340 exhaust manifold studs leaks coolant

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1968340S

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Rescue, Calif.
1968 Barracuda 340 block
My passenger side exhaust stud located in the head leaks coolant. Just got the car running and noticed that the exhaust manifold had a small hole. So I remove the manfold to repair and noticed some liquid on the threads on the far back stud ( eight bank ) off the head that holds the manifold. I removed the stud and coolant started to flow out. The studs are stock and don't know if someone drilled to retap and went to deep into the passage? Is this proper that the stud is also used as a plug for the coolant passage. If so what needs to be done. Silicone on the threads or is it something else. Have no idea?

AAWJ 360 Heads
3671587-10

Thanks,
Chris
 
Yes, coolant runs out, it sucks but that is the design, :angry7: I would put some sealant on the stud before you run it back in.
 
Get that hole and stud nice and dry. Use some Permatex High Temp RTV, bronze tube, and put it on the threads of the stud and screw it in there. Only the 4 ends ones need to be sealed. The inside ones are not wet.
 
Well I'll have to drain out the coolant, because the coolant really flows out.
What will happen if I did not seal the studs. I mean the passenger side is off and thats not a problem. On the other hand the drive side as you no is a pain. Should I just bite the bullet and just do it. I know I should but what if.
This is my first small block and some of the design is on this block has cause me alot of extra work compared to a big block. Live and learn
 
If you don't seal them you will have to pull everything apart to seal them later when they do start to leak, it sucks believe me!
 
Yea I no what I have to do. I'm in for alot of work tomorrow. I love working on the car, but I hate having to redo. Engine is in the car, looking good. I just didn't no, but I will never forget what I've learned about small blocks.
 
360scamp said:
If you don't seal them you will have to pull everything apart to seal them later when they do start to leak, it sucks believe me!
Click to expand...

X2....the 2 end studs on each side of the block go into the water jackets. Need 2 seal them.
 
1968340S said:
Yea I no what I have to do. I'm in for alot of work tomorrow. I love working on the car, but I hate having to redo. Engine is in the car, looking good. I just didn't no, but I will never forget what I've learned about small blocks.
Click to expand...
Put some good pipe sealer on the studs. Put em in and I'd let em set up for a day just so everything is in dried and tight. Then put the exhaust back on. I'd drop the downfall pipe on the driver's side and just pull the exhaust off far enough to get the studs out clean and coat. If it were me, if the driver's side hasn't leaked, I'd forget it and just do what is leaking. Keep a check on it but if it's going to leak, it will leak at the beginning when the stuff hasn't gone through and heat cycles. To be honest, I'd work on small block stuff anytime compared to some of the big block stuff. Of course everyone talks about Cheby and Ord stuff, I've fooled with both, Mopar is still to me easier all the way around. I can get the '71 Duster to run better at the drag strip than the other guys can with some gear and torque converter changes. Allen
 
my ole 318 car, someone used bolts on all the exh. manifold holes. As said before, fix it right. The end hole (2 per head) are wet and studs are the best bet. I've used RTV, non hardening Permatex and also teflon paste and tape, all with success on the studs. IF the hole was helicoiled in the past, use a liberal amount of a sealer (not tape). Helicoils are a little more difficult to seal due to the double threads (in and out) on the helicoil.

Open the block drains on each side, and just take some out of the block. It won't take much to lower the level below the head holes.

Do youself a favor, do them all at once. You'll thank yourself later.
Happy New Year!
Mike
 
I just drained a little coolant from the radiator and pulled off one of the studs to let pressure out. That worked well. The driver side I'll try the double nut lock and try to remove the two wet studs keeping the manifold on. Their not tight so I think that will work. Not much room on the driver side I have power brakes. Thank guys and Have a Great New Year.

Chris
 
Yup Big Block heads are the same way and have caused me grief. Helicoils are great but are a pain in the a$$ on the exhaust manifold side for sealing... it would have been great if they were cast blind! I see many alluminum heads actually tell you thiers are blind as a selling point! lol
 
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