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By 62bigwindow - 7 Years Ago
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I had to buy a new damper for my car. For some reason the replacements ID is smaller than the original Ford damper. So I'm going to have to have it honed out . How much press should it have? I was thinking maybe less than .001 Would be sufficient. Also I read somewhere once where the key slot is in relation to the TDC mark but I can't seem to find that info. Can anyone help me out with either. Thanks
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By aussiebill - 7 Years Ago
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, I have also found them to be tight fit and polished out to orig size, as bolt holds in in place should need to be too tight.
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By Tedster - 7 Years Ago
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Replaced the damper on my stock 292 with a Powerbond brand, at the time it was the only source available for new. Anyway it fits perfectly. Honing should never be required, they are designed with a very close interference fit or they won't work right and the keyway (in theory anyway) may possibly be damaged, or worse.
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By 62bigwindow - 7 Years Ago
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There's no way it's going on. It started to and then stopped, galled the shaft some and had a hell of a time getting it off. I rough measured it with a pair of calipers and it about .003 small.
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By ian57tbird - 7 Years Ago
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Not that I have ever measured any but I would have thought that ever the crank or the damper would have a slight taper because they start of loose until about halfway then you need the bolt to pull them up. I would suspect almost no interference on the fit with the amount of surface area otherwise it would become tight too early. It might be difficult to hone or ream with the keyway being there. I would do it in stages until it felt correct when going on.
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By Tedster - 7 Years Ago
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They can be a $&@!! to install, but they shouldn't be. Powerbond makes good stuff.
Here's some information about the measurements to bring to your machinist:
http://www.crankshaftcoalition.com/wiki/Harmonic_balancer/damper_-_How_to_remove_and_install#Harmonic_damper_install-_honing_to_fit
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By miker - 7 Years Ago
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That article is more precise, but 50 years ago when Mom wasn’t home, I used the oven at 300 degrees. It was a bitch to get off, but it went back on pretty easy. Did some parts in the dishwasher, too. Ran in the family, grandpa and grandma came back early and caught Dad rebuilding a flathead in the living room.
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By MoonShadow - 7 Years Ago
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I've had stock dampers that were difficult to get on. Cleaned up the crank with emery cloth and found some highs and lows. Patient polishing with a long strip finally did the job. I didn't want to take too much off.
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By 62bigwindow - 7 Years Ago
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I've had the stock one off and on a couple times with no problems. The replacement is just too tight. My thinking is if you have to freeze one and heat another to get it together then something's off. If there is that much interference fit then there is no way it'll come back off without alot of effort. I work with stuff everyday that has that much interference and I can say from experience it's no fun to take apart. I was thinking maybe .0005-.001 would be plenty.
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By MoonShadow - 7 Years Ago
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It does sound like you have a clearance problem. Did you contact Powerbond? Sometimes quality control slips. When I got my AOD adapter everything was find except the crank adapter wouldn't fit over the flange and had to be remachined. It happens.
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By Tedster - 7 Years Ago
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"My thinking is if you have to freeze one and heat another to get it together then something's off. If there is that much interference fit then there is no way it'll come back off without alot of effort."
No, they are made to fit extremely close by design. A puller is the only practical way to remove them. It is kind of a pain. If they just slipped on and off though, they wouldn't be able to perform their function. The crankshaft itself twists as much as 2° at times, the heavy outer steel inertia ring is bonded to the basket by rubber and absorbs torsional vibration by leading and lagging somewhat. Remember that crank is turning 3000, 4000, 5000 RPM at times. Pretty cool, huh?
What would happen otherwise is a crankshaft at a certain RPM would reach a point of resonance. This is a Bad Thing, cracks might develop or the crankshaft can even break. I'd talk to the folks at Powerbond, maybe it's defective. Or have the original rebuilt, the cost is a little better than buying new. Maybe a little quality time polishing the snout, removing any burrs, etc.
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By charliemccraney - 7 Years Ago
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If the id of the damper really is too small, send an email to Powerbond about it so that they are aware and can make a change, if they choose. Having it honed a couple thousandths should not be a problem.
A caliper is not the best tool for measuring diameter, particularly smaller ones like the damper bore. It will indicate a slightly smaller diameter because of the way the jaws are offset. So the actual measurement may be slightly larger than you see indicated.
Within reason, the tighter the fit the better, for keeping everything concentric. If it is at a point where it is difficult to install or remove, at room temperature, with the proper tools, then it is too tight.
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By Ted - 7 Years Ago
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62bigwindow (12/17/2017)
........Also I read somewhere once where the key slot is in relation to the TDC mark but I can't seem to find that info. Can anyone help me out with either. Thanks.
See if this picture helps in regards to the TDC placement on the damper.
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By 62bigwindow - 7 Years Ago
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Thanks Ted. That is what I was looking for. I dropped off the damper at the machine shop with the old one. Guy said he's seen the same problem often. I figured if he honed it to the same size as the original I couldn't go wrong.
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By Ted - 7 Years Ago
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62bigwindow (12/17/2017)
I had to buy a new damper for my car. For some reason the replacements ID is smaller than the original Ford damper. So I'm going to have to have it honed out . How much press should it have? I was thinking maybe less than .001 Would be sufficient. ....
My preference for the interference fit for the damper to the crankshaft is 0.0005"-0.0010”. If honing, then it’s desirable to use a hone that’s specific to honing holes with a key slot in them. This requires a hone with wide shoes and stones.
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By 62bigwindow - 7 Years Ago
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Thought I post a follow up on this. The machine shop had to open it up .001. I also cheated a little and set it on top of wood stove for a bit to warm it up some. Now I have a secondary question. After I got it all back together I checked the timing and it was at 38° at idle. I find this a little odd as the car starts fine and seems to run decent. I knew it was off some but I would think that far advanced it wouldn't even start. I haven't had a chance to look into it yet. Was hoping to get a couple suggestions. The vac advance was unhooked and idle was at 850. Idle is that high due to cam size any lower and it won't idle well.
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By Tedster - 7 Years Ago
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It may not idle well but at least for test purposes I'd want the idle RPM lower than say, 650 - otherwise the centrifugal advance probably starts to tip in. Light springs?
Even so that seems like an awful lot of timing advance! If I didn't know better it sounds like vacuum advance connected to a manifold port. Nothing wrong with that but, what you are describing is something different.
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By MoonShadow - 7 Years Ago
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Does the timing jump up when you rev the engine? If not then the vacuum advance is probably all in. Easy to check.
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By charliemccraney - 7 Years Ago
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It won't start with 38 degrees of advance so 38 probably is not the initial setting. Since vacuum advance was disconnected, it was not adding to initial to make it appear to be 38. Rev it some and see if the advance increases. If it does not, then it is probably getting full advance at idle. If it does advance, see if it provides the normal amount If it advances normally from 38, then you are probably getting an inaccurate indication some how.
Did you verify that the marks on the new damper are correct? Ted's drawing provides you with a way to check, if you don't have a known good original for comparison.
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By 62bigwindow - 7 Years Ago
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It seemed very close to the drawing Ted posted. I was going to put the motor at tdc to double check. I do have lighter springs in the dizzy(MSD) but they are supposed to be all in at 2500. Just got the first snow of the season today so I'll have all winter to figure it out now.
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By 62bigwindow - 7 Years Ago
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Ok. I had some free time and did a little work on the car. I changed out the advance bushing to a 18° and put in a little heavier springs. Still at 38°. If I rev the engine the marks advance. I'm beginning to have my suspicition about the marks on the balancer. I got to say so far I'm not too impressed with the Power Bond damper. I'll find TDC soon to confirm but it's got to be that. Nothing else has been changed.
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By 57RancheroJim - 7 Years Ago
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I guess it's possible that you got a bad one. I installed mine before putting the heads on checked it when #1 was on TDC the mark on the Power Bond was right on..
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By ian57tbird - 7 Years Ago
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Just another thought. What sort of timing light are you using? I have my suspicions about some of those that are adjustable to dial in the advance.
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By 62bigwindow - 7 Years Ago
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It is a dial back. I've never had an issue with it before but anything's possible. I checked it's accuracy before but I can check it again. The thought has crossed my mind. I have a Sun timing light to compare it to.
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By Ted - 7 Years Ago
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I’ve used a number of Powerbond harmonic dampers on the Y engines and never had any that was more than 2° off when checking TDC with the water-pump mounted timing pointer. In Powerbond’s defense, I’ve found the same discrepancy when checking TDC on the factory dampers. Besides the accuracy of the markings on the damper, there are many other factors to explain why the damper TDC does not agree with the timing pointer. In most cases, a slight tweak of the timing pointer puts the TDC mark on the damper ‘right on’.
I second the thoughts on the ‘dial back’ timing lights in regards to inaccuracy. While 8° is the most I’ve found them off, it does has an electrical circuit board so anything is possible. Besides the timing light age being a factor, any time it has been dropped the accuracy becomes questionable.
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By 62bigwindow - 7 Years Ago
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I have a notion its a combination of the slipped original damper,timing marks off a bit,and the timing light. Just using the numbers Ted offered and how much my damper has slipped(didn't notice until I had moved the timing) that would put me close to where I had the base set.
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By Tedster - 7 Years Ago
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That doesn't really make sense if you think about it. Seems to me a more likely situation would be 38° Timing indication with a slipped damper.
Once that has been replaced with a serviceable unit timing is going to display something reasonable like 12° or whatever.
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By 62bigwindow - 7 Years Ago
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If the new damper is off 2° then my timing light reads 8-10° off then its already at 10-12° false advance reading. My old damper had slipped 6-8°. I was shooting for a base of 21° at the time. This is assuming that the light and new damper are reading advanced. Taking all that in consideration then the 38° base I'm getting now is plausible. Im just spitballing as i havent checked TDC yet. Waiting on a piston stop to get here.
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