TR5/TR250 Rope trick on a broke valve spring

Went to the store last week and decided to take the 250 and upon start up I heard a strange noise coming from the valve train. Sure enough it was a broken valve spring. #7. Amazing and after a 250 mile trip to the Pittsburgh Vintage Grand Prix with out a hitch. Drove it a couple of times after that.
One of my customers who was a Triumph mechanic in the day told me this story when he was racing his Mini and on the way to the race the truck broke a valve spring. He watched his friend shove a use a clothes line rope into the cylinder bore and bring the pistons up to hold the valves closed and tight to the top. Changed it on the side of the road. I wasn't about to take the head off and do it the conventional way. I just don't have the time and why go through all that if there is a shorter way. I've also been meaning to make a air pressure fitting out of a used sparkingplug in case this ever happens but there is a risk with doing it that way too. Another customer told me that he used too much air pressure and walked away and the air pushed the piston down and the valve fell into the cylinder.
Anyway a 15 hour project came down to a half hour. Now that I know how to do this I could do one in 15 minutes. The valve spring compressor I used is one I made back in 1970 when I used to work on lawn mowers. Worked better the a tool my 2nd customer gave me and couldn't even figure out how to use it. After I was done I took a extension magnet and went into the push rod holes to get any potential chips out of there. There were a few too.

When I tried compressed air I found that there was insufficient force (even when over 100 PSI) to keep the valves seated to release the valve keeper collets. I'd push on the spring compressor and the valve would just move down and open.

I have used the "rope trick" both to hold valves up for seal replacement and to prevent the engine from turning when undoing rotating parts. It does work. The only caveat I will add is that you need to make 100% certain that you are feeding the rope in while the piston is coming up on the firing stroke so both valves are closed. You can cause damage if the engine is a revolution out and you are on the stroke where both valves are open.

How long have you had those rocker arms on the engine ?
While I'm asking, what's the ratio ?

I remove the rocker shaft assembly before inserting the rope, this eliminates the chance of damaging an open valve. Here is a pic. of a couple of home made tools that I carry along with a length of rope, extra valve spring,and keepers.The bar on top is drilled to fit over the rocker pedestal studs (after removing the rocker assembly). The part on the bottom fits over the valve retainer and under the top part. Pushing down on the bottom part compresses the valve to allow the keeper to be removed. Before using it is a good practice to pack rags into all of the openings in the head to prevent the keepers from ending up in the pan or lost. Also, a small pencil sized magnet is usefull to pick up the keepers.
I probably will never need the tools, having only broke one valve spring in my life.
Berry

Good idea on the rags to block and plug the oil drain holes in the head. Fortunately I haven't lost the collets (yet ! ). I'll remember the rags next time !

Rockers were installed when the car was restored and was put on the road Aug 2006. 1.56:1. Love how they quite down the valve train.

Berry; do you push down manually and does the bottom attach to the top bar or is the top bar for a leverage point?

Got_All_4 said:

Berry; do you push down manually and does the bottom attach to the top bar or is the top bar for a leverage point?

Click to expand...

Yes. I probably did a poor job of explaining. The bar is placed on the pedestal studs and held in place with the nuts. The bar is just a leverage point for the bottom piece. The hole in the bot. part is about 3/4", not critical, just needs to be large enough to go over the keepers, but smaller than the retaining collar.
This whole discussion got me to thinking that we are lucky to have dual valve springs (at least on the later heads). If only single springs were used, wouldn't the valve drop into the bore if the spring broke?
Berry

My thoughts exactly on the duel springs. I was toiling whether or not to add them when I was building the engine. I hate to think of the results if I had not or have gone with the highest rocker ratio. Glad I did now and will probably do the same to my 69 tr6 when I get to it.