N47 into an N42

[bernie lomax]

can the sleeves inserted into the N47's exhaust ports be removed? if so, is it a fairly easy job or a real time consuming pain? if the sleeves were removed from the N47, would I now have rectangular shaped exhaust ports & essentially an N42 head? is the only other difference between N47/N42 the EGR opening?

 

if more low-mid range torque from my pretty much stock 78 L28 is the gameplan, would ditching the N47 & buying an N42 head be the thing to do? or should I work w/ the N47 which I already have? proposed modifications would be a header, a mild cam & possibly shaving the head

 

comments are appreciated

[PalmettoZ]

Hey-

 

I am currently building a 3.1L motor and have both and N42 and N47 head that I can use. I opted to use the N47 for a couple of reasons. Firstly, the exhaust difference in flow is relatively the same according to flow data posted by 1fastz on this website. The liners don't restrict the flow, although they appear that they would.

 

For the intake side of the heads, the N47 head has a slightly different shape to it with a D shape in the port which helps with the torque. I built my N47 with new Stainless undercut valves and did an unshrouding of the combustion chamber at a machine shop. Also blended the ridges inside of the ports where the valve seat meets the port on the short side radius as well.

 

I think that this is all that you would need for the street unless you want an all out racing head which comprimises low end torque for HP. I have not finished the build yet but plan on around a 290 duration with 480" lift cam.

 

The second reason that I used the N47 was that it uses the internal oiling (a cam with holes in the lobes for lubrication) instead of the spraybar that the older heads used. My N42 has this spraybar and I am not that crazy about the design.

 

Also for what it's worth I think it would be very difficult to remove the liners and since the data shows that it is not a restriction, why bother. If you want more info on it, search the N42/N47 threads.