1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

four port 13b how rare ?

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Old Feb 27, 2004 | 12:15 AM
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From: LaCrescenta Ca/Fort Hood Tx
four port 13b how rare ?

what year car do these SOB's come in?
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Old Feb 27, 2004 | 12:28 AM
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Ryan
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early truck motors and TII...why??? Need one? I got one for sale and you could also use SE housings and 12 end plates and come out 4 port.

-Ryan
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Old Feb 27, 2004 | 12:29 AM
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any turbo 7

my car

Rx4, Repu, Old Cosmo?

or you can make one from a 13b and 12a end plates.
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Old Feb 27, 2004 | 12:31 AM
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NOt quite..
old 4 port 13-B = RX-4, RX-5 Cosmo, REPU.

Now for the GSL-SE, use the 12-A intermediate and side plates and you will end up with a 4port 13-B.

TII and TT are 4ports
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Old Feb 27, 2004 | 12:31 AM
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hey we posted at the same time! ! !
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Old Feb 27, 2004 | 12:36 AM
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Old Feb 27, 2004 | 12:38 AM
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Ryan
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u postwhore...
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Old Feb 27, 2004 | 12:41 AM
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Old Feb 27, 2004 | 11:58 AM
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The '74-'75 4-port 13B motors had the largest stock ports of the old-school 13Bs. In 1976 the ports were restricted as a response to the fabled "energy crisis" of the '70s. Also, 4-port 13b motors were produced for the Japanese market much later. These motors have fairly restrictive intake porting, the primaries being the most affected. The Japan-port motors have the added advantage of using newer-style gas-nitrided side and center housings, which are actually easier to port as the metal is softer once the gas-nitrided layer is passed.
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Old Feb 27, 2004 | 12:07 PM
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The R5 13B I mention sometimes has four ports and nitriding with rotor housings that were meant for cats. No US spec car ever had an engine like this.
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Old Feb 27, 2004 | 12:20 PM
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Originally posted by Wankelguy
The '74-'75 4-port 13B motors had the largest stock ports of the old-school 13Bs. In 1976 the ports were restricted as a response to the fabled "energy crisis" of the '70s.

If that is true, why are the intake ports on a 76 RX-4 and RX-5 Cosmo’s are taller than the 74’s.
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Old Feb 27, 2004 | 12:41 PM
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Intermediate ports are. The end plate ports are the same height. For what reason? Hmm I know the Cosmo had a reversed runner intake manifold where the primaries had long runners into the end plates, and the secondaries had short runners into the intermediate plate. Maybe this was part of Mazda's AP (anti pollution) program in '76?
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Old Feb 27, 2004 | 12:49 PM
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i have several 13-B intake manifolds (74 - 76) at home. I will take pix
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