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Discussion Starter #1
Alright well I own a 1966 Mustang Coupe. I have never like the engine it has. The previous owner just put it all together to sell it and get rid of it. It has a 1985 5.0. The code on the bottom of the engine reads E5AB C3B. I'm not sure what the C3B means but I know it's a generic full size ford engine, which was not specifically a mustang engine.

The problem is that it runs terribly. I've been driving it around for the last few weeks as my daily but a couple of days ago I went to go get gas and it wouldn't run right at all. It was worse than before. It now sounds like it's running on 5 or 6 cylinders. My dad says he thinks it's the carburetor and it's related to fuel. I think it just wore down passed the point where I can drive it. He says the gas tank (which is new) had some crap in it and it clogged the carburetor, although I put in a new fuel filter a couple of months ago. I know the engine is worn but I want to know more than that.

What can I do to figure out what's wrong? I know it can be either valves or rings. If I take off the valve covers, is there anything that can point of valves (if it is the valves). Or are there any other signs that point to something more specific?

I did a compression test and it all seems fine. The number 8 spark plug is fouled up with oil but it still had good compression.

Sorry I typed up a bit too much.

Thanks
 

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Good compression = good valves. #8 fouled could be bad valve stem seal and/or crossfiring due to improperly routed and bad plug wires. Do not run #7 and #8 along side each other (looks neat but prone to cross firing).

If crud got into the carb a new filter won't help. The crud can keep finding new hole/passages to foul up. You may need carb rebuild.

The 302 has been stalwart for many years as it's a really good almost bullet proof engine.
 

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There was really no unique Mustang engine, that "E5A" code only means the full-size engineering group paid for the planning.

As for wear, I've had engines worn to the point where they smoked like a factory, and still ran like a scalded dog, so you have to look elsewhere.

Does the car smoke? Does it smoke more on acceleration or deceleration? Have you performed a wet/dry compression test? If compression is fairly good, the engine should run strong, even if worn. If the compression is not good, by running a wet/dry compression test, you'll know what's wrong. Check the compression, write down the numbers. Check again, this time, before each cylinder is checked, put a couple of good squirts of motor oil in the cylinder. If the compression increases a lot, the rings are shot, if about the same, it's the valves. If you get smoke on decel, it means the valves are sucking oil. Often this means the valve guides are bad, but it's also possible the guides are acceptable, but the seals on top are shot. Look them over. They should be like little rubber umbrellas riding up and down on the valve stem. If they slide down, or are in pieces, replace them, and it'll run a lot better. You can replace these seals with the heads installed, takes a couple hours.
 

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...I'll add, when you perform the compression check, use a screw in type gauge, pull all of the plugs, block the throttle plates open, and crank each cylinder a number of cycles. Also, while you are at it, get a check of your engine vacuum and whether or not the needle is steady. Actually, do the engine vac test before you do a compression test and report back with your findings. This check can be very telling.
Hang in there!
 

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Discussion Starter #5
I've done a vac test. I wish I could get the video on here but I don't know how. It was around 17 inches of mercury and it wasn't too steady. It went up and down about an inch or so.

I spoke to someone who told me it could be valve guides or maybe adjustment of the valve springs. What could I do? Should I take the valve covers off and try to see if everything looks ok? I'm just trying to get it running decently until next year when I plan to completely rebuild it.

So as of now, compression was good, I haven't done a leakdown test or much else since I don't have to equipment for that. The vacuum was decent but it varied plus or minus an inch. I'll do another vacuum test since the way it runs has changed since the last time and I'll let everyone know what happened. I welcome all suggestions and please help me figure out what I can do.

Thank you.
 

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Just curious, are you sure the plug wires are routed for the proper firing order? IIRC that's an H.O motor...
 

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Discussion Starter #7
Yeah I have the HO firing order (1-3-7-2-6-5-4-8) on it. When we first got the car that was a bit of a mystery to us so we tried both and the HO worked (the non HO didn't work well at all). Does this necessarily mean that it's an HO? How can I know for sure?
 

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I've done a vac test. I wish I could get the video on here but I don't know how. It was around 17 inches of mercury and it wasn't too steady. It went up and down about an inch or so.

I spoke to someone who told me it could be valve guides or maybe adjustment of the valve springs. What could I do? Should I take the valve covers off and try to see if everything looks ok? I'm just trying to get it running decently until next year when I plan to completely rebuild it.

So as of now, compression was good, I haven't done a leakdown test or much else since I don't have to equipment for that. The vacuum was decent but it varied plus or minus an inch. I'll do another vacuum test since the way it runs has changed since the last time and I'll let everyone know what happened. I welcome all suggestions and please help me figure out what I can do.

Thank you.
I have link that has 6-8 scenarios of possible valve or engine issues depending the action of the gauge. BTW, your vac seems good, but, I afraid there be a valve issue. PM me for the link, as I don't think the admins will allow me to post it, but I'll try.
Here goes: Login
Check it out.
Good Luck!
 

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Compression test is the first thing you need to do. Then check the valvetrain.
 
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