How To Fix Stripped Caliper Bolt Hole

I finally collected all the parts to assemble my small-block Chevy 350 only when I torqued the head bolts, 1 of the holes stripped. I've heard there's a way to set up this with a thread insert kit, but I've never done it before. Do I have to have the engine to a machine store to get this done, or can I do it myself? I'm kinda stuck until I get this repaired. Luckily, the engine is out of the motorcar if I have to take it to the car shop.

Grand.M.

Jeff Smith: The proficient news is that you can repair this trouble yourself with just a few simple hand tools and a ½-inch drill motor. There are several kits on the market place for thread repair, but I've used the Heli-Coil kits in the past with good results. In the case of the modest-block Chevy, the head bolt is 7/16-inch with 14 threads per inch. So this will require the Heli-Coil kit PN5521-vii. The kit comes with the unique tap, insert tool, and six thread inserts. You lot will as well need a 29/64-inch drill bit to open the hole upwardly for the required tap. The most important point of this operation is to make certain the hole you drill is perpendicular to the deck. To ensure that the commodities hole is in fact perpendicular to the deck, you will demand a drill guide.

Y'all can purchase dedicated drill guides designed for iii/viii-inch drill motors, just these tools are mainly designed for woodworking and the reviews I've seen are critical of the quality. A better idea is to brand your own. There are a bunch of different ideas for creating ane. The simplest is an aluminum or steel block about two inches thick and roughly six or seven inches long. The block must be perfectly flat on the cylinder block face. Next, you could apply transfer punches and a cylinder head as a guide to drill 3 holes. The first two are used to position head bolt holes that volition locate the drill guide on the engine cake. The third hole is the near important ane. Information technology needs to be larger – plenty to conform a length of hardened steel drill guide material. This bushing will be the same inside bore equally the outside diameter of the drill flake–29/64 or 0.4531-inch. The guide will so be pressed into the cake to securely locate it. That might exist a job for a local machine shop. Once that's done, you tin use this block to center the drill bit over the head bolt hole. You can double-cheque your work by threading a head commodities into the block from your made drill guide. If the bolt won't spiral in, then the position is off. You lot don't need a depth limiter for enlarging the stripped hole since all product pocket-size-block Chevy head bolt holes open into the water jacket. If you were doing this on an engine with bullheaded head bolt holes, you would definitely desire to indicate drill depth with a mark on the drill bit. With the block accurately in place, you can use information technology to guide your drill bit through the engine block. I know this sounds like a lot of work, but information technology's of import that drilling the Heli-Coil hole is as perfect as possible. Information technology'south a agglomeration of piece of work to ensure that the twenty seconds it takes to drill the hole that information technology's as authentic as possible. Our machinist friend Don Barrington said that you demand to be careful with caput bolt holes nearest the cylinder as they have a tendency to crack correct into the cylinder wall while you are drilling. When that happens, y'all accept a much larger trouble! Simply exist careful and don't say we didn't warn you.

Next step is to tap your newly-drilled hole with the supplied Heli-Coil tap. This will besides require the tap to be perpendicular to the block. I would suggest using the drill guide to help start the threads. In one case the tap has started, you can back it out, remove the drill guide, so finish cutting the threads. Finally, follow the instructions for installing the thread insert. It may crave a 2nd insert stacked on top of the offset. Y'all will also have to break off the tang at the lesser of the insert to allow the head bolt to fully appoint. One time the offending caput commodities hole has been repaired, y'all should clean the other holes. But don't use a normal tap. Normal thread taps remove block textile that will only increase the chances of pulling threads in other holes. ARP makes a thread cleaning tap that is designed to sweep the threads but not remove metal. For your 7/xvi x 14 head bolts, the cleaning tap is PN 911-0004. This is expensive, just considering the alternative of installing several more than Heli-Gyre inserts into your block, the price doesn't seem so bad.

I would also warn against using stock head bolts and I certainly avoid no-name "high performance" Grade viii caput bolts. Many years ago, the guys at ARP showed me what's wrong with these generic loftier performance fasteners. I chose a hole in a SBC block and threaded a stock head commodities in about four or five turns into the block. The commodities wiggled a picayune fleck, which meant there was quite a bit of clearance between the commodities and the female block threads. Then I tried a generic operation bolt and the "wobble" clearance was shocking. The bolt moved so much it seemed similar the threads were undersized–which they are. The thread overlap in these bolts is marginal, which tin and nigh frequently contributes to pulling threads out of the block. The concluding bolt I tried was an ARP bolt. It actually required slightly more try to thread it into the block in the exact same hole. This revealed the increased thread engagement with the ARP commodities compared to the other two bolts. That's why at present I only get together an engine with ARP head bolts. In your case, assuming stock head bolt lengths, the ARP kit is 134-3601. I clean the cake with the ARP thread-cleaning tap, glaze the threads with thread sealer (for whatever commodities holes that extend into the water jacket) and use ARP's Ultra-Torque underneath the bolt head flange and on both sides of the washer. All ARP head commodities washers come with a relief on ane side that is designed to match the radius on the underside of the ARP bolt caput. Make sure the washer radius is installed correctly.

This may seem similar a lot of effort for merely bolting on a ready of heads, but it all will pb to a properly assembled engine where you won't take whatsoever head gasket problems because the load is even across the unabridged face of the cylinder caput. If you accept intendance of the details, the details will accept intendance of you.

Source: https://www.onallcylinders.com/2014/12/05/how-to-fix-a-stripped-head-bolt/

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