There are only two causes of broken valve springs...

1. CHEAP SPRINGS.
'Economy' springs are inferior in every way.
They will be too soft or too hard, they will be of larger diameter wire to keep up seat pressure, but larger wire will bind. Always use quality springs from a reputable manufacturer.

2. WRONG INSTALL HEIGHT/ WRONG SPRING FOR APPLICATION.
If you use springs that are too tall, they will bind and break. This is true with big cams binding springs, too short of an install height.
Higher ratio rocker arms can cause coil binding, but only if there is a problem to start with.
Always have valve train work done by a KNOWLEDGEABLE PROFESSIONAL...
Check for total install height, total lift, coil bind, seat pressure, and proper locks & spring retainers for the springs you are using.
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IF IT'S NOT HAMMERING LIKE CRAZY...

Here is a tip, and it only works once in every hundred times a valve gets dropped...
(but I'm rooting for you!!)

Take one of those pencil type magnets, (like the kind that have a scribe or punch at one end and a magnet at the other) and go fishing down the valve guide hole...
Once in a blue moon you will get lucky (I've got my fingers crossed for you!).

Also, you can crank the engine over BY HAND... If the valve stem appears at TDC for the cylinder, YOU WIN!

If you DO have a hammer or knock...

Take out the spark plug and use a 'pen light'... Most of the time if a valve has been flattened or mangled, you will be able to see it (or part of it) through the plug hole when you bring the piston up by HAND CRANKING the engine.
This won't change anything, but it will give you a better idea of what you are up against.

 

I don't think I will be lucky. It was making a rattling noise before it quit and I had it towed home. The intake valve is not all the way closed and the spark plug was missing the ground and some ceramic. I was the one that rebuilt this engine 7 years ago. It is a 1978 engine with the original valve springs. I don't have a wild cam in it or aftermarket rockers. My dad and I ground the valve seats and the valves ourselves. We measured the valve height before disassembling the head and ground the stems to be the same height after. We also put shims under the stock springs (not sure what thickness now) to account for the locks being slightly higher due to grinding valves and seats. I think it is just 27 year old valve springs that are worn out.

I am planning on pulling at least the one head to check the cylinder walls and I won't be surprised if I have one bent valve. I will replace all the valve springs but might just use the rope trick for the other head.

 

If it wiped out the spark plug, you are DONE!

Check CLOSELY for cracked piston, crap in bedded in the piston top or edges or rings with sh!t welded to them.

Have the head magnafluxed for cracks before reusing. Especally between the valve seats...

Old valve springs are like old condoms, as cheap as they are, it's a REALLY bad idea to try and reuse them ... /ubbthreads/images/graemlins/blush.gif

 

Got as far as pulling the intake tonight. Chalk up 2 bent pushrods and one lifter with parts missing.

 

Pulled the head tonight. One bent intake valve and one missing exhaust valve. /ubbthreads/images/graemlins/shocked.gif

Mystery solved. There's part of the missing valve.

 

Sorry to see that Will. I was hoping for better. Does the cylinder look to be alright?

 

weeeeellll.. THAT SUX! But I think you're right, I think you found the rattle... /ubbthreads/images/graemlins/grin.gif

 

Find that lifter!

What does the cylinder bore look like?

 

I've broken 2 valve springs in my 79 F250 400M over the years. Rebuilt the motor in, dam, around 1992 I guess it was. Reused the springs. Since then, have broken 2 valve springs. Both times the valve retainer halves were firmly seated in their washer cup (whatever you want to call it) and the top half of the broken spring. The valves never dropped. The springs both broke in approx. the middle, and thus only drop maybe 1/4", and the broken top half rests on the coils of the bottom half.

Pressurize cylinder to hold up valve, replace spring, no issues.

I guess I just got lucky both times?

Sorry for your bad luck
Pete

 

I removed the lifter before taking the picture. The pushrod got shoved into it.

Last year I broke one valve spring on the #8 cylinder. (#6 this time) It only broke in one place. This one broke is several places which is why the keepers fell off. The cylinder above the piston has no scratches. I need to remove the pan and the piston to see about the rest of the cylinder. I have a shop lined up to magnaflux the head and replace the 2 valves, seats and guides if the cylinder is not scratched.

 

Make sure you replace that connecting rod.
The valve put way more shock loading on that rod than it was ever ment to have...

Remember, cast iron rods in a V-8, so don't take chances while you have the bottom opened up.

Check that head for cracks, especally between the valve seats.
Valve heads are REALLY hard on the thin, very hot cast iron there.

 

Sorry Will, that sucks man. You gonna just fix the one cylinder and move on? What kind of pressure does something like that put on your crank shaft bearings, etc. Seems like you would need to do a complete lower tear down to make sure the bearings, crank etc. were ok....

 

I feel your pain.....
That is the exact reason I used different valve springs on my 4.2 heads when I had them rebuilt. The stock spring does not have the inner dampner spring.....my machinest, being the racing type at heart, 'modified' the head...reground the spring seat and used Ford 302 HP springs which gave me the second inner spring.....just in case one breaks.

7 Years? ah....you wanted to rebuild it again anyway.....maybe it's time to find that TBI or TPI engine...go electronic and never flood on a hill again.

 

In 7 years, I have about 60k miles on it. It is TBI with a Holley Pro-jection. I don't flood on hills. If I swap anything in, it will be the original 304 after getting rebuilt.