[DeTomaso] Questions on 4v heads

[cengles at cox.net]

Dear Jack,

About twenty years ago I used MPG intake and exhaust port plates. While I thought that they made more power, that was mostly a hope and a guess and it was never measured. In my review of exhaust port plates, they are usually described as improving exhaust flow and they usually *imply* improved power, but I could never find any dyno evidence of actual benefit.

Recently Dan Jones' Great 351C Dyno project actually tested the MPG Stinger Port "plates". They are bronze and have a solid tongue or stinger of brass that sits low on the floor of the exhaust port. Dan's dyno testing showed (I am going on memory here and I have slept since he posted it) only about 5 horsepower improvement. It was way less than 20 hp.

I think that properly used with a complimentary intake manifold and cam, intake port stuffers can give an honest 20-30 hp. I think that the HP benefits with the exhaust port stuffers is much more modest. [....but five hp *is* hp....]. Cost per the MPG website is $90 for a set of intake&exhaust stainless steel port plates and $175 for a set of Exhaust Stinger Port Plates. Again, as I glanced at the website they allege 20 hp and 20 ft-lbs improvement with their steel set, but not dyno sheets are shown nor provided...........

Warmest regards, Chuck Engles


---- JDeRyke at aol.com wrote:
> In a message dated 10/25/10 7:19:04 AM, dave at damardirect.com writes:
>
> > Hi Jack,
> > What is your opinion on exhaust port plates? W/o intake port stuffers?
> >
> Never actually used either; I got lucky in 1990 and found a lightly used
> pair of SVO aluminum heads that already had closed chambers, adjustable
> valvetrain and raised ports. Generalizations are worth what you pay for them ($0
> here), but my understanding on 351-Cs is,
> 1)- intake port stuffers can make maybe 20-30 bhp extra (~10%) on a real
> 350+bhp engine, at some rpm levels, depending on the intake & carb they're
> paired with.
> 2)- Exhaust plates do less than intakes but can pick up maybe 10-20 more
> bhp (~3-5%) on a real 350+ horse engine, again over certain rpm levels. Lots
> of caveats- including starting with closed-chamber iron heads, semi-equal
> length headers and more open exhausts than stock Ansas. There are 2 designs I'm
> aware of: cast-stainless or cast-bronze to take the heat, and are bolt-ons
> between the heads and header flanges, not welded, pinned or glued.
> Port plates are Band-Aids for head design problems. Both intake or exhaust
> plates need replacement or at least tuning of other engine parts for most
> drivers to even notice them except that they may change the exhaust note. A
> couple of vendors sell these; I'd call around and ask them what effect they've
> seen on something like your engine- and have a parts list handy 'cause they
> will ask whats in there. FWIW- J DeRyke
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