Bolt thread in fuel injection servo

[ctennis]

On the fuel injection servo there are four 1/4x20 bolts that connect the air intake box. Unfortunately as I was doing some fitting as I backed out one of the bolts, it also removed the internal "spring" link mechanism that provides the receiving threads in one of the bolt holes (see pic below, bottom right hole).

I can't seem to get this internal spring mechanism to rethread back into the hole, it's too tight. I probably need some way to compress the spring, but I don't know a creative way to do that AND get it pushed back into the hole. Anyone else run into this before? Hopefully I don't need to send the unit out, I still haven't even fired the engine up yet!

[rleffler]

I would give Don or Kyle a call at Airflow Performance. They can service other brands of FI other than their own. They're great folks and tend to be very helpful. (864) 576-4512, don@airflowperformance.com

Although, be advised that they may be at SnF this week.

[kkmarshall]

The "spring thing" is a Helicoil and a new one can be inserted easily but you will need the insertion tool. A new insert has a tang at the rear of the insert which is scored,the tool grabs that,tightens the coil as it's inserted and then you remove the tool and snap off the scored tang. NAPA should have the helicoil kit as well as other sources.

Keith

[brad walton]

Same thing happened to me. And yes you can get the proper helicoil and insertion tool at a local auto parts store. Quarter inch course thread if I recall correctly.

[snopercod]

I used to be a machinist, but I've never inserted a Heli-Coil. I did find some Instructions, though. I guess it's a little more complicated than just screwing the old one back in. (The last step in the installation procedure is to break off the tang, so you can't reuse the old one anyway.) All my life I've wanted to do everything myself - "How hard can it be?", I've always said. But this might be one of those jobs better left to a pro. First, you're going to have to buy a new Heli-Coil. How are you going to specify that? You'll need some way to accurately measure the hole size (drill rods?). Then you're going to have to buy the insertion tool(s). I wonder why did the insert come out in the first place? Was the hole in the casting drilled and tapped improperly originally? If so, the new insert may back out as well. Did they use the wrong Heli-Coil?

The instructions did mention:

One of the reasons that HeliCoils fail in service is that they are improperly installed initially.

Possible warranty claim? Sometimes it's better to send the part to a shop that has the parts, tools, and knowledge. JMHO...

[ctennis]

Thanks for the updates everyone, this is great information! Will dig into it, but at least I know the terminology now.