miss under load
Cargo Master
Joined: Sep 2007
Posts: 2,095
Likes: 2
From: Wahpeton ND
I had this happen to me just recently. The cause of my miss was loose rockers on a 300. I had a miss at idle and while crusing. Under load the engine ran great. This being the oppisate of what is supposed to happen.
Your cause is a little easier. If your valves are not opening fully you are not drawing a full shot of fuel and air in to the cylinder. at idle or while cruising your temps and pressures are moderated some what. When under load or high speed the engine builds up more heat and pressure and with a lean mixture this can cause detonation.
Your cause is a little easier. If your valves are not opening fully you are not drawing a full shot of fuel and air in to the cylinder. at idle or while cruising your temps and pressures are moderated some what. When under load or high speed the engine builds up more heat and pressure and with a lean mixture this can cause detonation.
Cargo Master
Joined: Apr 2003
Posts: 2,389
Likes: 58
There are several easy ways to check for valve train failure. The easiest is to check your valve adjustment. Get the valves adjusted. When that's done, take a close look at all of the screws. Does one appear to be in a different position than the rest?
If it is the cam, then it's possible it wont show up without turning the engine over and watching the movement of the valve. So the next step is to check for any worn lobes.
If you think you have good eyes, crank the engine over with the ignition off or disconnected and watch the valves. If you're running an electronic ignition, take any necessary precautions so you do not fry it while doing this test. Does one not open as far as the others?
If you have bad eyes, grab a ruler and measure the valves one at a time when fully open. A ruler should be fine for detecting a cam that is on the way out. If you really want to get fancy, you can buy a dial indicator but they are kinda a pita to set up in the vehicle to check every valve.
If it is the cam, then it's possible it wont show up without turning the engine over and watching the movement of the valve. So the next step is to check for any worn lobes.
If you think you have good eyes, crank the engine over with the ignition off or disconnected and watch the valves. If you're running an electronic ignition, take any necessary precautions so you do not fry it while doing this test. Does one not open as far as the others?
If you have bad eyes, grab a ruler and measure the valves one at a time when fully open. A ruler should be fine for detecting a cam that is on the way out. If you really want to get fancy, you can buy a dial indicator but they are kinda a pita to set up in the vehicle to check every valve.
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Freshman User
Joined: Feb 2010
Posts: 36
Likes: 0
Good idea. I'll check it out as soon as I get a chance, which may be awhile. I'm moving to Alabama next week. Once I get there I may just tear the engine down and start over. I'm hoping it'll be easier to find parts there cuz it can be a real challenge out here in CA.
Cargo Master
Joined: Sep 2007
Posts: 2,095
Likes: 2
From: Wahpeton ND
How many miles are on the engine curently? If you rebuilt it say only 50k ago Simply installing a cam would probobly suffice. All the major parts for a Y are available at most auto stores. NAPA, ORileys, Auto Zone all have the parts for a complete rebuild. BTW if you look on ebay and craigslist about half of the parts sold on there are out of California.
Try setting your lash like charlie said. Look for a loose screw and the like. This will cost you nothing and take only an hour. You may just have a set screw that is backed off.
Try setting your lash like charlie said. Look for a loose screw and the like. This will cost you nothing and take only an hour. You may just have a set screw that is backed off.
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Freshman User
Joined: Feb 2010
Posts: 36
Likes: 0
I just hope it doesnt turn out to be a loose nut behind the wheel. 
I'm also thinking about the fact that the engine still burn's and leak's alot of oil. So I could actually kill several bird's with one stone.
I'm also thinking about the fact that the engine still burn's and leak's alot of oil. So I could actually kill several bird's with one stone.
Cargo Master
Joined: Sep 2007
Posts: 2,095
Likes: 2
From: Wahpeton ND
I wouldent think that it is time for a rebuild with only 10k on her. Burning oil and a bad cam sound like a botched job on the rebuild. If you did it yourself please dont take offense but someone or somthing is serriously screwed up here. Did you have it professionaly done or is it a crate engine? I would look into some things here.
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Cargo Master
Joined: Apr 2003
Posts: 2,389
Likes: 58
Just how many miles are on it? If it's near 10k, then it's probably something pretty simple. A cam will usually go out pretty quick but, they do sometimes wear very slowly. I've known several racers who've pulled a motor apart to check things out and freshen it up or put in a new rotating assembly for more displacement, etc to find a cam that was worn even though the engine ran like a scalded dog.
Check your valve train and compression and that will give you a very good idea of how the rebuild went and the current condition of the motor.
Check your valve train and compression and that will give you a very good idea of how the rebuild went and the current condition of the motor.
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Freshman User
Joined: Feb 2010
Posts: 36
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update
I took the truck to a proffesional shop, and it turn's out the old girl was suffering from a multitude of sin's. First the cam was badly worn at least partially due to the fact that the cam seal on the back of the block was my source of oil hemoraging. Secondly the guy that rebuilt it before put standard size ring's back in without resizing the cylinders, therebye causing the blow by and heavy oil burning. Thirdly, to add insult to injury there is a 16 inch crack in the block on the driver's side. I'm not sure this engine would even make a descent boat achor at this point. Luckily the shop had a recently rebuilt short block that they made me a pretty good "installed" deal on. They're redoing my head's and putting it all back the right way. It's supposed to be ready for me to pick up this afternoon. I'll let you guy's know how it is.
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Freshman User
Joined: Feb 2010
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It Lives
Got the truck back and it run's great. The only issues are for one, the engines tighter than a frog's ***, which is to be expected, and it has a small coolent leak somewhere. I'll try to find that tomarrow when it's light out. Also the new clutch need's to be adjusted, but that's super easy. The best new's though is it goes up long grades without any miss, or backfire. 
Next stop Huntsville, AL.
Next stop Huntsville, AL.