[Cliff R]

"Cliff, Jim, With the knowledge you have now, of using the 041 cam in a 10:1 455 street engine. Are there somethings you might experiment with to make the 041 cam even better? or is it at the edge of doing the best it can, for what it is???"

For sure high ratio rockers really help that cam. I ran 1.73 Ford rockers on mine, pretty sure Jim ran Harland Sharp 1.65's (1.71 actual ratio) on his. It's also a huge cam, even in a 455, so if you want great idle quality Rhoads lifters are really going to help it. I would add here that I ran mine for quite a while with std Johnson HT-951R lifters, then swapped in the Rhoads lifters and immediately saw about 2" vacuum improvement at idle speed. The car ran no quicker with them, but my converter "flashes" well past 3000rpm's, so they are well pumped-up by then anyhow. They did improve idle and off idle smoothness, so I did see a benefit from them on the street and driving around in the pits. I would also add that an engine that idles smooth and strong against the converter also makes the car easier to stage without coming up against the brakes, so another side benefit for using them if you are a "foot-brake" drag racer.

The 041 cam is just a great cam for the 455 engine, maybe by coincidence or the fact that the engineers at GM really did know what they were doing WAY back in the 1960's. As good as the 041 cam is, it's not the best choice for the smaller 400 engines in most cases. Even in the big 455's, it really likes to be at least 9.5 to 1 compression, and 10 to 1 is even better. My old 455 with iron heads was right at 10 to 1, and it would manage any octane of pump fuel that I wanted to put in it. One of the first years I attended the Norwalk race with that engine in place I entered the street car race that required that we go off the track and run a 20 mile loop, then return to the track, fill up with pump gas right before we got back, and make 3 runs without shutting the engine down.

It just so happened we stopped at a station that only had 89 or 90 octane, no 92-93. It was one of the hottest days I can ever remember at Norwalk. LOTS of the other participants were dropping out with overheating issues, and one guy blew up his engine (high compression) making runs when we got back.

My 455 never even thought about running hot, overheating, and made three perfect runs back to back without shutting it off. After that experience I'm sure I could have ran closer to 10.5 or even a bit higher compression and still easily managed pump fuel with that engine.

Shortly after those runs we pulled the engine for the KRE head testing and HPP/Popular Hot Rodding articles that followed:

http://www.hotrod.com/how-to/engine/...-dyno-results/

http://www.hotrod.com/how-to/engine/...track-results/

With the new heads and higher compression ratio the engine still easily managed pump fuel, but I didn't play around much with anything less than 92 or 93 octane.

I still kept the original iron head testing in the back of my mind and decided to build the next 455 with smaller 76cc chamber heads, bigger cam, and 11 to 1 compression. Working directly with Dave at SD we got one of the first sets of his KRE ported heads and teamed them up with his "Old Faithful" camshaft. It turned out to be a great success, and the current 455 easily runs on 87 octane fuel at 11 to 1 compression. I even tried adding higher octane fuel to it at the track, and it slows it down a few hundreths, so it really likes and runs well on lower octane fuel.

This sort of throws a monkey wrench into the proverbial "brick wall" theory of 9.5 to 1 compression for pump fuel, and I think the folks that make that remark are talking about 92-93 octane, not 87 or 89.

I certainly do NOT recommend for folks to do the "high compression pump gas deal", but we have shown that with careful engine building, and full control of timing/fuel curves that you can EASILY manage pretty high compression in one of these engines. It involves tight quench, and the right cam more than anything else. Of course you have to be able to keep the engine cool, so a small radiator and electric fans may not be in your future with that deal. I tried a big single electric fan for a while and it kept killing the battery trying to keep the engine cool on race days in really hot weather, so I went back to the stock set-up and all has been fine since.

The camshaft topic ALWAYS gets kicked all over the place on the Boards, so for the most part I sit back and watch the threads run. I have been paying close attention to folks who have came up WAY short in power with 455 builds, and they almost ALWAYS have chosen the smaller cams mentioned in this thread. I have also had a number of those engines brought here to tune, or set up carbs for them, and to date haven't been impressed in the least by any of them. I knew those cams weren't making the grade, so finally we had a professionally built engine by a well known shop try that deal, and we ended up getting dyno sheets on it, which prompted me to go public with the information. I certainly hope that it helps some folks out with cam choices for these engines......Cliff