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PERA’s Core Corner
Help, Mr. Wizard! I Don’t Want To Be A Rebuilder Any More!
By Roy Berndt
In this month’s Core Corner we are going techno and we’ll look at an issue that has come up often enough
that it is certainly worth mentioning. It has to do with the GM/Chevrolet Gen III small blocks – the 4.8L, 5.3L, 5.7L and 6.0L engines. The first of these was released in 1997 as the 5.7L/LS1 Corvette engine, and the truck applications for the remaining displacements followed in 1999. The component that we are taking a look at is the crankshaft.
So how hard can this be? Hard enough that you may want to paraphrase those familiar words of the little dreaming turtle that used to be on the old "Rocky and Bullwinkle" show: "Help, Mr. Wizard I don’t want to be an engine builder anymore." Then, of course, the
Wizard uttered "Trizzle trazzle truzzle trome, time for this one to come home," and all was safe and well again.
Let’s begin with a little history. The Gen III small block, although still called a small block and still a push rod engine, was in fact a clean sheet development and the crankshaft was no exception. The crankshaft material is nodular iron and cast in the green sand process. The design incorporates variable fillets/radii for improved fatigue strength.
It actually uses both a 1.30 mm radius on the outer edge toward the counter weights and a .60 mm radius on the inboard or journal side thereby allowing an increase of .4 mm of bearing length. Try and duplicate that! Then in the rear of the crankshaft (see illustrations A and B at left and below) there is a complex pre-assembled two-piece
encoded crankshaft position sensing ring. Why was it put in the rear? To minimize angular position error from crankshaft torsional deflection.
Total Indicated Run-out (TIR) in excess of .020˝ of this ring will render this engine unable to start or run. In fact there is no timing adjustment on these engines; you start the engine and go let it idle in the parking lot and allow the learn process to take place. The sensor will read off the ring and measure increases and decreases of crank speed based upon the correct firing taking place.
Since this stamped steel, spot welded two-piece reluctor ring (illustration C on page 18) is by no means the Rock of Gibraltar and it would take little impact or load to permanently deflect or damage, and that there is no alignment notch or key to align for replacement (+/- 2 crank angle degrees), and it sits on a very narrow ledge (see illustration B), we have a serious problem.
There is a happy note to all of this, however. The reluctor ring is available both OE and aftermarket.
Of course, now we have the install problem. Well, this is one of those times where we get to applaud the entrepreneurial spirit of the
automotive aftermarket industry. There is an installation tool available to properly align the reluctor ring indexing upon the dowel pinhole of the crankshaft and an indexing hole in the ring (see illustrations C, and D and E).
Match the hole and pin indicated in the illustrations by the diamonds (for the ring and tool); and then match the hole and pin as indicated by the square in the illustrations for the tool and crankshaft. Once the reluctor ring has been heated to 450° F all you need to is install and match (see Illustration F). It’s that simple.
The lesson here is that unless you can put this crankshaft in a cocoon and keep all harmful sources away, you are better off removing the ring and throwing it away. That way you know that you’re always covered and you will not get into hours and hours of no-start diagnostics, and then come to find out that you have to pull the engine out to replace the reluctor ring.
Special Note: Without the help and tenacity of Larry Ericsson at Crankshaft Rebuilders and David Monyhan of Goodson this article and tooling would not have been possible. Also the first person to email me as to the name of the little turtle from the Bullwinkle show will get a free release of SourcePERA – a $500 value.
I guess there is one thing that we can always count on and that is change. Not only has PERA gone through change on the administrative level, but we have moved the research offices as well. The research offices are now located at 836 S. Arlington Heights Road, #329, Elk Grove Village, IL 60007. The new phone numbers are (847) 258-3727; the fax number is (847) 258-3671. Email and Web site addresses are still the same.