[Bill Eveland]

I'm looking at a few options on buying some heads for a future build. Maybe upgrade what I have now , but i'm running a hydraulic flat and my future motor will be solid flat cam. And if given installed heights are the same between the 2 .
I know solid roller springs are quite differant , but what about the differance between solid flat and hydraulic flat?

[tc]

You can use the same springs. Pressure is a little more on the solid. You'll need to check the pressure of the used spring. For a .550 lift ( actual lift, after setting the lash ) solid flat cam, I'd say 125-140 seat and 325-375 open spring pressures.

[gtofreek]

When I set up heads at work, I look at the duration @ .050" numbers and the total duration numbers. The closer these number are, the more aggressive the cam lobe is. Closer numbers means more open spring pressure. You can use this as a guide line:

TC is real close there. Hydraulic flat tappets with 30° intake valve seats, run at least 120 LBS. on the seat. Depending on duration, 300-325 open pressure, more on really aggressive hydraulic flat tappet cams.

On solid flat tappets, I would shoot for 135-150 on the seat, with 350-400 Open depending on cam specs.

If you post your cam specs that you intend on running, I can make a better recommendation. Heads are my specialty at work. I would like to see duration @ .050", advertised duration, lobe sep and lift. That would help me make a recommendation. Spring installed height on your heads and what heads your running would help also.

Always remember, a little too much pressure is way better than a little too little pressure. Especially seat pressure with a 30° valve seat. This flat seat angle has a tendency to bounce the valve off the seat, especially at higher RPM's. Even on a stock rebuild with 30° seats, I shoot for a minimum of 115 lbs. on the seat with the mildest cams.

We don't have cam failures using this guide line, and the valve train is much happier.

Most hydraulic roller cams can usually be set up just like a solid flat tappet cam.

[Bill Eveland]

I'm using an older Herold Brookshire UD/Lunati cam

either 62 or 670 heads will be going on a flat top 455

288/296 @.020
255/263 @.050
Lift .540 in, .556 ex
LS 108, installed @102

[gtofreek]

Harold makes the best cams. He's a good friend of ours, and we use his cams almost exclusively. Those heads both have 30° seats so you definitely want some seat pressure.

That cam has a major intensity number of 33°. That's the difference between @ .020" and .050" duration. This cam will need 150-160 Lbs. on the seat, minimum, and 350-400 open. A little more would be a good thing if you can find a spring that will work with that installed height.

Do you know what the installed height is by chance? Are you running RAIV valves?

Now, the lobe profile is pretty fast but not so fast that you will need lifter bore bracing. You should be fine. When the Major Intensity Number[MIN for short] gets below 30°, you better start thinking about lifter bore reinforcement or an aftermarket block.

I can look up some springs for you if like. I just need to know installed height.

[Bill Eveland]

The 288/296 is the advertised duration listed on the cam card, I copied the @.020 from somewhere else (not listed on the cam card) and what could be incorrect to lead to believe it's a solid roller. It does not have the wide lobes like a solid roller cam. I don't know the installed height yet.

Part# 407A3LUN, grind # 07-UF1-UF5-08.

[gtofreek]

Originally Posted by Bill Eveland

The 288/296 is the advertised duration listed on the cam card, I copied the @.020 from somewhere else (not listed on the cam card) and what could be incorrect to lead to believe it's a solid roller. It does not have the wide lobes like a solid roller cam. I don't know the installed height yet.

Part# 407A3LUN, grind # 07-UF1-UF5-08.

Yes, I saw it was a solid flat tappet, at first the specs sounded solid roller. I edited my post.

[android 211]

Is it necessary to use roller rockers with hydraulic roller cams? Can you use the stock rockers?

[gtofreek]

They may work for a while. I would worry about the stamped steel rocker breaking from the extra spring pressure. Also, the added friction at the ball pivot from the added spring pressure may cause the rocker to turn blue. I have never done it though. Maybe someone else has and can chime in here. Personally, I wouldn't do it.