Ken,
According to this album date, I first filled an intake manifold's exhaust
crossover in 2007:
http://www.gmcmhphotos.com/photos/g3115-plugging-intake-manifold-exhaust-crossover.html
The rally we had at Lake Park, GA where we filled some more was probably in
2008 or so.
The manifold I first filled stayed on the 455, undamaged, until I changed
to the Cad500 a few years later. It's either just been installed, or is
about to be, on the 455 of a friend who's gotten disgusted with the "dog
house" required over his Edelbrock manifold. He'll use SS plates as well.
Another block off method that I haven't seen mentioned is one I heard Alex
Sirum used to do. I did it to someone's manifold with good results: Using
an ordinary router with a straight 1/4" carbide bit, cut a 1/8"x1/8" groove
around the exhaust port on each side of the manifold. Into that recess,
fit a piece of steel to sit flush with the manifold flange. AFAIK, that's
worked well.
The material I always used to fill manifolds was "Mondello Metal" -- a zinc
alloy, IIRC. I don't know whether his successors stil sell it. I've heard
of others using old aluminum pistons. The iron skillet and fish cooker
shown in my album would probably work with that also. I have no
experience, nor confidence in, the "hard block" compounds, even though John
Beaver, my local NASCAR engine builder uses it frequently in dragster
engines. The objective there is not to provide sealing, as is needed for a
cracked manifold. BWDIK?
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, Troy-Bilt APU, etc., etc., etc.
www.gmcwipersetc.com
On Mon, Mar 4, 2019 at 4:22 AM Ken Burton via Gmclist <
> You use the stainless steel block off plates to prevent very hot exhaust
> flow from the exhaust ports in the intake manifold. Then the intake is
> running at near engine temperature around 200 degrees. With out the
> plates the intake manifold in that area runs very hot and changes
> temperature
> constantly depending on engine load. Every GMC I have ever seen has run
> hot enough I have not measured the temp there but I would have to guess that
> it is constantly changing between 500 and 1500 based on engine load, and
> crossover exhaust flow under the changing loads. Restricted mufflers just
> exacerbate the problem. So put the plates in and resolve the problem.
> The manifold will then run at near constant engine temperatures of 200 F.
> or
> less.
>
> Filling the manifold after installing the plates is a different issue. It
> is only necessary if you are attempting to seal an existing manifold
> crack. I'll let others comment on what to use but keeping mind the
> filler material only has to withstand temps of a little over 200 degrees or
> so
> rather than the original 500 to 1500 that was necessary before the plates
> were installed. It seems to me that anything with a melting point of over
> 300 degrees ought to work. The rate of expansion between 0 and 200
> degrees when compared to the cast manifold might be a concern when choosing
> the
> filler. Choose the filler that others like Larry or Col. Ken have
> successfully used in the past and be done with it.
>
> I have no suggestion on which filler which is best. My intake is blocked
> and I never needed to fill the manifold. I did watch Col. Ken at a rally 10
> to 15 years ago with a cast frying fan and a big torch, heat up some metal
> and fill a manifold. I thought the metal was old pistons but it may have
> been the Mondello stuff.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
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