Balancer slides in on install

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mshred

mshred

The Green Manalishi
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Working on a 70s 360, and upon putting it back together, the damper slid right over the snout of the crank by hand. I found this strange, as I did have to use a puller to remove it on tear down, albeit it came off super easy. Its a factory balancer, and it appears to be in good shape in terms of inner and outer pieces. Lubed it up good, slid it on, and torqued the balancer bolt to the 100ft/lb torque spec in my 1971 service manual.

The balancer has no play once tightened, and it is definitely on all the way. Just wondering if I should be concerned at all about this...should I up the torque on the bolt to be safe? This engine ran for a couple of months in my possession and had no vibrations or issues during that time, the rebuild was more of a freshen up and to install hotter cam, heads and intake while going over everything else.
 
mshred said:
Working on a 70s 360, and upon putting it back together, the damper slid right over the snout of the crank by hand. I found this strange, as I did have to use a puller to remove it on tear down, albeit it came off super easy. Its a factory balancer, and it appears to be in good shape in terms of inner and outer pieces. Lubed it up good, slid it on, and torqued the balancer bolt to the 100ft/lb torque spec in my 1971 service manual.

The balancer has no play once tightened, and it is definitely on all the way. Just wondering if I should be concerned at all about this...should I up the torque on the bolt to be safe? This engine ran for a couple of months in my possession and had no vibrations or issues during that time, the rebuild was more of a freshen up and to install hotter cam, heads and intake while going over everything else.
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If the woodruff key is there and in good condition, I wouldn’t worry about it since you have a good torque on it.

I might be tempted to do a little blue loctite on the bolt threads.

Don’t over torque it.
Too risky.
 
Fix it. You’ll kill the crank. Those dampers need a press fit. Either the crank is under sized or the damper is blown out.

Either way, you need to fix it.
 
I tend to agree about correcting it. I have honed some aftermarket balancers to fit a bit less snug, because some of them fit REALLY tight, but it still should be a press fit, as designed.
 
Well this crank was turned 10/10 before I got to it (found on disassembly it was turned and cylinders bored .030 over), so Im gonna be hopeful and doubt on the side of caution that they didnt miss an undersized snout....so in that case a new balancer maybe will be a bit snugger on there?

I wasnt sure if the press fit was a requirement for the balancers install on these engines or not. I know they typically are snug and have an interference fit, just wasnt sure if that was a spec they have to have.
 
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You removed the balancer, it was snug. Its now 10/10. and now its not snug. Is it your crank, or someone else?
 
Max1196 said:
You removed the balancer, it was snug. Its now 10/10. and now its not snug. Is it your crank, or someone else?
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Sorry, I need to edit my post...
It was turned 10/10 by whoever was in it last, BEFORE me
 
It will be ok, but you need more tq on the bolt. Millions of Pontiac engines had dampeners that slid in place by hand...............& didn't fail. They used a 5/8" bolt that was torqued to 160. Nothing special about the bolt except it was grade 8. From memory, Chrys used a 3/4" bolt, so proportionally more tq.
 
A harmonic dampers job is to reduce harmonics. If it doesn't fit tight on the crankshaft it can't do it's job.

When you buy an ATI aftermarket damper it tells you in directions how much press fit the damper needs be it a steel or aluminum hub.

It also tells you to put the damper in hot/ boiling water to open up the clearance to make it easier to install.

Also a crankshaft bolt is only to keep it on the crank and in no way helps it fit tighter on the snout of the crankshaft.

Either the crank or the damper is bad and the engine will be short lived if you run it as is.

Tom
 
Id find a good second hand one, just to check.

if it fits tight, you know its not your crank and you can then make your decision on whether its a good enough replacement for your application or you want aftermarket

ROMAC does or Did do a range of sizes to cater for re-claimed cranks or indeed to cater for situations where 2 parts were at the extreme ends of standard factory tolerance .
 
I agree with above- the balancer needs to fit at least snug or the single job it has it cannot do. When they machined the crank they may have polished the end snout to remove burrs or drop dent or scratches. They may had put a locking compound like a sleeve retainer on it because they polished it too much. Ask on here for a factory diameter or an un molested crank and check yours. If okay- then check your balancer. I believe the balancer should be .001-.003” smaller than the crank. Might even be less than that like .0015”

Sorry - dampener has 2 jobs- vibration is 1st and turning belts that 2nd. Without the first it cannot do the 2nd for long. lol!
 
Would anybody happen to know the factory spec for the snout diameter on a cast 360 crank? That might be easier then trying to wait on finding a used balancer to check, since I can get the balancer off after work tonight to measure mine
 
Bewy said:
It will be ok, but you need more tq on the bolt. Millions of Pontiac engines had dampeners that slid in place by hand...............& didn't fail. They used a 5/8" bolt that was torqued to 160. Nothing special about the bolt except it was grade 8. From memory, Chrys used a 3/4" bolt, so proportionally more tq.
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Great advice IF he was building a Pontiac. He's not. Pontiac is the ONLY American V8 that I know of that doesn't use a press fit.

Chevrolet built engines without a crank bolt in the damper. Press fit held it on.

The key is not designed to carry the load, so that's another issue with slipping it on.

The key is there to make timing the engine quick and easy. You can leave the key out if it has press and it won't hurt a thing. That key makes assembling the engines when new much easier. They literally just stick the damper on. They don't verify TDC or anything.
 
Newbomb Turk said:
The key is there to make timing the engine quick and easy. You can leave the key out if it has press and it won't hurt a thing. That key makes assembling the engines when new much easier. They literally just stick the damper on. They don't verify TDC or anything.
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This only holds true on a neutral balanced engine. You can't just stick an external balanced damper on where you like.

Tom
 
mshred said:
Would anybody happen to know the factory spec for the snout diameter on a cast 360 crank? That might be easier then trying to wait on finding a used balancer to check, since I can get the balancer off after work tonight to measure mine
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New Scat crank 1.5319
used 360 1.5312
used 318 1.5312
used poly 1.5308
some for a comparison
 
Max1196 said:
New Scat crank 1.5319
used 360 1.5312
used 318 1.5312
used poly 1.5308
some for a comparison
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Thank you! Going to measure tonight, really hoping mine is in spec and its just a balancer replacement that's needed.
 
mshred said:
Thank you! Going to measure tonight, really hoping mine is in spec and its just a balancer replacement that's needed.
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That’s a HUGE swing from the biggest to smallest crank.

The .0004 isn’t so bad but .0011 is a mile when the press fit should be (as a general rule) .0005-.0010.
 
Newbomb Turk said:
That’s a HUGE swing from the biggest to smallest crank.

The .0004 isn’t so bad but .0011 is a mile when the press fit should be (as a general rule) .0005-.0010.
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What exactly are you saying? Maybe I am misunderstanding, but I am also getting some numbers from elsewhere and I just want to find a decent range that hopefully lands me in the middle. I am also going to measure the inside of the balancer.
 
4 more for comparison, BUT these are in a 40F shed, temp matters.
Used 360 1.5310
cast 318 1.5310
used 360 1.5311
used 360 1.5311
 
mshred said:
What exactly are you saying? Maybe I am misunderstanding, but I am also getting some numbers from elsewhere and I just want to find a decent range that hopefully lands me in the middle. I am also going to measure the inside of the balancer.
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What he's saying is ignore the measurement on the Scat crank... It's oversized & most dampers would likely bind..

FWIW I agree with the majority of the posters, this isn't a Pontiac.. The key aligns parts, it doesn't prevent rotation...

And your 100 ft/lbs is a little light... Back in the day I remember the manual showing 175 ft/lbs... I looked at online specs & found 135 ft/lbs... So I checked an SAE reference based on the bolt being 3/4-16 & grade 8... And the SAE recommended spec is 420 ft/lbs...
 
No, this isn't a Pontiac, but it works exactly the same: conrods, crank, pistons, timing chain etc, etc.

If you do the bolt up tight enough, the dampener won't move [ it is not a balancer, it is a harmonic dampener that has been balanced ].

There has never been any problems such as broken cranks on Pontiac engines, any more so than on other engine brand, because of the way the dampener is retained.
 
Bewy said:
No, this isn't a Pontiac, but it works exactly the same: conrods, crank, pistons, timing chain etc, etc.

If you do the bolt up tight enough, the dampener won't move [ it is not a balancer, it is a harmonic dampener that has been balanced ].

There has never been any problems such as broken cranks on Pontiac engines, any more so than on other engine brand, because of the way the dampener is retained.
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Parse it any way you want, but dampers (other than a Pontiac) require press fit to work. Simple as that.
 
It is an interesting question and I don't know the answer. Some OEM engineers didn't think a press fit was a requirement, others did. A lot of Ford engines used a slip fit damper. It all worked okay for passenger car use. For a low budget rebuild on a passenger car engine I wouldn't be afraid of a slip fit. I'd rather not have a slip fit, but if it was my only option I'd take it.
For racing the recommendation is always use a slight press fit. Somewhere in the 0.0005 to 0.001 range depending on the size of the crank snout.
 
A lot of imports use a slip fit. Almost every Toyota balancer I removed doing timing belts at the dealer was not a press fit. You could remove the bolt, give the balancer a shake or two by hand and it would usually slide right off. Of course that's comparing apples to oranges here.
 
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