Reply With Quotethings tend to break... :crossx:
what happens when you have a cam with to much intake or exhaust lift
things tend to break... :crossx:
Not much once you go past the head's (and the valve sizes) ability to flow the air .
For example, the BB Chevy 236 peanut (small oval) port head data I have:
(2.06" intake valves)
.400" lift, 215cfm
.500" lift, 233cfm
.600" lift, 235cfm
.700" lift, 235cfm
Exhaust was similar, 130/144/150/155
The 049 large oval port maxes out @ .600", same valves
232/250/264/264/265 (.400 to .800)
Anything higher is just wasted lift/spring pressure/valve-train stress & wear for the most part.
I'm sure the max point can be moved a bit with reduced stem dia valves like Manley Pro-flows if it fits an engine build..
what happens when you have a cam with to much intake or exhaust lift
depends on what you mean by "too much". as smokin said, heads need to be good. to me, "too much" is more than the heads can handle. upgrade the heads, then you need more spring pressure. more spring pressure wears out more quickly. if the rocker setup isn't stable (solid), lash will fluctuate, plus you can break rocker studs; gotta check 'em more frequently. if you get up much beyond .740-.750 with a full roller setup, it can be set up to last a long time, but you have to check things a lot more frequently and replace stuff BEFORE it gets to the edge.
TO MUCH CAM??? NEVER TO MUCH :crossx: :crossx: JUST MAKE CHANGES TO MAKE IT ALL WORK :rollside: :rollside: AND MAKE MORE POWER
jet,
there is really not enough information in your question to give a specific answer.
In general terms though ... when you increase lift you also increase duration this is true more so with flat tappets than rollers and is necessary because of the ramps required to reliably work with a flat tappet.
It is the increased duration that will likely cause issues (assuming proper clearances) ... as duration rises, drivability problems can result especially if the engine does not have very much compression. The drivability problems usually show up as poor "low rpm" throttle response and just overall poor low rpm performance.
Although this is running down a rabbit trail ... I generally disagree with the information above about using static pressure flow bench data to determine that ~.500in lift is enough in the posted example.
When talking about flow through a poppet valve there are two different areas to be concerned with depending on how much the valve is lifted off of the seat. The first being the "curtain area" which is the circumference of the valve multiplied by the valve distance from the seat. As the cam continues to lift the valve, the limiting area will change from the curtain area to the throat area of the port.
In the example posted above the engine will almost always increase in power by using a larger lift cam (obviously there are limits to how much larger). The primary reason for this is that larger lift cam allows a the valve to stay open longer at points where the port can flow its' max.
Again, your question needs more details for a specific answer.
Corey
In real world terms your boat will be a pig!!!
If your heads start to make power at 2,300 rpm and you have a cam that doesnt' start to work until 4,000, and at the same time your pump only allows 5,000 rpm, you will have NOTING that is working together. A friend of mine had that problem last year, alot of cam, stock junk heads, no intake to speak of and a stock pump. Boat would hardly run 73 mph. Changed to a good set of square ports and installed a good tunnel ram and now runs 82+ mph (hasn't touched the stock pump yet but that's next). He changed his combo to work with his cam.
Big cams sound great, but unless you have the goods on top, your not going anywhere in a real hurry.
Most important your engine needs to breath horsepower needs to breath
Cam size simply depends on application. What are you going to use the boat for? What size is the boat, which impeller(AA,A,B,etc), what rpm's do you want to run. What engine Shitty, Ford, Mopar. Due to head config, cam spec between engines will be different and what type of induction, compression ignition, exhaust, or NOS etc,etc
Im currious TopCat, what would be shitty ??
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