Please help a beginner ☺ with Valve Spring Questions

you'd want any dead weight under the spring where it doesn't move, otherwise the spring needs to control that weight for no good reason

machining spring seat pads for alternate springs is common. if there's not enough material around the remaining perimeter you can use a locator cup to center on the outside diameter of the valve guide to hold the base of the spacer/spring in place. addition material equal to the thickness of the locator cup will also need to be removed to achieve correct valve spring installed height/pressure

All valve springs are designed to work in combination with the camshaft. If you don't buy them together you must do the research yourself to ensure they work together. You will may also need the services of an automobile machine shop.

I bought crane 99839-16 Springs ,
CCA-4779-8 comp spacers
And a comp cam : CL32-239-4
Also scorpion roller rockers and manley race master valves.
Do you think this combination works?
Thanks

The 351C is equipped with a “big block” style valve train, meaning large (heavy) valves, large (1.5” diameter) valve springs, high ratio rocker arms, sturdy push rods, and sturdy (thick walled) tappets. Valve springs for flat tappet camshaft applications should have 115 to 130 pounds seated force and 300 to 330 pounds force at maximum lift (over-the-nose). Valve springs for roller tappet camshaft applications should have 150 to 160 pounds seated force and 370 to 400 pounds force at maximum lift. As a generalization valve springs for the 351C are sourced from valve springs designed for the big block Chevy. However, be aware that the installed height of a 351C valve spring is shorter (1.82”) than the installed height of a BBC spring. Shortening the installed height of a valve spring increases the seated force and shortens the spring’s maximum lift spec. The maximum lift should not exceed the valve spring’s “coil bind height” + 0.100”. The installed height of a spring can be increased by fly-cutting the spring seats or by installing valves with 0.100” longer stems. Longer valves impact rocker arm geometry however (as do higher lift camshafts).

I've been working on the following flat tappet valve spring chart, but its incomplete. The info in red has not been verified, and there is one blank field too.

You make no mention of your application (street or racing) or any of the engine parameters. For instance what's the stroke? This makes it difficult to comment on the camshaft.

Although its rated at 294 degrees duration, that's measured at 0.015", the standard for rating the duration of a solid tappet camshaft however is 0.020". Therefore the cam looks a bit bigger than it really is when compared to other cams. However based on the lash specification the cam will begin lifting the valves at 0.013", so the advertised valve events aren't too far off.

Based on the advertised valve events the cam's overlap is 74 degrees. I do not recommend anything greater than 60 degrees overlap for a street engine. Peak horsepower shall occur at about 4000 FPM mean piston speed, which with a 3.500 crank is equivalent to 6850 RPM.

The net valve lift is 0.585" which is compatible with the Crane spring.

Net Lift = (0.351 lobe lift x 1.73 rocker ratio) - 0.022" lash

George thanks a lot for your words.
It is a stock 2 bolt block. The pistons are flat with 2 relieves for the valves
The car should drive on the street but sometimes on the racetrack.
I want to use webers .

For your described application I would suggest a solid tappet camshaft similar to this:

274°/288° duration @ 0.020 (advertised)
113°/116° lobe centerlines
238°/252° duration @ 0.050
36° Major Intensity
52° overlap
114.5° LSA

Such a cam will make peak BHP at approximately 3500 FPM mean piston speed, which is equivalent to 6000 rpm with a 3.500" stroke crankshaft. This complements the 4V cylinder heads. It will still rev as high as is "prudent" with an engine equipped with the factory connecting rods (~7000 rpm); but it will behave much better at lower rpm for street operation ... and with the Webers.

Food for thought.

Hi George, thanks for your words again.
I did not found a cam like this, so I bought the cam allready

George, what do you think ? Should I buy a new cam ? The Problem is : I can only buy from Summit. I can not buy from to much diffrent stores, beccause of the tax and shipping costs.
I have to pay about 20 USD per packet only for custom clereance+ tax . Also the freight costs are verry high from smaler suppliers.

So I would like to buy , what summit have.

The next problem is: I can not balance the crank , because nobody have masterweights for the V8 crank:-( What do you think is the max RPM for a stock Engine with ARP nuts ?

Do you know a good harmonic balancer for external balancing ?

Peter are you saying that you will not be balancing the rotating assembly? are you replacing any components such as pistons? I don't think this is such a good idea.

Hello Peter. Tony (Ital Ford) is a craftsman, his advice is worth listening to.

I will search some of the camshaft catalogs, that might be represented by Summit. I'll start with Crane and Crower, because they are most likely to have cams with 112 LSA or more. You're welcome to do the same.

Ital Ford, no the engine is balanced , because it is stock. We changend the bearings and the stock nuts.

but : when you change only the pistons , you do not need to balance the engine !
Only when you change the connecting rods you have to balance it. The piston is a part wich moves only up and down and do not have anything to do with the rotating parts.

George, thanks again.

All cams from Summit I found are between 108 and 110 LSA, when they have a higher lift.

Its realy difficult to find one... I will ask summit , if they have parts wich where not listed in their online catoalog...

an other question :
Why do I need spacers for the 99839-16 Springs?

it seems that my stock 4V Springs and the new sprigs have the same high and they look like the same ...

thanks

https://www.summitracing.com/i...crn-363841/overview/

this is the only one I found ...

sorry , this is for a windsor..

Crower #15388 is similar to the Windsor cam above, but it is for the 351C.

About 61° overlap, 112° LSA.

The advertised lift is 0.524/0.533
The "net" lift is 0.502/0.509

Obviously we can do better in terms of valve lift if we do a custom cam.

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The best Crane cam I found was #521131, the valve lift was better. It had about 60° overlap, but 108° LSA. The exhaust valve opened too late, the intake valve closed too early. Altering the cam timing to improve one aspect only makes the other worse.

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The cam grinders are capable of producing better work, but the marketplace, magazines, SEMA, don't demand it from them. Their bottom line is to manufacture and market what sells, and what is competitive with the other cam grinders.

George, what about using the cam I have ordered ?
And a other verry silly question :

What about making the cam I have ordered more round ? We have cam grinders here in Europe - but they are specialised in European Engines .
They can machine the cam a little bit ...

FYI if you call Comp Cams and give them the specs you want they will grind almost anything you want custom. They give you a part number. Then call Summit and say you want to order xxx part number. That is one option.

Yes I will try it. Thank you.
I looked at the ordered cam and Summit says
It works from 3000 to 6500. Is this a mistake from Summit or comp?