C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

1995 lt1, harmonic balancer wobbling off.

 
Old 02-16-2019, 05:49 PM
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Droldaerd
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Default 1995 lt1, harmonic balancer wobbling off.

I heard a noise coming from the engine, checked the bay and notice the harmonic balancer wobbling. I cannot get a good view of it, but it feels like there is one bolt still in, keeping it from completely turning off the mount. I found a random bolt near it on the frame. Accidently mixed it with some.other loose bolts I have.

I found something online that said 3/8 24 fine? Is 24 the length? What unit is it? Then a mention on the center being a 9/16 "tight" thread. Does that mean fine thread? And what length should I get? Washers needed for it? Ect..


So I'd like to know the sizes of the 3 bolts that mount the harmonic balancer to the engine, the size of the center bolt I need to hold the crank in place to torque. If I need any washers. If I need to apply loctyte, if so which color. Lastly, do I neeeeeddd to remove the water pump to tighten it back down, or can I comfortably work around it?

She's slowly coming around, its been a bigger project than I hoped, my bikes haven't been getting any love. Of course I decided to make things worse for myself by losing my only ignition key. Ouch. Waiting the mechanical key from the dealer so I can bypass the ignition and find out whichs vats key it is. Ill be sure to cut two keys once I revert the system back!

Last edited by Droldaerd; 02-16-2019 at 05:53 PM.
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Old 02-16-2019, 07:35 PM
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drcook
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this is in case no one else jumps in

the balancer just attaches to the hub (the hub attaches to the crank) on a LT1. if you put the car on ramps you probably can get to it. if you loosen the belt to take tension off the balancer, you can probably take that bolt out and get matches for it, of course the balancer/pulley is going to be loose but there is only 1 way it can go back together because of the bolt pattern (if I remember correctly)

make some witness marks with chalk if you can

I have not taken mine off yet, so hopefully one of the folks that have can give some better advice

I found something online that said 3/8 24 fine? Is 24 the length? What unit is it? Then a mention on the center being a 9/16 "tight" thread. Does that mean fine thread? And what length should I get? Washers needed for it? Ect..
24 is the pitch of the threads, ie: 24 threads per inch, if it is 3/8-24 then it is English, but most of the bolts I have dealt with on my 96 have been metric. can't say positively about those though

Blue loctite. Not red ! Red is permanent. It can be removed with heat, but you don't want to have to do that. Blue loctite will break loose with just a wrench.

Last edited by drcook; 02-16-2019 at 07:40 PM.
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Old 02-17-2019, 10:15 AM
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You should take your vehicle to a shop that understands the balancer.
1. Balancer HUB not keyed although crank is - now is the time to replace with a keyed hub.
2. Not fixing properly might damage your crankshaft !!!
3. Balancer so old should be replaced no matter what !
4. ATI SuperDamper good choice.
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Old 02-17-2019, 12:22 PM
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drcook
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2. Not fixing properly might damage your crankshaft !!!
3. Balancer so old should be replaced no matter what !
I wholeheartedly agree with these 2 points.

For the average daily driver, simply replacing or rebuilding the oem one (there are companies that will remove and replace the rubber) is all that is needed. As rubber ages and gets hard (just like in a suspension) it loses its dampening/vibration absorption qualities and simply becomes a spinning mass. I bet a lot of folks experiencing a mild vibration of the engine would find out that if they simply replaced the balancer, the engine would be showroom smooth (or closer to it) again.

With a bit of research, there is no reason the OP can't deal with it unless for one reason or another the OP doesn't work on cars or have the tools, capacities to do it. For an LT1 it is simply a bolt on, you can't get it wrong due to the bolt pattern. Replacing the hub is one thing, simply replacing the balancer another as long as the replacement is correct for the car.

As far as the ATI balancer, for a "built" engine it is probably a good idea, but I bet there are lots of folks running built engines with oem grade balancers due to the balancing nature of the LTx based engines.

I know I will be purchasing an upgraded balancer, in fact, besides injectors, seals and gaskets, that is all I have left to purchase unless I go the stroker cam route, which changes the picture.
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Old 02-17-2019, 05:59 PM
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Originally Posted by BlowerWorks View Post
You should take your vehicle to a shop that understands the balancer.
I do all my own work besides machining.
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Old 02-17-2019, 06:04 PM
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Originally Posted by drcook View Post
but most of the bolts I have dealt with on my 96 have been metric
Bolts into the block are standard, accessory items tend to be metric. Thank you for your input.

Last edited by Droldaerd; 02-17-2019 at 06:05 PM.
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Old 02-17-2019, 06:12 PM
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@drcook
Eventually I'll build this engine up some more. It has some work done, but id like to pump it up. Youd recommend upgrading the balancer then eh? Do I need to upgrade the part it attaches to? I was gonna save it till I was ready to do the cam chain swap later this year. Would it be better to wait till then I swap the balancer and just remount the current one?
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Old 02-19-2019, 08:55 AM
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Originally Posted by Droldaerd View Post
I do all my own work besides machining.
And you don't know thread designations?

If that is harsh, I don't mean it to be. It is a reality check. Thread designations such as 1/4-20 3/8-24 is common shop lingo as much as asking for a 1/2" socket.

Do your homework here... the balancer protects the bottom end.
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Old 02-19-2019, 11:07 AM
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Originally Posted by drcook View Post
I wholeheartedly agree with these 2 points.

For the average daily driver, simply replacing or rebuilding the oem one (there are companies that will remove and replace the rubber) is all that is needed. As rubber ages and gets hard (just like in a suspension) it loses its dampening/vibration absorption qualities and simply becomes a spinning mass. I bet a lot of folks experiencing a mild vibration of the engine would find out that if they simply replaced the balancer, the engine would be showroom smooth (or closer to it) again.
I checked mine when I was doing the opti and it does have dry rubber in it. Since I am bone stock, I have been trying to find a good rebuilder. I tried to contact Damper Doctor but they did not respond to phone or email messages. Any other suggestions? I'd prefer a solution that does not require hub removal. I tried an aftermarket from the LPS but the outer ring was not centered on the inner ring. You could see it with the engine running.
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Old 02-19-2019, 11:54 AM
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You can get to those bolts with a long extension from underneath just above the cross member. Check out my thread:
https://www.corvetteforum.com/forums...r-lt1-lt4.html
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Old 02-19-2019, 12:13 PM
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bud40oz
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you sure it was the balancer falling off and not just the crank pulley? the 3 fine thread bolts you are talking about hold the pulley on and have nothing to do with keeping the harmonic balancer in place. or did i miss something in the posts the crank pulley is also a pretty common known issue to go bad in these years of any 5.7 small block engine. and to actually answer your question, which i am not sure anyone did.. the 24 in that case is the thread pitch of the bolt, 3/8" diamete with 24 threads per inch aka 3/8's fine thread, a standard 3/8'th bolt is 3/8 x 16.. or 16 threads per inch those are the 3 bolts holding the lower crank pulley to the harmonic balancer, the center crank bolt, which goes trough the balancer to the crank should be 7/16 x 20 thread.. also fine threaded. if you do decide to remove the balancer yourself and have the harmonic balancer removal/install tool. make sure you put the bolt in the crank hole before you go running the removal tool down into the threads and smoke the threads, thats just ugliness. don't do that,.... put the bolt back in the crank after you remove the big washer from it.. and push off the bolt head. not the open hole in the crank.

Last edited by bud40oz; 02-19-2019 at 12:31 PM.
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Old 02-19-2019, 12:32 PM
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Originally Posted by bud40oz View Post
you sure it was the balancer falling off and not just the crank pulley? the 3 fine thread bolts you are talking about hold the pulley on and have nothing to do with keeping the harmonic balancer in place. or did i miss something in the posts the crank pulley is also a pretty common known issue to go bad in these years of any 5.7 small block engine
Understand that we are talking about an LT1 engine. The pulley and balancer are one assy. The hub mounts to the crank and the balancer/pulley assy mounts as one to the hub with 3 bolts..
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Old 02-19-2019, 12:39 PM
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vette196
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I was looking at the ATI super damper and they are super expensive. It looked like a good add to cars revving over 6K rpms.....so is it really needed for a high HP (400 rwhp) street/strip/cruiser?
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Old 02-19-2019, 01:50 PM
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Originally Posted by KyleF View Post
And you don't know thread designations?

If that is harsh, I don't mean it to be. It is a reality check. Thread designations such as 1/4-20 3/8-24 is common shop lingo as much as asking for a 1/2" socket.

Do your homework here... the balancer protects the bottom end.
Sorry not knowing your "shop lingo" warranted an attack an my character and ability, but posing questions on this forum is to "help me do my homework." For a guy so well versed in "shop lingo" you offered nothing to the thread. If that is harsh, I dont mean it to be. Its just a reality check.
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Old 02-19-2019, 01:52 PM
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Originally Posted by vette196 View Post
I was looking at the ATI super damper and they are super expensive. It looked like a good add to cars revving over 6K rpms.....so is it really needed for a high HP (400 rwhp) street/strip/cruiser?
My feelings exactly. Part of the reason I wanted to wait till i do the cam chain, is the $400 price for the really only available dampener that I prefer not to spend till later this year.
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Old 02-19-2019, 02:03 PM
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Originally Posted by bud40oz View Post
you sure it was the balancer falling off and not just the crank pulley? the 3 fine thread bolts you are talking about hold the pulley on and have nothing to do with keeping the harmonic balancer in place. or did i miss something in the posts the crank pulley is also a pretty common known issue to go bad in these years of any 5.7 small block engine. and to actually answer your question, which i am not sure anyone did.. the 24 in that case is the thread pitch of the bolt, 3/8" diamete with 24 threads per inch aka 3/8's fine thread, a standard 3/8'th bolt is 3/8 x 16.. or 16 threads per inch those are the 3 bolts holding the lower crank pulley to the harmonic balancer, the center crank bolt, which goes trough the balancer to the crank should be 7/16 x 20 thread.. also fine threaded. if you do decide to remove the balancer yourself and have the harmonic balancer removal/install tool. make sure you put the bolt in the crank hole before you go running the removal tool down into the threads and smoke the threads, thats just ugliness. don't do that,.... put the bolt back in the crank after you remove the big washer from it.. and push off the bolt head. not the open hole in the crank.
Lots of good information. Thank you! I was mistaking the pulley as part of thr balancer. So the hub piece is the balancer and the large disc is only the pulley? The pulley is what has come undone. 2 missing bolts, one still holding it on. As for the bolts, you're saying that the correct bolts are 3/8-16 and not 3/8-24 like I previously saw in another post?
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Old 02-19-2019, 05:33 PM
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Originally Posted by Droldaerd View Post
Lots of good information. Thank you! I was mistaking the pulley as part of thr balancer. So the hub piece is the balancer and the large disc is only the pulley? The pulley is what has come undone. 2 missing bolts, one still holding it on. As for the bolts, you're saying that the correct bolts are 3/8-16 and not 3/8-24 like I previously saw in another post?
There is a difference between a Small Block Chevy and an LT1. On a SBC the harmonic balancer is held by a bolt and has a pulley bolted to it.

An LT1 has a hub held by one bolt and it is NOT keyed so if it is removed you must mark it and the engine to ensure it is reinstalled in the same position. The balancer/pulley is one unit and it is held by 3 bolts.

I haven't seen it mentioned but if you have 2 bolts missing from the balancer. you need to verify the threaded holes in the hub are not damaged.
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Old 02-19-2019, 05:48 PM
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Originally Posted by Droldaerd View Post
Sorry not knowing your "shop lingo" warranted an attack an my character and ability, but posing questions on this forum is to "help me do my homework." For a guy so well versed in "shop lingo" you offered nothing to the thread. If that is harsh, I dont mean it to be. Its just a reality check.
Easy there, I did not attack your character in the slightest.

My contribution is this, a man who can't go to the hardware store and as for a bolt/screw/nut by size is about to start screwing with something he may not realize is a critical component of his engine. Saying do your homework means just that. To be honest, you didn't need this thread anyway. This has been covered and to re-type the same stuff again is pointless. Just use the search feature. You would probably find all you need.

Here is a contribution to help you with your fasteners:
The1/4-20 designated the thread outer diameter (.25") and the threads per inch in SAE sized fasteners. 20 threads in an inch means it takes 20 revolutions of the fastener to travel 1in, or 1 turn is 1/20th of an inch. Unfortunately, SAE fasteners basically require a Tap/Drill chart fro the various sizes if you are creating a new hole, or "drilling" something out and re-tapping a new hole.

In metric a M6X1.0 gives you the outer diameter (6mm in this case) and pitch of the threads . Meaning in, 1 turn will move the fastener 1mm. For metric fasteners, using a normal cut tap, drill the hole by the diameter minus the pitch. No tap/drill chart needed. A M6X1.0 tap would use a 5.0mm hole. M8X1.25 would use a 6.75mm drill. And so on.
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Old 02-19-2019, 06:18 PM
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Originally Posted by belairbrian View Post
I haven't seen it mentioned but if you have 2 bolts missing from the balancer. you need to verify the threaded holes in the hub are not damaged.
Thank you for the information. That is precisely my concern. Previous owner did a lot of shotty work. Trying to repair his work now. Had to already replace the accessory bracket because one alternator mount was snapped off and the power steering threads were disengrated from loose/improper bolts. PS pump shaft was bent from wobbling about. Anyways, the remaing bolt isnt flush with the pulley but held solid. Im worried its the wrong bolt. I was hoping I could find out the exact bolt (3) that is suppose to be there so that if I couldnt thread them properly, that I would then know that I need to replace the hub too.
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Old 02-19-2019, 06:28 PM
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Originally Posted by KyleF View Post
Easy there, I did not attack your character in the slightest.

My contribution is this, a man who can't go to the hardware store and as for a bolt/screw/nut by size is about to start screwing with something he may not realize is a critical component of his engine.
Oh I am well aware how to find a missing bolt. My problem is that I am repairing a car that a "mechanic" consistently botched in repairs. My newest issue is that i have a pulley dangling by one bolt that I am not even sure is the correct one. There is mismatched bolts, metric in sae spots, sae in metric, where they shouldn't be. I did a search and initially found a reference to their sizes but no confirmation and nothing about their lengths needed, so i was hoping someone could verify it for me before I buy multiple bolts and play the guessing game.

I am thankful for the enlightenment on how the bolt patterns were developed though, it made a lot of sense.
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