Another weekend, and a few more intake tests on my 428CJ. See my previous posts for a description of the components in this motor. So far on this engine I have tested the following intakes: Blue Thunder 428CJ, Edelbrock Streetmaster, Edelbrock Performer RPM, Factory PI, Edelbrock F427, Edelbrock Performer, and Edelbrock SP2P. Here's a chart of the 7 intakes showing the HP curves:
And, here are the torque curves:
As you can see, the SP2P is simply not a performance intake, but if you are looking for torque at 3000 RPM and below, the SP2P may be your manifold. Also, although the Performer also did not acquit itself well as a performance engine intake, it did narrowly post the highest torque number of all the intakes, and from 3000 to 3500 RPM torque is very strong with this manifold. The Streetmaster, in port matched condition, kind of takes over from 4000 up to 5400 RPM or so, but it falls of more rapidly than the Performer RPM and the BT, which are showing more HP at the end of the pull than the Streetmaster.
Here is a table summarizing the peak and average (3000 - 5500 RPM) results for torque and HP:
One thing that stood out in these tests is that the PI intake showed third best for peak HP, moving ahead of the BT intake. For my brother's 428, the BT intake peaked at about 5 HP higher than the PI, but in this engine's case the PI sneaks ahead of the BT by a couple of HP. Average HP and torque numbers still favor the BT over the PI, though.
After running all these tests now I was hoping to be able to draw some conclusions about open spacers vs. 4 hole spacers on dual plane intakes, for this engine. But, the data is mixed. Here is the spacer comparison for the Blue Thunder intake:
Clearly, in this case, the 4 hole spacer is superior. Now, look at the Performer RPM with this same set of spacers:
In this case, it is not so clear cut, and in fact the open spacer looks a little better than the 4 hole. Here is the PI intake spacer data:
Again, I think the open spacer looks a little better. Finally, here's the F427 data:
Of course, in this case the 4 hole spacer is clearly superior. At this point, without running this test on other engines, its difficult to say whether or not to use an open spacer under the carb on the dual plane intakes. The theory is that high RPM performace will be improved with an open spacer, but obviously in some cases this is true, and in others its not.
One other intake modification I wanted to investigate was the effect of port matching the intake to the heads. I will be port matching both the F427 and the PI intake sometime this week, to add to this data, but so far I have this data for the Performer RPM intake and the Streetmaster intake. Here are the unported vs. port matched curves for these two intakes:
Obviously in the case of the Streetmaster, the improvement is very clear, but not so clear in the case of the Performer RPM. I will continue to test other manifolds for this characteristic.
I'm hoping to test a couple more intakes next weekend, perhaps the port matched versions of the PI and F427, and maybe the Sidewinder or the Offy 360. However, its my wife's birthday next weekend, and she is bent on having me build her a chicken coop. Yes, she wants to get chickens; she says if I can have a dyno, she can have chickens. The absurdity of the whole thing is a little too much for me right now, but in any case I may have to call off the dyno activity next weekend, to build a coop. My neighbor says, "Glad I'm not you!" In any case, I'll have more dyno results in two weeks at the latest.
1968 Shelby GT 500 Convertible, all aluminum 489" 1030 HP Supercharged FE
1969 XL Convertible, 460
1969 R code Mach 1, 706 HP 511" all aluminum FE, 10.457 @ 127.47, 2005 Drag Week Winner, Naturally Aspirated Big Block