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The Gentleman's Express: Tech-Tips from the JIOC

Table of Contents

Recurving the Distributor

Author: CFF

Why recurve it? What’s involved? The purpose of recurving a distributor is to obtain the proper amount of spark advance in timing at the correct time in the rpm range. Let us assume that your distributor is in good shape and that there is zero play or ‘slop’ in its bushings. Assume that you also need:

X degrees initial advance-obtain by manual movement of thedistributor.

Y degrees primary advance - controlled by the vacuum advance unit

Z degrees secondary advance - governed by the cam, weights&springs

Now, you time your engine’s initial advance using a timing light. This is done by almost all service centers and does not involve the use of a dyno; just your car’s tachometer and a good timing light are all that are needed.

Primary and secondary advance: To correctly set these you have to know exactly when your engine needs Y degrees and Z degrees of advance and how much Y and Z equal, and which combination of vacuum units, weights, spring tensions and distributor ~cams will work best to obtain Y and Z. These figures can only be found out by using a dyno, although educated guesses can come pretty close, at least close enough for government work.

If you know your engine’s cam, its profile and rpm range, and if you’ve picked the correct intake manifold and carburetor to flow fuel properly for use with your cam, then you can buy a number of recurve kits from Chrysler to set your distributor up. And, after a few tries, you might just get it right! But, a quick trip down to a GOOD dyno shop and a few dollars investment will take all the guesswork out of it and you’ll be more pleased with the return on your investment.

On older engines things change, parts wear, profiles change, slop develops and you can no longer say how many degrees of advance you need because of these variations to the original specs. Again, you need a dyno.

So, to be specific, distributor curving simply means that your spark plugs are firing at exactly the right time when your valves and pistons are at the absolutely correct position in their cycle in order to obtain maximum combustion of fuel and maximum performance. The two go hand-in-hand! We could show graphs and provide specs but what’s good for my car orJoe’s car or even Harry’s car does not mean that it’s good for your car. So take my advice and next time you put out money for a tune-up, add a little extra to it and have the distributor recurved and dyno’ed to custom fit your car’s demands. You’ll be glad you did.

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Contents copyright 2008, 2009 - Jody F. Kerr

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