Loose Manifold Stud
 

I was having great difficulty getting "Trudy" to start and run for any length of time. Discovered that the exhaust manifold stud furthest to the rear was stripped, resulting in a loose fit at that end of the exhaust manifold. Does anybody know if that condition could be contributory to poor starting/running?

Re: Loose Manifold Stud
 

i would think yes plus she is probably, running a little loud as well.
if you have the brass nuts your head studs maybe ok

Re: Loose Manifold Stud
 

Helicoil, or such.

Re: Loose Manifold Stud
 

I have a waffle manifold for a heater
Evidently when I removed the heater in the spring I didn't tighten the rear bolt enough and it came out. My car ran terrible. I really didn't think the bolt would make much difference other than the noise. Replaced the bolt and it started and ran like it should


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Re: Loose Manifold Stud
 

I would think that the effect of the stripped manifold stud on the running of the engine would be related to a loose intake manifold, i.e. sucking air, and not so much the effect of the loose exhaust manifold (other than added exhaust noise which sometimes is mistaken as an engine tapping sound). Careful drilling, tapping, insertion of the correct helicoil and new stud should solve the problem. If done with the engine in the car the challenge will be to get the drill to run straight and true into the block.

Re: Loose Manifold Stud
 

Go with EZ-LOK thread insert, not helicoil , they're 100% better.

Re: Loose Manifold Stud
 

For readers who may not know this:



Common Helicoil problems.


1. Drilling too deep so that the hole goes into the water jacket.


2. Failure to use Bottoming tap in the hole. If not done the last 4 to 5 threads are tapered (smaller in diameter) which causes stud to jam in the hole before it reaches the bottom.



Also a problem on open end holes like the 5/16ths-18 Zenith mounting bolt holes on the one bolt which will break "the ear" off if bolt is too long.


If bottoming tap is not used the bolt will jam the last 2 -3 threads and rip Helicoil out of the hole.


3. As mentioned in post #5, use drill blocks for straight holes, guides and other ideas for angled holes can be found here on Google.

https://www.google.com/search?client...rill+guide+jig

click above link

Re: Loose Manifold Stud
 

Had slightly poor running, would not idle down smoothly. Spent weeks fiddling with the Carb, electrical, and troubleshooting for intake and exhaust manifold leaks. Finally temporarily ran a metal dryer vent hose from the carb air intake to just behind the radiator and issue disappeared. Finally found a small leak (small enough there was no audible sound from it) where the exhaust manifold was clamped to the muffler. Fixed leak - issue solved. Best guess is exhaust gas was getting into the carb air intake.

Re: Loose Manifold Stud
 

Thanks all. Sounds like I am going to learn how to install a thread repair kit of some kind. Leaning away from heli-coil. Can anyone confirm the stud diameter and pitch/threads per inch of the manifold studs?

Re: Loose Manifold Stud
 

Thanks all. Sounds like I am going to learn how to install a thread repair kit of some kind. Leaning away from heli-coil. Can anyone confirm the stud diameter and pitch/threads per inch of the manifold studs?

Re: Loose Manifold Stud
 

Same as the head studs . Off the top of my head the best that I remember , the manifold studs are seven sixteenths by 20 threads per inch .

Re: Loose Manifold Stud
 

Here are some photos of the HeliCoil Kit and drill (29/64) that was used to repair a broken head stud this past spring. Someone mentioned above that the manifold studs are the same size as the head studs (7/16" - 14), but to be safe you should confirm that. The HeliCoil kit included the bottom tap and installation tool.

Re: Loose Manifold Stud
 

When you drill for the helicoil have someone else there with you to help keep the bit straight. You can eye the bit so it stays straight left and right and your helper can be 90 degrees to the side making sure you keep it level up and down.
Really is a bummer to drill one and have the stud crooked coming out of the block.

Re: Loose Manifold Stud
 

When reinstalling make sure you know the correct torque. Some references are incorrect. It was just done by feel at the factory. I use 30-35#, and redo them after things are used a bit.

Re: Loose Manifold Stud
 

Thanks dpson. That looks like the ticket. I did confirm 7/16 x 14 is the correct manifold bolt.

Re: Loose Manifold Stud
 

You're welcome. I did this myself and I'm a shade tree mechanic. I started drilling at center of the broken stud with a small drill and kept moving up in size to the 29/64. Fortunately the old head stud was relatively soft and it drilled out fairly easily. As noted above keeping the drill straight and true was a challenge, but I eyeballed it and it worked out well. I thought about using a drill guide as shown below and if I did it again would use one.

Re: Loose Manifold Stud
 

Actually the manifold studs have a different thread count on each end . The end that the manifold nuts connect to is 7/16 by 20 . The end of the manifold stud that enters the block is coarse thread and the thread count 7/16 X 14 .

Re: Loose Manifold Stud
 

Thanks, correct. I was referring to the block side thread count only as being 14. Good catch.