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Time-sert Installation/Walkthrough on a cylinder head

What are Time-serts?

Time-serts are thread repair inserts. Very similar to Heli-coils, but superior in design and strength. Time-serts feature a flange at the top to offer a positive stop and not allow the insert to thread down further than intended. They also expand into the hole as to not accidently spin out when a bolt is removed from the inset. Lastly, they do not have a pigtail at the bottom like a Heli-coil does, so a fastener can pass through and beyond a Time-sert insert.

These are excellent for repairing threads, but they are also great for offering a stronger threaded hole. In my case, I am Time-serting all of the exhaust manifold holes and all of the valve cover holes. I'm adding the inserts to gain strength and prevent future thread stripping, so I'm doing it as an upgrade not as a repair.

These aren't cheap by any means. They are about twice as expensive as Heli-coils. Whether they are worth the cost is up to you. The kits and replacement inserts can be found on Amazon.com among other places. The exhaust manifold studs are M8 x 1.25 and the valve cover is M6 x 1.0. See part numbers below:

M8x1.25 kit: 1812
M8x1.25x11.7 replacement insert: 18121
M8x1.25 tap guide: 38125
M6x1.0 kit: 1610
M6x1.0x9.4 replacement insert: 16101
M6x1.0 tap guide: 36105

Time-sert offers various length inserts. But the above lengths are what I found to be ideal for the exhaust manifold studs and the valve cover bolts.

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Each kit contains a drill bit, counterbore cutter, a tap, a driver, and 5 steel inserts. (The pictured tap guide is sold seperately)



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99gst_racer

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Apr 5, 2003
Coloma, Michigan
Step 1: Drill out the holes to be Time-serted. It is important to not drill the existing hole any deeper. Extra depth is not needed and you don't want to be drilling beyond and into anything important. I measured the 8mm exhaust manifold stud holes at roughly .800" depth. So I marked my drill bit to that depth and wrapped masking tape around it to act as a guide to prevent drilling any deeper. Drill slowly. It will get away from you and pull itself inward very quickly if you're not careful.

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99gst_racer

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Apr 5, 2003
Coloma, Michigan
Step 2: Now that the drilling is done, it's time to counterbore each hole. The counterbore cutter is a simple cutter that cuts an internal step for the flange of the insert to lock against. It is designed to cut to the exact depth and will not go further.

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99gst_racer

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11,903
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Apr 5, 2003
Coloma, Michigan
Step 3: Now that the holes are all counterbored, it's time to tap the holes. This is where the optional tap guide comes into play. It's a simple machined sleeve that sits flat against the surface that is being tapped (in this case, the cylinder head). The tap slides into it and as long as you can hold the guide flat against the head, the tap will cut perfectly straight threads every time. It also saves a lot of time by greatly speeding up the tapping process and removes any doubt of straightness. The tap guide is a 'must have' in my opinion. Be sure to use some form of cutting oil on the tap. It helps cut a nice thread without causing damage. I prefer Tap magic. Run the tap all the way in until it bottoms out. Once you're finishing tapping all holes, you'll need to clean out all of the aluminum shavings in the holes. For this, I held the head with the hole upside-down and I blasted compressed air into the holes. It worked very well for me.


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99gst_racer

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Apr 5, 2003
Coloma, Michigan
Step 4: Now it's time to drive the threaded inserts in. You'll always want to drive the driver in about a ¼" beyond the end of the threaded insert. But you must be sure not to bottom out the driver. Bottoming out the driver can cause it to mechanically lock in place and you might have a hell of a time getting it back out. So, out comes the masking tape again. Line up the driver along the insert with ¼" hanging past, and mark your stopping point on the driver. After that, put a drop of Tap Magic (or the like) on the driver threads and thread on an insert. The insert won't thread on all the way, but that OK – it doesn't need to. By design, the internal threads at the bottom of the insert are only partially formed. When the driver passes through the bottom, it cold-forms the internal thread and that in turn expands the insert to cause it to self-lock in the hole. This is what prevents them from coming loose. So, thread the driver in until you reach your tape line, and then thread it out.

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99gst_racer

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11,903
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Apr 5, 2003
Coloma, Michigan
And that's it. Easy as that. Enjoy your stronger threaded holes. The process for the valve cover it the same. Just measure your depth before drilling and driving.

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