Need a cam recomendation for a 12:1 motor
05-25-2005, 01:56 AM
#22
Doug,
Those flow numbers aren't bad... the exhaust side should do pretty well with a header or pipe on it.... I would probably back the exhaust duration off from normal because of that. If it was NA it would most likely see a single pattern or reverse split.... It would be better to cram a bigger intake valve on the seat and gain more intake flow and have everything optimized with a single pattern. We don't have to worry about that because of the jug so lets move on.
Your 200 shot is not massive but it should make up for the 3.42's and 3700lbs at launch when you are on the jug so you could go a little bigger with the cam.
Normally I don't post specs but for the sake of discussion here is an example....
If I was doing it I would be in the 234/238 .600 lift area on a 112 LSA with a 110 ICL, it would still run on a 110LSA straight up as well, but that will get you some more overlap. 12 degs of overlap @ .050" is still happy on a street car so it should still drive nicely, but more LSA and the motor will be down on power so 112 it is.
If you have 12:1, then that should start to get the dynamic compression down into the 8.6-8.7 range, which is boarderline if you don't pay attention to it but you would probably pull timing out of the motor on the bottom end below stall anyways just to be safe... having too little cam duration here will cause you to pull out even more timing and the TQ levels will be the same anyways. This is really a comprimise here, you can't have too much duration for street driving and you also can't have too little or you will not have enough overlap & lobe area and too much DCR.
The CamMotions cam will have a even higher DCR at 8.8-8.9 unless they have really tame ramps, which would get it closer to 8.75 DCR, still a lot. The overlap at .050 is 9 degs which should be tame but there is power left on the table with the EVO point being where it is there. I think there is some more power left on the table between 5500-7000rpm on the jug in this instance because of the EVO and overlap of the cam.
The 226/232 115 LSA cam (if you could make it) Would also be a bit thin in the 5500-7000rpm range, but it would have TONS of vacuum with the -1 overlap at .050". From what I have seen I just don't see enough overlap for this cam to do really well in the higher part of the RPM range here. The motor still has to suck the air/fuel/N2O into the cylinder so some scavenging would work out really well here. I don't know how crazy of lobes you would use here Preditor, but a tame lobe would be giving you a 8.5 DCR and maybe .1 more if the lobes where more aggressive. That's a bit iffy with the cylinder filling in the lower RPM and this duration so you will take a little MORE timing out of it to reduce detonation. The reason why I said the duration was a bit small for this setup because it will probably never see 3500rpm or even 3800rpm at WOT on the bottle. Making that additional TQ below the stall is not going to help it out much and the car can sacrafice some vacuum since it's 12:1 and you are probably have about 2-3" more than you need, and the car would still be very liveable. Too much vacuum is a good thing if it's a Old Man Cam, but they will always leave HP on the table if that happens. NOTE: static compression and dynamic compression will add vacuum so you can have more overlap in a motor like this.
If you weren't daily driving this thing I would probably go a bit higher with the duration here. You could see some nice gains with more duration but the overlap might become too much for day to day life on the street, all depends on what you consider tame and how good your tuning is. Also I would look at a larger diameter header too, especially if you plan to twist the motor to 7200rpm or more. The gains from 6000 and up would be worth it. With the bigger cam and larger headers....you would see gains from 5000 and up and close to 30hp in the 7000rpm range. That could be as much as 1-2mph in the 1/4. Only problem with more RPM is you would have to start paying attention to valve mass and adding lots of spring pressure if you wanted to go higher than 7200rpm to still have good power with good valve control.
Thats my toughts...
Bret
Those flow numbers aren't bad... the exhaust side should do pretty well with a header or pipe on it.... I would probably back the exhaust duration off from normal because of that. If it was NA it would most likely see a single pattern or reverse split.... It would be better to cram a bigger intake valve on the seat and gain more intake flow and have everything optimized with a single pattern. We don't have to worry about that because of the jug so lets move on.
Your 200 shot is not massive but it should make up for the 3.42's and 3700lbs at launch when you are on the jug so you could go a little bigger with the cam.
Normally I don't post specs but for the sake of discussion here is an example....
If I was doing it I would be in the 234/238 .600 lift area on a 112 LSA with a 110 ICL, it would still run on a 110LSA straight up as well, but that will get you some more overlap. 12 degs of overlap @ .050" is still happy on a street car so it should still drive nicely, but more LSA and the motor will be down on power so 112 it is.
If you have 12:1, then that should start to get the dynamic compression down into the 8.6-8.7 range, which is boarderline if you don't pay attention to it but you would probably pull timing out of the motor on the bottom end below stall anyways just to be safe... having too little cam duration here will cause you to pull out even more timing and the TQ levels will be the same anyways. This is really a comprimise here, you can't have too much duration for street driving and you also can't have too little or you will not have enough overlap & lobe area and too much DCR.
The CamMotions cam will have a even higher DCR at 8.8-8.9 unless they have really tame ramps, which would get it closer to 8.75 DCR, still a lot. The overlap at .050 is 9 degs which should be tame but there is power left on the table with the EVO point being where it is there. I think there is some more power left on the table between 5500-7000rpm on the jug in this instance because of the EVO and overlap of the cam.
The 226/232 115 LSA cam (if you could make it) Would also be a bit thin in the 5500-7000rpm range, but it would have TONS of vacuum with the -1 overlap at .050". From what I have seen I just don't see enough overlap for this cam to do really well in the higher part of the RPM range here. The motor still has to suck the air/fuel/N2O into the cylinder so some scavenging would work out really well here. I don't know how crazy of lobes you would use here Preditor, but a tame lobe would be giving you a 8.5 DCR and maybe .1 more if the lobes where more aggressive. That's a bit iffy with the cylinder filling in the lower RPM and this duration so you will take a little MORE timing out of it to reduce detonation. The reason why I said the duration was a bit small for this setup because it will probably never see 3500rpm or even 3800rpm at WOT on the bottle. Making that additional TQ below the stall is not going to help it out much and the car can sacrafice some vacuum since it's 12:1 and you are probably have about 2-3" more than you need, and the car would still be very liveable. Too much vacuum is a good thing if it's a Old Man Cam, but they will always leave HP on the table if that happens. NOTE: static compression and dynamic compression will add vacuum so you can have more overlap in a motor like this.
If you weren't daily driving this thing I would probably go a bit higher with the duration here. You could see some nice gains with more duration but the overlap might become too much for day to day life on the street, all depends on what you consider tame and how good your tuning is. Also I would look at a larger diameter header too, especially if you plan to twist the motor to 7200rpm or more. The gains from 6000 and up would be worth it. With the bigger cam and larger headers....you would see gains from 5000 and up and close to 30hp in the 7000rpm range. That could be as much as 1-2mph in the 1/4. Only problem with more RPM is you would have to start paying attention to valve mass and adding lots of spring pressure if you wanted to go higher than 7200rpm to still have good power with good valve control.
Thats my toughts...
Bret
Last edited by SStrokerAce; 05-25-2005 at 02:02 AM.
05-25-2005, 06:22 AM
#23
TECH Senior Member
but more LSA and the motor will be down on power so 112 it is.
I've even run reverse splits (2 degree duration dif.) on a tight 110 with up to 200 shots with excellent results, but while my 1/8th benefited a lot, my 1/4 was not as good as when I eventually started using higher lsa cams.
I guess it has a lot to do with the total car combo too.
05-25-2005, 06:25 AM
#24
TECH Senior Member
Bottom line take your head specs & flowchart to whoever is going to design you a cam and give him specifics about what you need and ideally, maximise the cam for these heads
05-25-2005, 06:36 AM
#25
FormerVendor
I probably wouldn't run that much compression on the street. I don't care what the DCR is unless your motor is a hooptie the idea is to trap as much air and gas as possible. If you are efficiently doing this then 12 to 1 will probably cause you some problems down the road with detonation. We run around 11-11.25 to 1 and even then with really good heads and cams I am a little scared! I do work on a lot of the 12+ to 1 deals on this site and many are pretty beat up and don't make the power they should when the tune is backed off since they have too much compression. Not trying to ruffle everyones feathers but I would back off the compression somewhat if you are really wanting to run everyday on pump gas since unless you are really putting a GIANT cam in for the street the idea is to actually INCREASE VE not decrease it. Just a thought!
05-25-2005, 07:45 AM
#26
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Originally Posted by racer7088
I probably wouldn't run that much compression on the street.
He should put a good set of heads, a moderate cam and build something around 11:1 or lower.
05-25-2005, 12:07 PM
#27
I agree on the compression... I would rather have about 1/2 a point less here, but that's not the case. You can back the timing off in the lower part of RPM band and get rid of most of your problems, the higher part of the curve is less likely to have detonation problems, so you could be safe.... Either way more cam or less compression would make it safer.
bickelfirebird , with the air up there, you should be fine. The denser the air the more problems you will have with detonation.
PREDATOR-Z, Most of that seems to fly right past you if all you do is pick on my LSA choice.... I guess you just haven't seen what gains you can get from overlap in a cam yet. LSA is a byproduct of valve events, a proper cam is not designed with a set LSA.... you gotta understand that before you get how it works. More duration will bring with it more overlap on the same LSA cam, but also less DCR because of the later IVC. That's why you also drop the LSA with the higher duration to get the IVC back to the proper spot and you also get more overlap. You seem to think its a bad thing, which it's not. Don't even go to the "well I can advance the cam and get the IVC back with the high LSA" because that just screws your exhaust over to get that. That's why I limit the LSA on a cam... "Higher lsa will stretch that powerband a little further" No a higer LSA will move the IVC later so that will make the powerband higher, the problem is it will also have a narrower powerband as well and not do as well as the proper cam would in the top end while they would be equal at stall and thru the midrange. Good luck, there are lots of things to learn about cams and you want to argue about LSA with me, keep reading.
Bret
bickelfirebird , with the air up there, you should be fine. The denser the air the more problems you will have with detonation.
PREDATOR-Z, Most of that seems to fly right past you if all you do is pick on my LSA choice.... I guess you just haven't seen what gains you can get from overlap in a cam yet. LSA is a byproduct of valve events, a proper cam is not designed with a set LSA.... you gotta understand that before you get how it works. More duration will bring with it more overlap on the same LSA cam, but also less DCR because of the later IVC. That's why you also drop the LSA with the higher duration to get the IVC back to the proper spot and you also get more overlap. You seem to think its a bad thing, which it's not. Don't even go to the "well I can advance the cam and get the IVC back with the high LSA" because that just screws your exhaust over to get that. That's why I limit the LSA on a cam... "Higher lsa will stretch that powerband a little further" No a higer LSA will move the IVC later so that will make the powerband higher, the problem is it will also have a narrower powerband as well and not do as well as the proper cam would in the top end while they would be equal at stall and thru the midrange. Good luck, there are lots of things to learn about cams and you want to argue about LSA with me, keep reading.
Bret
05-25-2005, 02:12 PM
#28
TECH Senior Member
Originally Posted by SStrokerAce
PREDATOR-Z, Most of that seems to fly right past you if all you do is pick on my LSA choice.... I guess you just haven't seen what gains you can get from overlap in a cam yet. LSA is a byproduct of valve events, a proper cam is not designed with a set LSA.... you gotta understand that before you get how it works. More duration will bring with it more overlap on the same LSA cam, but also less DCR because of the later IVC. That's why you also drop the LSA with the higher duration to get the IVC back to the proper spot and you also get more overlap. You seem to think its a bad thing, which it's not. Don't even go to the "well I can advance the cam and get the IVC back with the high LSA" because that just screws your exhaust over to get that. That's why I limit the LSA on a cam... "Higher lsa will stretch that powerband a little further" No a higer LSA will move the IVC later so that will make the powerband higher, the problem is it will also have a narrower powerband as well and not do as well as the proper cam would in the top end while they would be equal at stall and thru the midrange. Good luck, there are lots of things to learn about cams and you want to argue about LSA with me, keep reading.
Bret
Otherwise, there will only be one way to design cams and all the suppliers would have no "proprietary grinds", different theories, research and applications.
05-25-2005, 02:27 PM
#29
Z, I work on tons of street/strip motors all day long.
Some of us belive in my way or the wrong way... I'm just one of them sorry.
I would just keep learning more man, that's all. Cam design has a lot of details to it more than some duration numbers and a LSA. Just keep reading and learning and TRYING new things and you will get there.
Bret
Some of us belive in my way or the wrong way... I'm just one of them sorry.
I would just keep learning more man, that's all. Cam design has a lot of details to it more than some duration numbers and a LSA. Just keep reading and learning and TRYING new things and you will get there.
Bret
05-25-2005, 03:48 PM
#30
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Originally Posted by SStrokerAce
Z, I work on tons of street/strip motors all day long.
Some of us belive in my way or the wrong way... I'm just one of them sorry.
I would just keep learning more man, that's all. Cam design has a lot of details to it more than some duration numbers and a LSA. Just keep reading and learning and TRYING new things and you will get there.
Bret
Some of us belive in my way or the wrong way... I'm just one of them sorry.
I would just keep learning more man, that's all. Cam design has a lot of details to it more than some duration numbers and a LSA. Just keep reading and learning and TRYING new things and you will get there.
Bret
"In a perpetual mode of thirst for knowledge" 
