Me too, Chuck. And on the 455 I rebuilt in '98, there were "EGR nubs" (or
some such terminology) in the ports. At that time, the fad was to grind
those smooth, so I did so. At the time I had only 850 miles of GMC/Olds
experience, so I have no idea what the effect was. But, I understand that
the overall port smoothing which was in vogue at that time is no longer
considered advisable -- something about generating turbulence for mixture
improvement.
That should be enough to stimulate some discussion.
Ken H.
On Wed, Dec 16, 2020 at 7:27 AM Charles Boyd via Gmclist <
> Good morning Ken, it is my understanding that all Olds small block
> intakes will bolt up to the 403. I have always “gasket matched” any intake
> manifold that I install. I take the intake gasket that I plan to use and
> lay it on the intake with the bolts in the holes to line it up and mark the
> area of the intake inside the gasket with a sharpie. I then use a Dremel
> grinder to remove the marked area to match the intake with the gasket for a
> smoother flow pattern over the jointing point. If I have the heads off I
> also use the same gasket to match the head intake ports the same way. I
> believe this is called “porting” in the hot rod terminology.
>
>
>
>
> > I just got a note from another GMCer to the effect that ALL Olds 403
> > manifolds are interchangeable, car or motorhome. The ports are identical
> > too. He's running an aluminum manifold from a 307; BUT, it must have the
> > letters "AG" cast near the thermostat or it will have small ports.
> >
> > JWHS (Just What He Said).
> >
> > Ken H.
> >
> >
> > On Wed, Dec 16, 2020 at 2:03 AM Ken Burton via Gmclist <
> >
> > > Intake and oil pans are the same except Toro has a provision for an
> EGR on
> > > the intake. When used on a non-EGR installation like a GMC, you put a
> > > simple 2 bolt plate over the EGR port (Jim K has them). I have a
> Toro one
> > > right now soaking in my parts washer. Been there for a long time. I
> need
> > > to pull it out of the washer, bead blast it, and paint it. I have
> seen a
> > > couple of them installed on GMCs. At one GMCMI rally Dick Paterson
> donated
> > > a Toro manifold for the raffle.
> > > --
> > > Ken Burton - N9KB
> > > 76 Palm Beach
> > > Hebron, Indiana
> > >
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>
> --
> C. Boyd
> 76 Crestmont
> East Tennessee
>
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