hey



so i pulled my engine down today (bad water seals) its a 13b bridge port rx4 style, and i was going to get the exhaust ports opened up but when comparing them to a racing beat template mine were huge.



i will post pics up tomorrow of the port itself but what they have done is removed the exhaust sleeve and then cut the port into a large rectangle.



so my question what difference in charactiristics does a rather square port have over the usual "D" shaped port?



any insight would be much appriciated.

 

I think folks may be waiting for those pictures. And is it a turbo or NA? The "D" shape gives a longer smoother pulse and is a bit quieter than the flat floor port. The flat floor if opening early will reduce torque down low. If it is huge as you describe it will be generating lots of overlap as well. Good for top end power, but also very bad down low. Probably not as good for a turbo either. And makes more noise.



In the turbo there will be back pressure nearly all of the time, and staying close to stock timing is one way to keep a bit of off idle torque for street driving. Making the port wider without changing the timing gets you the flow you want for the turbo without screwing the off turbo low speed torque. Leave enough to support the apex seals.



Thats a start.



Lynn E. Hanover

 

Im glad you said that because I did just that. Its always been advised not to it because of seal support, but I felt within reason it would be OK.

 

hey



been mad bussy at work hence why the pics are a bit late but yeah,theres a ruler in there to help give ya's an idea of just how big it is .

 

sorry and its also an n/a engine