does my cam choice fly

[baxsom]

i just dont want it to be a dog off the line.

i was originally looking at the xe274h which requires the 2500 stall and the headers but it was suggested that i might lose so much bottom that i wont like the take off.

the CR is definitely under 10
its more like 8.8

 

[Rodney Gold]

As I said , any of those cams would work well , a 454 produces a lot of torque and I cant see any of em reducing bottom end , with repect to any other , but more than 10lb/ft or so and I cant see any of em having some wierd and wonderful peaky torque curve. Im not sure if the Xe274 requires a high Cr to work properly , but it will most likely allow higher rpm which would increase your "embarrasingly" low top end. (my 1.5l VTEC Jazz/fit with a cvt can beat you on top end , but would take about 10x longer to get there)
Losing bottom end in a 454 , especially with your setup , is not really a bad thing , I cannot imagine that you can get traction if you flash the motor to 2500 on the line? If you arent violently spinning the tyres when doing that , especially with a 3.5 rear end , then there is something drastically wrong with the motor...........
PS don't launch by trying to hold the motor at its stall against the brakes , you will wind up the suspension etc..the way to use a 2500 stall to launch , if you dont have a transbrake , is to mash the pedal from idle....

 

[baxsom]

from a dead when i stomp the pedal now, the wheels start spinning and the entire car shifts left until it catches second and then will straighten up
i just want to make sure i dont lose that by shifting the power band too high.

using camquest it says that the #1 cam for my engine is the xe256h

346hp at 4000hp and 511ft/lbs at 2500rpms
thats right at my stall speed

the xe268h rates at
370hp at 4500 and 491ft/lbs at 2500

the xe274 projects
375hp at 4500
and 477ft/lbs at 2500

no one has ever suggested the xe256h for a 454.
so would it be better to sacrifice 20 or so ft/lbs of torque on the low end to gain 20 or so hp on the upper end.

in my uneducated perspective i think that the torque to get the car moving would be more needed than the high end getting close to redline increase in hp.

 

[Rodney Gold]

The stall is there to bring the car to the powerband more quickly than stock, You need RPM to get a decent top end , a cam that ends at 5000 rpm is wasting the other stuff you got on the car...the 20lbs loss will actually be beneficial as you might spin a little less and get way more traction and thus get a far quicker pullaway.
Go for the 268...you wont be sorry.

 

[baxsom]

Go for the 268...you wont be sorry.

the xtreme energy 268 or the high energy 268

 

[Peer81]

Keep in mind that DC is more important than CR. CR is a good impression on what you have but if your CR is only 8.8 and you get a to big cam then the real compression DR will drop to (just an example) 6:1 or less. I don't know what is a minimum DR for a engine to operate the right way but I think its usefull to find out. Good luck

Groeten Peter

 

[baxsom]

thats my only worry. i dont want to go too big. id rather get a cam that might be one size too small than be too big.

comp ratio is the main thing i am worried about. stock 72 454 comp ratio is 8.5:1 with 113cc chambers

i have heads from a 66 L36 427 which supposedly are 98.4cc. i found specs that said that the L36 was 11:1

so if nothing else changes and you drop the combustion chamber 15cc per cylinder how does that affect ratio? i would guess it would go up but by how much is the question

 

[Rodney Gold]

Go for the High energy 268h...its a fine choice - as I said , I use one in my 454.........

 

[baxsom]

Go for the High energy 268h...its a fine choice - as I said , I use one in my 454.........

the comp cams simulator puts them really close in performance plus the added benefit of an easier break in.

what else has been done to your motor to go along with the 268

 

[Rodney Gold]

Nothing much really , a set of headers , a decent msd Distibutor and a MSD6al....it has got slightly stiffer double valve springs in from the more radical cam , but stock rect port heads and stock intake...
I had an airgap and a Edlebrock 800 on prior to cam swap...but as I said before , after fairly radical de tuning to a more driveable condition...it lost all of 0.05 secs on the 1/4 mile
Heres an ad featuring the car and some pics of the motor (prior to detune with 800cfm carb but stock intake , the wide angle one is after the detune - burnouts on strip pre and in parking lot prior...)
Chev beast - 454 el Camino - Cape Town used car for sale - Gumtree Cape Town Free Classifieds

 

[baxsom]

looks like i know which one is going in then.