Originally Posted by phunk

OK Well I was unable to start a thread this week... between a batch of VHR fuel rails that were fighting back the entire time and removing / cleaning / packaging my greddy turbo kit for shipping, on top of the typical weeks work... i just couldnt get deep into making an official thread this week. I am leaving town tomorrow and coming back Tuesday.

Really there are 2 major decisions to make that are currently keeping me from running full speed ahead.

1: Continue with adapter plate based design, or run all the way down to the cylinder heads.

2: How to deal with the oil filler neck and cap.


Now that I have a "good" aluminum casting source, I am not really bothered to just go all the way to the heads.

Going all the way to the heads will allow for a more optimized and controlled runner shape, length, and taper. It will also be slightly lighter weight. It will cost more, and take longer. Precisely how much more and how much longer is difficult to gauge. Its not the CAD design work I am worried about, its the prototype to production casting process I fear will take much longer to finalize. This direction will almost definitely require proprietary fuel rails.

Leaving it as it is, and adapting to the factory lower intake runners will cost a little less and can be finished up a bit quicker. The adapter design is already "done" and fits, and if I use it, I only intend to make some minor improvements to it (along with adding a 3rd fuel rail option). I could have a fabricated prototype done in a week or two. This would allow existing rails to be used, meaning no major fuel system reworking.

As for the oil filler neck. It is *directly* in the way of cylinder 1. To work around it will mean compromises in the runners and plenum shape. I have some ideas for working around it but it would certainly be "easier" to cut it off. I put that in quotes because its obviously easier as far as the intake manifold... but now it requires removing the valvecover to cut it off and block it off, and then an alternate oil filling location has to be improvised. I expect a new valvecover from Nissan is probably around $200-250.

Once I come to terms on these issues, I can move along pretty quickly. Most of my boundaries are already in CAD... so once I know exactly where I am headed I can finish the drawing and start building.