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Old 09-24-2008, 05:39 PM
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Accessory hole screw up

I tried to salvage a couple of 487 heads that a friend gave me. They were given to him after original owner broke off a couple of bolts in the accessory holes. The first one only had one bolt broke off on the end with three accessory holes. No big problem, I drilled it and got the old bolt out with an ease out.
The other head was a little worse off, not as bad as it is after I worked on it
They had managed to break off one bolt, possibly two. One of the holes had a big heli coil installed in it but someone had tried to remove it, the other hole they tried to drill but the bit went off to one side and almost came out of the bolt boss, almost but not all the way through.
I drilled out the first one that looked the easiest with a 17/32 bit, then tapped it with a 5/8 tap. I then screwed in a 5/8 bolt and sawed it off. I then drilled it and tapped it for a 3/8 bolt. No problems, it worked great.
I decided to try the other one with the same method even though part of the original 3/8 bolt was still in the hole. I was skeptical but proceeded anyway. I took a three hole bracket and bolted up the two good bolts and sacrificed the bracket and drilled it through with the 17/32 bit. After getting it started good I took off the bracket and slowly drilled some of the meat off with a smaller bit. I was careful checking the depth as I went.
When I started tapping out the hole it went fine until the last turn, the tap pushed out the weak side of the boss.
My only question is, can I go ahead and drill it on through, then finish tapping it, put the 5/8 bolt in the hole then saw it off and still use this head with the accessory holes to the back of the engine?
I know I should have just quit while I was ahead, and used that side on the back but the thought of taking that thing to the machine shop in that kind of shape just made me shudder.
Is the head anchor material now or can it be salvaged?

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Old 09-24-2008, 06:38 PM
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hole thru bolt boss,,,,

Hi,i would do as you said,i would drill all the way thru,then tap the hole to the required size,i would take a bolt oil the bolt up good,then run the bolt thru the hole a few times,til it goes thru fairly easy. then i would see (measure) how deep i needed the threaded part to be,after carefully measuring,i i would cut off the size plug i needed (from bolt) then cut a good screwdriver slot into plug (bolt) then wash oil out of hole VERY GOOD with acetone,using a touch up gun,do it really good,same to the plug (bolt) from the back side of the tapped hole,i would take a toothpick and put loctite 268 (its a gel) on the appropriate threads.using a big screwdriver,screw in plug (bolt) til it bottoms (really where the bottom should be)try not to get locktite on upper might have a hard time removing the bolt you want to use,alternative to the loctite would be,JB WELD,again ONLY on bottom threads..let us know how it worked for you..
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Old 09-24-2008, 08:12 PM
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Thanks for the reply, I appreciate it. I guess I should have left that one alone, they really went off to the side when the they tried to drill it out the first time. Too much of the side of the boss was gone into to allow the 5/8 tap to work.
The right side of the back of the hole came out into the intake port. I still wonder if it will be a problem. I was hoping for a little more feedback. I'll try again to attach pics to this post.
Thanks again.
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