Tallyho Posted July 30, 2018 Share Posted July 30, 2018 After changing the oil using amsoil 10-30 zrod I ran the truck about we 100 miles trouble free. Next day went out for a short ride and only got about 2 miles when it started running rough. Got it home and after not finding anything obvious I did a compression test. Here are the numbers. Warm with throttle blocked open... #4 0psi. #8. 132psi #3. 149psi. #7. 148psi #2. 155psi. #6. 157psi #1. 140psi. #5. 145psi Pulled the valve cover and everything looks great and operating properly. There is absolutely no compression on #4. Wont even move the gauge. Did find the casting # on the head... D3ve a2a Any thoughts? Link to comment Share on other sites More sharing options...
85lebaront2 Posted July 30, 2018 Share Posted July 30, 2018 Do both valves appear to be the same height? If nothing else, can you use the compression gauge hose with the valve core removed and put air in the cylinder so you can at least get an idea whether it is valves or rings. Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 30, 2018 Share Posted July 30, 2018 Do both valves appear to be the same height? If nothing else, can you use the compression gauge hose with the valve core removed and put air in the cylinder so you can at least get an idea whether it is valves or rings. To further what Bill said, he's suggesting a quick and dirty leak-down test. You'll have air coming through something, and most likely a valve that is stuck open. So put air into the cylinder and listen in the tail pipe and in the intake and you should hear a lot of escaping air sounds in one or the other. But, if not listen in the sump by placing a hose to your ear and placing the other end to the dip stick tube or into the valve cover oil fill hole. Link to comment Share on other sites More sharing options...
Tallyho Posted July 30, 2018 Author Share Posted July 30, 2018 To further what Bill said, he's suggesting a quick and dirty leak-down test. You'll have air coming through something, and most likely a valve that is stuck open. So put air into the cylinder and listen in the tail pipe and in the intake and you should hear a lot of escaping air sounds in one or the other. But, if not listen in the sump by placing a hose to your ear and placing the other end to the dip stick tube or into the valve cover oil fill hole. Thanks Guys. I'll work on trying the leak test and get back to you.. Link to comment Share on other sites More sharing options...
Tallyho Posted July 30, 2018 Author Share Posted July 30, 2018 Thanks Guys. I'll work on trying the leak test and get back to you.. I have surgery escaping from the carb Link to comment Share on other sites More sharing options...
Tallyho Posted July 30, 2018 Author Share Posted July 30, 2018 I have surgery escaping from the carb I meant air Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 30, 2018 Share Posted July 30, 2018 I have surgery escaping from the carb You have an intake valve stuck open, which is why you have no compression. Some times you can rap a rocker arm with a mallet and get the valve to spring shut. But you'll have to figure out why it is stuck open. Link to comment Share on other sites More sharing options...
Tallyho Posted July 30, 2018 Author Share Posted July 30, 2018 You have an intake valve stuck open, which is why you have no compression. Some times you can rap a rocker arm with a mallet and get the valve to spring shut. But you'll have to figure out why it is stuck open. I got ahead of myself... I should find tdc on that cylinder first... Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 30, 2018 Share Posted July 30, 2018 I got ahead of myself... I should find tdc on that cylinder first... YES!!!! Should have said that. And, it should be TDC on the compression stroke. Link to comment Share on other sites More sharing options...
Tallyho Posted July 30, 2018 Author Share Posted July 30, 2018 YES!!!! Should have said that. And, it should be TDC on the compression stroke. I'm struggling with find tdc on the compression stroke without compression. Its the rear cylinder which is too tight to insert something. Can I use the rockers position to find it? Link to comment Share on other sites More sharing options...
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