Intake to exhaust bolt size ?

D

Dennis/CT

Senior Member
Both bolts broke off my exhaust while removing my intake.What size thread are they? I need to drill and tap the holes. Thanks to all, Dennis/CT
 
Intake to exhaust manifold bolts are 5/16 - 18tpi X 3/4" long.

Manifold to block studs are 7/16 - 14 (block end) X 7/16 - 20 (nuts & washers) X 2 3/16" long.

Hope this helps
John
 
Start out by center punching the exact center of the broken bolt, then use a 1/8" drill and be sure to stop as soon as you feel the bit leave the bolt, so you don't drill all the way through. Keep working up in drill bit size until the edge of the manifold thread just starts to show. At this point you can use a dental pick to pull out the remaining bolt thread. If you are good with a torch with a fine point, you can also heat the remaining bolt thread and burn it out. It'll heat much quicker than the casting and it'll ball up so you can pick it out.

If you can get at least a couple threads down, then the tap will usually grab the remianing threads and turn them loose or pull them out. Very seldom that I need to actually rethread a hole when I try these steps first.

Another good thing to try is to weld a flat washer to the broken bolt, then weld a nut to the flat washer. let it cool and try to turn the nut and broken bolt out. This proceedure is on Vince's website.

On those 2 bolts on the exhaust manifold I usually heat the bumps of cast iron, the bolt pockets on the backside (inside) of the exhaust manifold to red hot, then try to remove the bolts.
 
I'd really Try the Welding, use of a Washer and Nut First. This is a very easy process. Usully the broken piece is frozen in the Block, The heat form the welding will break it loose.
Even if the bolt is broken a little into the hole, Why take a chance of messing up the Threads in the Block, and maybe Coumpounding your problem by snapping off a Not so Easy-Out.

Here is a Link to explain the Welding of Washer and nut to Broken Bolts or Studs.
http://www.youtube.com/watch?v=4BFUfGKU_ts
 
Jazzjr said:
I'd really Try the Welding, use of a Washer and Nut First. This is a very easy process. Usully the broken piece is frozen in the Block, The heat form the welding will break it loose.
Even if the bolt is broken a little into the hole, Why take a chance of messing up the Threads in the Block, and maybe Coumpounding your problem by snapping off a Not so Easy-Out.

Here is a Link to explain the Welding of Washer and nut to Broken Bolts or Studs.
http://www.youtube.com/watch?v=4BFUfGKU_ts
Click to expand...

I agree with Jazzjr to try the welding first. If the weld breaks, then try it again. So far I've had success on either the first or second welding. The second welding (if needed) actually gives the broken bolt a second heat cooling cycle, and helps to break it loose.
 
Tom Wesenberg said:
On those 2 bolts on the exhaust manifold I usually heat the bumps of cast iron, the bolt pockets on the backside (inside) of the exhaust manifold to red hot, then try to remove the bolts.
Click to expand...

I've had to heat those bumps many times even when using the weld on nut method because the bolts were rusted in so tight and in such a shape that the weak metal next to the welds would break.

I always slowly warm up the whole casting before heating the bumps red and occasionally divert the torch to continue to re-warm the whole casting during the process. Then allow the casting to slowly cool off in a warm covered area.
 
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