I don't know if I'm an idiot or something, but I don't see a tech article about heads.
If possible could someone point me to a tech article, a website, or give an explanation of what I should be looking for in buying a new set of cylinder heads? Also can someone explain to me why different cylinder heads make better HP than others.. I know squat when it comes to cylinder heads, and would hate to just go out and buy something like lt-1 heads when I could do way way better.
-Justin
If possible could someone point me to a tech article, a website, or give an explanation of what I should be looking for in buying a new set of cylinder heads? Also can someone explain to me why different cylinder heads make better HP than others.. I know squat when it comes to cylinder heads, and would hate to just go out and buy something like lt-1 heads when I could do way way better.
-Justin
Man, someone posted a great link about heads not long ago in one of my posts.
What I would do if you get no luck, search Mark A Shields on this board, and look for head posts by me. It will be in there somewhere.
Some basics, higher compression means more HP on Naturally Aspirated engines at least. You can go up to 10:1 comp on pump gas.
The lower the CC rating of the head the higher the compression it will make on a motor.
Also, heads allow air flow thru the engine, so the better the flow of the heads the more HP you'll get.
What I would do if you get no luck, search Mark A Shields on this board, and look for head posts by me. It will be in there somewhere.
Some basics, higher compression means more HP on Naturally Aspirated engines at least. You can go up to 10:1 comp on pump gas.
The lower the CC rating of the head the higher the compression it will make on a motor.
Also, heads allow air flow thru the engine, so the better the flow of the heads the more HP you'll get.
Here's a good link.
http://www.chevyhiperformance.com/ed...e.jsp?id=41598
http://www.chevyhiperformance.com/ed...e.jsp?id=41598
It's been said more than once that all the power in a small block is in the heads and cam. That is probably as close to true as any such generalized statement can be.
There is no Tech Article on heads that I've seen, because there are no exact formulas to follow. Also, there are a lot of variables. The most important thing to determine is where you want your peak power to occur.
If you are building a low-RPM torque monster for short races, the head design would be vastly different than building a high-RPM horsepower engine, such as for oval track racers. Low-RPM power will require the sacrifice of some flow to maintain maximum flow velocity at low engine RPM to affect the best cylinder charging at low intake resonant frequencies. Of course, to maximize this you would select a longer intake runner length (as in a TPI or CFI) and a cam profile with relatively short durations and little overlap, installed a few degrees advanced to maximize fuel charge capture at low RPMs. The valve size is a little less significant, as long as it matches the combination. The port volumes on this head would be smaller and longer to help maintain the necessary flow velocity. Exhaust tubes would also have to be smaller and longer to provide teh maximum scavenging at the desired RPM.
Building for high-RPM power output will require a lot less velocity at low engine RPMs to allow for the greater flow volume at higher RPMs to support power production at those speeds. You would likely also select an intake with very short runner lengths (like an LT1 or SuperRam) to maintain resonant charging at the higher RPMs. The camshaft for this engine would have longer durations to maximize scavenging and fuel charging at upper RPM ranges, and it would probably be installed a few degrees retarded to help in that effort. Valves in this engine would be as large as possible to allow the maximum flow volume. Additionally, the intake and exhaust port designs should be shorter and larger to support the required flow volume with the least restriction. As you probably have guessed, the exhaust tubes on this engine would be very large and very short, and would be best with megaphones or some sort of expansion chamber to maximize the high-RPM scavenging.
As you can see, having both would be nearly impossible, so for most of us a compromise is what is required. In any case, that selection will tend to lean toward either torque at low RPM or power at higher RPM. You'll have to decide.
There is no Tech Article on heads that I've seen, because there are no exact formulas to follow. Also, there are a lot of variables. The most important thing to determine is where you want your peak power to occur.
If you are building a low-RPM torque monster for short races, the head design would be vastly different than building a high-RPM horsepower engine, such as for oval track racers. Low-RPM power will require the sacrifice of some flow to maintain maximum flow velocity at low engine RPM to affect the best cylinder charging at low intake resonant frequencies. Of course, to maximize this you would select a longer intake runner length (as in a TPI or CFI) and a cam profile with relatively short durations and little overlap, installed a few degrees advanced to maximize fuel charge capture at low RPMs. The valve size is a little less significant, as long as it matches the combination. The port volumes on this head would be smaller and longer to help maintain the necessary flow velocity. Exhaust tubes would also have to be smaller and longer to provide teh maximum scavenging at the desired RPM.
Building for high-RPM power output will require a lot less velocity at low engine RPMs to allow for the greater flow volume at higher RPMs to support power production at those speeds. You would likely also select an intake with very short runner lengths (like an LT1 or SuperRam) to maintain resonant charging at the higher RPMs. The camshaft for this engine would have longer durations to maximize scavenging and fuel charging at upper RPM ranges, and it would probably be installed a few degrees retarded to help in that effort. Valves in this engine would be as large as possible to allow the maximum flow volume. Additionally, the intake and exhaust port designs should be shorter and larger to support the required flow volume with the least restriction. As you probably have guessed, the exhaust tubes on this engine would be very large and very short, and would be best with megaphones or some sort of expansion chamber to maximize the high-RPM scavenging.
As you can see, having both would be nearly impossible, so for most of us a compromise is what is required. In any case, that selection will tend to lean toward either torque at low RPM or power at higher RPM. You'll have to decide.
Thanks a lot both of you.
This definately taught me something new today.
This definately taught me something new today.