c6 batmobile

Just doing a little research trying to improve my knowledge. How much of an effect on HP does cam lift have. Lets say I have a cam with a 230 xer lobe which has about .588 lift I think and I change it to a 230 xfi lobe which has about .612 lift (not sure if those number are accurate) what would the gain in HP be if any?

carlrx7

20ft tq

c6 batmobile

Any increase in HP too or just TQ?

SpinMonster

The question doesnt reduce down to a set amount of power. The use of a a faster ramp rate depends on how the additional airflow will react to your specific head's runner and flow characteristics at various valve lifts and not just peak lift. An XFI has more lift at each valve lift measurement off the seat and thus will depend on how your head flows at each of those lifts. The initial ramp rate can be more aggressive at say 49 than a lobe with greater lift and a softer ramp rate. Sometimes its better to let more air in at a given lift and reduce duration than to keep it open longer with less lift. To sum up, cars make more power when you get more a/f in so the use of aggressive lobes makes more power and more lift tends to be free power. HP & TQ are related to each other so both go up.

That said, I have seen a 228/232 make 424rwhp and 390rwtq while a 230 XFI on the same set-up then made 436/404. Its as close as I can say for a given car that did the swap.

The LS3 heads like the XFI lobe due to the way the head performs at each valve lift position and I have mixed views on the LSL lobe on that head while others think its the greatest. XFI's are a softer ramp rate than the XER sothey are easier on the valve/seats.

c6 batmobile

Ok good to know. Is there a way to tell where each lobe is at during the lift? Basically how would I tell if an XFI lobe is better than and XER for a Trick Flow head or a 243 head?

SpinMonster

You would need to have the values for both heads and lobes at each lift:

.100
.200
.300
ect.....

I can give you the shortie on it now. XFI lobes make more power on every head except the exhaust side of the LS3 head. On the LS3, you need to use much shorter duration on the exhaust side to make more power from the XFI. I found single pattern cams with the LS3's work with XFI's on both sides. I tried a 230XFI/236XFI and it made less power than a 230XFI/230XFI and a 230XFI/234XER.

I guess it an observation from using a few cams. I didnt look at lift values and then pick lift values for cams.

c6 batmobile

Does the XFI make less power on LS3 exhuast end because of the square ports or the size of the runner or an entirely different reason all together?

SpinMonster

It makes less power because if the exhaust stalls it will take the path of least resistence out the intake runner. This is why overlap is a killer with these heads. You want one path without stalling the air out the exhaust side.

As I said, you can use the XFI on the exhaust side if you decrease exhaust duration.

c6 batmobile

Ok I understand how it works a little better now. There is a lot of knowledge to be gained and when you understand how things work its makes the choices you make a lot easier. Thanks for the explanation.

SpinMonster

I suggest you do a search on these topics online to get other input. While I'm volunteering info, my understanding isnt the best thats out there. I volunteer something to get it going. Often others like to jump in to correct posts rather than be the first to answer a question. I tried to get it going for you.

c6 batmobile

Well not to inflate your ego but a lot of the information I get from you is pretty solid. I dont have a problem listening to your advice.

theofel

Ditto!!!!