We had this debate in our shop a long time ago when we heard that guys were trying to use RTV the somehow adapt these PI intakes to a non-PI head. We thought it was a joke at first, but sure enough they were serious. Then due to popular demand from customers and friends, we were asked to use our flow bench to do some testing, I happily obliged.
The below flow data was obtained from a Superflow SF-600 testing a bone stock non-PI head, the same non-PI head with RTV between the PI intake and non-PI head, and the same non-PI head with the correct adaptor plates. I let someone else apply the RTV that had done it before, I have a professional reputation to uphold.
Stock non-PI head:
View attachment 403104
Stock non-PI head with the RTV:
View attachment 403106
Stock non-PI head with correct adaptors:
View attachment 403107
As you can see the graph displaying the non-PI head without the adaptor plates is indicative of what is referred to as boundary layer shear and some mid-lift tumble. That is why you see the mid-lift surges and poor overall flow compared to the adaptor plates. The mismatch between the non-PI head and the PI intake are responsible for this. Boundary layer shear and tumble not only hurt flow and velocity characteristics, but they also inhibit the the proper pressure wave sequence that aids in scavenging during overlap, which is critical especially on stock non-PI heads and cams and will hurt power. This power is hurt especially in the low to mid RPM's where most of your street driving occurs.
Then we spent an entire weekend on our neighbor's engine dyno (SF-901). The adaptor plates showed a 13 HP peak increase over the RTV'ed intake. Now that may not sound like much of a loss, but the area under the curve it's what's really important, especially on a street car. There was as much as a 21 HP increase under the curve between 2k RPM’s and 4500 RPM’s. Some shops we have spoken with have see a bigger difference under the curve than we found. That is very significant especially on a street driven car.
There are 3 main types of fuel injector spray patterns, conical, fan, and pulse stream. We have a fan type pattern. The absolute ONLY thing that will affect the type of fuel injector pattern is to change the type of injector. Raising the bottom of the intake manifold runner ½” off the entrance to the cylinder head intake runner has absolutely no effect on the fuel injector pattern. The air being drawn into the cylinder is moving at 550-600 MPH and sometimes approaching sonic speed. The instant the fuel leaves the injector, it is immediately pulled into the extremely fast moving air charge and immediately conforms to the geometry of the airstream. The extra ½” that the adaptors provide not only help to increase fuel atomization by keeping the fuel suspended for a split second longer, but they effectively increase the volume of the intake runner and therefore increase power by allowing more air/fuel to be drawn in during overlap.
Adaptor plates may not be cheap, but there is no question that they make more power and improve fuel economy.
I'll have to ask Matt or Ronnie if they remember. I would think I would have remembered if it was the Livernois adapator, but I really can't say for sure.
I've never read anything about them.
