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

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.

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.

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.

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.

Double post. First post did not show up for a while.

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.

i have 4 nos ones. just have to find them

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.

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.

You were talking about cast pulleys? I was talking about the stamped steel ones cracking. Sorry if I misled you.

Yes, the part number I posted is for 1967-68 3 groove cast pulleys used with short water pump configuration. As far as I can come up with from research, they will work for 1965-66 also, but not correct part number.

I didn't know you were talking about a cast pulley. Maybe you could use a billet aluminum pulley and paint it cast iron gray. Mine is stamped steel. I have access to lots of CNC equipment so I might make a plate to go inside mine.

That would be cool to reinforce yours.
I found a billet pulley on-line last night in Black, but it doesn't seem to exist anymore. I should call the manufacturer and ask.

Well you all scared me enough to do something about it.

Very nice, Freddie. Maybe you can market that...:dunno:

Save your dust up and get an oem one....the gm pieces are not much more than the repo unlike the 291ab

3869978 is the correct original part number for all 65 Z16's (which all had PS), for all 66 L78's (regardless of whether the car had PS or not - if the car doesn't have PS then the third groove is just empty - don't ask me why they didn't use a 2-groove pulley), and for 67 L78's with PS.

Had exactly the same situation. Can't understand the disclaimer considering the original application is for 425 and 450hp cars, although looking the other posts seems to answer that question. I ended up getting the same pulley from Heartbeat.....without the disclaimer. There appears to be Chinesium and American made versions available but identical in appearance. I do have an original but it looks like it has been repaired as per the descriptions above regarding durability, so I opted not to use it.
Sounds like there is an opportunity for someone to offer a more suitable product.
In the meantime, won't be revving my 427 L72 to 7K rpm

I see I never followed up on this. I did call the manufacturer/distributor and the grooves are standard depth, so mostly a stock replacement, or dress up part.

I've been running standard pulleys up to 7200 RPM without any problems. As long as your brackets are sturdy and the pulleys are lined up correctly you shouldn't have any problems.

I've seen OEM ones crack also FTM. Freddie's fix is the way to go. Relieve the center out about 0.005 to 0.010 and leave about a 1/4" clamp area margin around the perimeter. You can sometimes hear a cracked one. It will click sometimes.

Freddie, can a billet aluminium or steel one be made to mimic the original deep groove 3 pulley part? I guess it would need some testing.....although it looks like the other products including the OE pulleys where never really tested!

Also (and I think someone has already pointed this out) surely GM knew about this and put out a better pulley on later Hi- Perf big blocks.....like LS6 454?

I guess when they stopped using the short water pump they no longer used cast iron pulleys. As far as I know all of the pulleys for the long water pump were steel.

Looks like 3921923 Crank Pulley is listed for all big blocks that used the deep groove.. L72, L78, L89, LS6. This could be in correct, as it's info I got off the web...:dunno: