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Old 08-13-2019, 07:32 PM   #1
frnkeore
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Default FH Valve Springs

I have another question for the guy's that run, hotter cams.

What is the minimum, installed pressure and the maximum open pressure, for a .375, lift cam, that will turn 5500 rpm?

Pictured is Isky's valve spring spec's, are they good for 5500 rpm?

Also, I have read on this forum, that you have to watch out for higher pressure springs, because they will wear the cam out.

What is the reason that the cam will wear so fast, with what I think are fairly low pressures. In modern, OHV valve engines, we run 300+ lb, open pressures, w/o any cam failure issues.

Thank you,

Frank
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Old 08-13-2019, 07:46 PM   #2
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Default Re: FH Valve Springs

The Isky 185-G spring is just fine for what you're doing - install it at 2.00". What you didn't mention was size/weight of valves, what type of lifters, etc.. With just a .375 lift cam and 5500 redline, you'll have no problem with just about any valve gear you're using - 85 lbs on the seat is actually more than you'll need. You can easily get away with LZ springs - which at 2" are closer to 80 lbs. (I just checked some for Mac VanPelt today).

If you want a set of LZ springs, call Mac VanPelt -- the part number is 864-6513. They should be a bit cheaper than the 185-Gs . . . and should perform just as well for your application.

B&S
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Old 08-13-2019, 07:50 PM   #3
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Default Re: FH Valve Springs

Reason for wearing out: Can be many things (like material/alloys of the lifters, etc). What you should ponder is the overall SIZE of the flathead performance profile . . . has a LOT less surface area (if you traced the path/length of a lobe) than a modern OHV engine and a much smaller base-circle - so you get more flex in the cam as well - which also wears things faster. Another thing to think about is that flatheads don't have rocker arms - so when you have a higher lift cam like a .425 Potvin, this would be .637 lift on a simple 1.5 rocker. So, to get higher lifts on a flathead, the profile has to be pretty aggressive . . .which also leads to more wear.
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Old 08-13-2019, 10:28 PM   #4
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Default Re: FH Valve Springs

I use 50 lbs on the L-100 cam and turn it 5k. When we ran the 400 jr in the stock car we ran 65 lbs at one time we were running 85 lbs but the lifter were taking a beating. But that ea over 50 years ago and the oil is better now.
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Old 08-14-2019, 10:24 AM   #5
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Default Re: FH Valve Springs

Quote:
Originally Posted by Bored&Stroked View Post
Another thing to think about is that flatheads don't have rocker arms - so when you have a higher lift cam like a .425 Potvin, this would be .637 lift on a simple 1.5 rocker. So, to get higher lifts on a flathead, the profile has to be pretty aggressive . . .which also leads to more wear.
You have to remember that I'm reverse engineering on this forum. This is my first FH build, since 1959-60 era and it was my best friends car.

In the case of the SBC (1.5 rocker) that .637 lift, would put a load of 450 lb on the lifter (300 lb spring) and the SB lifter, is only .843 in diameter and not able to take the same lift rate as a 1" FH lifter. Not to mention (I love that term) that springs for that lift, would normally be North of 380 lb. The FE's use a ratio form 1.72-1.75 but, a slightly larger, .875 lifter. With a .600 lift cam and 380 lb springs, that's 675 lb on the lifter and cam.

I only ask this, because , I've read, more than once, that you have to be careful of what seems to me, fairly low spring pressure or the cam will wear. I just got some hollow Hi Lift Johnson adjustable lifters and I want to make sure I won't have any issues. I'm hoping to have Howard's grind a Schneider 250F cam for this, unless that cam is available, off the shelf somewhere.

Most flat tappet OHV engines, use cast cams, are the early Ford cams, so soft that they can't be hardened to modern spec's and that is the reason they wear?

Frank
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Old 08-14-2019, 12:09 PM   #6
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Default Re: FH Valve Springs

Everything in an engine that is moving consumes energy. You want the lowest valve spring pressures that will keep the valve train following the cam profile and avoid valve float. Flatheads don't require near the spring pressure of an OHV engine to accomplish that. And if you did float a valve it is not much of an issue.

Most of the metals used in early Fords are of high quality. I don't know anything specific about the material used in Ford cams vs modern cams, but would assume the early Ford cast cams would have been of high quality. Some flathead cams were steel, not cast and favored for some high performance applications.

Pete here on the Barn is a cam expert, he might have an input.
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Old 08-14-2019, 09:59 PM   #7
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Default Re: FH Valve Springs

If it was mine, I'd go with the LZ springs from Van Pelt and install them at about 2.0625 - should give you about 65 lbs on the seat . . . more than enough for almost any cam in the .375 lift range. I don't have the numbers for "on the nose" pressure . . . but it is probably closer to 180 lbs.

Flatheads don't have rockers or many moving parts - so we don't use a lot of spring pressure. There is really no need to run even 80 lbs on the seat - unless you're going to put some boost into it or rev it higher than 5500.

In my 32 Cab, I have a very stout street engine with a roller cam with .420 lift and very aggressive profiles, I run about 90 lbs on the seat . . . but that is also on a hardened 8620 billet and with a roller lifter - so I'm not worried about that sort of spring pressure wearing out the cam.
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Old 08-15-2019, 03:19 PM   #8
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Default Re: FH Valve Springs

One more question, related to this issue:

Does anyone drill the hollow lifters to lube the cam lobes? If so, what size do they make the hole?

Frank
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Old 08-15-2019, 05:15 PM   #9
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Default Re: FH Valve Springs

Never heard of it.
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Old 08-15-2019, 06:05 PM   #10
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Default Re: FH Valve Springs

I'm not sure what you are referring to either. Is that a practice on some other motor? There is no oil in the lifter, so you can't feed the cam lobe from it. It all gets lubed from oil splashed from the rods.

Mart.
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Old 08-15-2019, 06:08 PM   #11
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Default Re: FH Valve Springs

After hearing of the cam lobe failures, with higher pressure springs, it seems like it might cure that. You could also do it with solid lifters, by drilling a side hole, to meet the cam lobe face hole.

They would be easy to drill, with a 1/8" solid, carbide drill. 3/32" would be a a little harder to do and if you go smaller than that, you'd have to do it with EDM.

Just a thought, I'd be supersized if it hadn't been tried at some point.
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Old 08-15-2019, 06:15 PM   #12
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Default Re: FH Valve Springs

Quote:
Originally Posted by Mart View Post
I'm not sure what you are referring to either. Is that a practice on some other motor? There is no oil in the lifter, so you can't feed the cam lobe from it. It all gets lubed from oil splashed from the rods.

Mart.
I was speaking, primarily about the hollow lifters. I just got some in the mail today. and while looking them over, I thought of it. Although you could do it with solids by drilling side holes to mate.

I can't think of the application, at the moment but, yes, it's been done before.
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Old 08-15-2019, 06:22 PM   #13
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Default Re: FH Valve Springs

But there is no reason to run higher spring pressure except in extreme competition and it those cases it normally requires a roller lifter or a wide based lifter. The issue is the small base circle and fast ramp rates.
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Old 08-15-2019, 06:51 PM   #14
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Default Re: FH Valve Springs

Yes, high rpm was what I was referring to as that's where the high pressure springs are need BUT, I'm thinking of making my own guilds out of aluminum (bushing the EX with aluminum bronze) and using low pressure SBC springs and retainers (about 200 - 210 lb open) maybe even PC seals.

My engine won't go above 5500 though.

Why? Just because I can. Also, I can never stop thinking of why something works (or not) and always trying to improve, either by lowering weight, making it stronger or lasting longer. It's just how I've always been.

Frank
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Old 08-15-2019, 06:58 PM   #15
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Default Re: FH Valve Springs

Quote:
Originally Posted by frnkeore View Post
Yes, high rpm was what I was referring to as that's where the high pressure springs are need BUT, I'm thinking of making my own guilds out of aluminum (bushing the EX with aluminum bronze) and using low pressure SBC springs and retainers (about 200 - 210 lb open) maybe even PC seals.

My engine won't go above 5500 though.

Why? Just because I can. Also, I can never stop thinking of why something works (or not) and always trying to improve, either by lowering weight, making it stronger or lasting longer. It's just how I've always been.

Frank
That's a common trait amount Hot Rodders! With a flathead it's hard to come up with something that hasn't already been tried many times, just the way it is with these engines. There have been some wild and crazy things tried!
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Old 08-15-2019, 07:26 PM   #16
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Default Re: FH Valve Springs

So where is this magic oil in the lifters coming from? No modern engine here with pressure fed hydraulics
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Old 08-15-2019, 07:51 PM   #17
frnkeore
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Default Re: FH Valve Springs

It wouldn't be pressurized but, threw the drilled, lifter adjusting holes in the lifter bosses. Using hollow lifters.
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Old 08-15-2019, 07:59 PM   #18
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Default Re: FH Valve Springs

Yikes
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Old 08-15-2019, 08:14 PM   #19
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Default Re: FH Valve Springs

Great imagination but sorry not enough oil there period.
Good luck.
Cheers
Tony
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Old 08-15-2019, 09:32 PM   #20
frnkeore
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Default Re: FH Valve Springs

Tony, how do you know that there isn't enough oil?

Would there be more oil transferred to the cam nose at it's highest spring pressure that way?

If you'd like to try, along with me, I'll drill your lifters for free.

The hot rod movement of the 50's was all about trying new, unproven things. Some failed but, some lead to where we are today and that includes reliable, NASCAR 9500 rpm engines.

Frank
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