Thread:

Three pattern bbc cams

Custom cams of this nature are not cheap as the grinder has 2 set ups. On the plus side on OEM heads and engines needed every ounce of power they are killer.

Originally Posted by flat screwd

Wouldnt a cam profile for every cylinder respective to its own unique flow data yeild a engine thats unpredictible ? In essence confuse the engine ?

Before symmetrical ports and cnc porting this was done. NHRA pro stock engines had 16 different lobes back in the early 80's

Originally Posted by flat screwd

Wouldnt a cam profile for every cylinder respective to its own unique flow data yeild a engine thats unpredictible ? In essence confuse the engine ?

The idea is to equalize/balance all your cylinders which frees up power buy making smother power instead of having 4 that are stronger than the others


If each cylinder is not feed the same its allready confused

Originally Posted by flat screwd

Wouldnt a cam profile for every cylinder respective to its own unique flow data yeild a engine thats unpredictible ? In essence confuse the engine ?

You're looking at this from the wrong angle. Imagine an engine that was made up of 8 individual engines, all with different port flows but all with the same cam profile.
Ideally you want all the ports to flow the same, and the same cam profile for all the cylinders. But with the OEM BBC heads, that not the case. Even with the newest CNC heads, their is a good port and a bad port. The main reason behind the symetrical port heads.

In a couple of PM's with bowtiebro, I was pointing out that in the BIG BOY ranks, they have the port flow equalizing down pretty good now, and have moved on to controlled, seperate equalized water flow over the combustion chambers, and the oil pans are compartmentized into paired left-right cylinders with the oil pan acting like 4 oil pans and the windage down to 2 cylinders per compartment.

The closer they can get the engine to behave like 8 individual, tunable cylinders, the more power they make.

Originally Posted by gn7

You're looking at this from the wrong angle. Imagine an engine that was made up of 8 individual engines, all with different port flows but all with the same cam profile.
Ideally you want all the ports to flow the same, and the same cam profile for all the cylinders. But with the OEM BBC heads, that not the case. Even with the newest CNC heads, their is a good port and a bad port. The main reason behind the symetrical port heads.

In a couple of PM's with bowtiebro, I was pointing out that in the BIG BOY ranks, they have the port flow equalizing down pretty good now, and have moved on to controlled, seperate equalized water flow over the combustion chambers, and the oil pans are compartmentized into paired left-right cylinders with the oil pan acting like 4 oil pans and the windage down to 2 cylinders per compartment.

The closer they can get the engine to behave like 8 individual, tunable cylinders, the more power they make.

Just to add:
The output of an engine is the sum of all the cylinders working together. One cylinder making less power than the rest is not "holding the engine back". They all contribute. Obviously, getting them to all make the same power as the best cylinder is ideal, but that seldom happens. The conventional headed BB Chevy is a perfect example with it's asymmetrical port layout. The left turn ports are inferior to the rigtht turn ports. Even the spread port heads are similar, but not quite as bad. If the difference between the two ports isn't that bad, (as with most aftermarket heads) you usually find an average between the good and bad, and cam accordingly. The lobe won't be "perfect" for either port. -or- depending on how close the ports are, you can maximize either port and let the other fall where it may. A lot of times the cam designer only has "good port" info to work with. However, on OEM heads, the difference between the good port and bad port can be as much as 30cfm in some ranges of valve lift...usually the worst at .500" which can be a very critical lift on some engines. I'll do the very best I can with both ports, not trying to balance them, just trying to get the most I can out of either port. In the end it is what it is and if it's bad enough, as this thread is about, we can put more lobe on the bad port to help make it "work" like the better port. The lobe for the good port is dictated by the parameters of the build.

Agreed, any power from any cylinder is power added, as opposed to a dead hole. Ideally they would all make the same power, but not at the expense of dragging good cylinders down to the level of bad ones. That would be a "socialitic" approach.

Its one of the reasons for the thinking behind individual timing as well. Don't time the engine to the limits of the detonation prone cylinders, time each one to its maximum output.