351w with 302 cam?

Xzkittle01

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Jul 26, 2018
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I have a 1994 mustang it has a carberated 1994 truck 351w in it. I just put gt40p heads on a week ago and I think I have a collapsed lifter on the 7th cylinder. Or maybe a bad spring. 3rd one from the back to be exact. How can I tell the difference between a bad spring or a collapsed lifter?

Also if it's the lifter can I use a 1993 302 ho cam in it and just replace the back lifters? I'm not loaded with money so the easier way to make it run right is the route I'm going for.

If it's a bad spring, what set of springs should I get that will work without valve modifications?
 
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John Dirks Jr

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Jun 28, 2013
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A valve spring can be broken and you would see that on visual inspection. A valve spring can also be weak. You can't see that by looking. To verify a weak valve spring, a special compression rate measuring tool is needed.

A collapsed lifter means the hydraulic plunger inside of the lifter is not pumping up with oil pressure as it should. In this event you may have excess valve lash or low valve lift.

You could also have bent pushrod, wiped cam lobe, failed valve keepers. Lot's of things could be wrong. I think before asking for specific recommendations on how to fix it, you first need to get in there and see what happened. At least do some visual and look for obvious things.
 

Xzkittle01

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Jul 26, 2018
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West Virginia
A valve spring can be broken and you would see that on visual inspection. A valve spring can also be weak. You can't see that by looking. To verify a weak valve spring, a special compression rate measuring tool is needed.

A collapsed lifter means the hydraulic plunger inside of the lifter is not pumping up with oil pressure as it should. In this event you may have excess valve lash or low valve lift.

You could also have bent pushrod, wiped cam lobe, failed valve keepers. Lot's of things could be wrong. I think before asking for specific recommendations on how to fix it, you first need to get in there and see what happened. At least do some visual and look for obvious things.

I checked the lifters, pushrods and cam and they all look to be fine.little wear on them but nothing to bad to cause any problems. I didnt do a spring test yet. That will be next.
 

John Dirks Jr

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Jun 28, 2013
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So what are the symptoms that make you think you have a valve train problem? Mechanical noise? Engine miss? Anything else?
 

Xzkittle01

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Jul 26, 2018
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So what are the symptoms that make you think you have a valve train problem? Mechanical noise? Engine miss? Anything else?

It just has a small tick when you give it gas and it comes back down. I just made sure all the plugs are in tight and the 7th was a little lose so maybe I could hear the noise from it possibly? The gap is all still good on the plugs. Headers are tight. I'll give an update as soon as I get the carb rebuild.
 

John Dirks Jr

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Jun 28, 2013
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Might wanna check lifter preload. It could be that the combination of wear in rocker arm, rocker pedestal and pushrod add up to an amount thats too sloppy.
 

John Dirks Jr

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Jun 28, 2013
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Exhaust leaks can sound like a valve tap. Especially on acceleration. Exhaust leaks are noisy when you step on the gas, and quiet down when you let off.

You say headers are tight. Just because the bolts are tight does not mean the gaskets are sealing properly.
 
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Xzkittle01

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Jul 26, 2018
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Exhaust leaks can sound like a valve tap. Especially on acceleration. Exhaust leaks are noisy when you step on the gas, and quiet down when you let off.

You say headers are tight. Just because the bolts are tight does not mean the gaskets are sealing properly.
I'll check into it and see if the gaskets need replaced. Thanks for the help!