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Username Post: 1986,454 head bolt torque specs?        (Topic#349333)
100 CHEVY 
Dedicated Enthusiast
Posts: 6257
100 CHEVY
Loc: Helena,Missippi,U.S.A.
Reg: 12-09-04
01-25-18 06:50 PM - Post#2722143    

I'm getting 75/80 on the long bolts and 65/68 on the short bolts.
Is this the correct numbers?
It's a 1986,454 truck engine from a motorhome.
All stock as it came new.
Thanks,Mike,

"You gonna leave it like that?
http://www.picturetrail.com/100chevy


 




Shepherd 
Frequent Contributor
Posts: 1154

Loc: Lake George, NY
Reg: 11-11-15
01-25-18 07:15 PM - Post#2722147    
    In response to 100 CHEVY

http://www.gtsparkplugs.com/BBC-Head-Torque-Seque n...



 
IgnitionMan 
Valued Contributor
Posts: 3256

Reg: 04-15-05
01-26-18 04:37 AM - Post#2722164    
    In response to 100 CHEVY

I would add to make sure those bolts, if stock, are NOT "Torque To Yield" types.

If they are, you might want to NOT use them, go with non-TTY types.

Torque to yield bolts are stretch set ('torqued') by attaining an initial tightening setting, then adding a set rotational turn. They are a one shot deal, should be replaced when they are un-torqued.

Example of TTY: "tighten to 45 ft-lbs, then, continue to tighten an additional 1/4 turn".

Quiet a few of the full gasket sets that had new head bolts included in them had Torque To Yield bolts, not conventional ones.



 
100 CHEVY 
Dedicated Enthusiast
Posts: 6257
100 CHEVY
Loc: Helena,Missippi,U.S.A.
Reg: 12-09-04
01-26-18 07:03 AM - Post#2722185    
    In response to IgnitionMan

How would I recognize the difference?
My gasket set (Felpro)doesn't have new bolts in it.
Mike.

"You gonna leave it like that?
http://www.picturetrail.com/100chevy


 
Shepherd 
Frequent Contributor
Posts: 1154

Loc: Lake George, NY
Reg: 11-11-15
01-26-18 07:33 AM - Post#2722194    
    In response to 100 CHEVY

If Tty bolts were included in the gasket kit, they usually include instructions on the torqueing procedure. If I remember correctly, they do not have the grade 8 markings on the head. Plus I don't think the 86 oe bolts were Tty.



 
100 CHEVY 
Dedicated Enthusiast
Posts: 6257
100 CHEVY
Loc: Helena,Missippi,U.S.A.
Reg: 12-09-04
01-26-18 09:19 AM - Post#2722211    
    In response to Shepherd

The instructions I got with the gasket set just says to go to the O.E. for torque specs.
I rebuilt my 88,454 a few years ago and don't remember anything different about the head bolts.
Reason I come here!
Mike.

"You gonna leave it like that?
http://www.picturetrail.com/100chevy


 
IgnitionMan 
Valued Contributor
Posts: 3256

Reg: 04-15-05
01-26-18 03:54 PM - Post#2722254    
    In response to 100 CHEVY

Sounds like you are good to go.

Another thing to remember, blocks, heads, manifolds use what is described as a "roll" thread for their bolt holes.

A roll thread does not come to a point at the end of a thread, both thread angle flutes end before intersecting, in a flat area. These threads are significantly stronger than a typical regular tap and dye set cut thread.

Many people are not aware using a cut thread tap in a roll thread cuts away the end strength of the thread, making that thread a whole bunch weaker than when it was a roll thread.

So, they innocently, unknowingly use a cut thread tap to do a "clean and chase the thread", weakening the thread in the bolt hole.

To see what a typical roll thread looks like, look closely at the threads of a dedicated Head, main bolt, and you should see the flats on both ends, inner and outer, of the roll thread.



 
Shepherd 
Frequent Contributor
Posts: 1154

Loc: Lake George, NY
Reg: 11-11-15
01-26-18 04:51 PM - Post#2722267    
    In response to IgnitionMan

Good point, common mistake, did this myself years ago.



 
100 CHEVY 
Dedicated Enthusiast
Posts: 6257
100 CHEVY
Loc: Helena,Missippi,U.S.A.
Reg: 12-09-04
01-26-18 06:01 PM - Post#2722284    
    In response to IgnitionMan

Well,I looked at some of my 454's today.
3 of the 80's engines had the same head bolts with a large + on them.
Another,a 99 Vortec 454 had the smaller head on the head bolts.
The last,a 70's 454,I couldn't reach because it's hanging up high on a beam.
I won't chase the threads,I'll use a wire brush in a drill to clean inside the holes and on the bolts.
Cleaned and measured the one head today and it's within the specs (.004)for flat.So is the block surface.
Looks like age and corrosion caused it to start drinking antifreeze on #6.The only way I knew it was leaking was the random small bubbles in the radiator and the plain water I put in it turned a black color from combustion gasses.And,an over-rich carb.
I still can't find where the actual leak was!
Mike.

"You gonna leave it like that?
http://www.picturetrail.com/100chevy


 
IgnitionMan 
Valued Contributor
Posts: 3256

Reg: 04-15-05
01-26-18 06:13 PM - Post#2722287    
    In response to 100 CHEVY

To possibly learn more about Torque To Yield bolts, try googling that subject.



 




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