Wow!! jays heads may not be what you want for a truck on the street, unless you are running a very large cubic inch engine. Yes, he has designed a great head but it leans more to racing. With the flow #s His runners have, I believe i saw 345 cfm from the get go? That's where others end after porting pretty much. 500+ci and 5000 rpm and his heads are now awake and ready for action. anything around 2500rpm (street ish) wont be very responsive. I would love to have his set up but the 482 street with lots of strip time that i'm planning wont be enough for his set up i'm afraid. Would definitely need to run the 8 stack unit on the street as his other intakes would really hurt low end performance.
I certainly don't agree with most of these comments. I will try to explain why.
First, it is important to realize that
flow numbers are not everything! Flow velocity through the port is at least as important, and perhaps more important, because it directly impacts how quickly the cylinder fills after the valve opens, and how long it keeps filling as the valve is closing, while the piston is coming up from bottom dead center on the compression stroke.
On other FE cylinder heads, the only way to get big flow numbers is to increase the size of the port. This increase in cross sectional area of the port reduces port velocity at a given airflow rate, making for a low velocity, sluggish port with a 425-440 cubic inch engine. Especially at lower engine speeds, a low velocity port is going to make for lower torque numbers and a less responsive engine. In that case you need a lot of cubes to increase the airflow and get up to a decent port velocity, so that you get good cylinder filling as the valve is opening and closing, and good low end torque.
My cylinder heads, on the other hand, do not have a significant increase in the port's cross sectional area. The cross sectional area at the port opening in my heads is about 4% larger than a factory medium riser port, and quite a bit smaller than a factory 428CJ port. So, for the same given airflow rate, the velocity through the ports in my heads will be about the same as for a good stock or aftermarket head.
The reason my heads flow so much better than other heads is that the port is raised nearly an inch and a half over the stock medium riser port location. This makes the short turn dramatically better than any head that relies on the stock port configuration. Also, since the ports in my heads are straight in like a tunnel port or a cammer, rather than hooking towards the center of the engine and aiming the flow at the cylinder wall, flow into the cylinder is much improved.
At the higher airflow rates, velocity through the ports in my heads will be much higher than can be achieved with a stock type or aftermarket head. Again this is achievable because of the very generous short term radius, and the straight shot into the cylinder. Without going into all the details, an increase in port velocity without separation of the flow from the port wall is going to result in better cylinder filling and more power.
I think it is probably true that the 4V and 8V intake manifolds would cost some low end torque when compared to something like a dual plane manifold. However, it's possible that the heads may crutch that to an extent, making the combination of my heads and intake as good or better than a stock type head with a dual plane intake. I won't know on that until I do some dyno testing on a smaller engine, like a 390 stroker.
For what it's worth, I do plan to make a version of my heads available with a smaller intake valve, and a slightly reduced port size, so that they can be used on a 4.08" bore. I'll reduce the size of the runners in the intake to match. I'll build a 390 stroker to test these heads, and probably make it a 600-650 HP engine, so that I can compare it with some other aftermarket heads. It will be a while before I can get to that, though
Also for what it's worth, I plan to run the existing heads on all my street cars. I expect that they will perform better than any aftermarket head that is currently available.
Once again, flow numbers are not everything. Drawing conclusions based only on flow numbers will only lead you astray in your quest for performance.
