Does anyone know the exhaust opening/closing timing (EO=?° BBDC, EC=?°ATDC) for a 3rd gen 13b with the exhaust sleeves removed and the housings ported smoothly? Also, what is the cross sectional area of this port? Is it round or rectangular?

Any info would be apreciated,

Glenn
'93 CYM

 

Anyone? RICE RACING?

 

When you take out the sleeves ONLY, it shouldn't affect the timing at all.

Depending on how you port the exhaust, you can change the timing. The further up you port, it'll lengthen the exhaust stroke. Careful since you'll have more overlap as you increase the exhaust timing window.

My exhaust ports have a bit of a longer window, but I believe the major benefits will come with the tapering of the port.

Once you remove the sleeves, you can port any shape you'd want for the exhaust. From what I can see on my housings, the sleeve is rectangular. The box exhaust port style is old school. I do like the slight "D" shape better since it reduces area of apex seal flex as it rides over the exhaust port.

There are threads on porting exhaust ports with/without sleeves.

I can measure the stock exhaust port cross sectional area when I'm at home. I'm pretty sure I have some spare housings that aren't ported.

IMHO, you don't need to port the exhaust to the point where you would remove the sleeve.

J