[steve25]

What level of power are you looking for out of this 480 plus CID motor , and maybe even more importantly what do you see the average and peak rpm range of this motor being ?

Conversions / modifications that lean back the roof of the runners to gain more volume are not a bad thing in and of itself, because it does help to equalize the runner length difference between the overall length of the roof path and the floor path within the whole intake tract , and this at least in theory helps peak air flow.

In terms of tuning for the rpm of peak HP Your dealing with two major factors with mods like your looking into.

.1) how it effects pulse tuning rpm of the intake .

2) the rpm of ram tuning.
Ram tuning is highly dependent on the overlap of the Cam and if the exh header is tuned real well so a vacuum is presented to the cylinder while the intake valve is open during the number of degrees the Cam has for overlap.

Unfortunately whatever you do to a NA motor to maximize the power in what is always a narrow power band will detract from the power level that there could be either above or below that narrow rpm band .

Here’s an example for the pulse tuning effect provided by the Superflow corp in there general information section of there supplied flow bench guides.

There are 3 Harmonic pulses in a V8 engine you can choose to tune for.

Make note of how tuning off of the 2nd Harmonic produces not only the strongest pulse, but the widest rpm range of usefulness .

If your running your motor to 6800 rpm then your 2nd Harmonic tuned length would be 19.4”.

If you where shooting for a peak Hp rpm of 7500 then that length drops down to 17.6”.

The runner length in your heads is around 5”, so now look at the stock average runner length of the intakes your thinking of using on this motor.

Here’s the chart and the formula.

The shown example formula is using 8000 rpm as an example.

Just be sure to note that this is total intake runner length from the back side of the intake then up thru the centerline of the head runner and then on up thru the centerline of the manifold runner until it terminates at the start of the Plenum.