215 CAM BEARING OIL PORTS

jon-p · Sep 10, 2017

Jim Blackwood said: ↑

forumI would go to 5/8" personally. The V6 pickup from TA uses a 5/8" tube so that would match. The aluminum blocks have more metal there than the iron ones do. With a piloted drill you are pretty safe against breaking through, and if you did it could be heliarced. I drilled my 340 block out to 9/16" and that has worked out well, so you could get by with that but I don't see any reason not to go full sized if you're going to the trouble of having the bit made. I had enough metal in my iron block to do it, but I made up the 9/16" bit and then would have had to make up another to go to 5/8" so I didn't.

Jim
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I'm planning to attempt a home made piloted bit as per some instruction I've received on "The Bench" forum. Next step is the
TA booster plate to repair the end clearance which doesn't look that bad and a V6 pickup tube. Then..... oh well, one step at a time.
Can't waste time; the Goodguys SE Nats is October 20-22, and I do love getting to play for at least 3 laps on the 1 1/2 mile Charlotte speedway.

jon-p · Sep 10, 2017

300sbb_overkill said: ↑

Its actually an off the shelf Comp Cams XFI grind, still works great even with a carb! This is the cam I have;

https://www.summitracing.com/parts/cca-12-464-8/overview/

This cam calls for 1.6:1 rockers to get the lift it has. I got away without having to use a small base circle cam because I used 5.7" rods and it helped that the cam called for the 1.6:1 rockers because there is less lobe lift so no rod to cam interference. When I change the springs I want to try some 1.7:1 roller rockers(might as well, the new springs I have are good to .600" lift) with this cam if the new springs don't get me in the 12s if I can ever get back to working on my cars!

With even more lift the engine should be a little bit more efficient and possibly get a bit better mpg? Instead of using more duration to keep the valve opened longer with the trade off of less low end torque, I like to open the valve higher to get the port past its max flow lift so the valve hits that point twice. Just because the valve went past the point where max flow is doesn't mean that flow stops, it just doesn't flow anymore than max but still flows close to max.

The farther past max flow the valve can open the faster it will be in the max flow lift range filling the cylinder with more air and fuel. This means with less throttle angle the engine will make more power in the cam's low RPM power band because of the lower duration it has. That makes it able to cruise on the freeway at a lower RPM without lugging the engine down in o/d.(that's how I see it anyway, seems to work pretty good even if I am wrong how I explained it?)
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Good theory and the results speak for themselves. Conventional wisdom says that overlap kills fuel economy so it appears that the short duration with less overlap works with a lot of lift to fill the cylinders. Exceed max flow lift asap and put more area under the lift/duration curve.

Speaking of max flow lift, I raced a 2000 cc 4 cyl Pinto in Sports Car Club events. The heads were really lousy , max flow was at .400"lift. No real horsepower potential so I just ran 600 lbs under legal weight. Makes up for no horsepower.

If IRMA misses Atlanta, I'll be back at it tomorrow.

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215 CAM BEARING OIL PORTS

jon-p Little olds

jon-p Little olds

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