Red96GT said:
Ok I see. I remember talking to DropTopPony a while ago and him telling me the limiting factor on our 4.6s is the bore and how small it is. Since our stroke is already nearly that of a 351, it is where our displacement and power comes from.
Another question I have is why a tune is highly recommended after the swap? Air/fuel ratio, timing, etc? I'm not trying to cut corners, I am just wondering what they would be making adjustments to.
If its raw naturally aspirated power, then sometimes displacement can have an effect on hp...BUT....the 4.6 having a small bore and large stroke is not entirely limiting. This would be equivalent to large bore small stroke....Power is found in the overall "heads/cam(s)/intake" combination, and of course the extra displacment via longer stroke, bigger bore certainly helps as well....
When it comes to the 4.6, it already has a big stroke..and it would make more power with a slightly larger bore....but then you need a good head (ie 4v head as apposed to 2v head) to help feed the cylinders with air.....
But overall, a topic like this can get very deep in to the technical mumbo jumbo...
Youre second question, why have the car tuned...well since you are allowing the engine to ingest more air = need in more fuel (A/F ratio), and playing with the timing etc to maximize the power safely.....you can run around with the PI swap without a tune, but you'll benefit more with a tune....