84z4me

Hydraulic Flat Tappet And Solid Flat Tappet is it just in the lifters?

Summit Cam
Cam Style Hydraulic flat tappet
Basic Operating RPM Range 3,000-6,200 RPM
Intake Duration 050 inch Lift 234
Exhaust Duration 050 inch Lift 234
Advertised Intake Duration 292
Advertised Exhaust Duration 292
Intake Valve Lift with Factory Rocker Arm Ratio 0.488
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.488

Lunati
Cam Style Hydraulic flat tappet
Basic Operating RPM Range 2,000-6,000 RPM
Intake Duration 050 inch Lift 230
Exhaust Duration 050 inch Lift 230
Advertised Intake Duration 292
Advertised Exhaust Duration 292
Intake Valve Lift with Factory Rocker Arm Ratio 0.480
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.480

I was thinking of getting one of these cams. I've got 416's sitting in the garage ready for some porting. Im running a 355 weiand stealth intake, a 650 dp, dont know what the pistons are.
1. Im runnin 3.73 And i know ill need a stall how high of one would help?
2. What rockers should i use 1.5's or 1.6s?
3. I also need to know what valves springs to use, if i should get new pushrods and what valves to run thinkin 1.9 and 1.6 but would really like to know what would be best?
Any help would be greatly appreciated.

five7kid

iTrader: (14)

As has been discussed many times, the cam has to be made for the type of lifters that will be used. You can't use roller solid lifters on a cam designed for roller hydraulic lifters; you can't use roller lifters on a cam designed for flat tappet and vice versa. Etc., etc., etc.

Why do you ask about solids? Both cams say hydraulic.

It's impossible to say exactly how each cam would perform using only the info provided. There is a lot more than lift, duration, and duration @ .050" to a lobe design. The "basic operating range" doesn't mean a whole lot, either, as the "real" powerband will be function of the total engine package. In general, though, the Summit cams tend to be older profiles that cause a rougher idle, narrower powerband, and reduced driveability compared to the newer profiles being produced by the "majors" (like Lunati, Crane, Comp, etc.).

You need a converter that stalls at or above where the engine powerband "comes in". Crane says my cam has a basic operating range of 2200-5200, but it really kicks in at 3000 and pulls well to 5500. 2300 stall turns out to be too little.

1.5 rockers is probably best unless the cam is intended for the higher ratio (like the LT4 Hotcam). Use the valve springs recommended by the cam manufacturer of the cam you end up getting.

On a 350, 1.94" intake and 1.60" exhaust is fine for 416 heads.

ljnowell

I know this has always been the truth, or accepted as the truth. I dont disagree at all with the fact that a flat tappet cam cannot take roller lifters, and a roller cam wont take flat tappets. That is definately true. I did read an article in Chevy high performance where the used solid rollers on a Hyd Roller cam, and Hyd Rollers on a solid roller cam. There were no adverse effects. Where it isnt recommended by the manufacturer, it didnt cause any damage either.

I am not saying that I would do this, I am just saying that it has been done.

five7kid

iTrader: (14)

And it was only for a short time that they were run that way, IIRC.

The effects would probably be the worst with solids on a hydraulic cam, because of the intial shock effect with no lash take-up ramp. Still, the chances of getting positive results - i.e., improvement - are pretty slim.

ljnowell

Actually they showed no difference, just slight variance that is common to dyno testing. I dont know how much of a difference it would make long term, both being rollers, but who can tell without trying it? I know I wont try it anytime soon though.