Timing mark mystery, Please help me solve |
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Timing mark mystery, Please help me solve |
bbrock |
Dec 29 2018, 05:54 PM
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#1
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains |
Cleaned up the impeller on the 2.0 liter today and need to repaint the timing mark. To my surprise, I found two marks to choose from (IMG:style_emoticons/default/new_shocked.gif) The mark on the right (nearest TDC) was cut with a file and is exactly 52.5mm from the center of the "0" for TDC. According to Haynes, that is the correct distance for 27 degrees BTDC. The farther mark looks to be original and is about 57.25mm from TDC. If Haynes and my math are correct, that would be around 29ish degrees BTDC.
Now I have a vague memory of cutting a mark on an impeller of one of the five Type 4 engines I've worked on, but too much alcohol has swashed through my brain in the 35+ years since that event could have happen to remember why. I can think of two reason: the original had a broken fin and I stole this one from a bus engine, or I just put a mark in where Haynes said it should be, assuming the other was wrong. What really bothers me is this image from another thread has a pic with 27 BTDC marked exactly where my original mark is not at 52.5mm where Haynes says it should be, but TDC in that pic is not where mine is using the impeller blades as a guide. So can anyone help me figure out which frickin' mark is the right one? Is Haynes wrong? If it is the one I cut, any idea why the other one is there? Did buses have a different mark? So confused. (IMG:style_emoticons/default/confused24.gif) (IMG:http://www.914world.com/bbs2/uploads/post-8384-1196294703.jpg) |
jmalone |
Dec 29 2018, 06:26 PM
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#2
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Member Group: Members Posts: 119 Joined: 3-July 09 From: reno,NV Member No.: 10,529 Region Association: Northern California |
You will want to re-balance that fan unless you indexed it so that it can be assembled again exactly as it was.
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bbrock |
Dec 29 2018, 06:28 PM
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#3
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains |
You will want to re-balance that fan unless you indexed it so that it can be assembled again exactly as it was. I did. At least I did something right (IMG:style_emoticons/default/beerchug.gif) |
914_teener |
Jan 3 2019, 11:57 AM
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#4
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914 Guru Group: Members Posts: 5,204 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern California |
You will want to re-balance that fan unless you indexed it so that it can be assembled again exactly as it was. I did. At least I did something right (IMG:style_emoticons/default/beerchug.gif) How was it done? |
bbrock |
Jan 3 2019, 12:08 PM
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#5
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains |
You will want to re-balance that fan unless you indexed it so that it can be assembled again exactly as it was. I did. At least I did something right (IMG:style_emoticons/default/beerchug.gif) How was it done? I have corresponding marks notched in the pulley ring that correspond with the timing marks so the pulley can be put back on in the same position it came off. I don't know if the D-shaped washers are used in addition to the weight crimped into the pulley for balancing but all of mine are the same size and thickness so I'm assuming equal weight. I wouldn't mind having the balance rechecked before putting it on the engine though. Would most machine shops be able to do this? |
914_teener |
Jan 3 2019, 11:26 PM
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#6
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914 Guru Group: Members Posts: 5,204 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern California |
You will want to re-balance that fan unless you indexed it so that it can be assembled again exactly as it was. I did. At least I did something right (IMG:style_emoticons/default/beerchug.gif) How was it done? I have corresponding marks notched in the pulley ring that correspond with the timing marks so the pulley can be put back on in the same position it came off. I don't know if the D-shaped washers are used in addition to the weight crimped into the pulley for balancing but all of mine are the same size and thickness so I'm assuming equal weight. I wouldn't mind having the balance rechecked before putting it on the engine though. Would most machine shops be able to do this? The weight is used to balance it. DO NOT drill out or machine any of the fan to balance it unless you want shards of of a fan in your housing. Seen it happen. I'd have it dynamically balanced by a competent shop. |
bbrock |
Jan 3 2019, 11:41 PM
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#7
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains |
The weight is used to balance it. DO NOT drill out or machine any of the fan to balance it unless you want shards of of a fan in your housing. Seen it happen. I'd have it dynamically balanced by a competent shop. But what qualifies as a "competent shop" for this? A competent machine shop or does it need to be someone who knows these engines? The latter might be hard to find around here. |
914_teener |
Jan 4 2019, 06:53 AM
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#8
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914 Guru Group: Members Posts: 5,204 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern California |
The weight is used to balance it. DO NOT drill out or machine any of the fan to balance it unless you want shards of of a fan in your housing. Seen it happen. I'd have it dynamically balanced by a competent shop. But what qualifies as a "competent shop" for this? A competent machine shop or does it need to be someone who knows these engines? The latter might be hard to find around here. If you put the fan back together the way it was and the weight is still there then you are probably ok. As far as competancy, there are shops that just do fan and pulley balancing. There are lots here ...not sure about Montana. I.m an engineer so any mass spinning at 5k rpm should be balanced. But that's my OCD. I have seen a couple of fans on T4 motors come apart because they machined metal away from the fan on the metal lip. This caused it to crack and come apart. |
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