When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Drilled out exhaust manifold bolt: Helicoil or Tap it?
My new to me motor (2004 5.3) had a head bolt broken off. I couldn't get it out so I had to drill it out. The bit sticking out is the same depth as the other manifold bolt holes. Would it be better to helicoil this or drill and tap it?
Doing a HeliCoil involves drilling and tapping anyway. You drill out the original hole, tap it a size up from original, then thread the HeliCoil into it.
As mentioned in the other thread, welding is the preferred way. But drilling oversize and tapping is fine--I've done that when the original thread were stripped.
Helicoil or keensert would probably make a stronger thread but those bolts don't go very tight--like 25ft/lb or so.
Worse comes to worst, dorman makes a decent kludge fix. 917-107 is the part number.
They will hold FAR more torque than the original aluminum threads, and don't require the use of a "special" size bolt that's different from everything else. Just altogether the ONLY RIGHT way to fix that sort of thing.
Drill the hole to the correct size tor that Heli-Coil to the FULL depth of the hole. (don't go an farther though, you might do something stooopid, like, hit water) Install the insert with the last thread about ½ turn below the surface, use a punch to break off the tang, blow the remains out with compressed air, use a normal bolt. 25 ft-lbs is about right for those, or for any other bolt of that size (since torque generally goes with hardware size, not anything about the application itself).
In fact it wouldn't be a bad idea to do all 12. I usually do.
The answer depends on what you did to get it out and what you have left
Did you drill and ease out the old bolt? Did it unthread out? If so just stick a new bolt in.
Or did you have to completely drill the bolt and hole. If you had to completely drill it then you've now enlarged the hole and you'll have to heli coil it. Other wise you would have to tap the hole to a larger size then you would have an oddball sized bolt in that one hole and you'd have to drill your header/manifold hole out larger too.
I put a helicoil in today. The kit was $38.00. I wasn't expecting it to be that high. It went in OK. I haven't test fit anything yet, but it seems like it will be OK.
06-28-2018, 09:08 PM
Drilled out exhaust manifold bolt: Helicoil or Tap it? 
