Access for Torquing Head Bolts?

I'm going to install a cylinder head temperature gauge on my OB. The sensor mounts by removing one of the upper head bolts and bolting it on. I'm thinking it might be appropriate to re-torque all of my head bolts when I do this. Problem is, the two lowest head bolts are not accessable with a torque wrench fitted with the appropriate sized socket (at least not the kind of torque wrenches I have). The lower housing blocks this access.

Short of pulling the power head for access, anybody have any slick tricks for properly torquing these lower head bolts?

Re: Access for Torquing Head Bolts?

remove the chaps?

Re: Access for Torquing Head Bolts?

I should have been more specific - it's my outboard motor, not my horse

(what are the "chaps"?)

Re: Access for Torquing Head Bolts?

What engine are we talking about?

Re: Access for Torquing Head Bolts?

79Merc80 said:

What engine are we talking about?

Click to expand...

1982 Mariner 30 HP. From the Service Manual it looks like to remove the lower cowl (which would provide access to the two lower bolts) one would have to remove the power head. That goes way beyond my desire to simply make sure the head bolts are torqued to specs.

Re: Access for Torquing Head Bolts?

Pretty much the main object of torqueing hardware is to get even pressure on that which is to be secured to maintain the integrety of the gasketed surfaces.

Additionally, sometimes the torque spec is designed to put the bolt in a certain amount of tension (rod/main engine bolts for one), and then there is the issue of breaking the bolt in half or stripping the threads, especially in cast aluminum blocks.

For a reference, we were working a problem on water jacked covers for the cylinder area and the exhaust area for a 90 hp Merc and the torque specs were like 16 and 22 ft-lbs. These numbers are tighter than "good and snug"....reference for what I am about to say:

Do whatever prep that suits your fancy prior to installing the gasket and cover. Then insert all your bolts and in a criss cross pattern (like doing heads) center to outer edge, snug up good.

Then take your torque wrench and at the center of the cover, torque a couple or so of the bolts to spec. Remove your torque wrench and with the wrench you plan to use on the bolts you can't reach, work the torqued bolt(s) back and forth getting the feel for what the specific torqued bolt feels like. Then, while your memory is fresh, work your way out to the end with your torque wrench, swap wrenches and finish the job.

HTH,

Mark

Re: Access for Torquing Head Bolts?

"Then take your torque wrench and at the center of the cover, torque a couple or so of the bolts to spec. Remove your torque wrench and with the wrench you plan to use on the bolts you can't reach, work the torqued bolt(s) back and forth getting the feel for what the specific torqued bolt feels like. Then, while your memory is fresh, work your way out to the end with your torque wrench, swap wrenches and finish the job."

Ahhh, the "calibrated arm" technique. I could do that since the two lower bolts can be reached with a box end wrench.

Re: Access for Torquing Head Bolts?

Turns out I can access the lower bolts with a crows foot (12 mm) on my small torque wrench. The crows foot adds a maximum of 7/8 inch to the 8 1/2 inch effective length of the torque wrench. That equates to an actual applied torque of, at most, 10% higher than indicated by the reading on the torque wrench.

I doubt if my torque wrench is much better than 10% accuracy (it is HF), so I'm thinking if I set the torque wrench near the lower end of the cylinder head torque spec range, and use the crows foot on all of the bolts, for consistency, that will be as good as I could do even if I pulled the power head for access.

The torque spec for the cylinder head bolts is 18-25 foot lbs. - heck, the "calibrated arm" technique would probably suffice after all

Re: Access for Torquing Head Bolts?

Turns out the crows foot would reach the bottom bolt on one side of the cylinder head, but did not have enough clearance to rotate (tighten) on the other side. So, I came up with the attached, using a 12 mm box/open end wrench, a bolt, a couple of nuts and three washers (I had to file the flats down on one of the nuts to make it fit in the 12 mm open end wrench).

This put a 4 1/2 inch extension on my 8 1/2 inch torque wrench - resulting in an increase in torque of 53%.

I used this rig on all of the cylinder head bolts, for consistency. I'm glad I went through this exercise because a couple of the bolts were kind of loose.