Technical Removing cylinder head bolts, your thoughts?:

Should cylinder head bolts be removed in sequence and incrementally?

Or does it not matter?

Small block chevy with iron heads.

Your thoughts?

 

Air gun & impact socket ...

 

I do it sequentially, but I dont think it makes any difference, just a habit with me. Even Im not compulsive enough to do them incrementally, I just crack 'em all with a breaker bar, then spin 'em out with a T bar and extension.

 

Impact gun, no order. Discard. Replace.

 

I usually do them in reverse order that I tighten them. I don't know why.

 

Doesn't matter how you take them out, it does how you put them in. Head bolts were reusable up to the early or mid 80s, since then many are one use only.

 

I'm with Gimpy, I blast them out with the impact gun and discard them. New ARP bolts on the install.

 

I almost always reuse them, too. I don't work on late models much!

I wonder why we torque them in a certain pattern?

 

I was taught that we torque them in sequence to make sure that the gasket spreads correctly. It could be totally unnecessary given today's new materials in gasket construction, but I'm pretty sure I will continue to use the sequence as long as I can still put enough force to the torque wrench to make it click!

 

I always "break" the bolts first, in the same order that they are tighten. Once the pressure is released, then I use a ratchet to remove the bolts in random order. I've always reused the same bolts on the old Chevy motors but on new motors, the head bolts should be replaced, because they can break if retorqued.
Also, for example on a 235 Chevy 6, the torque spec for the head bolts is 90-95 ft lbs, so what I do is I torque the head in increments, starting at 30-35 ft lb.

 

Bolts are cheap. Engine failures are not.

I will not trust a $3-14k build on 30-70 year-old bolts in unknown condition.

 

That's funny! I just helped my neighbor out yesterday replacing head gaskets on his diesel pick up. Final torque was 210lbs!!! We both were pulling on the wrench, but couldn't get to click point, had to put a pipe on it to get there. Manual says not to do that, but there was no way we could get it done without one.

 

break them loose in the reverse order of tightening then remove them , inspect them and reuse them , if its a race motor it gets studs after it comes back from the machine work ( except lower end as they have to align bore it after it gets studded )

 

need to get one of my wrenches thats made for that, its 4' long and can go to 600 LBft , and its a dial type . I have a special hydraulic one we use on EMD's as the crab head nuts ( head retainer) torque out at 1900lbft the old wrench one we had was 8' long and it doesn't work well when the motor is still in the unit .

 

We torque headbolts in pattern to prevent warping the head casting.If you notice you will see we always start in the middle and work out toward the ends.This keeps the head casting flat on the block.I usually loosen headbolts in pattern.Some engine manufacturers are very specific about loosening incrementally and in pattern.IME those will usually be engines that have aluminum heads and not enough head bolts.

 

As far as reusing the bolts, how "old" is old and how new is new as far as engines/engine type?

i'm not opposed to buying new bolts, i'm just curious. In my case, it appears that the engine has never been rebuilt.

 

Yes, i'm getting the impression that iron, it doesn't matter, aluminum probably does.

 

it depends alot of the condition of the shank ( nicks , rust ) and the threads , and unless you know someone who does NDT testing the only real way is to measure the length to see if they are stretching , but you have to know the length of them before they were put in . so if your worried about it , chuck them and get new ones .and use a rolled thread replacement not cut threads ..

 

Look up the torque specs, if they mention turning some fraction of a turn after reaching a certain torque value, then they're probably torque to yield design, and need to be replaced.

I trust 70 year old bolts more than I trust new stuff of unknown origin. But yeah, you need to inspect them and make some judgements based on experience.

 

For squirrel, The reason heads bolts are torqued from the inside out is to allow the gasket to expand outward as we tourque. If we were to torque the outside bolts first we would "trap" the gasket thus not allowing it to spread.

 

Ahhhh..........I.C.

 

Sounds a bit strange to me....I once asked my gaskets if they were worried about feeling trapped, and they didn't seem to concerned about it.

 

I break them loose by hand, half a turn, mostly to be sure they're breaking loose and not seized, then buzz them out with impact. I mainly build sbc's and reuse head bolts unless I see something wrong. Buy bolts on anything hi-po.

 

All gaskets must "flow" in order to fill the gaps in the machined surfaces they are in contact with. Obviously rubber or cork gaskets will fill larger grooves whereas copper or steel gaskets (like head gaskets) can only fill much smaller grooves. By torquing from the insde out the gasket "flow" is allowed to work outward as we tighten thus not being "trapped" causing the gasket to bunch up, thus forcing the mating surfaces apart and possibly causing a leak.

 

ALL bolted connections should be detensioned in the reverse order they were torqued.

 

S.A.E. dictated 'bolt stretch' to ascertain steady 'clamping' during the life of the gasket; torque specs to 'guarantee' tightness when hot and when cold.
Do A.R.P. bolts have the same elasticity specs as factory O.E.M.?
ARP spec sheets liken con rod bolts to possess the hardness of the Hubs of Hades. 'Bolt Stretch? Not on this train...'

When the 'art of Angle Torquing' came about (BMW factory specs) I took it as ludicrous. Two of our apprentices were convicted of pulling studs @ 30 degrees. A long probationary period ensued...
Parts Dep't was optimistic they'd make a killing in s**** metal for the stretched bolts that were replaced with every head gasket replacement.
I longed for the 'good old days'...

 

I give about a quarter turn in reverse order and then remove them in the same order. Had an old shop teacher that worked for Mercedes and they removed them with an impact. Probably doesn't matter on removal but I don't think I'll change.

 

We don't need head bolts!

 

In the case of a SBC the only bad thing you can do is loosen all bolts except bottom row! You know the ones hidden by the exhaust!

 

first time I took heads off a SBC, it was an old 283 before PCV, the heads were covered with sludge, I was 14 years old...I was prying for a while before I looked and found those other two bolts near the ends, way down in there. Didn't break anything, I wasn't strong enough to.