Replacing Valve Springs

[rsev216]

A valve spring broke last fall in my 65 289 and I had it replaced to get to a show the next week. The mechanic that did the work said everything looked good and he saw no reason for the problem. I plan to replace all the springs with the heads on the engine before the snow melts. Is there anything special that I need to know? Any tips would be appreciated.

 

[woodsnake]

It may not be a common problem, (I haven't heard it's a common failure) but those springs perform a mechanical function, compressing and expanding millions of times over their duty cycle. I would say if there was nothing else laying there, then it was just fatigue.

 

[Pony66]

Ive read a couple tips here to keep the valve from falling into the cylinder when changing the springs. Some say to pull a spark plug and feed a bunch of rope into the cylinder. Some say rotate the engine to bring the piston up for each valve as you change the springs. I wonder if you could just use some blue tape?
I would spend $5 and replace the valve stem seals while your doing it.
Of course you will need a valve spring compressor.

 

[rsev216]

Thanks for the suggestions! I have an air hold tool lined up to use with my compressor so hopefully I won't lose the valve. How can I tell when the piston is TDC?

 

[j69302]

Thanks for the suggestions! I have an air hold tool lined up to use with my compressor so hopefully I won't lose the valve. How can I tell when the piston is TDC?

You can take the spark plug out of the cylinder you are going to work on. Put your finger up to the spark plug hole, rotate the engine by hand in the correct direction of engine rotation, feel for it to blow air out to ensure you are on the compression stroke. Then sometime you can shine a flashlight in there enough to see the piston, rotate it slowly until the piston stops moving.

Another way, probably easier, is to remove the distributor cap, and rotate engine until the rotor is pointing to the spark plug terminal for the cylinder you are working on, then use the finger method to ensure engine is top dead center.

It is important to ensure the cylinder is at TOP DEAD CENTER. if it is not, the engine COULD spin if enough air pressure is introduced. If it is TOP DEAD CENTER it will be VERY hard for it to spin by itself.

If you have a manual trans mission, I would make sure that it is in gear to prevent the engine from spinning.

 

[blown65]

I always did mine with TDC. Get #1 at TDC then mark your balancer in 90 degree spacings. After each cylinder then it's a quick turn to your next mark and the next cylinder in your firing order.

It's how I do my valve lashing also.

You can do air but I like the mechanical backup of keeping the valve where it belongs.

Our BBC wouldn't break the locks with just air either. Had t use the piston to break it loose. Damn things were stuck bigtime.

 

[woodsnake]

I didn't see the part about installing all new springs, with out pulling the heads. To me, that seems like a lot more work. If you are replacing the springs "just to be on the safe side", I wouldn't do it. I would pull the heads to get them rebuilt, with new valve guides and seats, to make it all worthwhile though. Comparing the 20 head bolts and two gaksets, to the hassle of messing with the springs on the head, with the heads off the car, I'll pull the heads off every time...

 

[blown65]

Maybe the case on a street car but if you have nothing else wrong but some weak old springs it's a hell of alot easier to do it on the car.

Also mine has head studs. Those heads aren't coming off without the motor being removed.