300 inline
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300 inline
Hey guys, I have a 300 inline that hasn’t run in several years, did a comp test, two front cylinders are at 125 the rest are at 180, I going to run the motor a bit to see if the two front cylinders come up, but if not what’s my next step ? Thanks for the advise.
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First step is thread moved to the six forum.
Is this the same engine?
https://www.ford-trucks.com/forums/1...l#post16245318
Running it and retesting is a good idea. How does it run?
Have you checked your intake/exhaust manifolds to make sure they are tight?
It might purr like a kitten, or you may need plugs, wires, a carb rebuild....
See how it runs.
Is this the same engine?
https://www.ford-trucks.com/forums/1...l#post16245318
Running it and retesting is a good idea. How does it run?
Have you checked your intake/exhaust manifolds to make sure they are tight?
It might purr like a kitten, or you may need plugs, wires, a carb rebuild....
See how it runs.
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Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Hi Biff, and welcome.
If you have two adjacent cylinders that are lower on compression like that, but the rest are great, I would not run it. This is usually indicative of a blown head gasket.
It'd be fine to try to get it started up, and maybe run some Marvel's Mystery Oil through it at idle to see if by chance it's something with the valves, but I wouldn't drive it until you're sure.
Have you checked the coolant for oil? Have you drained and done an oil change and checked the oil for coolant?
Head gaskets can be a little involved (if you have EFI, even more so), but not too bad. Drain the coolant, remove the intake/exhaust manifolds, remove the valve cover, and then remove the head. Have the head checked at a machine shop for flatness and cracks, and then reinstall with a new head gasket.
If it's not a blown head gasket, there are tricks you can do to see if it's the rings (which requires a rebuild) or the valves (which requires headwork). A leak down test can help with this too.
If you have two adjacent cylinders that are lower on compression like that, but the rest are great, I would not run it. This is usually indicative of a blown head gasket.
It'd be fine to try to get it started up, and maybe run some Marvel's Mystery Oil through it at idle to see if by chance it's something with the valves, but I wouldn't drive it until you're sure.
Have you checked the coolant for oil? Have you drained and done an oil change and checked the oil for coolant?
Head gaskets can be a little involved (if you have EFI, even more so), but not too bad. Drain the coolant, remove the intake/exhaust manifolds, remove the valve cover, and then remove the head. Have the head checked at a machine shop for flatness and cracks, and then reinstall with a new head gasket.
If it's not a blown head gasket, there are tricks you can do to see if it's the rings (which requires a rebuild) or the valves (which requires headwork). A leak down test can help with this too.
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Thanks for the advise, it’s a 1975 engine and it’s mounted in a 47 ton and a half truck, front end off so engine is easy to get to, just got it running to determine if it needs rebuild, I will hook up the radiator and check for coolant in the oil.
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Joined: Nov 2015
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From: Angier, NC
You did the first easy test, compression now a leak down test will tell you where you need to look next.
You dont really need the fancy gauge set up just a air supply.
It will be hard to set each hole at TDC for the test but as long as both valves are closed is all that is needed.
Put air in the hole that is at TDC and see where the air is coming out of.
Out the tail pipe its an EXH valve that is not holding.
Out the carb / intake its an intake valve that is not holding.
Out the valve cover breather its piston rings that are not holding.
Now with the 2 not high on compression (#1 & #2?) and the other holes for the heck of it, check the radiator for bubbling or air coming out.
This could be a bad head gasket or a crack in the head or block.
Good luck
Dave ----
You dont really need the fancy gauge set up just a air supply.
It will be hard to set each hole at TDC for the test but as long as both valves are closed is all that is needed.
Put air in the hole that is at TDC and see where the air is coming out of.
Out the tail pipe its an EXH valve that is not holding.
Out the carb / intake its an intake valve that is not holding.
Out the valve cover breather its piston rings that are not holding.
Now with the 2 not high on compression (#1 & #2?) and the other holes for the heck of it, check the radiator for bubbling or air coming out.
This could be a bad head gasket or a crack in the head or block.
Good luck
Dave ----
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