Re: Building a 350 Vortec motor
http://www.nastyz28.com/forum/showthread.php?t=56505&page=2
First off, a warning: This post is a sig-hunter’s dream. I will be using phrases like “pinning the rocker stud,” or “studs pulling-out” or even, “I prefer tapping the stud-bosses.” Please get all of your chuckles out of the way now .
That being said, one of the most common mods done to stock Vortec heads is upgrading the pressed-in rocker studs. Many will argue that the modern Vortec pressed-in studs are not as prone to pulling out as they were in older heads. While that is true, wilder Vortec engine combos with fully ported heads and higher valve lift are becoming more common and securing the studs is cheap insurance, IMO.
There are several methods to choose from for securing rocker studs. The first is pinning the stock studs. My current Vortec heads have pinned studs, but they were done by the previous owner. I don’t have any info on this method so I’ll let someone else discuss it.
The second method, and the one I’m going to discuss, is machining the head for screw-in studs WITHOUT GUIDEPLATES. To do this you will need a set of 3/8” shoulder-less screw-in rocker studs, five of the pivot balls from the rockers, the rocker stud nuts, a rocker-stud tap-guide and arbor (sold by ProForm and other manufacturers for about $13), a 7/16” – 14 self-bottoming tap, the biggest t-handle you can find, a socket set, a breaker bar or long-handled ratchet, and one non-self-locking nut to fit over the studs. You can also do this with an air-ratchet but it’s easier to screw up (no pun intended). The procedure is as follows:
1. Remove the pressed-in studs:
- Stack 3 pivot balls over the first rocker stud
- Tighten nut on to the stud slowly, using the breaker bar and socket. Make sure you don’t bottom the nut out on the threads. This is why using an air tool is dangerous.
- When you get close to running out of threads, remove the nut, stack another pivot ball on to the stud and continue to tighten the nut. Repeat this until the stud pulls out completely.
- Use this procedure on the other studs. Only remove EVERY OTHER STUD at this point. For example, remove all the exhaust studs or intake studs only. You will need the others to be in the head.
2. Install the tap guide:
- The tap guide is made up of two parts: an arbor (this part fits into the hole left by the stud) and the guide itself, a block of steel with a hole that fits over the stud left in the head and a partially threaded hole that guides the tap. Place the tap over the first pair of stud bosses. The threaded side of the tap guide should be facing down (against the hole left by the stud).
- Insert the arbor into the hole to line up the guide and tighten a rocker nut down onto the adjacent stud. This will keep it in place while you tap the threads.
3. Tap the threads:
- After making sure the tap guide assembly is all squared-up, thread the tap into the hole through the guide. Cast iron is soft so lubricant is not necessary. Plus, it makes clean-up a mess.
- Go slowly, keeping the tap vertical and back it out every so often to break up any big chunks. Keep going ‘til it bottoms out.
- Use a vacuum to clean out the threads and use a screw-in stud to check for the right thread depth. Rocker studs can be found here:
http://midwestmotorsportsinc.com/ord...RM348&line=PNR
- Once the stud fits, remove the tap guide and follow the steps for removing the adjacent pressed in stud.
- Temporarily install the screw-in stud in the threaded hole and set up the tap guide as described above. Use a non-self locking nut to tighten down the guide.
- Follow the steps for tapping the threads. Repeat for each pair of studs.
4. Install the screw-in studs:
- Once the threads are thoroughly cleaned, screw-in the studs.
- Remember to apply thread sealer to the studs that penetrate the water passages and oil on the others.
- Torque the studs down to 50 ft. lbs. using two nuts locked against each other.
- Stand back, look at the bruises on your hands and ask yourself why you didn’t just pay a machine shop to do this for you........
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