Stefano, Talk to Dan Marvin and John Norman. They will give you pretty specific guidance and they're local. When I had my 2 liter head done by Dan, I asked him to do whatever mild porting/manifold matching that made sense for a "breathed on" street motor. These guys have a lot of experience (as do many list members). Eliminating steps is a good detail, ultimately, it's a detail that may not show up on a dyno, depending on what else you've done to the motor and where you want the power curve. I just moved and found my copy of Ricardo's "The High Speed Internal Combustion Engine" and look forward to reading it. A lot of work has been done since both that and Phil Irving's "Tuning For Speed", but it's a classic. I have a couple of copies of TfS, including the one I bought as a teenager from CycleWorld books. Stevan Thomas San Francisco Bay Arear 73 Berlina 83 GTV6
In a message dated 5/12/2011 11:16:03 AM Pacific Daylight Time, [email protected] writes: > Does it make sense to do any grinding on the inside of the > manifold at the mating surface on either of these? I wonder > how exact the head port and manifold port are to each other. > I wanted to alleviate the possibility of a step on the exhaust > side. I was wondering if the head prep on the Nord engine > has widened the port at all (I can't remember exactly the > prep, but it may have been just a polish on the exhaust > since I did not increase the valve size there). Since the TS > is stock, I was wondering if a little grinding wouldn't help > anyway, introducing a negative step. > > I was thinking about using one of those tri-stone things you > put on a drill and taking off a few mm of this edge. I don't want > to do anything stupid, so I would never attempt it before asking > those who know more than me. I have not even purchased > this stone attachment. > > I have never heard anyone discuss this, so I am prepared > for the wrath of the digest. Fire away if this is a bad idea > or just not worth it. -- to be removed from alfa, see http://www.digest.net/bin/digest-subs.cgi or email "unsubscribe alfa" to [email protected]
