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SpectatorRacing | Would an Eagle crank have a different thread for the damper bolt? | ||
Elite Guru
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The hub/damper bolt backed out of my crank at the end of last season and is gone. I bought a standard SBC crank bolt from ARP but can't get it to thread in. The new bolt threads fine into the stock crank I have in the spare motor.
My motor has an Eagle crank. It's likely that the old bolt narfed the threads on it's way out, but before I go buy a tap and try to fix it is it possible that Eagle cranks have a different thread? It's an LT1 motor... |
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Posted on: 2009/3/22 20:54
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BillH | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
The Stig Moderator
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I'd try a rethreading tap (rather than a regular) first if you can get a hold of one. I have a set of these I got at Sears and use them a lot.
I be very supprised if the Eagle had a different thread, just wouldn't make any sense. |
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Posted on: 2009/3/22 23:41
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SpectatorRacing | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
Elite Guru
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That's kind of what I was thinking...but I can't even get the bolt to start, as if it were the wrong size or thread. It's tough to see in there and i don't want to pull the motor, but it may come to that. A poor re-tap could trash the whole crank. Maybe I'll just take the impact gun and jam that sucker in permanantly |
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Posted on: 2009/3/22 23:48
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85L98-84L83 | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
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Definently the impact gun, rock that bolt hard.
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Posted on: 2009/3/23 1:18
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Josh | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
Guru
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The eagle crank in my L98 is the normal 7/16 fine thread.
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Posted on: 2009/3/23 3:41
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BillH | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
The Stig Moderator
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The rethreading taps will push deformed threads back into position most of the time. But if you have a regular tap, I'd try and just do the first couple of threads. Ha, I want pics if you can fit an impact gun in there. BTW, I can pull the motor in my racecar in under 45 min |
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Posted on: 2009/3/23 14:00
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SpectatorRacing | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
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I hate you right now, Bill! I have a 10 hour job ahead of me just to get it out. I can't even get the tap to bite on the first thread. Not only is it too risky to force the threads, but I want to be able to see in there and find out if there's anything else wrong. Plus, there seems to be a LOT of slop in the damper, so I'm thinking it's been wobbling for awhile and has worn away at the crank keyway. I may need a new damper, too. God forbid that the crank is damaged, it is a pricey lightweight jobber. I wonder if I had my chicken before the cart...er...the horse before the egg? Anyway...perhaps this has been loose for awhile and is the source of the vibration that caused all of my distributor problems last season. Who the f has ever heard of a crank bolt backing out? Grrrrr..... |
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Posted on: 2009/3/23 21:45
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BillH | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
The Stig Moderator
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Quote:
Yea, well I may be able to pull the motor in 45 ( remember our conversation about purpose built racecars?) but when I need a crank it's $850 for a SCAT. Since everything's F'd up any way, I'd try tapping lightly on the tap to see if you can get it started. have you rotated the motor while looking at the threads? |
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Posted on: 2009/3/23 21:59
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BrianCunningham | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
Senior Guru
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Is there any of the old bolt left in the hole?
ie) did it back out or break off? |
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Posted on: 2009/3/24 14:48
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dan0617 | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
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My sbc eagle forged crank uses the same bolt as a stock L98.
I once screwed up the threads on a stock L98 crank, had to drill it out one size bigger and rethread it. Worked fine. If I were you I, too, would try to re-tap it with the stock size bolt tap. Tap on the tap with a hammer and try to get it started, and if it starts in I'd run it the whole way in. If that works I'd put locktite on the bolt and torque it up 10 ft lbs or so tighter than called for by the repair manual. If you get that then you know it is fine. If you only get close to or a couple ft lbs past the called out torque setting and it strips then you know it never would have held. Drill it out and tap it 1 size bigger, put in a new bolt to match the new threads, and be done. As a side note, sometimes the stock bolts aren't long enough to engage most of the threads on an aftermarket crank. I know on my new crank the hole seems tapered a little and the threads start back farther in than on the stock crank. Perhaps you only engaged the first few threads, and the bolt took them out when it came out. There might be plenty of good thread back in there that you can't see, and a longer bolt is all you need. Tap it with a hammer to try to get it started, maybe try that before trying to run a tap in at all. |
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Posted on: 2009/3/24 20:56
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SpectatorRacing | Re: Would an Eagle crank have a different thread for the damper bolt? | ||
Elite Guru
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Thanks for the input. My hope is that only the first few threads were damaged, and I can either rethread them or drill out a few mm and have the remainder of the threads clean and usable. I can see that there is no obstruction (i.e. the old bolt broken inside) in the hole, but based on the LT1 configuration and the fact that it's an ATI damper (different than stock and impossible to see inside due to it's proximity to the rack) I'd rather mess with it out of the car.
We're pulling the motor next week, I'd rather do it right then cross thread the snout. It is good to know that I can go up a size safely if I need to. The biggest headache is that I can't do it at home, I'm going to be overseas for 10 days and really don't have the time to do it. It has to be running for April 18...everything's a friggin rush job on this car. |
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Posted on: 2009/3/25 15:21
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