A 72 owner is rebuilding engine and he was suggested to change its harmonic balancer due to aging (?). What is the correct unit for base manual 72? What problems could affect the balancer supposing it was extracted with the correct tools? Thanks in advance Roberto, NCRS #30019, RMC
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Re: 72 harmonic balancer
Roberto, The first thing I'd look for is the angular relationship of the keyway slot and the timing mark on the outside diameter. I know that 68's on back these two features are in line. Not sure on later vettes. There was a point in time that approximatly 6-8 degree shift took place. Maybe another reader can help you on that point. But if the rubber is not all cracked and the keyway and timing mark are in proper position, I would reuse it. -
your article on the NA9 CA emissions option
Robert, I read your well-written article recently about the NA9 CA emissions option with a fair degree of interest and curiosity. You see, I own a '70 CA car equipped with the LT-1 engine option; the tank sticker shows the NA9 evaporative emissions option. My question to you, since you have had experience in finding correct parts, is with the correct Holley carb. and cannister. Are your sources current with this type of one-of-a-kind part(s), or are we relegated to the car show flea markets...??? Thank you in advance for you input. Jeff B.Comment
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Re: your article on the NA9 CA emissions option
Having helped Roberto source his parts, I guarantee you it's a labor of love! There are some things you ought to act on NOW and perhaps you might want to contact me off-line. Roberto pointed out that about 10% of the '70 build was NA9 equipped. The interesting point in trying to find what's right/get what's right for Roberto's car, is former NTL, Terry McManmon, who has 'nosebleed' level judging field experience mentioned he could count on one hand the number of properly configured NA9 cars he'd seen in his career!!!! Tells you a little bit about how how well to factory stock these cars were maintained over their lives....Comment
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Re: your article on the NA9 CA emissions option
Well, Jack has explained it very well, it was very difficult to locate some parts, sometime on an exchange basis, a bit of luck and Uncle Jack who did a wonderful job helping me. If he suggested you to contact him, DO it because some parts are like the whales... Any way this proved something which is frequently mentioned here. Joining the club, being active and learning as much as possible is the way, a fun way, to improve the car and make friends. If I can help you in any way please let me know. Which # is your 70? All my best from Argentina, Roberto NCRS #30019, RMCComment
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Re: 72 harmonic balancer
Roberto----
The original balancer for the 1972 base engine was GM #6272221 and, incredibly, it's still available under the original part number for a GM list price of $63.12. There may be some deterioration of the elastomer ring on the old balancer, but generally, I have found these to be quite durable over the years. That's because they are not exposed to high heat conditions and, due to their location and design, are not exposed to sunlight, which is the arch-enemy of rubber.
More of a problem on balancers is grooving of the balancer hub front seal surface. There are "repair sleeves" available to repair this damage without the need to replace the balancer, and, although they would seem to have the potential to cure the problem, I've found that they just don't work. And, I've tried every concievable and recommended method of installing them, including the use of various sealers and locktite. The seals still end up leaking. So my practice now is: grooved balancer hub sealing surface=new balancer. That's an equation which avoids "re-do".
Incidentally, the timing mark change that Gene Manno referred to in his previous post occurred in 1969 for small blocks. 1968 and older balancers cannot be used on 1969+ engines without adjusting the timing mark. And, vice-versa, of course.In Appreciation of John HinckleyComment
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Re: your article on the NA9 CA emissions option
Roberto; Many thanks for your reply. My build date is an early one - Jan. 20, 1970, Vin # 01268: a cortez silver coupe with 51K orig. unrestored miles and a wonderful example of "what they were like"....Comment
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