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How to replace Harmonic Balancer on Stock 350

diesel4me said:
Is your engine original to the truck?..
You mentioned the balancer is 8" diameter--most I've seen that big were used on earlier 350's with 4 bolt mains...might be a good idea to look at the engine code and look it up to positively ID the year and CID..
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It is a 1975 Crate engine. It is not a 4 bolt main...The engine code said it was a 1975, but if you lookup parts for 74 or 75 they are rarely different
 
diesel4me said:
About the fan not being fully into the shroud--I've read the ideal fan position is 1/2 into the shroud and 1/2 out of it to get the best airflow--though posts like this linked below proves opinions vary.

Question RE: Fan depth in shroud [Archive] - TriFive.com, 1955 Chevy 1956 chevy 1957 Chevy Forum , Talk about your 55 chevy 56 chevy 57 chevy - Belair , 210, 150 sedans , Nomads and Trucks, Research, Free Tech Advice
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I prefer the fan to be in the shroud...it was with my standard clutch...I am not sure what changed...I don't remember looking at the height of the fan clutch. The only thing I know it that this clutch causes the fan to run all the time...it never stops...it's like a hurricane under the hood....you can feel air pressure blowing up the windshield wipers.
 
I do not know why this engine has an 8" harmonic balancer...obviously the timing cover was the type to accept the 8"
 
Obviously I don't know how the crate engine was put together, the PO that I bought it from told me it was a GM Crate engine, I don't know if it was a long bock but i think it was as all the numbers seem to match the 1975 era. The harmonic balancer should have been already on the crate engine? But who knows when or if it was replaced. When I had the engine on the stand and replaced all the seals, the existing seals didn't look like they needed to be replaced, in fact the engine looked like it has very little mileage on it.
I must have removed the harmonic balancer and replaced the front seal but I just don't remember...that's been a long time ago now.
 
GM did use a few different balancer diameters in the 70's,the "right" one is whatever was on the engine and matches up with the timing cover tab..all the small blocks except the 400 are internally balanced and you can swap whatever balancer size on that matches up with the timing cover tab..

If your fan clutch has the thermostatic spring,perhaps it was installed with the spring in the "locked on" position...or it could be the "extra heavy duty" one simply stays "locked" more than the original one..
If this clutch is shorter than the original, that may affect its ability to cool also..
 
diesel4me said:
GM did use a few different balancer diameters in the 70's,the "right" one is whatever was on the engine and matches up with the timing cover tab..all the small blocks except the 400 are internally balanced and you can swap whatever balancer size on that matches up with the timing cover tab..

If your fan clutch has the thermostatic spring,perhaps it was installed with the spring in the "locked on" position...or it could be the "extra heavy duty" one simply stays "locked" more than the original one..
If this clutch is shorter than the original, that may affect its ability to cool also..
Click to expand...

It has no problem cooling...I can't even get the engine very warm
 
I'm seeing the pulley(s) wobbling more so than the balancer too..
Most balancers fail when they "slip" on the rubber,so the timing mark gets thrown off and TDC is no longer "on the mark" on the tab..
If they get old or oil soaked rubber they can come apart unexpectedly,but as I said earlier its not common on street driven vehicles..

I'd be tempted to try "unlocking" the thermostatic spring and see if that makes any improvement..seeing you cant get it to reach operating temperature and its blowing that much air back at the firewall it does sound like its locked "on"..not in the thermostatic mode..
New parts aren't always "good" either nowadays either unfortunately..

Back when I worked parts counters the brand I sold (if I remember right it was an offshoot of the Standard/Blue Streak/Hygrade line) they had two choices for fan clutches--OEM ,or "Economy",the economy ones were simply a fluid coupling that only limited the top speed of the fan,and it didn't free wheel when cold as much as the factory type with the thermostat spring either..it had no spring..

I tried one of the "economy" ones and it seemed to stay "on" constantly,it made for lots of fan noise and though I had no cooling troubles like overheating or not heating up enough,I ended up putting a original one off a salvage yard truck on instead--immediately it was much quieter,and I could feel a slight increase in power--I also got a 7 blade fan that was on it too..
 
When I remove and replace a harmonic damper the first thing I do after first removing the crank shaft bolt is run a tap through it, blow it out with air, then spray it with penetrating oil, in order to clean out the rust and crud. After the balancer is removed then I use sand paper (or wire wheel) on the crank shaft snout to make a smooth surface for the balancer to be re-installed on. Doing these things will stop from having the balancer install tool or crank shaft bolt from binding up in the threads and snapping off inside the crank shaft bolt hole.
 
The only thing that concerns me on yours is it looks like the outer ring may have creeped back a little bit...the ring looks like there is more rubber showing, and it doesn't appear to be flush with the inner part. it may not be wobbling, but may have walked....

most new ones are close to being flush all the way across,, including the rubber.
 
I guess I've always kinda felt like balancers didn't wear out. How do you know if one is no good?
 
The most common symptom is you set the timing to spec,and find the engine either pings,or lacks power,because the timing mark on the balancer "moved",making the timing too far advanced or retarded..

If it flies apart when you boot in the 4 barrel,that is a sure sign it has failed..:eek:
 
I already have the new balancer, arrived today

Waiting on the new pulley and installer

Need to buy a new crank pulley bolt but those ARP are $30....not sure whether to get one or not and I don't have that socket
 
Better spray it with Lysol !..:eek:

I bet parts are going to be tough to get soon for any vehicle,saw a new report on that subject last night..
 
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