Do not stud a Northstar
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Northstar Engines and System Technical Discussion Discussion, Do not stud a Northstar in Cadillac Engine Technical Discussion; Does everyone understand why putting studs in the Northstar deck is not good? I have been over this many times. ...
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    AJxtcman's Avatar
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    Do not stud a Northstar

    Does everyone understand why putting studs in the Northstar deck is not good?

    I have been over this many times. Studs are too hard. The Head grows in size and the factory bolt are designed for this.

    Say the head grows .5mm at 225 degrees from 50 degrees F. You stud the block and this cause the head gasket sealing ring to be compressed. What do you think will happen when it is 0 degrees out? What do you think it will do to the treads in the block?

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    drewsdeville is offline Cadillac Owners Master
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    Re: Do not stud a northstar

    There's nothing wrong with studding itself...it's just a matter of whether or not the studs are produced with the same yield strength and modulus of elasticity as the factory head bolts (which they aren't). That said, I've been through this already in a discussion about whether or not overheating can cause a head gasket leak (and it can, for the same reasons you've just posted - the rate of expansion increases more than designed as temps rise higher than spec'd range - which crushes fire rings, stretches head bolts, and scrubs gaskets). I have found that most here think thermal expansion is a myth, which inherently tells us we don't need gaskets at all and should have no problem with todays manufacturing process machining the surfaces perfectly flat, torquing the heads down with 400 pounds on super hard fasteners, and installing 300 degree t-stats for ultra efficiency. But for some reason, no one does it!
    97EldoCoupe and 97EldoCoupe like this.

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    Re: Do not stud a northstar

    Quote Originally Posted by drewsdeville View Post
    There's nothing wrong with studding itself...it's just a matter of whether or not the studs are produced with the same yield strength and modulus of elasticity as the factory head bolts (which they aren't). That said, I've been through this already in a discussion about whether or not overheating can cause a head gasket leak (and it can, for the same reasons you've just posted - the rate of expansion increases more than designed as temps rise higher than spec'd range - which crushes fire rings, stretches head bolts, and scrubs gaskets). I have found that most here think thermal expansion is a myth, which inherently tells us we don't need gaskets at all and should have no problem with todays manufacturing process machining the surfaces perfectly flat, torquing the heads down with 400 pounds on super hard fasteners, and installing 300 degree t-stats for ultra efficiency. But for some reason, no one does it!
    Have you looked at the quality of the aluminum?

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    vincentm's Avatar
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    My Northstar is the first one to use Tim Carrol's studs and so far it's a happy engine. Ive put on at least 8000 miles since getting this new rebuild (new crank, pistons, rings etc, the whole works)
    Speedygman and Speedygman like this.

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    Manic Mechanic is offline Cadillac Owners Fanatic
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    Re: Do not stud a northstar

    AJ in your example even the highest expanding cast aluminum alloy's can not grow 0.5 mm. I don't have the measurement but "let's say" seems to work for you. If the compressed head thickness was let's say 3" and we torqued the heads down at 50* F. Then at 225* F the expansion under the head stud would be, remember worse case scenario, 0.176 mm (0.00692"). I myself believe this to be within the elasticity of the gasket materials and the castings. In fact I would say the pressure against them generated by torque is much higher than that increase by temperature.

    I'll go with the prevailing wisdom on this one, in fact I already have. Also when I torqued my heads down I'm pretty sure it was warmer out, probably at least 70*F LOL.

    Bolts are an accountants choice, an engineer will choose studs. I don't want any give with my gaskets, so the harder the better for me. Also I don't put my engine to the test before reaching normal operating temperatures. No need to temp fate unless lives are on the line.

    Vernon

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    JoeTahoe is offline Cadillac Owners Fanatic
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    I am on my 4th studded northstar with Northstar Performance studs, the first three are doing fine the first one I did was over three years ago. Mine was done two years ago and I have beaten the crap out of it with no problems. This has been my experience

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    stoveguyy is online now Cadillac Owners Connoisseur
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    Steel studs vs steel headbolts. Please provide info on difference between these 2 different steels? We are not talking alum bolts vs steel bolts. If u can provide info which shows the difference in thermal expansion for each fastener than we can discuss.

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    Re: Do not stud a northstar

    Stoveguyy, what the discussion is about it not the expansion of the fastener length, though that is a good point. Rather it's about the expansion of the cylinder head itself, which is clamped down under pressure by said bolts or studs. AJ beleives that the studs won't stretch as much as the OEM bolts and therefore the heat induced expansion will crush the gaskets or pull threads out because the studs don't give. I think he overestimates the expansion of the heads. A five minute Google search provided me with the expansion rates of aluminum alloys per inch by degree F, Onlinecoversion.com allowed me to scale it back to mm. The reality is that's it's less than 20% of his guesstimate.

    I think it's a long and thouroughly proven commodity and don't see any reason to fight against known reality's on this.

    Vernon

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    Re: Do not stud a northstar

    I worked at a Standalone Cadillac dealer for almost 6 years and then went to a Caddy chevy dealer. Just between those 2 GM dealers I have amost 10 years working on Caddy's and I have been with GM since 1999. I have repaired well over 100 Northstar's and I have never had a failure using GM bolts

    GM bolts are Torque to Yeild
    Some Studs are Grade 8
    Other Studs are Tool Steel

    ----------

    This is another issue
    The casting have a tendency to shift or warp.
    I have ran the GM tool down the bolt holes. This tool is a REAM type. You will some that are straight and other hole on the same block on the same bank that are bowed.
    Now say you down have that long ream type drill bit. You drill the holes out and they are off a little bit. The Studs are too hard to flex.
    And another issue
    Some studs are placed up at the deck. Everyone should know that you would NEVER want to do this. It can distort the deck surface after torqued or even when going through a heat cycle
    Studs are great for race engines, but what is the expected life of a race engine? 20k?

    ----------

    I have a brand new set of 1999 cylinder heads. I will pull a head off the shelf and running it in my parts washer. I will mic it out before and after.

    BTW these head are an alloy and not 100% aluminum.

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    Re: Do not stud a northstar

    Digital thermometer says 74 deg
    Digital Caliper shows 4.5645



    ----------

    Digital thermometer read 121 degrees. It feels hotter, but my parts washer uses a home hot water heater element and thermostat.
    The digital caliper read 4.5895

    temp only went up 47 degrees and the head grew .025"



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    Re: Do not stud a northstar

    I'd like to see you take a head bolt and a stud, compare lengths at room temp and 200F.

    Another thought: Bolts are torque to yield, they stretch some during installation when approaching the intended clamping force. So, if the head grows .030 in height wouldn't the torque to yield bolts be subject to additional stretching, losing almost if not all clamping force when the engine cools?

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    Re: Do not stud a northstar

    They work like a spring hose clamp instead of a worm/screw hose clamp. That is a very big part of my point.

    The Main Bolt are hard and sound like you are breaking glass when you crack them loose and the main bolts are reusable.

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    Re: Do not stud a northstar

    Great to see you back AJ. A little off topic, do you think the new bolts in the 2006-2011 DTS Northstars have helped? ( solved ) the bolt pulling problem?

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    Quote Originally Posted by JoeTahoe
    I am on my 4th studded northstar with Northstar Performance studs, the first three are doing fine the first one I did was over three years ago. Mine was done two years ago and I have beaten the crap out of it with no problems. This has been my experience
    I also have studded several, more the 20 with zero failures. Northstar performance has sold several thousand kits with zero failures. They also have the best warranty available on their rebuilt northstar engines which are studded with a 5 year, 100,000 miles warranty. Theories are one thing, but I go by real world performance and from what I've seen, studding is the way to go

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    drewsdeville is offline Cadillac Owners Master
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    Re: Do not stud a northstar

    Quote Originally Posted by 3redlines View Post
    I'd like to see you take a head bolt and a stud, compare lengths at room temp and 200F.

    Another thought: Bolts are torque to yield, they stretch some during installation when approaching the intended clamping force. So, if the head grows .030 in height wouldn't the torque to yield bolts be subject to additional stretching, losing almost if not all clamping force when the engine cools?
    deformation is elastic - like AJ said, like a spring, and that keeps the clamping force very even and uniform across the whole head. If the yield strength is surpassed, the deformation is plastic and permanent.

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