Just started my TH magna and have a wonderful noise. The crankshaft pulley outer ring (containing the grooves for belt for aircon and alternator) and the crankshaft pulley (wheel on crankshaft) have decided to separate ways. Has this happened to anyone before. Is it simply a matter of mating the two back together again or do I have to get a new one/secondhand to place in?

Any assistance appreciated

After speaking to the mechanic brother. Found out that I've killed the harmonic balancer. How hard is it to replace on a magna (only done 351's before)? Or are there any traps for young players?

Thanks in advance

Mate it's pretty easy. Not sure weather it's easier to take off the acc belts first, I didn't, Jam the pulley with something and try and crack the bolt. I think you can put a breaker bar on it, and get it to crack via using the starter motor (i.e. crank car and bar will slam down on crossmember jamming the pulley and cracking the bolt)
One from the wreckers shouldn't set you back more then $40. Also check the condition of your acc belts while you are down there.

Pretty sure that Precision Parts make suitable replacement.
You can order from pretty well any auto spares store.

Gerry

If its seperated he wont be able to brace the pulley, by what he says its seperated fully. On this topic, wouldnt the replacement billet alloy versions that are lightweight, be unable to tame the harmonics that the factory one aims to kill?

Try these numbers MD333325 or HB1471-N from the Powerbond range.

Gerry

If its seperated he wont be able to brace the pulley, by what he says its seperated fully. On this topic, wouldnt the replacement billet alloy versions that are lightweight, be unable to tame the harmonics that the factory one aims to kill?

On 3si (6G72/4 motors) they mostly do not like them, but reckon the damper only NEEDS to be on in 500HP+ applications.

yes, most aftermarket lightweight pulleys don't act as a proper harmonic balancer. it's unclear how much not having a harmonic balancer will shorten your engine life - keep in mind manufacturers do put those things in the crank pulley for a reason!

Running a solid pulley won't shorten the engine life, but it will shorten the life of the BELTS the pulley drives.

Running a solid pulley won't shorten the engine life, but it will shorten the life of the BELTS the pulley drives.

Explain how.

I suppose the rubber join would act as a shock absorber when you floor it or let it off, and stop the belt taking suden changes in engine speed, and when aircon is turned on.

High frequency vibrations from the engine are filtered out by the harmonic balancer before they reach the belts and makes life easier for the belts and bearings in the aircon compressor, alternator and steering pump. A lot of websites, including Wikipedia, say it stops high frequency vibrations from harming the engine, but I call BS on that, unless there is some engineering magic involved I'm not aware of.

Correct me if I'm wrong, I'm here to learn! lol

With a solid pulley you might notice more vibration in the belts (flapping about a bit more) but the high performance boys might prefer the reliability a solid pulley offers.

High frequency vibrations from the engine are filtered out by the harmonic balancer before they reach the belts and makes life easier for the belts and bearings in the aircon compressor, alternator and steering pump. A lot of websites, including Wikipedia, say it stops high frequency vibrations from harming the engine, but I call BS on that, unless there is some engineering magic involved I'm not aware of.

Correct me if I'm wrong, I'm here to learn! lol

With a solid pulley you might notice more vibration in the belts (flapping about a bit more) but the high performance boys might prefer the reliability a solid pulley offers.

yeah, you're wrong mate. sorry. the harmonic balancer is there to filter out vibrations from the engine, but it's got absolutely nothing to do with increasing the life of the belt or accessory pulleys.

the thinking is that over the course of 100's of thousands of KM, harmonic vibrations can eventually harm the crankshaft and related attachments such as the gearbox, essentially rattling them to pieces. this sort of stuff doesn't happen overnight, so if you fit a lightened aftermarket crank pulley you can drive problem free for another 1000km, 10000km, maybe 100000km - who knows? however doing so does expose the engine internals to greater wear and tear.

the 'hi po boys' if they are serious usually get the engine blueprinted and balanced, which reduces the need for a harmonic balancer.

Google Resonance frequency destruction, they can destroy anything. Some vibrations are bad.

ok, each to his own opinion. I'd like to hear from someone with a background in automotive engineering though.:tired:

Harmonic vibration applies to any rotating assembly, the better it is balanced, the less it will come into play. On a vehicle that is mass manufactured, the balancer cancels any vibration that may result from the crank, etc not been perfectly balanced. this reduces wear on bearings as even a minute difference will cause a vibration of a certain frequency to occur and cause premature wear. we know this occurs otherwise performance builders wouldnt be able to further refine them. the heavy balancer dampens these and stops them escalating.

ok, all good points. Here's a question though. If an engineer needed to put a rubber banded torsional vibration absorber on an engine, why put it on that end of the engine? Why not put it on the other end, ie the drive plate or flywheel? More room to make it larger, more effective and more robust. Think about it!

well one day at the workshop i was incorrectly supplied a VS balancer for a VR commodore... engine ran rough as guts.... without the belt on
so id say it has a dual purpose of balancing the engine and providing NVH control (some balancers are a solid metal construction and provide the later to a lesser extent)

well one day at the workshop i was incorrectly supplied a VS balancer for a VR commodore... engine ran rough as guts.... without the belt on
so id say it has a dual purpose of balancing the engine and providing NVH control (some balancers are a solid metal construction and provide the later to a lesser extent)

That's a shitbox commodore VR though :P, I've ran my DOHC motor with just a balancer and no belts before and it runs fine.
Madmax - on the 3000GT forums anyone above 500HP is advised to run a standard flywheel and standard crank pulley as with lightweight versions on both end's they have seen forged cranks snap. (I have a picture of one somewhere) I ran an aluminum crank pulley for about 5000k's but my timing belt decided to run off-course and wear some of the aluminum out for me so I reverted back to a standard one and noticed no difference in power at all (They claim a 5-8HP gain)

OK!! Thanks for all that info! I agree, the harmonic balancer is there for engine life and NVH, not just to protect acc belts. I can honestly say you guys rock!