Thread: tappet adjustment 350

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Streets,

I was TRYING to say your trick with the holes in the valve covers is really neat, and of course a milling machine would really do a clean job! In thinking it over I will try using a hole saw and hope it doesn't snag. You often give amazingly good suggestions mixed in with some other information which I don't always get. Here's my explanation, I find with every piece I add to my 350 that I am on totally unfamiliar ground with little transfer from VWs, MGs or flatheads, particularly all the brackets and so forth that I did not get with my bare block. Thus I try to trade some relatively abstract information that might apply to automobiles for information I need on SBC and TH350. I thought that anyone who might have struggled with a positive ground system would appreciate knowing why and to most British car fans the Lucas electrical system is infamous, but those who already have negative ground didn't even know there was a problem!

Screamer63,

If the picture on your signon is your jeep I can see why you have a question. Most CB antennas are "dipole" antennas consisting of a whip and a coil on the base. The EMF signal to the base coil energizes the whip during transmission, BUT the whip is only the top half of a figure-eight shaped oputput wave. On most vehicle mounting a mirror image of the top half is generated by a reflection of the EMF wave off the metal of the body shell. In your jeep you have a roll cage instead of a smooth metal trunk lid or cabin roof, AND on a jeep there is little space for a mount on a side of a fender. There is another consideration. If you mount the whip on the back of the roll cage you will have to make some modification of the soft top for rainy weather? If you mount it on the tail gate it should be vertical so that the figure-eight shaped wave is vertical. Maybe the most efficient location electrically would be in the middle of the hood since that would have a nice surface to reflect from, but I have never seen a jeep with a CB whip in the middle of the hood! Then again the hood would be near ignition parts which might interfere. I would ask around among other jeep owners and find out what they are using. In "theory" I think the best place for a CB antenna on a jeep might be somewhere along the midline of the hood, but you probably would have to use RF-suppressing ignition wires! As a practical matter you might have to install it vertically on the lip of the tail gate and hope the small surface of the tailgate will form the other half of the dipole figure-eight EMF field. One good thing is that CB antennas seem to work on a variety of mounting surfaces anyway somehow, but the signals will be cleaner/clearer if there can be a reflected wave. Then again I seem to recall that you can buy a CB antenna which is a whip with the coil half way up the whip (a bulge in the middle of the whip). In that case the antenna forms the full dipole figure-eight shape and would work anywhere you install it, even on the top of the back pipe of the cage. Try to get that kind of an antenna if you can. Then again, the military certainly solved this problem long ago using radios on the earlier jeeps before the Humvee, although they used other wavelengths with whips optimized for those wavelengths, some of which required fairly tall whips. Finally, if there is no other option just mount the whip to an angle iron next to the trailer hitch, but I doubt if that is optimum.

StuCool,

OK you say that the 1/4 turn gives slightly more duration, but may require more frequent adjustment. That is what the earlier article said but I guess that means that the oil trapped in the lifter is "hard" enough. I was confused (just slightly) in that I thought the slight pressure leakage in the lifter would provide a "squishy response" and it might be better to work from the bottom of the lifter. Anyway StuCool has answered the question and so 1/4 turn should give slightly longer cam duration! I guess I will ball park the settings cold just like the boat motor and then try the 1/4 or 1/3 turn when hot using my very own valve covers with holes!

Don Shillady
Retired Scientist/teen rodder