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Larger Valves NLA?

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BoatBum10
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Larger Valves NLA?

Post #1 by BoatBum10 » Thu Sep 03, 2020 5:59 pm

I recently picked up a 1968 f100 4x4 with a 300. It's pretty tired so I'm doing a rebuild this fall. Been collecting parts, and it appears the SI 1.600 exhaust valves are no longer available (in 4.810" length)? The part number I used is SEV-3005. Is there any alternative? Maybe a slightly longer valve that's close enough to raise the rockers and get longer pushrods without getting weird geometry?

If it makes any difference, I'm putting in harland 1.6 roller rockers, and with a towing cam hope to stay with the 3/8" pressed in studs. Nothing wrong with the OEM rockers, except this motor is so worn several lifters weren't feeding any oil up top. Almost seized one in the 10 mile trip home, several others sound like an old screen door. Got a deal on the roller rockers.
1968 F100 4x4 300cu. Clifford intake, efi exhaust, hei ign, disc front brakes, NP435, now it's time to refresh the internals and make it go

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Re: Larger Valves NLA?

Post #2 by bubba22349 » Thu Sep 03, 2020 10:41 pm

Many people have used the SBC (Chevy) valves they are a little longer but will work fine, also can be helpful when using a higher lift cam of around .500 or more. I haven't tried using them with the stock pressed in studs though usally also go with the screw in studs. :thumbup: :nod:
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BoatBum10
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Re: Larger Valves NLA?

Post #3 by BoatBum10 » Fri Sep 04, 2020 2:02 pm

Do most use the 300 springs and shim them? Or is there a taller spring?

Thanks
1968 F100 4x4 300cu. Clifford intake, efi exhaust, hei ign, disc front brakes, NP435, now it's time to refresh the internals and make it go

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Re: Larger Valves NLA?

Post #4 by pmuller9 » Fri Sep 04, 2020 7:49 pm

BoatBum10 wrote:Do most use the 300 springs and shim them? Or is there a taller spring?

Thanks

The closed valve spring pressure will depend on which cam you are going to use.
There are a few single coil valve springs that will fit the 300 head.

Which cam are you going to use?

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Re: Larger Valves NLA?

Post #5 by F-250 Restorer » Sat Sep 05, 2020 12:19 pm

I've been using SBC valves in my 300 head for about 10 years w/o issue. You will need to have the oem studs removed so that you can replace them with ARP screw in studs. I used SBC studs as well. If you are going to install an after market cam and springs, it would be a good idea to run all metal timing gears. Use either Comp or Cloyes. I installed a cheap set that came with a kit I bought. On the second day the cheap set made so much noise that I had to change them.

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Re: Larger Valves NLA?

Post #6 by sixtseventwo4d » Fri Sep 25, 2020 7:34 pm

I just ordered those same ones through Vintage Inlines, on the homepage here. They have them listed on their webpage now, as they weren't before. Only offered as a set though.

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THE FRENCHTOWN FLYER
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Re: Larger Valves NLA?

Post #7 by THE FRENCHTOWN FLYER » Sat Sep 26, 2020 6:07 am

BoatBum10 wrote:..If it makes any difference, I'm putting in harland 1.6 roller rockers, and with a towing cam hope to stay with the 3/8" pressed in studs. ...

I recently built a motor doing that very same thing - using Harland Sharp roller rockers and a stout cam with the pressed in studs. My theory being if side loading is eliminated (or greatly reduced) then the necessity of screw-in studs is eliminated. We test fired the engine on a test stand this week and nothing catastrophic has happened yet. Of course time will tell but I'm hoping the roller rockers plus the decades of the studs being micro-welded to the parent head metal will prevent a failure.
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Re: Larger Valves NLA?

Post #8 by Firepower354 » Sat Sep 26, 2020 11:08 am

THE FRENCHTOWN FLYER wrote: My theory being if side loading is eliminated (or greatly reduced) then the necessity of screw-in studs is eliminated.



I'm still not sure how much of the stud flexing forces are from tip drag on the valve stem, versus the changing angle of force through the lift arc.

If the travel is stopped at any point in the lift event, is the force on the fulcrum, perpendicular to a line drawn between the two ends? Or, averaged between the angles of the valve stem and pushrod? Or some other answer that I'd know if I made it past basic math?

I realize the SBC has a bigger angle between the pushrod and valve stem, potentially clouding the findings.
But, I also recall the 45 degree angle of the indicator makes the reading low by a factor of 1.4ish
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It gets 10MPG, but goes up to 14 if I lie.

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Re: Larger Valves NLA?

Post #9 by pmuller9 » Sat Sep 26, 2020 12:47 pm

Firepower354 wrote:
THE FRENCHTOWN FLYER wrote: My theory being if side loading is eliminated (or greatly reduced) then the necessity of screw-in studs is eliminated.

I'm still not sure how much of the stud flexing forces are from tip drag on the valve stem, versus the changing angle of force through the lift arc.

On a 300 six the pushrod is around 2 degrees of being parallel with the rocker arm stud.
If the Harland sharp rocker is set so it is 90 degrees with the stud at half lift, the change in distance from the pushrod to the rocker stud as it sweeps through a .3125" arc (.500" valve lift) is .012".
On a 10.1" pushrod that is an angular change of .07 degrees which is negligible.

The Sine of 2 degrees is .035
So if the open spring pressure is 250 lbs X 1.6 = 400 lbs at the pushrod the side force is 400 x .035 or 14 lbs static.
As the rpm increases the dynamic force due to component acceleration will be more.

If you look at the stock rocker arm with a dynamic coefficient of friction with oil of .08, at 250 lbs open spring pressure the side force will be 250 x .08 or 20 lbs.
Based on an open spring pressure of 250 lbs the rocker stud side forces are reduced by 20 lbs by using a roller rocker but the side force from the pushrod is still there.

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Re: Larger Valves NLA?

Post #10 by Wesman07 » Sat Sep 26, 2020 11:14 pm

I just talked to my local machine shop the other day about SI valves. He said he is a dealer for them and it wouldn’t be an issue getting the 1.94/1.6 at 4.810”. Checking your local machine shop might be a good plan B if Vintage Inlines falls through.

Switching subjects to studs.... what type of builds has the pressed in studs failed?
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Re: Larger Valves NLA?

Post #11 by Firepower354 » Sat Sep 26, 2020 11:25 pm

Aaaah. So, does the direction of force not change, as the rocker arm's 3 points of force are tilted through their travel?
That's what I was stuck on.
It gets 10MPG, but goes up to 14 if I lie.

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Re: Larger Valves NLA?

Post #12 by pmuller9 » Sun Sep 27, 2020 2:35 pm

Firepower354 wrote:Aaaah. So, does the direction of force not change, as the rocker arm's 3 points of force are tilted through their travel?
That's what I was stuck on.

The rocker arm tilts but the direction of the associated forces only change slightly on the pushrod side because the pushrod angle changes slightly with respect to the rocker stud.
On a 300 six with a long 10.1" pushrod and a .500" valve lift the pushrod to stud angle changes .07 degrees which is negligible.

The only other thing that the rotating rocker changes is the distance from the rocker stud to the pushrod tip and the contact point on the valve stem tip.
As the rocker tilts from 90 degrees to the rocker stud those two points get closer to the rocker stud but the force from valve spring stays vertical to the valve stem and the force from the pushrod remains in the direction of the pushrod.

With the rocker geometry optimized and .500" valve lift the rocker tip travels .020" along the top of the valve stem and the pushrod tip moves back and forth .012"

What does change significantly (and this is where the confusion is at) is the forces within the rocker itself.
When the rocker is at half valve lift and the 3 rocker points are near 90 degrees to the valve stem, stud and pushrod the forces are 90 degrees to the rocker beam and are mainly bending forces.
As the rocker beam rotates the forces move more along the length of the beam and there is less force 90 degrees to the beam.

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Re: Larger Valves NLA?

Post #13 by sixtseventwo4d » Mon Sep 28, 2020 5:06 pm

[quote="Wesman07"]I just talked to my local machine shop the other day about SI valves. He said he is a dealer for them and it wouldn’t be an issue getting the 1.94/1.6 at 4.810”. Checking your local machine shop might be a good plan B if Vintage Inlines falls through.

I would be interested to know if he can. When I had called Si, I was told the SEV-2533 and SEV-3005 would have to come through vintage Inlines as those were exclusive for them. I'm still waiting on them to be shipped

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Re: Larger Valves NLA?

Post #14 by Wesman07 » Mon Sep 28, 2020 11:09 pm

sixtseventwo4d

I’ll try and stop in there later this week in between job sites. I just can’t imagine that it’s a proprietary part for vintage inlines. It is more believable that they just don’t want to be their own retailer. That is what I took from our conversation at least.

Pmuller9

Your explanation is taking long than I’d like to admit to sink in. Without an assembled head sitting in front of me, I’m searching YouTube videos.

At what point would you say press in studs are unreliable? Is it lift or spring pressure?
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Re: Larger Valves NLA?

Post #15 by pmuller9 » Tue Sep 29, 2020 9:53 am

Wesman07 wrote:At what point would you say press in studs are unreliable? Is it lift or spring pressure?

Spring pressure.
I would trust the press in studs with stock spring pressure including using the 1.75 ratio Chevy six rockers with the stock cam.
If I'm rebuilding the head with higher pressure valve springs it's going to get screw in studs. Why take a chance?
You don't know what condition any one particular head is in.

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Re: Larger Valves NLA?

Post #16 by THE FRENCHTOWN FLYER » Tue Sep 29, 2020 12:51 pm

Wesman07 wrote:At what point would you say press in studs are unreliable? Is it lift or spring pressure?

I would say both lift and spring pressure, combined with operating RPM range.

The spring pressure element is obvious. The lift, and particularly ramp rates will affect the jerk factor, jerk factor mathematically being the third derivative of valve position with respect to time (and snap is the fourth derivative of valve position with respect to time). Aftermarket cam manufacturers often place higher priority on maximizing performance than reliability. After all, what NASCAR or Top Fuel team is going to expect to get 100,000 miles out of their camshaft. Cam grinders will sell you a cam that jerks the valves open at alarmingly high rates which will put extraordinary loads on the stud.

So to sum up, stock cams with low(er) lift, mild ramps, and lower RPM operating range are on one end of the scale in terms of going easy on the studs. Extreme performance cams with high lift, radical valve acceleration and higher operating range will definitely need a stud upgrade, or even total replacement with shaft mounted rocker arms. Ford used shaft mounted rocker arms on their 4.9 crossflow head, for which I am truly thankful.

On another thread I have spoken of using the pressed in studs with a roller rocker arm to minimize the stud bending forces, even with a performance hydraulic cam. We'll see how long that engine lives. It has run fine on my test installation. At least the risk of a catastrophic failure is low if a stud loosens up. Usually the cylinder will lose power. Then maybe a bent pushrod. Myeeh
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Re: Larger Valves NLA?

Post #17 by sixtseventwo4d » Tue Sep 29, 2020 7:14 pm

[quote="Wesman07"]sixtseventwo4d

I’ll try and stop in there later this week in between job sites. I just can’t imagine that it’s a proprietary part for vintage inlines. It is more believable that they just don’t want to be their own retailer. That is what I took from our conversation at least.

Thank you for offering but no need. Just minutes prior to posting, an email confirmation of shipping details has come through.

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