74-85 12A / 13B 4-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 done 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 exhaust 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".
Click here for the FAQ on how the porting is done.
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 (74-85 4-Port) to Add to your engine order:|
|SV-PORT-S4P||Porting of four intake ports and both exhaust ports|
|Other (Partial) Options: for housings sent in, or rebuild of previously ported engine -|
|SV-PORT-SEXH||Street Port two exhaust ports only|
|SV-PORT-SINT||Street Port four intake ports only|
|74-85 4-Port Street Porting Images|
Ported exhaust vs. original
Also, please remember that any porting is not emissions legal, and may result in your vehicle failing emissions testing.
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