84-85 13B 6-Port "Street Porting"
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Port "timing" in a Rotary Engine is equivalent to cam timing in a piston engine.
To change intake port timing
(as in street porting), the upper edge of the intake port is raised (later
intake closing and longer open duration), and the side is moved slightly
out (it can not be moved very much due to the corner seal and
apex end piece needing support).
To change exhaust port timing, the upper edge of the port is moved up (later closing) and/or the lower edge is moved down (earlier opening) which also gives more exhaust duration.
The port runners also are
This was a VERY simple explanation of what constitutes "street porting"
"Street Porting" began its' wide-spread use back in the 70's. On those early 4-port engines there was substantial amounts to be gained in porting. The intakes could be moved up a bunch, and the exhaust ports required a lot of work due to most of them being quite small.
Intake: The 6-port non-turbo 13B
engines (made from 84-92) are a totally different story for porting. The front
and rear side housings have the auxiliary ports in them, and the center housing
has very small ports. Additionally, there is not a lot of casting thickness
behind the upper part of the center port. This means if you go too far, you hit
the water jacket, and the housing is now junk. If the two smaller ports in the
end housings are made into one LARGE port, it is WAY too big. Therefore, the
end ports are not changed much, and the majority of the time is spent on the
We have a more detailed page showing the procedure at: 6-Port Intake Porting.
Exhaust: At least the exhaust ports are "normal" and do lend themselves to porting.
Do not expect substantial gains in power from "street porting" these engines - it's a worthwhile addition IF the engine is going to be apart anyway, but definitely not worth taking a running engine apart just to street port it.
We still adhere to our engine building policy of not wanting to increase the power of the base "A" level engines (using used rotors and used rotor housings). We therefore will only port "C" level and above, engines.
|Part Number (84-85 6-Port GSLSE) to Add to your engine order:|
|SV-PORT-S6P||Porting of all six intake ports and both exhaust ports|
|Other (Partial) Options: for housings sent in, or rebuild of previously ported engine -|
|SV-PORT-SEXH-TB||Street Port two exhaust ports only|
|SV-PORT-SINT-6P||Street Port all six intake ports only|
|84-85 Street Porting Images|
Also, please remember that any porting is not emissions legal, and may result in your vehicle failing emissions testing.
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