Choosing a Cam?
10-30-2005, 03:48 PM
#1
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Choosing a Cam? I want to know how many of yall would agree with this: i believe that with a bolt on stock heads LS1 only benefits so much from a certain size cam. I believe anything over a 240 duration and 600 lift is not really usable in this case. I dont want to start anything with the guys that are running the TREx and cams similar to that size but i just want to know everyones opinion on this or maybe even fact. To me cams that only make power very high in the RPM is not really usable on the street. So my question is where is the medium as far as bolt on, stock head, LS1. Would yall agree that anything over 240 duration and 600 lift is pointless on the street in these circumstances? Well i hope this all makes sense and doesnt start anything with the guys that did choose to run really big cams on the street.
10-30-2005, 06:18 PM
#2
I'd agree with that. Too much duration is going to limit low and midrange TQ. That along with the high LSA to get overlap down so the motor will idle don't help make it a street car cam. Even if you get the ICL down to where it needs to be with the high duration you will start making things worse with ECL for every degree of advance you throw in the cam.....
As for the lift, area is always helpfull, IMHO lift is only limited by valvespring coil bind and life on a street car.
Bret
As for the lift, area is always helpfull, IMHO lift is only limited by valvespring coil bind and life on a street car.
Bret
10-30-2005, 07:27 PM
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I don't think you have to install a bunch of cams in your daily driver to see this either. Just look at, or compare dyno graphs. There not always that accurate of a tool but, trends can be seen.
Brett, do you have any examples of camshafts you have installed in street cars? Mainly LSx motors...
Thanks.
Brett, do you have any examples of camshafts you have installed in street cars? Mainly LSx motors...
Thanks.
10-30-2005, 07:50 PM
#6
Punk,The lift and duration
you speak of will have anyone,unless its spec'd correctly ,
Replacing valves and pistons anyway on a stock shortblock..
It really comes down to the tuning as far as whats streetable and whats not..
you speak of will have anyone,unless its spec'd correctly ,
Replacing valves and pistons anyway on a stock shortblock..
It really comes down to the tuning as far as whats streetable and whats not..
10-30-2005, 08:18 PM
#7
The longer the runner length on the manifold usually will increase the split between intake and exhaust and can take more intake duration as well. The split usually occurs because the intake is more effective with the longer runner intakes and unless there is a increase in exhaust tuning as well you have to crutch the exhaust a little more.
I'm not one of those guys that likes to give out specs. I would say that between 215-235° on the intake would cover most street cams.
Bret
I'm not one of those guys that likes to give out specs. I would say that between 215-235° on the intake would cover most street cams.
Bret
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10-30-2005, 08:58 PM
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Originally Posted by SStrokerAce
The longer the runner length on the manifold usually will increase the split between intake and exhaust and can take more intake duration as well. The split usually occurs because the intake is more effective with the longer runner intakes and unless there is a increase in exhaust tuning as well you have to crutch the exhaust a little more.
I'm not one of those guys that likes to give out specs. I would say that between 215-235° on the intake would cover most street cams.
Bret
I'm not one of those guys that likes to give out specs. I would say that between 215-235° on the intake would cover most street cams.
Bret
How does a long runner EFI manifold respond to advance in the VEs? Possibly, do camshafts suited for street oriented applications respond better to later opening/closing points paired with more overlap?
Example: Which would you more likely use for a street setup, 6500 shift points with a decent flowing,off road exhaust?
1.220/224 112+4
2.220/224 110+0
Let me know if my questions are too intrusive of your knowledge. Thanks Brett.
10-30-2005, 09:23 PM
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Originally Posted by Joe Overton
Are you refering that a reverse split duration is ideal for a ls1 application??? I'm just asking you see...
I'd like to take a simple 220/224 example which is very common and have Brett's opinion on that. What he would prefer to see in the valve events. 110+0 and 112+4 (I think those were the lsa/icl I used)
Yeah I'm a fan of reverse oriented profiles for heavy, street vehicles with our head/intake/exhaust combinations. I don't know if I should feel bad because of that? LOL
Most of the cams being used are the complete opposite of what some of the cam grinders I listen to have stated. So, I'm interested in what works best so I can use that and have the edge.
Not trying to start anything. Just looking for more information like always.
10-30-2005, 09:30 PM
#11
Didnt we do this about 3 months ago in the AFR Reverse Split thread?
The long runner is going to need and like more time. Which means more duration. With that we discussed in that earlier thread about the faux boost from the longer runners helps the end of the intake valve closing cycle. The more runner length the more faux boost, so you want to keep the valve open a bit longer on the end of the intake cycle. So a latter IVC. This also helps because more intake tuning helps cylinder filling and even though you are lowering the DCR, you are most likely compressing more air/fuel and that can lead to more detonation at the same SCR, so the DCR should be lower.
BTW adding duration to the closing side of the intake events raises your ICL and duration.
By later opening and closing points you are reffering to the cam advance/retard? Because all of the events will be later when you retard the cam and earlier if you advance it. Or are you talking about half of the events (EVO and IVC) compared to the events that only effect overlap?
All depends on the idle quality you need and how important that is. How much compression you have.
BTW do you want the same ICL or not? That probably plays a bigger role in the camshaft than the overlap.
Bret
Originally Posted by Sport Side
What does a long runner length do to the placement of your VEs? What's goin' on with the ICL?
How does a long runner EFI manifold respond to advance in the VEs?
How does a long runner EFI manifold respond to advance in the VEs?
BTW adding duration to the closing side of the intake events raises your ICL and duration.
Originally Posted by Sport Side
Possibly, do camshafts suited for street oriented applications respond better to later opening/closing points paired with more overlap?
Originally Posted by Sport Side
Example: Which would you more likely use for a street setup, 6500 shift points with a decent flowing,off road exhaust?
1.220/224 112+4 108 ICL
2.220/224 110+0 110 ICL
1.220/224 112+4 108 ICL
2.220/224 110+0 110 ICL
BTW do you want the same ICL or not? That probably plays a bigger role in the camshaft than the overlap.
Bret
10-30-2005, 09:47 PM
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Joe, please comment if you would like.
Bret, what about your overlap VEs. Any opinions on where they should be set to? Centered around TDC, BTDC, ATDC? This was another of my concerns when dealing with the 220/224 grind.
10:1 Compression, LS1, Fair idle. Any more info needed to help you form an answer?
Thanks Bret.
Bret, what about your overlap VEs. Any opinions on where they should be set to? Centered around TDC, BTDC, ATDC? This was another of my concerns when dealing with the 220/224 grind.
10:1 Compression, LS1, Fair idle. Any more info needed to help you form an answer?
Thanks Bret.
Last edited by Sport Side; 10-30-2005 at 09:52 PM. Reason: There we go
10-30-2005, 10:05 PM
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Didnt we do this about 3 months ago in the AFR Reverse Split thread?
The long runner is going to need and like more time. Which means more duration. With that we discussed in that earlier thread about the faux boost from the longer runners helps the end of the intake valve closing cycle. The more runner length the more faux boost, so you want to keep the valve open a bit longer on the end of the intake cycle. So a latter IVC. This also helps because more intake tuning helps cylinder filling and even though you are lowering the DCR, you are most likely compressing more air/fuel and that can lead to more detonation at the same SCR, so the DCR should be lower.
BTW adding duration to the closing side of the intake events raises your ICL and duration.
By later opening and closing points you are reffering to the cam advance/retard? Because all of the events will be later when you retard the cam and earlier if you advance it. Or are you talking about half of the events (EVO and IVC) compared to the events that only effect overlap?
My question sort of implies that you would already know the LSA. Sorry to have to make you work backwards here.
All depends on the idle quality you need and how important that is. How much compression you have.
BTW do you want the same ICL or not? That probably plays a bigger role in the camshaft than the overlap.
BTW do you want the same ICL or not? That probably plays a bigger role in the camshaft than the overlap.
108LSA, straight up for the 2nd profile.
Thank you.
10-30-2005, 10:14 PM
#16
Originally Posted by Sport Side
Joe, please comment if you would like.
Bret, what about your overlap VEs. Any opinions on where they should be set to? Centered around TDC, BTDC, ATDC? This was another of my concerns when dealing with the 220/224 grind.
10:1 Compression, LS1, Fair idle. Any more info needed to help you form an answer?
Thanks Bret.
Bret, what about your overlap VEs. Any opinions on where they should be set to? Centered around TDC, BTDC, ATDC? This was another of my concerns when dealing with the 220/224 grind.
10:1 Compression, LS1, Fair idle. Any more info needed to help you form an answer?
Thanks Bret.
With the cam Advanced, the overlap area peak will be @ BTDC
With the cam straight up, the overlap area peak will be @ TDC
With the cam retarded, the overlap area peak will be @ ATDC
FWIW in theory I don't like the overlap area occuring before TDC just due to the piston moving up the bore, but then again the intake port velocity is increasing here anyways AND the air is not tied to the piston by a string, it has inertia so +/- 4 degrees doesn't really seem to make a whole hell of a difference there.... the +/- 4° of IVC has a much larger effect. The placement of the ICL has to do more with the IVC than anything else if duration stays the same.
As far as your cam you are talking about
The 4degs of overlap difference vs. the change in ICL whats going to work better in that instance? That's really the choice in the matter there, since it's not apples to apples.
But
#1. you have a very small amount of overlap in either case
#2. you have a relatively small duration
I dont see how increasing overlap or making the intake events happen later would be bad in this situation. It's not goint to make as much TQ in the sensitive 2200-3500rpm range but either way it's not going to change that area much. The drawback to the lower LSA is the drop in idle vacuum of about 1"
That help?
Bret
10-30-2005, 10:21 PM
#18
Originally Posted by Sport Side
Likin' it. That helps a lot.
Originally Posted by Sport Side
BTW adding duration to the closing side of the intake events raises your ICL and duration.
Could you rephrase that for me?
Could you rephrase that for me?
Originally Posted by Sport Side
108LSA, straight up for the 2nd profile.
Bret
10-30-2005, 10:22 PM
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Gotcha. Thanks for the link. I was just about to go dig it back up.
By the way... PunkNPonys. I stole the **** out of this thread. I apoligize.
Lastly, Joe Overton sucks for not posting.
By the way... PunkNPonys. I stole the **** out of this thread. I apoligize.
Lastly, Joe Overton sucks for not posting.