change the studs so that you can install the spacers (I used
spacers).

The best thing you can do is find a 261 block if you're doing a full
rebuild.  I found a good one for $150, bored it out, and am pretty darn
happy I did (*everything* from your 235 will fit except the connection rods
[their section modulus is too small]).  Need to drill 3 holes in your 848
head and you'll have a pleasing runner.

If you're not a member of Inliner's International.....join!  Then you'll
have access to Pat Smith, a walking encyclopedia on 235/261s, as well as
many other knowledgeable inliners who have worked on these beauties for the
last 50 years:  www.inliners.org.

Good luck!

Allen in Seattle
'50 3100
Inliner No. 2235

----- Original Message -----
From: "William M. Schickling" <wschick1@twcny.rr.com>
To: "Allen Jones" <jonesal@u.washington.edu>
Cc: "Oletrucks" <oletrucks@autox.team.net>
Sent: Sunday, December 10, 2000 6:20 PM
Subject: RE: [oletrucks] vacuum advance / lines


> Allen,
>
> Thanks.  It will be a while before I'm ready to make these changes. I
> haven't decided whether to try porting the head or not. I have the 848
> casting and I've heard that's a pretty good head to start with. Got any
> specific recommendations there ?
>
> My manifold currently doesn't have studs long enough to use the spacers
used
> on the original manifold. Pat's article strongly recommends getting the
carb
> up away from the heated manifold. Are you using spacers or are your carbs
> mounted right to the manifold ?
>
> Bill
>
> -----Original Message-----
> From: owner-oletrucks@autox.team.net
> [mailto:owner-oletrucks@autox.team.net]On Behalf Of Allen Jones
> Sent: Sunday, December 10, 2000 6:58 PM
> To: oletrucks@autox.team.net
> Subject: Re: [oletrucks] vacuum advance / lines
>
>
> As I am running Rochester's, yes, I have drilled the holes out (modified
the
> off idle circuit(s)).  Plugs eventually go back in (a lead plug on the
> inside and an aluminum plug on the outside, if I remember correctly), or
> you'd have bad gas/vacuum leak(s).  The tech article is pretty good (but
> brief) and there is a companion one out there running around too that is
> also good.  Can't remember where I got it, but it's floating around,
perhaps
> from Inliner's International (and it discusses this circuit vacuum vs.
> manifold vacuum stuff) or maybe from Pat directly (he's *very*
knowledgeable
> and a pleasure to speak with).  Be very careful and very patient or you'll
> ruin a perfectly good Rochester in one pass of the drill ("hole" size will
> vary depending on your manifold, carburetor, cam, and head porting).  The
> modification is the difference between night and day with multi carburetor
> intakes and results in some nice torque off idle into your power range
(and
> some good neck snap off idle).  It's fun!
>
> Allen in Seattle
> '50 3100
>
> ----- Original Message -----
> From: "William M. Schickling" <wschick1@twcny.rr.com>
> To: "Allen Jones" <jonesal@u.washington.edu>; <oletrucks@autox.team.net>
> Sent: Sunday, December 10, 2000 3:31 PM
> Subject: RE: [oletrucks] vacuum advance / lines
>
>
> > Allen,
> >
> > I printed out a couple pages from the web (Sorry, I'll have to go look
up
> > the URL) from someone that describes the modification your are talking
> > about. First you knock out some plugs then drill out the remaining
holes.
> > Alright, I went and found my print outs.
> >
> > It's an Inliners article from a Pat Smith, called: Improving
Driveability
> > with Multiple Rochesters.
> >
> > http://www.inliners.org/tech/tech4.html
> >
> > Pretty informative, but only talks about the carbs. Have you drilled the
> > holes out ?  Do the plugs go back in or do they stay out ?
> >
> > Bill
> >
> > -----Original Message-----
> > From: owner-oletrucks@autox.team.net
> > [mailto:owner-oletrucks@autox.team.net]On Behalf Of Allen Jones
> > Sent: Sunday, December 10, 2000 3:58 PM
> > To: oletrucks@autox.team.net
> > Subject: Re: [oletrucks] vacuum advance / lines
> >
> >
> > I'm not sure I agree with that.  With two carburetors, vacuum at the
port
> at
> > the base of the carburetor(s) will drop way off and you won't get near
the
> > advance you need.  I highly recommend going with an advance line
directly
> > off the manifold.  That's what I did with my Offenhauser dual set up,
and
> > unfortunately, I still don't get as much advance as I'd like (with
either
> my
> > HEI or the stock distributor w/ new advance bell).  But to answer your
> > question, yes, a vacuum advance dist is preferred.  Also, because you
> won't
> > be drawing near the volume of air through the carburetor, you will, in
> some
> > cases, need to modify the low end circuits so that they deliver enough
> > gasoline.  As an example, if running dual Rochester's, you will need to
> > drill out the off idle orifice so that there is no hesitation (because
of
> > low vacuum, and hence not enough petrol).  Regarding the Mallory, it
> depends
> > whether you're running dual point vacuum from the old days (acceptable
> > units), pure mechanical advance (troublesome), or newer vacuum advance
> > Mallory dist (won't touch 'em).
> >
> > Good luck!
> > Allen in Seattle
> > '50 3100
> >
> > ----- Original Message -----
> > From: <Passnb4U@aol.com>
> > To: <wschick1@twcny.rr.com>; <oletrucks@autox.team.net>
> > Sent: Saturday, December 09, 2000 6:33 PM
> > Subject: Re: [oletrucks] vacuum advance / lines
> >
> >
> > > In a message dated 12/9/00 5:32:40 PM Pacific Standard Time,
> > > wschick1@twcny.rr.com writes:
> > >
> > > > List,
> > > >
> > > >  My winter project is to rebuild a 235 for my truck. I am putting a
> dual
> > > >  intake manifold on and was wondering about the vacuum lines. each
> carb
> > has
> > > a
> > > >  spot for a vacuum line and the manifold has a spot for one as well.
> Is
> > it
> > > >  better to plug the carbs and run a line from the manifold ? Or try
to
> > > >  connect both carbs up to the vacuum advance ?  I have seen on
either
>
> > the
> > > >  stovebolt or inliners page that keeping a vacuum advance, even with
> > dual
> > > >  carbs is the preferred setup. Is this true even with the Mallory
dual
> > point
> > > >  or hei distributors ?
> > > >
> > > >  Any and all feedback welcome.
> > > >
> > > >  Bill Schickling
> > > >  1940 3/4 Ton
> > >
> > >
> > >   You'll want to use one off the carb' ported vac., assuming you're
> using
> > an
> > > original type distributor.
> > >
> > >   If you use intake vacuum, then intial advance will be too much, and
> > you'll
> > > get part throttle pinging...and if you set the timing back to
> compensate,
> > > your total advance will be too low for any mid to upper RPM use.
> > >
> > > Mike
> > > 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
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959

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