Q: Ram Air and 400
Some History, 400 Specs, and Ram Air Information.
A: I owned a 1968 convertable, ram air, and campaigned it as pure stock on the drag strips a while.
I had contacts in Pontiac engineering and was told that when Delorian was approached with the idea of a 160MPH car he said OK, but it has to be “safe”. That was the context of the trouble GM was having over the Corvair and “unsafe as any speed”. So a few specific changes were made that you may know, but didn’t mention. The rear spring shackles have triple welds. That is, they laid down two more over the origional one. The front end wishbones were lengthened longitudinal to the car. I think the rear attach point was 13 inches behind the axle. Gives you an awful lot of strength. None of this was on the Camaro or 350 for that matter. Exclusive to the 400. The Ram Air engine was made to hold together up to 8000 rpm. Special anti-pumpup lifters. But the rev limit was 5100, only because oil would accumulate under the valve covers faster that it could drain down via gravity. I blew a valve cover once, so point proven.
You may also have a problem with sustain high revs getting enough fuel. The problem is the float valve opening is too small. You could substitute the 1/8d. seat and float from the Buick Roadmaster and pretty much eliminate the problem. I also intalled an electric pump at the fuel tank as a booster. don’t know if it was really necessary, but it couldn’t hurt. No econo car this. At full song, I could actually watch the gas guage move – and high test at that. Four 1/4 mile runs looked something like 5 gallons. Street mileage with the 4.11 rear axle looked like about 8mpg. After I put back the standard rear (3.08) it “Jumped” to about 12. Horsepower is BTUs and BTUs are CCs of gas. I also put in the Corvette logrithmic throttle linkage. That gave you only up to 1/2 throttle until the last 1/8 inch then punched in the rest. That made it more drivable on the street. Before in the rain, it was almost impossible to not break the rear end loose when starting up. In effect, you drove around on the front barrels only, unless you really wanted to turn loose the ponies. With the 3.08, I did take it to 165. It redlined at 150, but the short blast into orbit was safe enough, provided you backed off quickly. The acceleration up convinced me there was plenty left. Turbulence was pretty rough. Made the ride a bit like a speedboat in chop. Needed better aerodynamics. I figure the 98 reprizes probably are better in that regard. Kind of fun picking on “Whale Tails”, but be a bit more respectful of Ferrari’s and HemiCuda’s. The RamAir had a special cam with more overlap and .100 more lift. To control that, they doubled the valve springs. You have to do that because the valve cam ramps are forced into becoming pretty severe. That’s a big part of the reason why just adding the ram air intake to the standard 400 doesn’t give you the hammer. Under standard conditions the RA intake does add about 15 HP though from volumetic efficiency conciderations. Hope some of this is helpful to provide a bit different dimension and understanding.
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Content last modified: January 19, 2014 at 6:10 pm