| Author | Message | ||
     Mark Aldridge Frequent User Username: mark_aldridge Post Number: 871 Registered: 10-2008 |
What thread is the exhaust manifold to block stud thread. I have a new manifold to replace mine which has cracked and it seems that I will have to slit the nuts to remove them. I will then have to run a die nut up the threads. To access the nuts it appears I will have to cut the manifold up in situ.The nuts do not wish to turn ! Thanks | ||
| Jason Watson Experienced User Username: crikeydawn Post Number: 162 Registered: 07-2023 |
Have you tried putting diesel on the nuts, or studs into the block. Let it sit for a day, then try and turn with a well fitting socket. If no movement re apply diesel, wait another day. Repeat until success. I now it sounds dumb, but it can tae up to a couple weeks. | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 640 Registered: 07-2018 |
Oxy/Acetylene torch always works. Heat one nut a time until it just starts to turn orange, try to move it at this point. If it wants to budge, even a little, don't keep reefing on it, let cool completely with your favourite penetrating oil. Once it's completely cooled, it should come right off. Repeat as necessary. I use lots of layers of aluminum foil to protect surrounding areas with the torch. The car should be standard SAE, to answer your question, so 1/4 inch is either 20 or 28 tpi. for course and fine. And 5/16 is 18 or 24 tpi. Probably fine thread. It will be either 1/4 or 5/16 inches. Use stainless nuts, not brass. I find brass nuts swell too much under manifold heat, and I have to be constantly snugging them up when things cool down. | ||
| ChristopherCarnley Unregistered guest Posted From: 3.8.155.170 |
They are UNF threads. (Message approved by david_gore) | ||
| Mark Aldridge Frequent User Username: mark_aldridge Post Number: 872 Registered: 10-2008 |
Thanks all, I will try heating and soaking with atf/acetone mix and diesel and see if they will turn. Would certainly be better than slitting the nuts. I have UNF die nuts to clean up the threads and will fit new nuts. | ||
| Jason Watson Experienced User Username: crikeydawn Post Number: 164 Registered: 07-2023 |
Mark, at it would have it I was looking for some suspension bolts today and found these. If you can make sense of the note well done. They are definitely fine thread both ends. Think others have covered it but will report back tomorrow with what sized threads they are. exhaust manifold studs for 4.9 Long is 68mm Med is 59mm Short is 51.5mm  | ||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 853 Registered: 11-2017 |
When exhaust manifold nuts are tightened beyond the suggested torque, they inhibit the expansion of the cast iron. Once this happens the cast iron cannot expand and often results in cracks. Exhaust manifolds usually have elongated holes and torqued to a low figure. A heavy hand is not in not needed. A micro torch will eventually break the bond with ATF/acetone mix. Give it time and constantly check. | ||
| Jason Watson Experienced User Username: crikeydawn Post Number: 166 Registered: 07-2023 |
studs are 5/16, 24 thread, UNF | ||
| NormanGeeson Unregistered guest Posted From: 81.98.117.162 |
Jason Now all you need are the correct bronze nuts to fit. (Message approved by david_gore) |
