SM, those of us who have raced know the differences in the design characteristics of various parts. No matter what anyone thinks, every part out there is going to shine in a given RPM range and utterly fail in others. We didn't cut corners trying to run wee camshafts, because those cams were designed to work at low RPM ranges. Those wee cams were always cheaper than the 55 MM cores we used, but they simply were not designed to work in the RPM ranges we were running. We didn't run dual plane intake manifolds with vacuum secondary carbs, because that stuff was all designed to work in a lower RPM range. There was no sense in running parts designed to work from 1500 - 5000 RPM, when we were shifting the car well in excess of 9000.
But for some reason, people want to build a motor for a street rod that will likely never see the north side of 4500 RPM and they want to use all of those race components to do it. And that completely bamboozles me.
When we sit down with a clean sheet of paper for a new motor, we start looking at what we're wanting to do with the motor and then we start selecting parts for it. If a motor is going to be run from idle to 4000, why in the world would we ever want to use a cam with duration numbers in the 290's at .050, with 1.125" of lift and separation angles in the 118° range? I spent enough years doing this stuff that I can tell you why - people want that drive-in idle quality, that's why. Never mind the motor won't make enough power off idle to pull a sick whore off a toilet stool, they want that rough idle. People forget their motor is going to spend the majority of its life running <2500 RPM, they just want that killer idle. But then they pitch a fit, because they don't want to spend upwards of $400/set for valve springs, because they are suddenly ready to admit they never plan to rev the motor over 4500.
Then they pitch a fit when they learn the open pressures on those springs are going to kill standard cam bearings and their blocks are going to have to have the tunnel bored for 55 MM roller bearings. They weren't planning on spending that much on their entire "rebuild", so they suddenly start backing down on cam designs.
When a guy would walk in the door wanting the "biggest cam I can run with a stock converter and stock valve springs," I knew we were dealing with a real engine-building genius.
We did a motor for the boss' '32. 355 CID, a steel crank, a set of ARP bolts in some carefully selected stock rod cores we polished the side beams on, a set of flat top pistons that netted us 9:1 CR, a 278° Cam Dynamics Energizer cam, a set of our drop-in replacement springs, stock pushrods, a set of stamped steel 1.5 rockers, a vacuum secondary 600 Holley on a Performer intake, with a 6 quart Corvette oil pan and a standard oil pump. Dave Coan built a converter that was about 500 RPM loose and there was a bone-stock T-350 in the car. The motor dynoed (a Superflow 901T with the big brake) at about 330 HP and 310 ft/lbs. of torque. It had a noticeable idle, but was still very friendly off idle. Actually, it would rip your head off, if you could make it get hold of the ground. Parts the average street rodder would sneer at, but the car would dance circles around anything sitting in the other lane at a stoplight. You could stand on it at 30 - 35 MPH and the car would get sideways in tire smoke. With the air conditioner running, BTW. Now, tell me, why would anyone want to give up that much fun by trying to run race parts on a street motor? The car would idle at a stop light forever, rip your head off when the light turned green and it never balked at running pump gas.
SM, I'm guessing something between 80% and 90% of everyone else has already quit reading by now. But we both know a short block is nothing more than the foundation of an air pump, whereas the cam, cylinder heads, intake, carb and headers are only going to determine the RPM range where that air pump will be the most efficient. And yes, it only makes common sense to carefully select those components so they will not only work well with one another, but will also sing harmony at the RPM range I am planning to run my motor in.
But since I have this old 327 sitting here, I think I'll run a DMPE M5 18-71 high-helix with a C.G. three hole composite hat and a Waterman Mega Bertha pump on it. Because, you know, it looks so cool. It's got stock, cast pistons in it, so I can still run pump gas, but I want to build about 50 PSI with it, so it will make really good power and produce that blower scream. Do you think I will be able to get it to idle smoothly at 500 RPM, so I can run a stock converter? And since I'm only driving this thing on the street, I won't need those big valve springs and 0.500" pushrods, will I? I can't afford to have the spring pockets opened up, so I'm hoping the stock springs will work.
