Does anyone sell a fixture for drilling broken exhaust studs

[Dan Mc Intyre]

Nice work everybody!


Maybe we can get John Walker to give one of those bad boys a test drive and post the results?!

[A Quiet Boom]

Originally posted by Dan Mc Intyre
Nice work everybody!


Maybe we can get John Walker to give one of those bad boys a test drive and post the results?!

He will be doing just that!

[A Quiet Boom]

Well, I've got everything set for the three sizes JW mentioned earlier. He was going to take some port measurements and get back to me. I reread my last reply and I think the meaning came out wrong. JW is getting a set of these and I assume he'll report back the results be they good or bad. I'll post some better pictures tonight I hope.

[A Quiet Boom]

I think I finally got the code where I want it, at least for a beginner CNC programmer. Here's a pic of the mill making parts.

[A Quiet Boom]

Guys, I've got 5 blanks made up. I'll be doing the final dimension on the lathe for the disc. JW was kind enough to get me a pretty good list of actual port sizes (thanks for measuring JW) I still need to get the ring size for a 3.6 though. Anyway anyone that needs one can email me their zip code year and model of engine to rsr911@neo.rr.com

-Christian

[Nathan]

Quick question what if both exhaust studs are broken?
How will it hold in line ?
Thanks.

[jpahemi]

Seems at that point the heads are coming out of the car.
J.P.

[A Quiet Boom]

Originally posted by Nathan
Quick question what if both exhaust studs are broken?
How will it hold in line ?
Thanks.

JW mentioned this earlier in the thread, you'd stand a better chance using this tool and might even get it right especially if part of one of the studs is still sticking out of the block to locate the tool. However I can't guarantee it will work. I suppose it's your call but it would seem wise to at least give it a shot before removing the engine and heads. The tool is primarily designed for use with only one broken stud per port. The insert should last far beyond the needs of most users.

Once again anyone needing one of these tools, I need the year and model of your engine before placing an order along with a zip code to calculate shipping. I can only deal with Fedex since there is one on my way home from work and I have an account. Email details to rsr911@neo.rr.com and I'll get back within 24hours max. I prefer paypal but can accept checks as long as the purchaser can wait for them to clear before shipment.

I will be offering a professional version of this tool with removable discs in the near future but I'm still figuring pricing since these are much more labor intensive. Also the tool at present has a 17/64" drill bushing pressed in place custom removeable sizes are available, please contact via email for pricing.

[A Quiet Boom]

Well I've shipped the first tool to Shuie, and I've finished one for another Pelican to ship tommorrow. I'm finishing the integral disc on my manual lathe for a close tolerance to the dimensions provided by JW or the users which makes the job go a little slower. After I get some feedback as to how well these work, I'll either setup a webpage (with help from a purchaser) or offer these to Wayne for sale through Pelican although I'll need a much more comprehensive listing of actual port sizes before I can do that. I've started a little database of port measurements as well as actual final dimensions for each serial number I've sold. Good luck guys, I've made these as accurate as possible and I'm confident the results will be pleasant.

[Joeaksa]

Christian,

You asked in your email to me to say which port size I need. Have no idea and the headers are on the engine now so cannot measure. To boot, am out on the road for the next 5 days so its a moot point now! (cannot look at the 48 volt power supply either!)

I have a 3.6 964 engine, if anyone knows what port size that is!

Thanks,

Joe

[A Quiet Boom]

Joe,

The problem, as expressed earlier in this post, with 3.6 engines is that the ports are rather rough compared to earlier engines. However there is a machined groove for an )-ring type gasket and I can locate the tool using this groove. I need the OD and ID of the groove so I can machine a ring rather than a disc to fit into that groove. Once I have these measurements I can make a tool very quickly. If anyone has a 3.6 and wouldn't mind taking a measurement please let us know.

[TurboBert]

I just placed an order with Christian. As I put it to him, I'm paying for a tool I hope to never use!

[racing97]

In the late 70's Jim Pendergrass made a jig for the 911 to repair stud breakage due to the Thermal Reactor situation. As well as a dirll bushing holder it used diametrically opposed set screws that fit inside the port to index in case of both studs being broken. I know he is still in buisness I think in Mid or Central Ca.
Pendergrass Tool Co.
Best regards

[A Quiet Boom]

Thanks for the order Steve.

As far as the Pendergrass tool, I've never seen one. The concept sounds interesting though. I question whether it would be accurate enough to only drill out the center of a stud leaving just the threads behind. I would probably work well if the intention was to tap the hole for a timecert.

Per feedback from my first two sales I need to make a minor adjustment to the tool. The corner of the tool was not clearing the cam tower. I've fixed this in the code to cut the tools and will be testing on my car later this evening.

[Shuie]

Ok everyone, here’s an update from one of the 1st 2.4 prototype tools.

1st thing:
Huge thanks to Chris for taking on this project, and to everyone else for helping out. This is the only place on the planet where I could post a question about a tool that doesn’t exist and have a functional prototype designed, manufactured, and in my hands within a couple of weeks. I could not own one of these cars without the Pelican forums.

I had to trim one side of the tool down a tad with a bandsaw so that it would clear the cam tower. Chris has already made an adjustment for this

John Walkers measurement for the 2.4 exhaust port was right on. The tool fastened up to the good rusty stud with no problems. I tapped it in place with a hammer and tightened down the good stud as much as I dared.

I drilled a little and unbolted the tool to check everything out before I got too far the threaded area of the head. Everything looked good, so I let it rip until the bit broke through the bottom of the stud. I was unable to save the threads, but that is not something I ever dreamed was possible when I posted this thread.

I already had an M8x1.25 helicoil kit ready for this and it looks like I’m still going to use it. I now have a good straight pilot hole for the helicoil though, and that’s all I was hoping for.

Saving the threads would have been great, but this is huge success IMHO. Chris's tool has saved me a tow and what would have undoubtedly have been a hefty bill from a local wrench to fix this.

Thanks again everyone!

[jpahemi]

Would it be possible, by using a smaller bushing in the tool, to save the threads on the head and not having to use a thread repair?
Regards,
J.P.

[Shuie]

I used a 17/64 bit and I would have sworn that I had everything squared up. This was a 1st run test tool but I'd be willing to bet that I screwed something up somewhere in between. If anything needs adjusting, Im sure Chris can get it to where you can save the threads.

[A Quiet Boom]

I've been thinking about this a bit and I've figured out where the problem areas lie. In order to drill just the center out of the stud the tool has to mate up perfectly. This means the tool has to fit tight into the port and must sit flat agains the head. Any exhaust gasket material must be removed and the head surface must be very clean otherwise the tool will sit a little crooked and the hole won't be concentric with the stud centerline. Also it's critical I get good measurements of the port dimension, another user sent me photos of his calipers measuring the port. I've got a pretty good list of measurements from JW but there are still quite a few that I need, like the 3.6 for example. On the first two tools I produced I made blanks on the mill and finished the disc on my lathe. I've thought about this and there is to much room for error with that method but I also has a little error in the blanks themselves. After checking with other machinists they made some recommendations including getting high quality NC tolerance endmills and using them only for the finish pass on the disc area. I tried this today and got a much better result, the disc runout was approximately 0.001" which is half of the previous error. There are a few other techniques I can apply but I'm going to wait until I can get a little more feedback before going that route. I made a tool for my car without an insert and it lined up dead center over both studs.

Shuie, when you drilled your studs, was the hole offset in the same direction both times? Was it offset parallel to the port or perpendicular? or was the hole angled? Angled means the tool didn't sit flat on the head or the bit was too loose in the bushing. Perpendicular to the port would mean the bolt center was slightly off and parallel to the port would mean I've got a clearance issue. It's entirely possible that I got the tool a little offset in the lathe when cutting the final pass on the disc area. I plan to remove this chance for human error by using the method I described earlier.

[Shuie]

That would make sense to me. For both studs, the offset was almost identical.

I did no prep work at all to the area. I just bolted the tool up and started drilling. I removed the tool a couple of times and checked the area I was drilling before the bt got too far down into the threaded area. It looked like it was centered everytime I unbolted the tool and only slightly off centered when I finished. If the surface was the slightest bit uneven I can see where it would cause the bore through the stud to be non concentric

[A Quiet Boom]

Here's a few pics of the updated tool. There was an interference problem between the corner of the old tool and the cam tower. Shuie fixed his and I fixed one for another customer. This one eliminates the problem area. Don't love R&D? LOL