Does anyone produce stiffer valve springs than the ones offered by the regular vendors?
Yep go here http://www.sbintl.com/valvesprings.html SBI has a download with all the info you would want for valve springs. They do not sell direct but their parts are sold by many of the parts houses...
In measuring, what criteria ? How many pounds compressed pressure at what measurement ?
Would shimming a weak spring be a alternative to replacement ?
Your application on a standard engine or modified ?
I have a stock engine, but it has a lifter that is too tight and won't let an exhaust valve close all the way so it runs on three cylinders with popping from the exhaust, the only solution i could come up with would be a stiffer spring. At this time i am trying to drive it more for the lifter to ear in.It is NOT a carbon build up as this has only 200 miles tops, but it does have power.I have no idea of which spring would work. I took the valves out and turned the crank the lifters all come up but one needs to be pushed firmly to get it back down so the stiffer spring might do the job without removing the engine and the cam to ream out the lifter guide. Any ideas or suggestions.
You can remove the cam without removing the engine from the car. I would do that, then ream the hole. It's not too hard, I did it in about 4 hours labor. You will have to remove the radiator, pan inspection door, cylinder head and the valves of course, again not complex or difficult.
A stiffer valve spring is probably going to ruin the cam and likely not fix the problem.
Place a couple of small washers between the spring and spring pin. This way you can adjust the tension by adding or removing washers. Once it is free enough that you don't need the extra tension you remove all the washers and your set. Be sure the pin can handle the extra tension, some of the pins are soft and will bend.
Dennis has an answer that might serve your purpose with a minimum of labor/cost. If you don't want to tear it apart this might be your best option.
You can find plenty of original springs around 24 to 30 lbs. Back many years ago my next door neighbor insisted I order in NEW SPRINGS. When they came in I put them in my spring checker and they were way weaker than his original springs. We ended up throwing the new ones in the garbage and using original springs.
Someone in your club surely has a spring checker if you don't have one. If you can't find one use a bathroom scale on your press.
I don't know what the "solid height" of a stock T spring is, but it is worth checking. If you shim so that the spring goes solid, something may break.
I Can't imagine anyone would have put it together that tight...
My fear would be that something that shouldn't be there is caught in the bore with the lifter, or that something maybe "bent" the lifter somehow? Either way, it might be a good idea to pull the cam, remove the lifter and see what the issue is before something maybe does more damage.
If you know that it was too tight when you put it together, I would still say that the cam should be pulled and the situation should be corrected instead of just trying to get it to "wear in". Occasionally things do "wear in", but in many cases where there is an "interference fit", galling will occur and it will just get tighter and tighter.
What is an "insignificant problem" that can be properly fixed in a few hours now, does have the potential to eventually cause a "big issue" if not properly repaired. Worst case scenario could be: Installing a stiffer spring causes the lifter to gaul in the block, seize up in the valve closed position, and bend the cam. Is heavy wear to the cam bearings and timing gear likely? Yes, it is Possible.
Rick, I've run Model A springs, I don't recommend using the A springs with stock keepers and retainers. If you've converted to modern valves this might work for you. I'd strongly recommend honing out the valve or tappet bore that is sticking, rather than running a stiffer spring.
Hey Rick, How about using some TimeSaver on that lifter? They advertise no need to clean up spent material like you would have with reaming.
It's an amazing product available at McMaster-Carr.
I like Gene's suggestion best. I have usually found that fixing the effect of a problem usually makes a new problem that ends up creating more work than fixing the original problem would have been.
The yellow TimeSaver is used on soft metals and breaks down quickly so cleanup is not absolutely required. Even so, I prefer to clean out as much as I can.
The green Timesaver is used on steel and does not break down. It needs to be thoroughly cleaned out just like valve grinding compound.