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Username Post: Harmonic Balancer        (Topic#345470)
Mr Twister 
Forum Newbie
Posts: 4

Reg: 06-16-17
06-16-17 08:44 PM - Post#2696203    

Could use some help here please. I used my old harmonic balancer from my old motor that I believe had a racing cam in it on a used remanufactured motor I put in my 72 pickup. Can't set timing according to specks 8*btdc@800 rpm. It seems to work better at about 20*btdc@800 rpm. Is there a difference between a stock harmonic balancer and a raised cam harmonic balancer?
Thanks!!
Mr Twister



 
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LUVmachine 
Frequent Contributor
Posts: 1453
LUVmachine
Age: 35
Loc: Redding Ca
Reg: 10-02-14
06-16-17 09:30 PM - Post#2696205    
    In response to Mr Twister

The balancer doesn't know what cam the motor has in it or does it know where the correct timing mark for tdc is on the #1 compression stroke. Sometimes on an old balancer the outer ring will slip making the timing marks on the balancer not be where they are supposed to be. That probably and all the other variables involved are is exactly why you should make,buy,or borrow a piston stop and verify the 0* mark is accurate. Over camming an engine with a power static compression ratio will result in an engine that likes a lot of initial timing.

What are the specs on your engine and how exactly is the timing setup now? Initial, vacuum advance and total at what RPM?

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Mr Twister 
Forum Newbie
Posts: 4

Reg: 06-16-17
06-17-17 09:23 AM - Post#2696231    
    In response to LUVmachine

OK thanks, I'll do the best I can explaining the issue. I use the truck 300-500 miles a year for church work. I put this used factory motor in 3 years ago and was able to get by so far. When I put the motor in I pulled the old points/distributor out and put in a used TDC distributor in. Also a used Rochester 2 brl carburetor. That being said that was three years ago so my memory is a bit fuzzy now. I think I pulled the original harmonic balancer off because I needed a two pulley one to run power steering. Your idea about the outer ring slipping could be the case. What if I try to check the timing with a vacuum gauge? I never tried that and don't know how accurate I could get with it. Right now I only have a bit of hesitation some of the time so I must be close....but the hesitation could be a gas problem too. That's why I'd like to get the timing right and move on to carburetor issues.
BTW does a TDC distributors have electronic advance instead of vacuum advance?
Thanks!
Mr Twister



 
LUVmachine 
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Posts: 1453
LUVmachine
Age: 35
Loc: Redding Ca
Reg: 10-02-14
06-17-17 10:52 AM - Post#2696245    
    In response to Mr Twister

Tdc is when the #1 piston is at top dead center of the compression stroke. The hei distributor is the large body distributor and unless you got one from something fuel injected it will have a vacuum advance just below the cap with a place to connect a vacuum line.

Setting timing requires a timing light. Using a vacuum gauge is a good idea but not for setting timing it will want you to advance the timing to far. Does the engine you are working on have an egr valve. I am assuming no and if it doesn't try bumping up the initial timing to 10-12* hook up your vacuum advance to a manifold vacuum source not ported and see where the timing is. It will probably be too high and the vacuum advance will need to be limited to around 6-8* this will give you a total of about 16-20* at idle. After you get the ignition system dialed in and right then move to the carb. By eliminating the ignition as a problem it will then be safe to move on to the fuel system.

Put your vacuum gauge on it and report back they are very good for trouble shooting if you know how to read it.

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raycow 
Honored Member
Posts: 26290
raycow
Loc: San Francisco, CA
Reg: 11-26-02
06-17-17 03:23 PM - Post#2696266    
    In response to Mr Twister

Not all balancers have their timing mark in the same position relative to the keyway. This was a year thing, but I don't know what year the change occurred. With that said, you can often use the "wrong" balancer on an engine as long as you also install the timing cover which matches the balancer.

As already stated, the outer ring can "slip" when the rubber-to-metal bond fails. The most reliable way to check this is with a TDC finder, which is another name for a piston stop.

Ray

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LUVmachine 
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Posts: 1453
LUVmachine
Age: 35
Loc: Redding Ca
Reg: 10-02-14
06-17-17 06:53 PM - Post#2696286    
    In response to raycow

Good point Ray there were also different timing pointers used in different models like vans.

71 Chevelle BBC powered
71 C-10 454 with weiand 177 (SOLD)
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Mr Twister 
Forum Newbie
Posts: 4

Reg: 06-16-17
06-18-17 03:35 PM - Post#2696415    
    In response to LUVmachine

Thanks guys for your help. Sounds like the first thing I need to do is verify #1 TDC. You made mention on making a tool to do this. Would there be more info on this somewhere else on this site.
Thanks Again.



 
LUVmachine 
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Posts: 1453
LUVmachine
Age: 35
Loc: Redding Ca
Reg: 10-02-14
06-18-17 05:40 PM - Post#2696428    
    In response to Mr Twister

I'm sure there is info on this site somewhere. Google piston stop it would probably be much easier to see it in pictures or even video than me trying to explain it. They are very simple and can be purchased for around $10 or you could make one out of a spark plug and a bolt. I made mine by breaking the porcelain out of an old spark plug and running a 3/8 tap through the remaining metal body of the spark plug and threading a nut on to the bolt before screwing the bolt into the spark plug.

I backed the rocker arms off off cylinder #1 after it was on the compression stroke. You can do this by cranking the engine over by hand with your finger on the spark plug hole.on the compression stroke it will blow your finger off the hole. When it does this thread in the piston stop and the rotate the engine over carefully until the piston stop hits the piston and stops you from rotating it any further. Make a mark on the damper where the timing pointer is pointing. Now rotate the engine the opposite way until it stops again and make a mark on the damper just like you did the first time. Now you have two marks on the outer ring of the damper/harmonic balancer. Measure carefully between the two marks and make another mark. The middle mark that you last made when lined up with the timing pointer will be the true 0* mark noting that #1 piston is at the top dead center. This will be your mark to set your timing off of.

Like I said it would probably be easier to Google it or pull it up on YouTube because I'm not good at writing things out.

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Keith_Knox 
Moderator and "15th Year" Gold Supporting Member
Posts: 5582
Keith_Knox
Age: 76
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Reg: 04-02-00
06-18-17 08:12 PM - Post#2696456    
    In response to LUVmachine

Sounded like a good explanation to me.

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Mr Twister 
Forum Newbie
Posts: 4

Reg: 06-16-17
06-18-17 08:17 PM - Post#2696457    
    In response to LUVmachine

Thanks so much for every ones help. I'll get to work and try all this out and let you know how I made out.
Mr Twister



 
LUVmachine 
Frequent Contributor
Posts: 1453
LUVmachine
Age: 35
Loc: Redding Ca
Reg: 10-02-14
06-18-17 08:39 PM - Post#2696460    
    In response to Mr Twister

  • Quote:
Sounded like a good explanation to me.




That's one of those things you do it without thinking about it but when you slow down and try to go step by step and write it out you could easily miss something simple.

71 Chevelle BBC powered
71 C-10 454 with weiand 177 (SOLD)
72 406 sbc powered Chevy LUV sleeper (SOLD)
2010 GMC Sierra crew cab 4X4
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Bel Air kiwi 
"2nd Year" Silver Supporting Member
Posts: 3320
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
06-19-17 04:41 AM - Post#2696490    
    In response to LUVmachine

Hi Guys, This may sound a bit pedantic, but no such thing as a harmonic balancer in engines.

They are harmonic dampeners and are specifically for dealing with the harmonics in a crankshaft called torsional vibration, which is due to the acceleration and deceleration of different parts of the crank through firing and compression stresses trying to wind and unwind the big end journals relative to each other rotationally.

The hub of a harmonic dampener may have an offset weight in its center, however that is directly keyed to the crank and is no different to a weight on a counterweight, flywheel, or torque converter. That is simply about whether the crank is internally or externally counter weighted. eg SBF 400SBC etc.

It doesn't make any difference to the converter if the mounting plate is used for crank balance and the same applies to the harmonic dampener.

Harmonic dampeners are not sized to camshafts but to specific engines and rpm ranges where uncontrolled torsional vibration would cause disruption of the oil film and damage to the bearings leading to a compound failure. They are to the crankshaft what a shock absorber is to a suspension system.

Cheers Kiwi


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Edited by Bel Air kiwi on 06-19-17 04:48 AM. Reason for edit: No reason given.

 
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