Rebuilt Flathead Problems.
- Thread starter GordonC
- Start date
JSeery
Member Emeritus
Valve spring height determines the valve seat pressure. Say you want 50 lbs of seat pressure, you would have to measure what spring height gives you the 50 lbs. Then the spring height needs to be set to that height on the valves. The install height is measured on the valve assembly without the spring and then shims added to archive the install height desired. I sure this is totally in-clear! You should be able to find a step by step procedure online.
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JSeery so to determine what height gives you that 50 lbs as in your example you need to check all the springs at a set height to see what pressure they give and then adjust from there? Not enough pressure add shims. What do you do for too much?? Is this done on just the valve springs by themselves?
I have been reading as much as I can find online about this stuff as I want to make sure that I only go through this once.
I have been reading as much as I can find online about this stuff as I want to make sure that I only go through this once.
JSeery
Member Emeritus
The springs should have a height associated with them and you check the pressure at that height. But, you don't have that information so you will have to determine what the spring pressure is for a given height. It is a little confusing to explain in text only (at least for me!).
Here's a link to a short video on checking valve springs.
https://www.youtube.com/watch?v=3Hyw3fantpk
Bob
https://www.youtube.com/watch?v=3Hyw3fantpk
Bob
JSeery
Member Emeritus
Disclaimer, I don't use rotators! So, keep that in mind, it is possible I'm not 100% correct on this information. What I looked up for 1952 is 39 - 40 lbs at 1.89 install height. Need to install a valve guide with a valve and the retainer assembly on the valve (a little weight check spring is helpful, but not required). With the valve assembly (minus the spring) in place, measure the install height (from the top of the retainer to spring seat on the guide). Inside measuring dividers (the compass type with the manual adjuster) work good for this. Then measure the calipers to determine the install height. Now measure the spring pressure at this height, if the pressure is to low at the install height, then determine the shims required to get the spring pressure correct. Clear as mud I'm sure! Slightly higher spring pressure at install height is ok, just don't want it too high, saw something like 50 max.
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JSeery
Member Emeritus
Depends on the parts you are using, how deep the value is setting in the seat, etc. I would a least want to know what seat pressure I was running.
The earlier valve spring free height should be around 2.5 inches and the later spring with the rotators should be around 2.2 inches.
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Installed valve spring seat pressure.
First off, Ol' Ron gets full credit for this method to measure installed height pressure...
With fully installed valve assembly resting off the lifter, measure the spring from the bottom of the guide to the top of the retainer with a divider or dowel.
Find or grind a bolt and nut to match this dimension.
Disassemble valve assembly.
Place a bathroom scale on the table of your drill press and cover it with a square of plywood so it doesn't get damaged.
Chuck an old valve in the drill press with a small block of wood handy.
Set the spring and measured bolt/nut assembly side-by-side on the plywood with the wood block over the top of spring.
Pull chuck down until spring is even with bolt assembly then read scale.
Note: Every valve may have a different reading.
Lonnie
First off, Ol' Ron gets full credit for this method to measure installed height pressure...
With fully installed valve assembly resting off the lifter, measure the spring from the bottom of the guide to the top of the retainer with a divider or dowel.
Find or grind a bolt and nut to match this dimension.
Disassemble valve assembly.
Place a bathroom scale on the table of your drill press and cover it with a square of plywood so it doesn't get damaged.
Chuck an old valve in the drill press with a small block of wood handy.
Set the spring and measured bolt/nut assembly side-by-side on the plywood with the wood block over the top of spring.
Pull chuck down until spring is even with bolt assembly then read scale.
Note: Every valve may have a different reading.
Lonnie
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GOSFAST
Well-known member
Hi Gordon, what I recall on your springs was the fact they were installed incorrectly.
They appeared to be a "progressive" wind and the closer wound coils need to be at towards the guides not towards the retainers?
Thanks, Gary in N.Y.
P.S. While you're this deep into checking I would strongly recommend installing some "bronze-lined" guides or down-the-road you run the risk of having to open it all up again to "free-up" any hung valves, not worth taking that risk in my opinion! Changing the guides at this time alone has no effect on anything else you've already done!
40cpe
Well-known member
Checking spring pressure: I had a hard time coordinating drill press with the spring not at eye level and reading the scale. I made this indicator to tell me when the spring and guide were at the same height. A carriage bolt through a piece of board with a ground wire at the bottom. Cut the bolt to the length of the shortest installed height you measured. Place a nut on the threads to adjust for varying heights. Use a flat, rigid, piece of steel to press the valve. Attach an analog ohm meter to the carriage bolt ground and to the flat piece on top of the valve. Press the valve until the analog meter swings and read the scale.
sorry about the rotated pictures, they were straight on my computer.
sorry about the rotated pictures, they were straight on my computer.
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Guys thanks for the additional info on using a home made tester to get the spring pressures. I will probably rig one up.
Gary what I am I looking at for a set of the bronze lined guides? Don't mind doing whatever makes sense.
Also guys I have asked this a couple times now but nobody has answered me on this yet. Do I need to worry about the different length valves? These are chevy 1.5" valves and they were anywhere from .035 under 4.9" to 4.910" length. If I can compensate for the variance using the adjustable lifter and the reground cam I can just forget about this if I can get an answer.
Gary what I am I looking at for a set of the bronze lined guides? Don't mind doing whatever makes sense.
Also guys I have asked this a couple times now but nobody has answered me on this yet. Do I need to worry about the different length valves? These are chevy 1.5" valves and they were anywhere from .035 under 4.9" to 4.910" length. If I can compensate for the variance using the adjustable lifter and the reground cam I can just forget about this if I can get an answer.
JSeery
Member Emeritus
The issues are: What springs do you have? And what spacer are going to be required to get to the spring pressure you are wanting? I provided the stock specifications, but that is of little value in this situation. You are not using a stock valve and the Chevy valves are longer, so you are going to have to figure out what is required to get to a usable spring pressure (50 lbs would be a good goal). Start by measuring a loose spring and see if it will help ID it. I have no idea what the setup will end up being with the rotator retainers, but a guess would be:
Pre rotators stock springs were 2.5 inches free height.
Post rotators stock springs were 2.2 inches free height.
So, there is a difference of .3 inches. If is also possible you have LZ springs.
It is difficult with a normal retainer and a Chevy valve to get enough shim to work properly. On of the folks here on the Barn who has a shop can provide a special made spacer for this application. But, I'm not sure how that would work with the rotators. Hopefully he will supply some answers!
Pre rotators stock springs were 2.5 inches free height.
Post rotators stock springs were 2.2 inches free height.
So, there is a difference of .3 inches. If is also possible you have LZ springs.
It is difficult with a normal retainer and a Chevy valve to get enough shim to work properly. On of the folks here on the Barn who has a shop can provide a special made spacer for this application. But, I'm not sure how that would work with the rotators. Hopefully he will supply some answers!
40cpe
Well-known member
I think you are going to have to install at least one valve assembly in your engine. Check the installed height of the spring and then your pressure at the installed height. We don't know what spring you have, and the rotators add another variable. If the valves were adjusted in the initial installation, you are probably OK with the Chevy valves.
GOSFAST
Well-known member
Hi Gordon, some are correct there and some aren't. Like I said above the closer wound coils go towards the guides!
I'll PM you later with the bronze-guide info!
Thanks, Gary in N.Y.
P.S. Here's a photo showing a quick method for measuring the spring hgts and pressures using a common bathroom scale and a drill press and a 6.000" pocket ruler! It is very accurate and it's all you really need to find the numbers!
