Guys my static comp is 11.2 to 1
I wanted to use BTR's stage 1 na cam. Intake valve closes at 44 abdc and using Wallace calculator gives me over 10 to 1 dynamic and I keep reading this is too high for pump gas. Comp and BTR both tell me I can be fine with 93 octane as long as it's tuned correctly. I am the tuner so I'm not worried about that, however I don't want to have to pull too much timing out, which kinda defeats the purpose
I will have more than adequate cooling and run a 160 tstat
what say you ?
370 lq4 with TEA 799 heads
And thanks in advance

 

DCR is calculated off the 006 IVC, not the 050 IVC. Your DCR is closer to 8.3 and is fine for 93 octane

 

You will typically have to add 15 degrees to your intake valve closing point depending on where the spec is taking place at on the lobe. Looking at the cam specs you will be fine in pump gas with that cam. You will know the timing limits by any knock retard you get but max timing does not always mean max power. I would sneak up on the tune and get the fuel right then play with the timing for power.

 

That cam is a bit on the small size for 370 cubes. I'd suggest the BTR stage 2. It drives almost like stock.

 

You'll be fine if tuned right, but if the car wants say 30 degrees for max performance, but you can only run 26 on pump gas, well then it will be somewhat octane limited of course

 

can you point me to what calculator you are using please ? Because the calc I use asks intake closing after bottom dead center which cam card shows as 44 degrees for that cam.

 

I agree and I am now getting recommended the stage 3 from BTR' s Nick from tech support but he also stated that dcr is too high for stage 1. He will get back to me tomorrow
I have the option of running 317 heads fully worked over with 72-74 combustion chamber which would put me at a little higher than 10 to 1 static

 

I understand your last part about timing and power but the first part about adding degrees to intake closing point loses me

 

11.8:1 is cutting really close but I've seen 12.1 on a couple.

 

I'm using the one written by piano prodigy, but you missed my point. Your cam card should also have the valve events at 0.006" lift in addition to the valve events at 0.050" lift. Your card is showing 44 degrees ABDC - At 0.050" lift.

You don't use the 050 IVC for DCR calculations. You use the 006 IVC, which on your cam is going to be about 71.5 degrees ABDC, depending on ramp rates (I used 54 degree ramp rate since it's a milder cam for approximation). Using 71.5 degrees, if your static compression is 11.2, your dynamic compression is 8.4. 8.3 in prior post was a rough estimate, because I was on my cell phone, so I did the math in my head. 8.39 is off the calculator assuming 62cc heads, 0.053 head gasket, resulting in 11.17 compression ratio.

 

I seen people get away with low 12's compression on 93 octane (myself included) by using a cam with really late IVC to compensate.

 

Darth you have no idea how much this helped me and I can't thank you enough. But I still have questions. First how did you figure the actual ABDC because cam card only shows @ .050 spec AND I cannot find info for this cam on Comps website nor on btr

 

Call Comp, they SHOULD tell you. If not, get another cam.... Comp...SMH....

 

I had to make an educated guess...

If you have not heard the term "ramp rate" before, it is simply the difference in duration between the 006 and 050 valve events. Longer ramp rates are gentler and shorter ramp rates are harsher. A quick example is a 224/230 cam at 050 that is 273/279 at 006. 273-224 is 49 degrees. This would be commonly called a 49 degree ramp rate. 49 degrees is rather harsh. That same 224/230 cam could have 006 events of 277/283 at 006, which would be a 54 degree ramp rate. This cam's valve train would likely be quieter vs the 49 degree ramp rate cam.

I've seen ramp rates on aftermarket cams ranging from 47 degrees to 56 degrees. There was a phase when shorter ramp rates were all the rage. Then, people started reporting they made more power with softer ramp rates, so the ramp rates kind of crept back up into the low to mid 50's. You used to see larger ramp rates advertised as "endurance lobes". Most of the commonly used ramp rates range from 51-55 degrees.

When I do not have the ramp rate, I use 54 for my calculations, since this is close enough to most current aftermarket cams, and will generally not be off by more than a degree from the actual 006 valve events on the cam. Hope that made sense.

 

You sir are quite the gear head !!! Kudos to you.
I actually just found the calculation of advertized intake duration, which this cam is 273. Divided by 2 = 136.5. Add lobe sep of 115 = 251.5. Subtract 180 = 71.5 and using that number in dynamic comp calc gives me 8.41
Excellent ! I still may go with the stage 2 which is slightly more aggressive BUT I really want torque down low. As much as possible. I am not really interested in HP at 6500 and instead average torque from say 2000 to 4000 rpms
Decisions
Thank you again

 

Similar to what Darth stated but was a quick and dirty estimate without having the info on the cam card. Darth covered everything in detail which shows you will be fine.

 

I have the BTR stage 2 on a 5.7L with ported 243 heads, Dorman LS2 intake and 92 tb. The cam starts to pull at 1500 and doesn't stop till 6800 rpm. I'm happy with the streetability.

 

what is the rest of your setup. Trans rear etc ? If auto are you using a stock converter ?

 

 

M6, 3.42 gears