Mighty Mo and Friends
Many times the intake / exhaust manifold bolts seem to be deficient in the strength to prevent their breakage when removing the manifold nuts. Knowing this I always heat the nuts prior to removing them. Well almost always. Below is how I repaired the situation when I skipped the heat the nut step.
I used a spare manifold as a drill guide. The hole in the manifold was 7/16". So a 7/16" drill was used to "center-drill" the stud. Then a small drill, 3/16", was used to drill completely through the stud. be very careful to drill perpendicular to the block. Other wise the threads in the block will be damaged.
After drilling through the stud, then I drilled out to the tap drill size. I did this in small steps so that I was sure I wasn't removing the threads in the block. Finish drilling with the tap drill, 5/16". Clean the drill chips out using a pencil magnet.
Before tapping the hole, pick the remaining metal from the stud out of top threads in the block. Now tap the hole with a 3/8"-16 tap. I recommend using a 2 flute tap, as these are the strongest and I REALLY don't want to break a tap off in there. I finished with a bottom tap to assure there was sufficient thread depth.
When installing the stud , be sure to use some thread sealer if the hole is into a water jacket. Also, I recomment using brass nuts for this application.
Visitors since March 21, 2004
Copyright Richard N. Meagley Sr.