Engine building - best practice.

[wristpin]

While back there was an article in a tractor mag about doing an engine rebuild and the it gave the same order for both undoing and tightening the cylinder head bolts which seemed odd as we were always taught that the releasing order was the reverse of tightening -but the article gave centre outward for both . Thought that it was a typo and dropped a line to the mag but never got a reply.
Now the same guy is doing a rebuild on another engine and has made a point of saying that the order is the same for both loosening and tightening - any thoughts?

 

[keithski122]

Never totally believe what a magazine prints.

 

[Justme]

The exact order is not critical.

What is important is a steady progression evenly over the full area.

That can be achieved by more than one pattern.

 

[rtbcomp]

I usually tighten down from the centre out so the head flattens, if you start from the outside-in you can get a hump in the middle.

 

[blenkie1]

Does the manufacturer not usually give a tightening sequence?

 

[BrokenBiker]

I always tighten anything like a head or anything with a lot of bolts sat around the outside of a part from the centre out and loosen from outside in but that's just habit. I was told by a mechanic that loosening didn't matter as long as they were all done a bit at a time if you wanted to keep the head or whatever it was you were removing

 

[sardine]

It with will say in the service manual. Do that.

 

[Bill Edwards]

If you have instructions for a specific engine follow them, but failing that just do them evenly, a small amount at a time to begin with if you're worried. You're not worrying about squeezing a gasket properly, just releasing it without leaving pressure on one side/part.

Always torque a head from the center out (you listening brokenbiker? ).

 

[BrokenBiker]

I do always torque from centre out, even says so above...

 

[Bill Edwards]

I do always torque from centre out, even says so above...

Oops sorry, I read that backwards!

 

[Turbo]

If I don't have an engine manual I usually start from the middle & work my way out in a spiral pattern when tightening, the reverse when loosening. I always do it in stages even it it doesn't say in the manual.

 

[zzr1200]

It with will say in the service manual. Do that.

In "Ye Oldie English" Service Manual.............


It's probably more important that the engine is cold when doing a major strip, especially aluminium engines.

When tightening middle outward, un-doing what ever takes your fancy.

 

[JohnRUFC]

I was taught that the pattern didn't matter while tightening them as long as you kept a relatively even pressure so the gasket couldn't move or distort. Then you torque it from the inside out working in diagonals.

 

[normspanners]

I tend to undo from the outside.

I used to do a print off from auto data for tightening then follow the sequence primarily to mark on the sheet, the bolts that had been tightened but now I put a tipex mark on the bolts as soon as the socket comes off that bolt, so that I know that particular one has been tightened, but if the marks are in the correct/same orientation on the bolt head compared to the cyl head, it is handy to see the same amount of rotation of each bolt and then visually check them as a whole if one has been missed or turned further etc it stands out. That can be handy when disturbed by the phone or an earthquake, or somesuch. Or for instance if there is a different setting on some head bolts, ie 300tdi

 

[eSCHEn]

I was taught to spiral out from centre when tightening and the opposite when loosening. I've always done this but the scientist in me has to ask:

Has anyone ever encountered direct causal evidence that tightening in the incorrect order (but with the correct torque) caused a problem or damage?

I'm in no way doubting that it would cause problems but I can't say I've ever met anyone who has seen the problems first hand.

 

[AndyStobbs]

In "Ye Oldie English" Service Manual.............


It's probably more important that the engine is cold when doing a major strip, especially aluminium engines.

When tightening middle outward, un-doing what ever takes your fancy.

Ha, have you ever tried to remove cylinder head parts from an engine at 80 degrees C. I don't think many people would do it twice.

 

[sardine]

There are very few if any engines around that you can't find a download or copy of the manual.

 

[normspanners]

Ha, have you ever tried to remove cylinder head parts from an engine at 80 degrees C. I don't think many people would do it twice.

I've done a few ZF gearboxes that have melted into the tarmac as we refitted the replacement,needless to say it didnt stay on your chest very long on the way out, it used to take 3 of us less than ten minutes from the car coming in to going down off the jack,

 

[zzr1200]

Ha, have you ever tried to remove cylinder head parts from an engine at 80 degrees C. I don't think many people would do it twice.

I have a few times, don't like it much but times money when you work for your self.

When I was an apprentice, the record for removing a Ford 4 Cyl D-series engine from the vehicle driving in, stopping in the work bay, to the engine sitting on the floor was 21 minutes held by a 50 year old fitter at F.G.Gates Ltd at Woodford. He had all the tools laid out before bringing in the vehicle, including the engine crane by his work bay...

 

[Robotstar5]

Ha, have you ever tried to remove cylinder head parts from an engine at 80 degrees C. I don't think many people would do it twice.

I've watched a rally service crew remove a turbo that was glowing dull red when the car pulled into the service area, first job was 5 gallons of water poured over it then the mechanics would work until it got too hot for them then another would take over.