Quote:
Originally Posted by PDUB
I know less than most of you about this stuff, but this is the way I would have generally guessed, as well... emphasis on guessed! I would not be able to predict a value for the difference, though... no way.
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That's kind of the point.
A cam grinder who doesn't work with engine builders on specific applications, or doesn't do dyno testing, won't have competitive products. Even then, unless you do back-to-back testing with the same engine, you won't learn much and it could be that you won't have the upper hand.
My first scenario with the 445 was a test that I did because practically every shelf cam is either a single pattern (intake and exhaust durations the same) or a split pattern with a 6° split. I can basically show with dyno testing that neither one of those are optimal for practically every FE engine out there. Would they work? Sure. Is there more to be had without losing anything? Absolutely.
Most FE head exhaust ports stink, putting out about 65-69% of the intake side's flow. There are exceptions to that, but all of your factory heads will stink and even the newer Trick Flow heads are less than desirable in that respect.
The difference in horsepower between the two was 11 hp and 13 lb-ft of torque, keeping the manifold vacuum exactly the same, street manners the same, etc. The winner was camshaft #1 there.
When hydraulic rollers first came out for the FE engine, we were reaching "walls" of about 6000 rpm where the engine just simply couldn't pull any higher. FE valvetrain is much heavier than most other engines, with some having 3/8" stem valves, large valves, heavy adjusters on the rear of the rocker arms, etc. The shelf cams from one of the biggest cam manufacturers used aggressive lobes because they were used to grinding cams for SBC's and other engines with lighter valvetrain. When we started experimenting with custom cams, the lightbulbs came on and we figured a bunch of stuff out. As of now, I have taken FE's with hydraulic rollers up to 7500 rpm.
The second scenario that I posted was a result from a custom cam grinder who wanted me to do business with him. He emailed me and asked me if there was an engine that I was working on that he could me a custom cam to use. If it worked, I could pay him for it. If it didn't work, I could send it back.
I told him that I had a 351C bracket race engine that I was building and already had a cam that I spec'd for it, but he was welcome to send one. He proceeded to ask all the engine specs and I gave him all the data that he asked for, and even sent him the specs for the cam that I had ground.
I degreed both cams in at build time and even ordered pushrods to favor *his* cam as the base circle was slightly different. On dyno day, I tried both cams within a couple hours of each other because I had a two piece timing cover and was able lift the lifters up out of the bores with some clothes hanger wire so that I didn't have to pull the intake.
The cam that Straub Technologies spec'd made 587 hp @ 7750. The cam I spec'd (camshaft #1) made 615 hp @ 8000. That's a difference of 28 hp at peak and there was a 10 *average* hp as well.