When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Depends on heads. If heads flow well up to .600 from .550 then there will be gains. If airflow remains the same or drops them no you wont gain power. On most ls2 heads I seriously doubt there will be gains from 550 to 600
I hear you, the 243 heads are mostly done at 550 lift on both sides. 3 more cfm going to 600 lift.
But like someone said, a lobe that gets to 550 quick could be worse than one that takes it's time getting to 600 or 625. If the time spent at the high flow areas is greater, then it should pick up power. How much? 10-20hp is what I'm told. From what I see the gains are very low at lower rpms. So for me, it's not worth it.
I used to hate that damn sissy ASA cam, but its growing on me......
These smaller cams are making the same, if not more power under the curve.
I hear you, the 243 heads are mostly done at 550 lift on both sides. 3 more cfm going to 600 lift.
But like someone said, a lobe that gets to 550 quick could be worse than one that takes it's time getting to 600 or 625. If the time spent at the high flow areas is greater, then it should pick up power. How much? 10-20hp is what I'm told. From what I see the gains are very low at lower rpms. So for me, it's not worth it.
I used to hate that damn sissy ASA cam, but its growing on me......
These smaller cams are making the same, if not more power under the curve.
if durations are the same between two cams but one has .650 and the other has .550 lift, they will open the valve to max lift at the same time but the .650 lift cam will open it faster. Now ideally you want the valves to open and close as fast as possible but because of physics there are challenges to overcome which make this difficult as you get valve action faster and faster. If your head flows 270 at .500, 275 at .550 and 277 @ .600, just hypothetically, then there will be minimal gains on the dyno and zero gains at the track. Your wasting energy compressing that spring and making the same power as you were at .550 lift. Now would I go out of my way to find a cam that only lifts to .567 and avoid .600 cams? No, it will be just fine. But of you find a cam that works and sits under .600 lift but above .550, I wouldnt pass it up due to its lift. I certainly wouldnt run a cam with, for example .630 lift in this scenario as that would begin to accelerate valve guide wear and reduce spring life while gaining me nothing.
And that also can bring us to another topi . Springs. More aggressive lobes will require higher pressure springs to control valve action. These springs require more energy to compress and will need to be changed more often. If you run a cam with .567 loft you could get away with a quality beehive and titanium retainer. Lightening up that valvetrain is more important than a small gain of lift.
if durations are the same between two cams but one has .650 and the other has .550 lift, they will open the valve to max lift at the same time but the .650 lift cam will open it faster. Now ideally you want the valves to open and close as fast as possible but because of physics there are challenges to overcome which make this difficult as you get valve action faster and faster. If your head flows 270 at .500, 275 at .550 and 277 @ .600, just hypothetically, then there will be minimal gains on the dyno and zero gains at the track. Your wasting energy compressing that spring and making the same power as you were at .550 lift. Now would I go out of my way to find a cam that only lifts to .567 and avoid .600 cams? No, it will be just fine. But of you find a cam that works and sits under .600 lift but above .550, I wouldnt pass it up due to its lift. I certainly wouldnt run a cam with, for example .630 lift in this scenario as that would begin to accelerate valve guide wear and reduce spring life while gaining me nothing.
I understand that, but a 550 lift cam or even 500 could still have very aggressive lobes. I suppose the ones that specify smooth lobes or easy on valve train are safe for decent life.
if durations are the same between two cams but one has .650 and the other has .550 lift, they will open the valve to max lift at the same time but the .650 lift cam will open it faster.
Hey Bspeck82, I respect your opinion and enjoy your posts.
I felt like the following should be pointed out. So with respect I kindly point out the following.
As written the statement in bold is inaccurate and easy to disprove. Two cams can definitely have ramp rates that are drastically different at the same duration and the one with the less lift have the faster nastier ramp rate.
Hey Bspeck82, I respect your opinion and enjoy your posts.
I felt like the following should be pointed out. So with respect I kindly point out the following.
As written the statement in bold is inaccurate and easy to disprove. Two cams can definitely have ramp rates that are drastically different at the same duration and the one with the less lift have the faster nastier ramp rate.
See pages 28 Xtreme Marine High Lift Cam vs page 31 XER Cam.
Example
Look at 236 duration for both Xtreme Marine High Lift & XER cams. The XER has the nastier fast ramp rate and the least lift.
236 xtreme marine high lift Ramp rate is a mellow 56 and it has more lidt than the 236 XER below.
236 XER ramp rate is a very nasty 49
The duration is the same at .050 but the. XER cam with less lift has the nastier ramp rate and is much harder on springs.
My point is one has to be very specific and look at the details to draw conclusions.
True, the XER is more aggressive from from advertised to .050 duration. However, also look at the .200 durations. The Marine has less duration @ .200 and yet more overall lift, which means it's ramps become more aggressive once it gets passed .2". That is going to be harder on springs than the initial opening will. However the X-ER, if it's not extremely asymmetrical, will be harder on the valves due to a much faster closing.
As someone said, one has to be very specific and look at the details to draw conclusions. :-)
That information is hard to find for most cams except comp.
So far comp is the only one that has mid lift vvt cams at 557, most others are 600+.
However the difference between adv dur and 050 dur is 48 for their xfi which seems pretty aggressive for a 220/23x 560 lift cam. They are also like $450 and a wide split exhaust duration for rec port heads. I have an ls2 and there are no factory vvt cathedral port engines. The "ls3" cam would work, but I can get less overlap with a shorter duration exhaust side. A custom cam is around $400.
So it looks like I'm just gonna have to call a cam dude. Not sure who yet. I know there's Pat G, EPS.....Mast is big into vvt....
Cams don't care which heads they open valves for. Check Richard Holdener's video on the subject. Cathedral cams work great on rectangular ports and vice-versa.
Batass the readily available info on the Comp lobes is a nice resource. Definitely would call one of the cam experts. I think you will come closer to getting the best overall result that way.
Originally Posted by 68Formula
True, the XER is more aggressive from from advertised to .050 duration. However, also look at the .200 durations. The Marine has less duration @ .200 and yet more overall lift, which means it's ramps become more aggressive once it gets passed .2". That is going to be harder on springs than the initial opening will. However the X-ER, if it's not extremely asymmetrical, will be harder on the valves due to a much faster closing.
As someone said, one has to be very specific and look at the details to draw conclusions. :-)
True
And the XER is hasher on the valve train than xtreme marine high lift based on what Brian Tooley has shared in the past. Likewise when we had a cam doctor profile of an XER it was pretty symmetrical and a slams the valve close.
It would be nice if there were specs readily available for the close rate of the cam too going down the other side.
Last edited by 99 Black Bird T/A; 05-31-2020 at 07:57 PM.
Cams don't care which heads they open valves for. Check Richard Holdener's video on the subject. Cathedral cams work great on rectangular ports and vice-versa.
I saw it. Rec port cam specs just seem they would be a little less efficient than cath head specs.
I saw it. Rec port cam specs just seem they would be a little less efficient than cath head specs.
You are correct. Although the cam does not care what engine it is in, it was still developed with a specific application in mind. Usually, this is to help make up for short comings and play in favour of the applications strengths.
Single pattern cams should always make more average torque then a dual pattern cam as long as your heads aren't garbage. On average most aftermarket LS cathedral style heads have an exhaust port that flows roughly 70-75% of what the intake flows. This is not terrible, the ls head just flows so very well to begin with, but it still needs a little bit of help to scavenge out those exhaust gasses efficiently. Now these flow benches leave out a very important factor and that is the negative pressure wave from the exhaust header that pulses back into the cylinder and aids the intake charge in filling the cylinder and getting exhaust gasses out. Very little split is needed in an ls cathedral application and Ed Isky
would always make it a point that from his testing single pattern cams always make more torque. And he who makes the most average torque will accelerate the fastest. There is a lot of things to consider when choosing a cam to ensure you get the right one for you.
Oh and yes, the XeR lobe does have less lift and is more aggressive but it also has less duration as lift increases. Those are very aggressive lobes for a hydraulic roller. I was talking about two identical cams with the same lobes but two different lift characteristics. It was hypothetical and not really an actual thing.
Back to heads, the most important thing about making power in a cylinder head is airspeed. You can hog out a set of ls6 heads and have terrific flow numbers but horrible airspeed. You can also have a set that flows meh but has crazy good airspeed. The head with the higher airspeed will respond much better in an engine and make significantly more power. Most aftermarket heads will flow very well and provide great airspeed characteristics but the ports are designed differently to accommodate different applications. A 245cc cathedral head would work great in a big bore 416+ radical strip engine while a 225cc head would work better in a smaller bore 346-408 street engine. Here is a very good tech podcast on Cylinder heads.
I have read that single pattern cams make more torque, like the old tr224 cam was great. Over around 224 duration seems to be where useable low end starts to get traded to up top.
Thanks fellas, this has been a very informative post and I appreciate all your input. I really enjoy it.
Another thing to watch for with high lift cams is potentially side loading the valves with stock style rocker arms. This causes premature valve guide wear.
They recommended the titan 1 for me. 218/222 570 580 lift roughly on a 112. Torquey with a bit of idle lump and very easy on the valve train.
Spread of adv dur to 050 is 55 on both sides. That's less aggressive than most others I've seen. So it must really ramp up after 050 but I was assured it should be 100k miles problem free. Hard to make that guarantee but makes me feel good.
They recommended the titan 1 for me. 218/222 570 580 lift roughly on a 112. Torquey with a bit of idle lump and very easy on the valve train.
Spread of adv dur to 050 is 55 on both sides. That's less aggressive than most others I've seen. So it must really ramp up after 050 but I was assured it should be 100k miles problem free. Hard to make that guarantee but makes me feel good.
That's good to hear. I've got a strong eyeball on that one. I imagine the DCR on the Titan 1 is a bit higher than the Stage 3?
That's good to hear. I've got a strong eyeball on that one. I imagine the DCR on the Titan 1 is a bit higher than the Stage 3?
Titan 1 is -4 overlap, stg 3 is -5. I dont really have all that figured out but that tells me the stg 3 would have a bit more dynamic compression at lower rpm but the titan 1 with more overlap will have more dynamic compression at higher rpm due to scavenging. I could be totally wrong there though.....
05-30-2020, 08:51 PM
