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Old 05-13-2010, 09:03 PM
motorman910 motorman910 is offline
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Default Proper Valve Stem Length

How would a guy go about measuring the length of the valve if the length was not known and get proper geometry? I'm sure there is a way, has to be. I'm just curious I guess, most of the time you can just get a +.100" stem length, but when you are setting up a valvetrain to run high RPM's in a head that length is unknown to you, how would be the best way to go about that? Are there special tools or stuff you guys have made yourselves to do this?
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Old 05-13-2010, 09:22 PM
rmcomprandy rmcomprandy is offline
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Quote:
Originally Posted by motorman910 View Post
How would a guy go about measuring the length of the valve if the length was not known and get proper geometry? I'm sure there is a way, has to be. I'm just curious I guess, most of the time you can just get a +.100" stem length, but when you are setting up a valvetrain to run high RPM's in a head that length is unknown to you, how would be the best way to go about that? Are there special tools or stuff you guys have made yourselves to do this?
The length of a valve is measured in OVER ALL LENGTH so, the thickness of the margin of the valve is part of that length. To get the tip of the valve where you want it to be, requires the thickness of the head be a known part of that equation.

A plus .100" STEM is NOT necessarily a plus .100" length.
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Old 05-13-2010, 09:56 PM
motorman910 motorman910 is offline
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So do you just take the rocker set up you want to run, get an idea of where it should be then measure the head iteself up through the guide? That is kinda what I'm asking. I know that the entire length of the valve is over all length, what I would like to know is how do you go about locating the lock groove, how much stem is on the rocker side of the guide, stuff like that. I know it may sound like a dumb question, but I have never had anyone explain it to me. What is screwed up is you have all these formulas for compression height, and rod ratio, etc, etc, and I have never come across a general conversation about valvestem lengths and rules of thumb for what you should look for. It is more of an eduacational question if anything, I could be just making things harder than they should be too....
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Old 05-13-2010, 10:33 PM
c.evans c.evans is offline
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Most cylinder heads have an intended valve spring installed height from the manufacturer. For example the older A-429 alum. heads had a 1.900 to 1.950" installed height. Then the A-460 heads had a 2.00" instaled height, the C-460 heads a 2.100" installed height, and so on. The proper valve length was determined by the manufacturer, at the time of the heads design.

Generally you can play with or vary the valve length some, and do a + or - .100" in length and things won't get to far out of wack. However, if you go with too much of a change in valve stem length, such as using a set of B. T. heads with an intended installed height of 1.900 and putting +.200 longer valves in them for a 2.100" Pacaloy # 948 triple valve spring, then you start having geometry problems with the tip of the stem and the roller rocker. The reason is because the valve stem and the rocker stud are inclined towards each other, like the sides of the roof of an A-frame house. Use dykem and always check the pattern of the roller's travel over the stem tip of the valve.

As far as the tip length of the valves, it is pretty much the performance industry standard to have a .250" tip length in stainless steel valves,,, and a .290"-.300" tip length with titanium valves.

There is also some degree of flexibility with + or - .050" valve locks, and +.050" and + .100" titanium 10* retainers verses standard steel 7* retainers.

Other things to be considered are the retainer to valve stem seal clearance, the retainer to underside of the rocker arm clearance, spring installed height and pressure, spring open pressure, coil bind, and of course the lift of the camshaft. If you get any of these factors wrong, it make for a really bad day with a racing engine.

Hope this helps,
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Old 05-13-2010, 11:31 PM
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DJOHAGIN DJOHAGIN is offline
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Originally Posted by c.evans View Post
such as using a set of B. T. heads with an intended installed height of 1.900 and putting +.200 longer valves in them for a 2.100" Pacaloy # 948 triple valve spring
Sounds like you have come across this, Charlie.



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Old 05-14-2010, 05:53 PM
motorman910 motorman910 is offline
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Thanks Charlie, that makes sence to me. I would assume that most cylinder head companys that have their own castings can tell you the valve length that the specific head was designed with. That is what I thought you could do, but I didn't know if there was any way you guys had used in the past to take a casting that is ready for assembly and mock up the valvetrain and get your stem lenths, the Rocker pad heights, push rod length, etc, etc. I have been around this stuff some, but just enough to get myself in trouble. Also, have any of you guys ever run a what we call a "top lock" valve stem with a lash cap? Some of the Cup engines I have worked on in the past have had these and the tip length was way less than .250" The lock was recessed with a provision for the lash cap to seat on the valve. I would guess the cylinder head guy's were trying to save a little weight. This was back when we were in the RPM wars back about 4 to 5 years ago, racing 10,500 for 500 miles at Texas, Atlanta, places like that.
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Old 05-14-2010, 06:13 PM
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Quote:
Originally Posted by motorman910 View Post
Thanks Charlie, that makes sence to me. I would assume that most cylinder head companys that have their own castings can tell you the valve length that the specific head was designed with. That is what I thought you could do, but I didn't know if there was any way you guys had used in the past to take a casting that is ready for assembly and mock up the valvetrain and get your stem lenths, the Rocker pad heights, push rod length, etc, etc. I have been around this stuff some, but just enough to get myself in trouble. Also, have any of you guys ever run a what we call a "top lock" valve stem with a lash cap? Some of the Cup engines I have worked on in the past have had these and the tip length was way less than .250" The lock was recessed with a provision for the lash cap to seat on the valve. I would guess the cylinder head guy's were trying to save a little weight. This was back when we were in the RPM wars back about 4 to 5 years ago, racing 10,500 for 500 miles at Texas, Atlanta, places like that.
what your saying about top lock/lash caps iis still used today.
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Old 05-14-2010, 09:17 PM
c.evans c.evans is offline
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For just about all the heads I do, I have an large assortment of R&D valves. These are stainless steel valves that I mock-up with and check for the proper depth of the valve job, etc. I use a height mike on the spring side and see how far off I am from the installed height I'm wanting. I like to use standard height locks, retainers, seat cups & etc. during this mock-up process. Then after I do the math and determine what is the proper length valve to order, I fill in the blueprint specs for those valves and fax them in to Victory 1 for the correct titanium valves. I hate to make a $2,000 mistake in regards to valve length, and all titanium custom valves are non-returnable, regardless of the manufacturer.

If we are really plowing new ground, then I send the complete head off to Wilfred at W.W. Engineering for him to determine the proper rocker stands for the shaft mounted rocker stuff. W.W., Jesel, and T&D all have some little geometry checking fixtures, in order to determine the proper amount of shims, (if any) to have under the stands.

It was Wilfred's suggestion that we start using the longer 1750 bodies (shaft mounted rockers) instead of the older 1650 bodies like the other guys use, on the new style 18 bolt TFS A-460 heads. Therefore when Lem and I made the proposed changes and upgrades to TFS, one of the changes was that we slotted the pushrod holes +.275 up towards the intake manifold. This provided the necessary pushrod clearance for the longer shaft mounted rocker arms. The longer bodies are better with the higher lift camshafts.

Yes, Lawes has used the captured lock NASCAR stuff in some of his engines. The main thing I'd like to stress is that anybody running titanium valves in todays world with these killer valve spring pressures, is that they should be using the radius groove or as Manley calls it the Bead-Loc groove keepers and valves. The old traditional square groove stuff for the locks, causes a stress riser and they will break from the corner of the groove, up to the post hole for the hardened tip. I've got some torn up and trashed parts here to show anybody that doesn't believe this.

The truck pullers seem to be harder on the valve train than most any of the drag racing boys, and as we all know they hold those engines between 8,000 to 9,000+ rpm for 18 seconds. IMO any serious truck puller must run titanium valves. I've seen some try to run stainless steel valves, and depending on valve weight, camshaft lobe specs, valve springs and etc., those engines get into valve float around 7,500 rpm or so.

Hope this helps,
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Old 05-15-2010, 07:13 AM
motorman910 motorman910 is offline
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It does help, a good bit Mr Evans. Thanks for your input. We use radius groove locks as well on everything we use. We even go a little bit further and radius the edges of the lock with a dremel tool and tumble them for a few hours to make sure they have zero sharp edges. As for the 1.650 body stuff, it used to be better for us to go that route on small block stuff (SB2). We tried the 1.750 and maybe even some 1.850 stuff and just couldn't get the dynamics right on the spintron. As far as the top lock stuff goes we only used them for a short while. We also were using 190 to 200 lbs on the seat with a roller set up too. Probably not as much pressure as the big block stuff you guys use. They were pretty hard on valve tips and were a pain in the butt for some reason on valvespring changes. It was almost like they seated in the retainer more or something and made them a bear to get off. Thanks for the input. Once again, great forum...
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