Quote:
Originally Posted by 1968GTO421
Thanks all. This is really good info to have. Appreciate it 
(Considering the 041 has an overlap of around 83* while the Voodoo 704 has an overlap of 60* , I can see where gearing and convertor would be definite careful considerations) |
This is were cams get confusing. It is so easy to take different tappet ratings then compare overlap attributes. It makes it look really really lopsided. In reality they are much closer than that.
At .006” tappet lift a 041 cam (the version melling sells as a Spc-8) has very close 70.5* of overlap.
At .006” tappet lift a Lunati 704 has very close to 65* of overlap.
Combining the 041s overlap with the opening and closing events makes it a pretty soggy cam in 400. The 455 fairs better. I think a 428 would be ok.
The rocker arms have an impact on this stuff to. If your want to make a 041 idle snarly run it with some 1.8 rockers.
The Crowers 60919s I have had (lately) were kind of in between those 2. If you have a 30 year old 60919 in an engine it might be different. No one changes the specs and keeps the part number the same though(LOL!).
The big difference between those cams is the way the Lunati is ground. It has a slower closing ramp and a faster opening ramp. It will send a little stronger vaccuum signal up to the FI system than if it were ground symmetrically like the 041 or one of the Crowers. Compared to a symmetrical cams (like a 041 ), the 704 will act like it is ground wider than 110, it will rev higher than what you would expect looking at the specs. When the 704 is widened out to a 112 LSA from the off the self 110 LSA it barely lopes in a 455. By my definition of barely anyway.
The seat timing “does not matter” and just look at the .050 numbers is kind of an ugly way to look at a cam profile. That means if a cam like a comp cams XE274 (230* @.050) was ground to have the same LSA and ICL as an 041 cam they would run the same, make the same vacuum, make the same power ect. The pressure differentials are always the highest at those low lifts. They have an impact on how the engine runs and operates. Especially at lower engine speeds.
I don’t have any experience with 421s or 428s. All the engines I have done were either 3.75” or 4.21 and 4.25”. Depending on the head flow and the compression there could be a place were the 041 might out shine other cams that have less seat timing. There are most likely better cams picks than the 041, but if it is for nostalgia it should work fine with most FI setups.
The Holley sniper you can go in and turn the closed loop off on the idle and set everything manually to get the idle you want. Then record those parameters and train the ICU instead of using the self learning features. I think Fast has that option too on some systems. Not sure if that is an option on the FI tech. On a really big cam your better off dialing in the idle that way than using the self learning feature. But that would be more something you would need if the 041 cam was going in a 303 RAV.