Re: Input needed on daily driver sbc truck build
Posted: Wed Oct 10, 2018 8:50 pm
I like the eq vortec idea but, i already have a street dominator 2 300-36 and i would really like the 10.0 -10.5 to 1 compression of the aluminum
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That cam will be 4 degree too wide if you are going to run 2.02/1.6 valve combo on a 400 inch build. It will cost at least 30 LBS FT and a like amount of HPhouser45 wrote: ↑Tue Oct 09, 2018 6:23 am I dont do a lot of street engines usually circle track engines so i am asking for advice on my shop truck build. Chevy 85’ square body 4x4. Nv 4500 3.73 gears 33” or 35” tires. 400 sbc. Cast crankshaft, prepped stock 5.7 rods, speed pro hyperutectic dished or flat top pistons. Depending on what chamber size. Compression ratio will be 10 to 1. Comp 268xe on 1.5/1.5 rockers. Budget Aluminum Assault sbc 200cc heads. 2.02/1.60. Possible Promaxx or Profiler 195’s? Just not wanting to break the bank on this one. Too much camshaft? Assault heads?
So would a better choice to drop down to the 262xe and have lsa narrowed to 107/108?David Vizard wrote: ↑Sun Oct 14, 2018 9:41 pmThat cam will be 4 degree too wide if you are going to run 2.02/1.6 valve combo on a 400 inch build. It will cost at least 30 LBS FT and a like amount of HPhouser45 wrote: ↑Tue Oct 09, 2018 6:23 am I dont do a lot of street engines usually circle track engines so i am asking for advice on my shop truck build. Chevy 85’ square body 4x4. Nv 4500 3.73 gears 33” or 35” tires. 400 sbc. Cast crankshaft, prepped stock 5.7 rods, speed pro hyperutectic dished or flat top pistons. Depending on what chamber size. Compression ratio will be 10 to 1. Comp 268xe on 1.5/1.5 rockers. Budget Aluminum Assault sbc 200cc heads. 2.02/1.60. Possible Promaxx or Profiler 195’s? Just not wanting to break the bank on this one. Too much camshaft? Assault heads?
DV
The cam LCA is not a factor that dictates the street-ability of the cam. If you have been told that a wide LCA is needed for the street and a narrower one for competition then you have been told wrong. The key factor is the overlap involved. For any given head, displacement and C R there is only one optimal LCA. It does not vary.
I believe that is true but...The cam LCA is not a factor that dictates the street-ability of the cam. If you have been told that a wide LCA is needed for the street and a narrower one for competition then you have been told wrong. The key factor is the overlap involved. For any given head, displacement and C R there is only one optimal LCA. It does not vary.
What happens to driveability in regard the subject criteria ( daily driver ) Idle characteristics, fuel mileage, type of fuel required, torque converter specs etc..If I were to run your engine spec through my highly accurate TorqueMaster cam selection program it would show a required LCA of 104 - 105. As such that 268 profile on both the intake and exhaust would make a dynamite selection for your 400
If you have to consider a wider LCA to get the idle vacuum sought then all you have done is chosen a cam with too much duration. Spreading the LCA my improve the idle but it costs torque and hp everywhere in the rpm range.gottago wrote: ↑Mon Oct 15, 2018 12:48 pmI believe that is true but...The cam LCA is not a factor that dictates the street-ability of the cam. If you have been told that a wide LCA is needed for the street and a narrower one for competition then you have been told wrong. The key factor is the overlap involved. For any given head, displacement and C R there is only one optimal LCA. It does not vary.What happens to driveability in regard the subject criteria ( daily driver ) Idle characteristics, fuel mileage, type of fuel required, torque converter specs etc..If I were to run your engine spec through my highly accurate TorqueMaster cam selection program it would show a required LCA of 104 - 105. As such that 268 profile on both the intake and exhaust would make a dynamite selection for your 400
If you try to maintain same idle characteristics as the xe 268 but on a 104-106 lsa you have to shorten durations but will that not shorten the powerband also? Soon you are driving a tractor..
thanks DV.. I like hearing that said although I've not been that successful in achieving the intended results. When I've locked in a duration that gave a nice smooth idle on a tighter lca I seem to shorten my rpm range. If I pick a duration that restores the upper rpm band, the idle goes away on me. Solution for me was to compromise and spread it out a bit on the lca. (daily driver builds) Perhaps the definition of daily driver is a bit different for everyone too.If you have to consider a wider LCA to get the idle vacuum sought then all you have done is chosen a cam with too much duration. Spreading the LCA my improve the idle but it costs torque and hp everywhere in the rpm range.
Selecting the optimal LCA first and then the overlap to give the desired idle qualities locks in the duration. Result - the BEST cam for the job.
My question is, how much rpm do you really need for a daily driver? I have never found a need for much more than 5500 rpm on my street cars. That's good for 100 mph in second gear in my Impala. The performance under 3000 rpm is really important, that is where the engine lives.gottago wrote: ↑Mon Oct 15, 2018 4:00 pmthanks DV.. I like hearing that said although I've not been that successful in achieving the intended results. When I've locked in a duration that gave a nice smooth idle on a tighter lca I seem to shorten my rpm range. If I pick a duration that restores the upper rpm band, the idle goes away on me. Solution for me was to compromise and spread it out a bit on the lca. (daily driver builds) Perhaps the definition of daily driver is a bit different for everyone too.If you have to consider a wider LCA to get the idle vacuum sought then all you have done is chosen a cam with too much duration. Spreading the LCA my improve the idle but it costs torque and hp everywhere in the rpm range.
Selecting the optimal LCA first and then the overlap to give the desired idle qualities locks in the duration. Result - the BEST cam for the job.
Having said that, If I could get a tighter lca to do the same as what I am doing by going wider lca and a bit more compression for a smoother idle and higher rpm band, I would.
gottogo,gottago wrote: ↑Mon Oct 15, 2018 4:00 pmthanks DV.. I like hearing that said although I've not been that successful in achieving the intended results. When I've locked in a duration that gave a nice smooth idle on a tighter lca I seem to shorten my rpm range. If I pick a duration that restores the upper rpm band, the idle goes away on me. Solution for me was to compromise and spread it out a bit on the lca. (daily driver builds) Perhaps the definition of daily driver is a bit different for everyone too.If you have to consider a wider LCA to get the idle vacuum sought then all you have done is chosen a cam with too much duration. Spreading the LCA my improve the idle but it costs torque and hp everywhere in the rpm range.
Selecting the optimal LCA first and then the overlap to give the desired idle qualities locks in the duration. Result - the BEST cam for the job.
Having said that, If I could get a tighter lca to do the same as what I am doing by going wider lca and a bit more compression for a smoother idle and higher rpm band, I would.
I'm good with the 5500 rpm range in most real daily drivers, big blocks for sure, smalls sometimes like to run them up a bit higher. All dependent on vehicle weight, gearing, usage etc..My question is, how much rpm do you really need for a daily driver? I have never found a need for much more than 5500 rpm on my street cars. That's good for 100 mph in second gear in my Impala. The performance under 3000 rpm is really important, that is where the engine lives.
You have not answered my questions.gottago wrote: ↑Tue Oct 16, 2018 1:28 pm D.V. thank you, will do! I apologize for the simplistic questions and sortof knew I was going way back into some pretty basic theory you have spoken on for years. But I did notice on many an auto talk site how common it is for this topic to come up in various ways. The term lsa or lca gets bandied about by everyone from the fuel mileage crowd to racers to vvt and dohc specs etc all claiming some characteristic and benefits of a wider or narrower lca. I've driven quite a few all the way from 104 to 117 lca. The lsa can change the way an engine responds quite dramatically. Knowing which lsa to use for the intended purpose in combination with everything else is a bit tricky. Even some of our terminology has differing interpretations, like the daily driver or the street/strip combo. One guys daily driver is another mans weekend racer etc..
I'm good with the 5500 rpm range in most real daily drivers, big blocks for sure, smalls sometimes like to run them up a bit higher. All dependent on vehicle weight, gearing, usage etc..My question is, how much rpm do you really need for a daily driver? I have never found a need for much more than 5500 rpm on my street cars. That's good for 100 mph in second gear in my Impala. The performance under 3000 rpm is really important, that is where the engine lives.