RDI Street 392 Crate Motor - Wicked Windsor In A Box, Part 2

Total Seal Test
After four days of rigorous dyno testing it was time to check the cylinders for compression pressure and leak down. Remember four cylinders of this engine are equipped with regular rings and four with Total Seal rings. The chart below shows how each type of ring fared. The leakage measure on each cylinder is shown within the bore and the compression pressure above or below. The cylinders with Total Seal rings in can easily be identified, as they are the ones with a zero leakage rate. Not only did the leak down prove to be far superior but, as you would expect, so did the compression readings. The cylinders with the Total Seal rings delivered, on average, 11 percent higher cranking pressure. With results like this why would you want to use anything else?

Shown here is a comparison between the cam used in a typical Ford 392 crate motor and RDI's Custom Crate motor. The key points are the superior output of the computed cam came from shorter duration but more appropriate valve opening and closing events. Along with this the computed cam also called for a 1.7/1 rocker on the intake as apposed to the 1.6 used by the factory motors.

Conclusions
Although our RDI motor did very well we did not actually see the best it would do if you were ordering a replica. First in anticipation that the motor would make about 475-480 hp I elected to test on 1 5/8 headers. At the power level achieved we would probably have had better results on 1 3/4 inch headers from about 4,500 rpm up. Also, the fact we had regular rings in four of the eight cylinders meant four cylinders were not being sealed up as well as they might. It would not be unreasonable to suspect our motor could be 2-3 hp down on that account.

Second all our testing was done on the mineral break-in oil. From past experience I know changing from a quality mineral oil to Mobil 1 synthetic is consistently worth 3-5 hp. What this means is, as good as the figures achieved were, a customer for one of these motors could be looking at 510 hp plus. Although this motor would be completely at home in a working truck or a Crown Victoria because of its excellent low-speed manners (what a stealth motor this is) we are going to put it into a 5.0 street/weekend warrior so look out for the subsequent story down the road.