Harmonic Balancer

[BigCat83]

My FSM very clearly says "Tighten the three M6 bolts to 12 N-m (106 lb ft). Which is why I asked the question. I will post an image of the page in the future.

Excellent post about an alternate way to drop the cradle...

[clarkz71]

I'll check my manual as well, but I can guarantee you as a professional auto technician that a M6 bolt is torqued in inch lbs.

[clarkz71]

Here you go. Look under tighten, it says (106 lbs in.)

[BodybyFisher]

I am glad you picked up that 106 ft lbs appeared excessive and asked the question! Good pick up and even better asking the question!

[KHE]

BigCat83,

Your manual must have an error - 12 N-m = 106 In-Lbs.. I just looked at my 1996 manual and it was 106 in-lbs. 100 ft-lbs is lug-nut torque - if you torque the small chaincase bolts to 106 ft-lbs, they WILL snap off long before the torque wrench clicks...

[clarkz71]

BigCat83,

Your manual must have an error - 12 N-m = 106 In-Lbs.. I just looked at my 1996 manual and it was 106 in-lbs. 100 ft-lbs is lug-nut torque - if you torque the small chaincase bolts to 106 ft-lbs, they WILL snap off long before the torque wrench clicks...

I'd like to see a scan of the page in his FSM showing 106 lbs ft.

[BigCat83]

I've done enough of this work over the years that when I saw 106 lb ft for those S-M-A-L-L bolts the red flag went up, which is why I asked the question.

When I finish up I'll post abuncha pics including that page from my FSM. Heads are torqued. I don't like the way two bolts (1 & 2) in the front head felt on the second 60 degree turn but they went in.

The cams are re-assembled tomorrow I'll time them and close up the front of the motor and install the water cross-over and all that crap. Home plate is in sight.

Then we'll see how this pig runs afterward...

[clarkz71]

I don't like the way two bolts (1 & 2) in the front head felt on the second 60 degree turn but they went in.

Don't you mean the third 60 deg. It's a total of 180 deg after the initial torque of 22 lbs ft (95 FSM)

[BigCat83]

I don't like the way two bolts (1 & 2) in the front head felt on the second 60 degree turn but they went in.

Don't you mean the third 60 deg. It's a total of 180 deg after the initial torque of 22 lbs ft (95 FSM)

Really???

My FSM says 2 turns at 60 degrees...?

If it's 3 @ 60 I'll turn 'em all one more time.

[clarkz71]

Check post 78, I scanned the page from my FSM on torque specs.

[BodybyFisher]

BigCat I posted all of the torque specs on the prior page, originally it was 22 ft lb then 60,60,60 = 180 degrees, but in 1999 it was revised to 30 ft lbs then 70,60,60 = 190 degrees, see the prior page here... Mike

[JimD]

Hope I am not adding confusion here folks, but the torque spec's. have changed a little since the paper Service Manuals you all are copying were printed.

Here is a service document that I found in '99 that applied to all years of Northstar engines up to and including 1999 production. If someone needs the sequence diagrams I will post them also.

[KHE]

I'm not sure when the torque spec. included the 70 degree pass but it is definitely three passes (after the initial static torrque of 22 ft-lbs.).

If you only turned them in 120 degrees (and you are sure of that), give them another 60 degrees.

Before starting the engine, bleed the power steering lines to purge the air. Also, with all the oil from machining the block, the engine will really smoke once the exhaust heats up... have a fire extinguisher handy just in case. The smoke should subside after a few minutes.

[BodybyFisher]

Hope I am not adding confusion here folks, but the torque spec's. have changed a little since the paper Service Manuals you all are copying were printed.

Here is a service document that I found in '99 that applied to all years of Northstar engines up to and including 1999 production. If someone needs the sequence diagrams I will post them also.

What you posted Jim agrees with what I posted on the prior page and just above your post. The only question I have is has the torque spec changed since 1999.

[JimD]

I have no knowledge of torque spec. changes that apply to 1999 and previous heads since that 10/04/1999 Bulletin.

The only difference I am aware of applies to later engines (2000+).

[KHE]

I'm going to print out that bulletin and insert it into my manual. Hopefully I don't have an issue with my engine. BigCat83 needs to torque to the third pass - since he went two passes at 60 degrees, I'm wondering if he should make the last pass at 60 degrees since he started at 22 ft-lbs static torque?

[BodybyFisher]

I'm going to print out that bulletin and insert it into my manual. Hopefully I don't have an issue with my engine. BigCat83 needs to torque to the third pass - since he went two passes at 60 degrees, I'm wondering if he should make the last pass at 60 degrees since he started at 22 ft-lbs static torque?

It seems to me that in 1999 more clamping force was called for because of this:

22 ft lb then 60,60,60 = 180 degrees, but in 1999 it was revised to 30 ft lbs then 70,60,60

I know myself, I would be tempted to retorque all of the bolts is that possible or are you looking for trouble doing that? Will the time-serts back out if he loosens the bolts? If he does this will the head gaskets need to be replaced?

[Cadillac Jim]

Reading Service Bulletin 641058 carefully, it says to torque the bolts 8 lb-ft tighter and turn it 10 degrees more on the first run. If you started out with 22 lb-ft and turned it 60 degrees twice, I would turn it 60 degrees one more time like your shop manual says, and look at the torque reading on the wrench. If they are all under 85 lb-ft, I would turn them all another 10 degrees. I wouldn't worry about the extra 8 lb-ft initial clamping torque unless you decide to pull the head bolts and start over.

One thing occurs to me -- the torque-and-turn specs are set up for a particular bolt. The torque bottoms the bolt head and clamps the gasket, and the turn sets the clamping force. The thread pitch, the amount that the gasket compresses, and the force required to stretch the bolt that much determines the clamping force. If they changed the head bolts to allow more head/block expansion with less clamping force change, they would need more turn to get the same cold clamping force, and that may be the extra 10 degrees. Are your new head bolts identical to your old head bolts, or are they a tad thinner, or even a different alloy? If so, I would definitely think about another 10 degrees.

Before you put on the front of the engine, you might consider a new oil pump. I've seen an occasional post about the oil light flickering at idle in very high mileage cars, and my old engine was doing that occasionally when I ran 5W-30 in it and came off the highway to a stop light in the summertime (about 110,000 miles). That's a classic indication of a worn oil pump. It's not a lot of money and here's your chance, you are looking at it.

[clarkz71]

It seems to me that in 1999 more clamping force was called for because of this:

22 ft lb then 60,60,60 = 180 degrees, but in 1999 it was revised to 30 ft lbs then 70,60,60

I know myself, I would be tempted to retorque all of the bolts is that possible or are you looking for trouble doing that? Will the time-serts back out if he loosens the bolts? If he does this will the head gaskets need to be replaced?

I read a post the GURU made on the other forum regarding this. He said you could loosen all the head bolts and retorque them as many times as you wanted as long as they weren't heat cycled. Same for the headgasket. If I were BigCat83 I would start fresh and use the updated spec.

[BodybyFisher]

Now that you mention it, I recall him saying that also!

[BigCat83]

I didn't use the updated spec. I turned all the headbolts the additional 60 degrees and let it go at that.

The cam cap screws and M6 bolts are torqued at 106 lb inches, the cams are timed and tomorrow is tensioners and closing up the timing cover. Before I do, I will turn the engine over several times by hand to be sure there is no interference between valves, pistons etc.

[KHE]

Reading Service Bulletin 641058 carefully, it says to torque the bolts 8 lb-ft tighter and turn it 10 degrees more on the first run. If you started out with 22 lb-ft and turned it 60 degrees twice, I would turn it 60 degrees one more time like your shop manual says, and look at the torque reading on the wrench. If they are all under 85 lb-ft, I would turn them all another 10 degrees. I wouldn't worry about the extra 8 lb-ft initial clamping torque unless you decide to pull the head bolts and start over.

One thing occurs to me -- the torque-and-turn specs are set up for a particular bolt. The torque bottoms the bolt head and clamps the gasket, and the turn sets the clamping force. The thread pitch, the amount that the gasket compresses, and the force required to stretch the bolt that much determines the clamping force. If they changed the head bolts to allow more head/block expansion with less clamping force change, they would need more turn to get the same cold clamping force, and that may be the extra 10 degrees. Are your new head bolts identical to your old head bolts, or are they a tad thinner, or even a different alloy? If so, I would definitely think about another 10 degrees.

Before you put on the front of the engine, you might consider a new oil pump. I've seen an occasional post about the oil light flickering at idle in very high mileage cars, and my old engine was doing that occasionally when I ran 5W-30 in it and came off the highway to a stop light in the summertime (about 110,000 miles). That's a classic indication of a worn oil pump. It's not a lot of money and here's your chance, you are looking at it.

Torque readings with a regular torque wrench on a bolt that has been tightened to a torque to angle spec. do not correlate to anything. The whole reason for a torque to angle spec. is to remove the friction component from the equation which results in more consistent clamping force.

The head bolts do not stretch like a torque to yield bolt. There will be slight deformation but it is neglected for the most part. The only reason the head bolts are not reused is there is no practical method to apply the drylock threadlocker in the field.

If it were my engine, I'd leave it at 60-60-60 and call it a day...

[BigCat83]

"If it were my engine, I'd leave it at 60-60-60 and call it a day..."

Exactly what I did. I've been screwin' around with this project long enough...

[BodybyFisher]

I didn't use the updated spec. I turned all the headbolts the additional 60 degrees and let it go at that.

The cam cap screws and M6 bolts are torqued at 106 lb inches, the cams are timed and tomorrow is tensioners and closing up the timing cover. Before I do, I will turn the engine over several times by hand to be sure there is no interference between valves, pistons etc.

Big Cat, you mentioned previously that a couple of bolts felt odd when you torqued them the second 60 degrees, how did they feel when you torqued them the final 60 degrees? Mike

[BigCat83]

I didn't use the updated spec. I turned all the headbolts the additional 60 degrees and let it go at that.

The cam cap screws and M6 bolts are torqued at 106 lb inches, the cams are timed and tomorrow is tensioners and closing up the timing cover. Before I do, I will turn the engine over several times by hand to be sure there is no interference between valves, pistons etc.

Big Cat, you mentioned previously that a couple of bolts felt odd when you torqued them the second 60 degrees, how did they feel when you torqued them the final 60 degrees? Mike

They felt fine. Hence the need for the 180 as opposed to 120 degrees... As the head bolts pull in the way they "feel" changes. I'm used to acorn nuts on studs and this Northstar with it's bolts was different - you can tell. I know what I'm saying appears odd but it's true.