Hi All,

When putting an engine back together after tear down, are there torque specs for the different bolts like the head bolts or back plate bolts? If so is there a small torque wrench that you use?

Thanks
Tom

None specified. Good snug and tight is all I go by, tightening the head and back plate on opposing ends as I go around, just a little at first, then a second time around to make it tight and even. When you took it apart, that gives you the idea how tight to make it.

I've seen numbers around 11 in-lbs for head bolts, the same ought to work for backplate bolts.

Overtightening head bolts can warp a head/sleeve

Depends on the size of the engine. 11 in lbs isn't going to work on a FX61 or BX-1 1.08. Might be good for a .15 OS FP. You'll probably strip the threads or snap the bolt before you warp a head. Warping comes from tightening in a circle and not staggering your bolts down.

11 is pretty high for 50 sized engines, 7 is about right and 4-5 for the back plate bolts. For M4 bolts 10 is good. I have a chart if anyone is interested.

Iuse the Allen wrench as my torque gage. Staggered tightening as suggested above is necessary. I do it over at least four steps. IEon the head there is usually 5 or 6 bolts. Holding the head in place bring down the screw so it is just touching the head Use the skip pattern and do the rest, Back to #1 and snug it using the small end of the wrench as your lever. Same pattern. Now use the long end and with your thumb on the upright pull with your fingers till you just feel some spring in the Allen wrench. Go over the pattern again. The repeat with the same feel when you feel the wrench spring just a bit, that is a tight as you need to go. When you loosen one of the bolts, they should snap when they let loose. It used to be good practice to go back and re-tighten the head bolts on a car after it had about 10 minutes warm up time. I've yet to see the need for this on our engines. The only screws I've seen loosen up were the set screw on the needle valve extension, and the exhaust manifold to head on four strokes.

The Allen wrench spring is goodup toabout a #10 in size. Mostof the head bolts are around 3mm so it works out just fine.
Don't forget a drop of oil on the threads before you start. They have been known to kind of weld them selfs to the head when put in dry.

By the way, a lot of the small torque wrenches, actually screw drivers, are a fixed torque. An adjustable one can cost nearly the price of ansmallengine, if you can find a used one. New, you can plan on well over a hundred, and depending on the wrench $200 might be closer.

Finally, the torque charts that I have been able to find usually drop of a about 1/4" or #10 size, so they are not much help for the screws we use.

I halve these numbers for most heads and quarter them for most backplate bolts. Glow plugs, I do at 22 inch lbs. At first 22 seems like a lot but I've never had one strip at that setting. The Tork-It wrench came from here.

http://torkit.com/

that's the same wrench I use.

My wrist is calibrated. I don't strip em' and they also don't vibrate loose.

Most of the time.

Exactly, it`s really that simple[8D]

I say :
And that completes the votes from the Norwegian jury.
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You guys bring back some memories.Just after I finished my apprenticeship in machine repair, I followed a Norwegian guy who was on first shift. Man was that guys wrist was calibrated. He tightened each and every screw to the point the head would break off, almost.I hated to work on a machine that he had worked on. Iask him one day how he managed to get them so tight and his response was to tighten them until they were about to break and then loosen them a 1/8 turn. Whathe was saying was that it is experience.

I've broken the heads off screws that shouldn't break, pulled the threads out on more than my share of screws. After some years, experience calibrates the wrist. It's kind of hard to tell that to a new guy though.

Don

I confer. I don't seem to have any trouble. They don't break and don't come loose.

I call it common sense

the tork-it wrench works well, I have a similar one, use it for everything. I can do the wrist thing also, but prefer consistency working with racing engines.