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Now lets look at a very similar 2 cam comparison between intake manifolds, but with the larger rectangle port heads. Notice how the larger, higher flow rectangle port heads affect the comparison.
The camshafts used in this comparison are the RaceDay SBE LS3 Cam vs the Top Dog Rectangle port Cam Top Dog Rectangle Port Cam: 232/249 on 111.5+4.5 .650"/.640" RaceDay SBE LS3 Cam: 236/249 112.5+3.5 .650"/.640"
These two cams have the exact same valve events except for one. The RaceDay SBE LS3 Cam has a 4 degree later IVC than the Top Dog Rectangle Port Cam Top Dog Rectangle Cam 9 degree IVO, 43 degree IVC, 60.5 degree EVO, 8.5 degree EVC RaceDay SBE LS3 Cam: 9 degree IVO, 47 degree IVC, 60.5 degree EVO, 8.5 degree EVC
This chart is the LY6 with 823 heads and long runner, plastic LS3 intake.
This chart is the LY6 shortblock with 823 heads and the Holley 300-291 split single plane intake.
Notice how the larger, higher flow head does not benefit as much from the increased duration and later intake valve close (IVC). And even more so the single plane intake does not appreciate the larger duration and/or later intake valve close (IVC).
This is a great illustration of how larger, higher flow heads do not need as much intake duration as a smaller, lessor flow head to tune them the a certain RPM in the same engine. Yet another example of why we create cams for rectangle port vs cathedral port and short runner intake manifolds vs long runner intake manifolds.
On a side note. Look at this badass 600+ hp at 7500 RPM race engine we got out of a junkyard. LOL
That pretty much shows that larger duration cams don't always make more power than a smaller cam(as far as real world driving). That difference is smaller than most would guess. I'd guess the 232 would do better at the drag strip as well.
Last edited by wannafbody; 07-08-2021 at 09:31 AM.
This thread is as good as it gets I agree, but then again I have two homemade n/a rides that see the real world, one with an LQ4 with LS3 pistons stock 706 heads and a 226/230 112+4 and the other is now an unopened cam only lq9 with a 233/243 114+5 because a rainstorm killed my old aluminum 5.7L 😥
Currently I have the TSP Stage 2 truck cam low lift 212/218. It is not so much a specific cam on this thread that makes me want to change but looking at cams makes me want to change haha
If I have to do something different I think I would go a little larger and go high lift. When I went to swap cams originally I had my eyes on that Summit 218/227 low lift or high lift and I almost pulled the trigger but changed my mind. I think a little less power in the low end and some more in the top end would make it a tad more fun. I don't floor it every day but I like to give it the juice every now and then and I just wonder maybe I should have went for something a little bigger. Especially with some extra mods like a different intake, heads etc etc
Some may call me dumb but I do enjoy the hot rodded sound and the looks you get when you have a little more chop. This factors in a tiny bit.
Actually the cam you mention is Summit's "improved" version of the GM Hot Cam, in that it has decent lift. It is actually a decent cam that would lope "just enough" yet keep the low end fairly strong while definitely picking up more on top.
I gotta say, though, that your present cam is very common for good reason; it WORKS! A tough act to follow, but the aforementioned Summit cam will also get the job done.
I don't know who Summit's cam guru is, but he is definitely on top of things.....
Huh I didn't know that was the "improved" GM Hot Cam, interesting I never knew that.
I agree with you though the cam works! No doubt about that and I am not knocking it in any way, shape or form. Hell I recommend this to every 5.3 guy or 6.0 guy that wants some extra power. Just for me though I think I'd like something else. Especially since earlier I didn't have money to get a TC and now I do so that would have changed my opinion haha
Hey Steven this is a joke question but what is the lowest possible LSA and what is the highest? Maybe this should be some sort of common sense thing but I was just thinking about it.
And an example of this like what if I took a 212/218 and put like a 107 LSA on it, 107 being the lowest I have ever seen, Just thinking crazy now. It's almost 5 I'm ready to go home lol
Hey Steven this is a joke question but what is the lowest possible LSA and what is the highest? Maybe this should be some sort of common sense thing but I was just thinking about it.
And an example of this like what if I took a 212/218 and put like a 107 LSA on it, 107 being the lowest I have ever seen, Just thinking crazy now. It's almost 5 I'm ready to go home lol
On LS stuff, I don't really see anyone order anything narrower than 104. On other stuff, I have seen some people order as narrow as 98. Those are highly unusual and they are not for any common application.
Stock eliminator racing comes to mind with terrible intake manifolds and cylinder heads and way too low of compression. I've seen 98-102 LSA on those applications.
On LS stuff, I don't really see anyone order anything narrower than 104. … … Those are highly unusual and they are not for any common application.
Just for fun, one cam you could build with a 104 LSA would be a 208/208 104+0. This would have essentially the same IVC and EVO events as the stock cam in my LM7, but 0 overlap at .050” instead of about -38 degrees. Since the lobes are 208 degrees duration rather than the stock LM7 191-ish, you’d be able to gain some valve lift.
In an otherwise stock LM7, I suspect this might be a nice towing cam. Not sure if the 0 overlap would lead to any noticeable idle. Not sure if this cam would have *any* more top end than the stock cam, even with the added overlap, since IVC and EVO are near stock.
Actual towing cams offered seem to utilize later IVC and earlier EVO and wind up with a bit more duration and wider LSA (110-ish seems common). I suspect that this is because people who buy “towing cams” want to see more power even at 6000 rpm, despite the fact that this has nothing to do with real world towing.
I’d be curious to hear input from CamMotion re: tradeoffs between the cam I suggested here and the towing cams commonly sold.
Stock LM7 is supposedly 190/191 on 114 ... I'll assume 114+0
That gives -37.5 degrees overlap at .050"
IVC 29ABDC, EVO 29.5 BBDC, IVO 19 ATDC, EVC 18.5 BTDC.
If I was **really** going to do a towing cam for my LM7, I'd probably want something like the 208 lobes above, but on a 109 LSA.
That would give -10 degrees overlap, and IVC 33, EVO 33 ... the slightly later IVC would allow 4.8 pistons in my LM7 for a little more compression, and probably better fuel economy. The -10 overlap would probably help the idle and low end compared to the crazy 104 LSA in the cam mentioned above.
Stock LM7 is supposedly 190/191 on 114 ... I'll assume 114+0
That gives -37.5 degrees overlap at .050"
IVC 29ABDC, EVO 29.5 BBDC, IVO 19 ATDC, EVC 18.5 BTDC.
If I was **really** going to do a towing cam for my LM7, I'd probably want something like the 208 lobes above, but on a 109 LSA.
That would give -10 degrees overlap, and IVC 33, EVO 33 ... the slightly later IVC would allow 4.8 pistons in my LM7 for a little more compression, and probably better fuel economy. The -10 overlap would probably help the idle and low end compared to the crazy 104 LSA in the cam mentioned above.
You are a mind reader! LOL I have often thought about taking the LM7 cam, bringing the LSA down to about 104 for a -19.5 overlap and 20 IVC.
I wonder if it would even run half decent.
You are a mind reader! LOL I have often thought about taking the LM7 cam, bringing the LSA down to about 104 for a -19.5 overlap and 20 IVC.
I wonder if it would even run half decent.
If CamMotion replies, they'll tell us why we're both insane. :-)
You are a mind reader! LOL I have often thought about taking the LM7 cam, bringing the LSA down to about 104 for a -19.5 overlap and 20 IVC.
I wonder if it would even run half decent.
With 20 IVC, I'm guessing dynamic compression might get a bit high. I'd bet it would pull stumps, though.
Just for fun, one cam you could build with a 104 LSA would be a 208/208 104+0. This would have essentially the same IVC and EVO events as the stock cam in my LM7, but 0 overlap at .050” instead of about -38 degrees. Since the lobes are 208 degrees duration rather than the stock LM7 191-ish, you’d be able to gain some valve lift.
In an otherwise stock LM7, I suspect this might be a nice towing cam. Not sure if the 0 overlap would lead to any noticeable idle. Not sure if this cam would have *any* more top end than the stock cam, even with the added overlap, since IVC and EVO are near stock.
Actual towing cams offered seem to utilize later IVC and earlier EVO and wind up with a bit more duration and wider LSA (110-ish seems common). I suspect that this is because people who buy “towing cams” want to see more power even at 6000 rpm, despite the fact that this has nothing to do with real world towing.
I’d be curious to hear input from CamMotion re: tradeoffs between the cam I suggested here and the towing cams commonly sold.
Originally Posted by grubinski
Stock LM7 is supposedly 190/191 on 114 ... I'll assume 114+0
That gives -37.5 degrees overlap at .050"
IVC 29ABDC, EVO 29.5 BBDC, IVO 19 ATDC, EVC 18.5 BTDC.
If I was **really** going to do a towing cam for my LM7, I'd probably want something like the 208 lobes above, but on a 109 LSA.
That would give -10 degrees overlap, and IVC 33, EVO 33 ... the slightly later IVC would allow 4.8 pistons in my LM7 for a little more compression, and probably better fuel economy. The -10 overlap would probably help the idle and low end compared to the crazy 104 LSA in the cam mentioned above.
Originally Posted by G Atsma
You are a mind reader! LOL I have often thought about taking the LM7 cam, bringing the LSA down to about 104 for a -19.5 overlap and 20 IVC.
I wonder if it would even run half decent.
Originally Posted by grubinski
If CamMotion replies, they'll tell us why we're both insane. :-)
Originally Posted by grubinski
With 20 IVC, I'm guessing dynamic compression might get a bit high. I'd bet it would pull stumps, though.
Insane? Absolutely not. Trying stuff is fun. If you want it, I will make it. But, because the specs are so unusual, I don't have any cores on the shelf that will make it. So, we would have to make it from scratch. This is not problem, but these "one-off" cams cost $650 and take about 8 weeks to make.
07-07-2021, 11:07 PM
I have never left anything alone for very long.
