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Old 07-10-2023, 11:32 AM
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Default L78 crank pulley, need help, experience, opinions

I've been attempting to find a 3869978 deep groove crank pulley to run on a 1970 454 engine with swp and PS in my '66 Chevelle.

I see HBC has one made in the US. No mention of any restrictions.

Camaro Central lists the same appearing pulley, made in America, but with a disclaimer.
Made in the U.S.A.

*Important Warning Concerning Crankshaft Pulleys. Stock replacement, aftermarket stamped steel or cast iron pulleys are not designed to exceed 400 horsepower or 6000 RPM. Using reproduction pulleys on engines in excess of these limits may result in catastrophic disintegration of the pulley causing severe damage to the engine, cooling system and body parts. Camaro Central assumes no liability for damages caused by improper usage of pulleys. Please be sure to install the pulley properly to avoid damages that could occur from improper installation or exceeding the recommended RPM limitations.

Is anyone running one of these pulleys ? Any experience with these aftermarket parts is welcome. I don't want to end up with out of round or inferior crap that is going to blow up at 6,500 rpm.
Thanks, guys
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1970 Chevelle SS
1966 Chevelle SS
1967 Camaro ss/rs
1938 Business coupe, street rod
2000 FXSTS, original owner, 13k miles
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Old 07-10-2023, 01:11 PM
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Don't have any experience with that pulley in particular, but my experience with aftermarket repop pulleys is not good.

Also, HBC doesn't make this stuff. Would be shocked if it is not the identical pulley listed by Camaro Central.

Put out some feelers for an original pulley.
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Old 07-10-2023, 01:27 PM
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Original would be my first choice, but they are difficult to find and my "disposable income" account is down to dust. My part time job went away 15 months ago. I really need to find another part time "parts" job this winter.
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Old 07-10-2023, 02:45 PM
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The Pennington F.A.S.T. racing crew has had similar experinces to what was described above with that type of reproduction pulleys. The centers cracked and broke out of them much faster than the original GM pulleys did. Of course, they are making way north of 400 horsepower, but even so, maybe changing them out should just be considered periodic maintence.
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Old 07-10-2023, 03:33 PM
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That repop pulley is $300 at HBC. The last real one I saw sell on Ebay was $275 plus $18.00 shipping.

John, are the real GM pulleys also coming apart? Just reading this: "The centers cracked and broke out of them much faster than the original GM pulleys did."

If so, maybe aftermarket billet aluminum? I don't even know if they are available.
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Old 07-10-2023, 03:36 PM
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Double post. First post did not show up for a while.
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Last edited by Lynn; 07-10-2023 at 03:36 PM. Reason: Double post
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Old 07-10-2023, 03:59 PM
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What about putting a reinforcement plate inside the pulley? Would that prevent it from cracking? I'm using a standard groove original GM pulley on mine and shifting gears at 7200 RPM. Now I'm wondering if mine needs to be reinforced.
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Old 07-10-2023, 04:00 PM
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i have 4 nos ones. just have to find them
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Old 07-10-2023, 04:33 PM
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The GM pulleys normally lasted a year year or more, but eventially they cracked too. At least they weren't coming completely apart. The reproductions were starting to crack after one or two races, and some of them had the centers break out of them. They must be more brittle than the GM ones were.
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Old 07-10-2023, 05:29 PM
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Quote:
Originally Posted by big gear head View Post
What about putting a reinforcement plate inside the pulley? Would that prevent it from cracking? I'm using a standard groove original GM pulley on mine and shifting gears at 7200 RPM. Now I'm wondering if mine needs to be reinforced.
Freddie, aren't your pulleys formed steel ? The pulley for the swp is cast. I'm surprised you don't have belts flying off the standard pulley's. Maybe I'm OK with that too. I will definitely change out the alternator pulley for the deep one, as that seems to be the source of that belt coming off.
I'm not way north of 400 hp, but it is a healthy 496, so probably 550 ? Seems the L88 and modified L72's should have been more than that, back in the day. Did they have issues with the cast pulley cracking ? I guess most of the that stuff came out more after the introduction of the lwp in 1969 and formed steel deep grove pulleys.
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