How do I fix a broken valve spring SBC ?

My new 406 SBC ran OK across Missouri then started running crummy. I noticed a lifter click. I thought it was just a loose rocker arm, but upon further inspection I discovered a broken valve spring.

The cam is not large, the spring are original to a set of rebuilt heads...882 casting.

Questions
...can I use a spring off the original 400 heads to replace the broken spring?
..How can I replace it without tearing it all apart...(I have very little compressed air in my compressor and no plug in this temp house in which to plug it in)

 

You might try the rope trick. HRP

 

there's a trick involving putting a rope into the spark plug hole to hold the valves up....kind of iffy....but might get you going for a while.

and you know more springs will break over time, I never reuse springs when doing a set of heads for that reason.

 

The rope trick works fine. Hand crank engine till piston in affected cylinder is just BTDC firing position (both valves normally closed). Then stuff as much 1/8 or 1/4 inch nylon rope as you can into the spark plug hole. Hand crank again till you can't hand crank it any more. Rope is now squished hard against the valves allowing you to compress the broken spring and remove the keepers.

Jack E/NJ

 

The idea is to get the piston to top dead center (it's lowest point) Then remove the exhaust rocker arm and push rod. Then feed in the rope and then rotate the crankshaft ... by using the harmonic balancer bolt.

When the piston was at almost top dead center ... the crankshaft would not move any higher ... I knew that the valve COULD NOT DROP ... So then the spring retainers can be removed... then the spring. Reverse the procedure and you can be up is and running again.

I learned this from Randy (Deuce Roadster) and it got me up and running again. HRP

 

Thanks for the rope trick info. I'll replace all of the springs.

Hopefully stock dual springs are not too expensive....

 

Make sure the springs you get are designed to work with the camshaft you have. Not too stiff, not too soft.

 

After we did the repair in the motel parking lot in Pigeon Forge I was up and running,,when I returned home we replaced all the valve springs.

I used new ones when the engine was built but I just feel better since I replaced them all. HRP

 

Although not mandatory this does make it easier

valve spring compressor tool

 

http://www.youtube.com/watch?v=2MvH3usFkAA

 

That's probably fine if your at home in your shop but out on the road several hundred miles from home most people don't have this in their emergency tool box. HRP

 

I do.....along with a few spare springs and a piece of rope. So far, it's kept the springs from breaking.

 

I used to be pretty good at the "rope trick", got it down to 10 minutes a "trick"! Ended up replacing 8 of the 16. Comp finally warranted the set.

 

"I foresee terrible trouble, but I stay here just the same"

 

ok friend of mine just went thru this. Broke a valve spring on world products head less than 4000 miles. put a z-28 spring on it, dropped it on the way to shades show. same spring. his motor is a roller cam motor, about 450 lift, I think I'm right) never sees more than 5000 rpm. ok gurus, what would cause valve spring failure like this. are we seeing a rash of cheap off shore valve springs or just one of those things.

 

Yes that's why I said not mandatory. I have "compressed" the spring with a big screwdriver on the opposing spring out in the field before. It can be tedious and keepers tend to ****ter with his method

 

OK...another question...The recommended matching Crane valve springs are part number 99848. They sell for $81 at Summit, plus shipping. I can buy others springs locally (designed for up to .550 lift) for $47. The pressures are different with the local ones having higher seat pressures. Is this an issue? Do I buy the Crane springs?

http://www.summitracing.com/parts/crn-99848-16/overview/

http://starperformanceproducts.com/Valve-Springs-Small-Block-1250-OD-OE-Style-5005.htm

 

You need to also look at the rocker ratio's...have the rocker arm's been upgraded or changed from original. The cam lift is multiplied by the rocker ratio...this can drastically change spring rates/ranges.

 

This was the first time I was faced with this kind of problem and I have driven thousands of miles around the country so I never thought about a valve spring problem,,,I do have a couple of valve springs and the tool I bought in Pigeon Forge to compress the spring to remove the keepers. HRP

 

There's a lot of mis information in this thread. Changing a broken spring to get home, is one thing. Just tossing springs in because they fit the pockets is wrong. Z28 springs are wrong for any roller cam.
If you are having spring issues, figure out why before throwing a band aid at it.

 

so i have done the rope trick on jap bikes, but on any SBC or whatever i just roll the piston up to TDC that way the valve can't fall down very far if at all, if it does want to drop down i just use a little blob of grease on the stem, usely the valve seal keeps the valve up.

 

I remember the engine builder saying he left the "rotators" on the valve stems. Is this an issue with a .454 exhaust lift and a 272 ADV /216 @50 duration on the exhaust valves? Can this combination of lift, duration and rotators cause the springs to break? Should I remove the rotators and replace all the retainers?

 

Yes.

 

machinist checked spring rate,said Z 28 was same pressure. Tell me why? and sorry really didn't mean to hijack thread.

 

The ramps on a roller are more aggressive and will easily float the valve leading to spring failures. Even with a hyd roller.

 

ok how do you fix it?

 

Nice work!

 

Back to my spring issue...can someone confirm if what I think is true?

1. The rotator is basically a special "and thicker" retainer on top of the exhaust valve spring.
2. To remove the rotator, I would need to add shims under the spring.
3. For the low RPM motor in my COE, the rotator is OK to use.
4. The spring pocket on the exhaust side of the 882 head is machined deeper to compensate for the extra rotator thickness. Both springs are the same length.
5. And lastly, I can buy a new set of springs matched to the cam and simply put them into the heads without any changes if I reuse the rotators...no measuring needed.

 

882 castings were used throughout the 70's...check the date code on the heads...
The 71 to about 75-76 standard type head used a short ex spring with the rotator.
Around 76-77 they started counterboring the ex spring seat so all 16 spring would be the same, and be able to use the rotator on the ex.
If you have a long spring on the early head with a rotator you can have all kinds of trouble. Not to mention wiped lobes and broken springs.
Even if you have the short spring and rotator the max valve lift is very low before you bind the spring

 

Yup.