Which would produce more power a ported and polished set of NPI heads or just regular PI heads with no port and polish.
This is what I'd recommend as well. The PI heads will give you a nice bump in compression, where the NPI heads will outflow them. So PI for a N/A or Nitrous car, ported NPI if you plan on adding a power adder.I think this is the way it would go down...if I am wrong someone please correct me.
The ported and polished NPI heads would flow better than the PI heads if done right. The PI heads would give you more power because of the smaller CC that increases the compression on NPI motors. So on that note what do you plan on doing in the future if you see a power adder then I suggest the worked NPI heads. It's not mainly the heads that hurt the NPI motors it's a combo of the heads, cams, and intake but mostly the intake, and cams.
That's been common knowledge for about 10 years, I don't know where you've been. The problem with NPI heads is actually their inability to handle larger lift cams without going into coil bind. This can be remedied by cutting the valve seats and guides down and installing offset retainers.Sorry, I'd have to see the numbers from a flow bench on that one. Nothing i've seen between the two in ported form confirms that. Just speaking from experience though.
Sorry, I'd have to see the numbers from a flow bench on that one. Nothing i've seen between the two in ported form confirms that. Just speaking from experience though.
Wow thanks for the info guys and as always especially you Bullitt I really dont have plans for either NOS or Induction as of now just wanted to get in that 300whp ballpark and have me a decent daily driver because as of right now its out of commission completely. I have a set of PI heads I picked up for 40 bucks but they have a small gouge on them and I know that the tolerance is very limited on them but the guy at the machine shop I checked thinks theyre definitely salvageable but for 400 bucks or so and Ive seen some people are running NPI heads P&P with PI intake and cams and making decent power so I was wondering what my best bet would be paying 400 bucks to P&P my NPI's my PI's or buying some complete PI's with no problems from what you said about the Hp gains from just the PI intake and PI cam I can see my options are very open as to what I can do.Renegade Racing was the first to discover that the NPI's actually flowed better at low and high lift than the PI's when ported quite a few years ago. That was backed up by numbers from Fox Lake, and then again by Nick from Modular Headshop.
This is hardly new or unheard of news in the 4.6 world. Johnny Langton and Renegade Racing were the pioneers of going fast with an NPI, and were the first to really try it. Him and Kris Danner were the ones who came up with the couple different ways to put a PI intake on the PI engine as well, and even epoxied a few PI intakes so they would match up with the ports on the NPI heads, since that and cams are the real problems with the NPI setup. I've seen 9rwhp just from swapping to a PI intake, and 12rwhp from putting PI cams in an NPI engine.
Great info on all the numbers but as I said before. I was just speaking from experience at the track.If I am not mistaking you can get on modularheadshop.com and check that for yourself cause I do believe Nick tells a little about the differences in the heads, pros and cons. If you wana call Nick out on his knowledge on the heads then I would just have to say your an idiot lol.