While bolting my engine back together with my rebuilt donor heads, I was a bit suprised when I went to bolt on the tensioner for the timing belt. There was no hole in the heads tapped for the tensioner! I looked at the 93 FSM, and it shows the tensioner bolted where I thought it should be, and my original 94 heads had a hole where the tensioner was bolted. Needless to say this realization dealt me a serious oh s&@!
Since I'd already gone through all the effort, and expense to put the rebuilt heads in, I wasn't about to give up. I measured the old head and found the holes are 58mm ctc. I was figuring I'd need to go and get a tap and pilot drill the following day, but decided to look through my set of taps. I've got about 2-3 ea of most SAE taps, and all of one metric taps, and I don't recall what project I'd gotten it for. Low and behold, my single metric tap was a 10X1.25, my luck was changing. I also dug through the drillbit pile, and found one that was a close sliding fit for the bolt, and according to my tap chart, I found a bit for the tap.
I don't know anyone who can free hand drill a hole square and accurately, I know I can't, so I needed a jig to line up the bit and tap. So I dig through my junk and find a piece of 1" sq aluminum. I marked out two points 58mm apart, drilled with a pilot drill, then drilled one hole for a 10mm clearance, and the other with the tap pilot drill.
I went and bolted the jig on the head, using the one 10mm hole that was there, and used the power steering bracket hole neerby to triangulate. The head w/o the hole needed a bit of grinding to clearance the tensioner, so a 1/2" carbide burr on foredom flex grinder was used as a hand mill. A bit of grinding and I was there.
I bolted the jig in place, triangulated it, then ran the tap pilot drill with a angle drill, just enough room to spare. Then I took off the jig, back to the drill press to drill out the tap pilot hole to tap dia, bolted it back in place and ran the tap in. Cleaned up the cuttings, and bolted the tensioner in place.
Just a heads up if you're planning to swap heads and find yourself in the same bind.
