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Difference between 98 and earlier heads and late 98 and later heads.

Slick2500

Slick2500

New member
So a bunch of us were in chat talking about Jared's top swap stuff, when Jared mentioned the heads he is getting are off a 98. I told him that the torque specs are different for 97-98 heads from these cars. Both heads are 37ft/lbs the 98 and older heads are +130* + 30* while the late 98 and new heads are just + 120*. Now the question is how are they different that they require a different torque spec? Are they slightly thinner? Are the spots where the head bolts set just recessed into the head slightly more?
 


I wonder if maybe the later head bolts used washers? Checking bolt part numbers might give a clue. Different tq on same castings or are they different?
 
Both use same head bolts and gaskets. I know Intense won't take 98 and earlier heads for core and this is what they have to say "The returned cylinder heads MUST be from a late 1998 or newer engine as prior to mid-1998, GM used smaller valvespring pilot seats and the heads were prone to cracking at these locations."
 
if you look it up they changed the sequence to add a second go at the middle 4 with the SI

they just changed and updated the tty specs and routine for better clamp load. pretty common updates to the assembly specs to cut assembly time/fix potential issues. the earlier 130+30 is only +30* on the center 4

there are 3 different routines over the years for the SI engines since they had 3 different length bolts.

the heads, bolts, threads never change just the assembly, and maybe bolt supplier....

i hate TTY, its a lazy out to proper prep and fastening/tqing, i still go over the middle 4 at a higher tq even with oe replacment bolts, studs i still do 30/30/60/90/90/and 93-95 on middle 4
 
Turbocharged400sbc said:
if you look it up they changed the sequence to add a second go at the middle 4 with the SI

they just changed and updated the tty specs and routine for better clamp load. pretty common updates to the assembly specs to cut assembly time/fix potential issues. the earlier 130+30 is only +30* on the center 4

there are 3 different routines over the years for the SI engines since they had 3 different length bolts.

the heads, bolts, threads never change just the assembly, and maybe bolt supplier....

i hate TTY, its a lazy out to proper prep and fastening/tqing, i still go over the middle 4 at a higher tq even with oe replacment bolts, studs i still do 30/30/60/90/90/and 93-95 on middle 4
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That cleared up a lot of confusion, thanks. So when you say the middle 4, do you mean the middle 2 on the top row and the middle 2 on the bottom row? And from what I read, the later engines changed specs just for quicker assembly and stuff, correct? So then do the 4 middle ones truly need to be torqued more than the others?
 


It's a 3800 man. You have to be literally retarded to scew
one up. I almost regret saying that because there are a few tards lingering around and their cars somehow are still running.
 
CrazyGuy03 said:
It's a 3800 man. You have to be literally retarded to scew
one up. I almost regret saying that because there are a few tards lingering around and their cars somehow are still running.
Click to expand...

Yeah, well I like my sh*t done right. Get it done right the first time.
 
CelibateHalibut said:
Yeah, well I like my sh*t done right. Get it done right the first time.
Click to expand...
well done right is key but over worrying is silly
now when I say done right it, it takes skill and money. Cause the amount of times I've done this crap, I noticed the more money you spend the easier it is lol
 
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So if you have pre 98 engine, it's better to stick with post 98 torque specs? I have a 1996 That I consider top swAp ...
 
id say use the most updated specs, I don't know though if it was a "we're crushing HG's" thing, or it was a "we can save at least 10 seconds per engine assembly time if we change the fastener tightening specs, engineering is pretty sure it wont affect reliability till over 100k miles"

pick yer poison
 
There's 8 bolts total... the middle four are the four he's talking about.

If you need to see what it looks like.. go look under "heads and rockers" in my pb account.
 


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