newb cam selection question set one
03-17-2006, 01:08 AM
#1
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newb cam selection question set one I love my LS1. I want to build another to put in my car, to have it ready when I wear the first one out.
Looking at the valve train I got what I think are some basic general questions.
1. How much can I change cam specs and still have the 'same' car?
An engine dyno should pick up tiny changes, the 1/4 slip will pick up pretty small ones. I am more of a driver than a garage type, but I am kind of a gear head. If company A, for instance wants to sell me a 224/224 cam and company B wants to sell me a 226/226, if everything else is the same I am not going to notice those 2 degrees, right? The cam guide sticky sort of suggests +/- 3 degrees is pretty much the same cam.
2. What about actual valve lift?
How much can I change that before I can feel it? A 0.550 lift cam on a 1.6 RR ought to give me 0.88" valve lift off the seat. The same .550 lift on a 1.7 RR ought to give me 0.935" of valve lift. Could I feel that? Could you? Would 'we' need the FAST intake to use it?
FWIW my intended application is going to be a street/interstate 5.7 Al block stroked to 381/383 cid. AFR 205s are in the budget. I would think the guys (and gals) building 408s and 427s for street/strip have similar questions.
TIA,
Scott
Looking at the valve train I got what I think are some basic general questions.
1. How much can I change cam specs and still have the 'same' car?
An engine dyno should pick up tiny changes, the 1/4 slip will pick up pretty small ones. I am more of a driver than a garage type, but I am kind of a gear head. If company A, for instance wants to sell me a 224/224 cam and company B wants to sell me a 226/226, if everything else is the same I am not going to notice those 2 degrees, right? The cam guide sticky sort of suggests +/- 3 degrees is pretty much the same cam.
2. What about actual valve lift?
How much can I change that before I can feel it? A 0.550 lift cam on a 1.6 RR ought to give me 0.88" valve lift off the seat. The same .550 lift on a 1.7 RR ought to give me 0.935" of valve lift. Could I feel that? Could you? Would 'we' need the FAST intake to use it?
FWIW my intended application is going to be a street/interstate 5.7 Al block stroked to 381/383 cid. AFR 205s are in the budget. I would think the guys (and gals) building 408s and 427s for street/strip have similar questions.
TIA,
Scott
03-17-2006, 08:07 AM
#2
1) The best way to look at it is to have significant effect on power, a change of 4* in overlap or more is needed. That can come by changing duration or by changing the LSA. How much you "feel" it is in the design you use which also factors in the amount of advance/retard used. With the same LSA and equalize advance, a 224/224 and 226/226 will not drive very differently.
2) There is no reason to change the rocker ratio. the higher lift cams have faster ramps. For a given duration, they will have less overlap at .006 (better idle) and more duration at .200 and above (better power). For a 346" motor, lift does not influence the use of the FAST intake; intended rpm range does. The FAST seems to be an improvement over the LS6 intake at higher rpms. There may be a benefit of a FAST in the midrange on a stroker motor, but it is something I have not looked into.
Make an honest assessment of how you will drive the car. Pick your cam, intake, heads, gears, and headers to match.
2) There is no reason to change the rocker ratio. the higher lift cams have faster ramps. For a given duration, they will have less overlap at .006 (better idle) and more duration at .200 and above (better power). For a 346" motor, lift does not influence the use of the FAST intake; intended rpm range does. The FAST seems to be an improvement over the LS6 intake at higher rpms. There may be a benefit of a FAST in the midrange on a stroker motor, but it is something I have not looked into.
Make an honest assessment of how you will drive the car. Pick your cam, intake, heads, gears, and headers to match.
03-17-2006, 11:25 AM
#3
Assuming you take the plunge on the 205 AFR's, why not use the cam we spent a lot of time perfecting for a "have your cake and eat it to" scenario (Our 224/228 cam of course....AFR PN 6016). It seems it's attributes covers most of what your looking for (perfect drivability with big power potential...especially with the right complimenting components, FAST 90, etc.)
Plenty of strong running AFR cars out there with our 6016 cam....you should give that cam strong consideration....I think its exactly what the doctor ordered IMO....
Tony
Plenty of strong running AFR cars out there with our 6016 cam....you should give that cam strong consideration....I think its exactly what the doctor ordered IMO....
Tony