Upon searching for cams for my new 400 build, I decided to run my old 355, iron phase 1 bowtie's 64cc, through Pat k's dcr calculator. And it comes up with a DCR of 9.10:1. 10.5:1, .005 in the hole, IC 42.0 ABDC, 5.7 rods. My thing is this motor does not detonate at all, and I have been running 92 octane in it for 19 years? Now the cam I was going to run in my 400 also comes out to 9.11:1? What's up?

Same results with this calculator:http://www.rbracing-rsr.com/comprAdvHD.htm

is it possible you made a mistake when entering the info into the calcs or a problem with your math? I have made MANY mistakes with my calculations and am fairly well educated. what are the specs on the cams, maybe someone else can run the numbers, I can't imagine a 9.1 DCR running on 92

Sure, I figure that you have the great old -929 cam in there at 195/202 at .050" when you really need the advertised duration numbers in the program b/c it is the intake valve closing point that need's to be inputted, not the duration at .050" number.

Regardless of what the program instructions say, imho!!

Pat K., where are you on this!!

pdq67

I am at 9.14 DCR on 93 octane (11.57:1 SCR)so if you have a very good tune its not unbelievable. I try to shoot for 9:1 when I build my street motors.

My cam in the 355 is a crower 00355 here is the link to the timing card:http://www.crower.com/misc/cam_spec/cam_finder.php?part_num=00350&x=30&y=12
Maybe I am doing something wrong, but I have tried it several times on both DCR calcs? I did freshin up the motor 3 years ago and there was no sign of any detonation, pistons, valves all in great shape. Never pings or runs on, temp a constant 185.

My new build is a 400.
dart little m block 4.125 bore, zero deck
scat 4340 rotating assy 6 in 7/16 I beam rods
srp 16 dish pistons
10.2 compression
.039 gasket
64 cc 197 jegs heads
rpm air gap
hooker super comps
crane gold rollers
stud girdels
750 dbl pump, billet metering blocks, proform main body, aed billet base plate.
I was going to use this Lunati solid ft #401b1lun on a 108 cl :http://www.holley.com/data/Products/Technical/401B1LUN.pdf
but this comes out to 9.1:1 dcr also?

Upon searching for cams for my new 400 build, I decided to run my old 355, iron phase 1 bowtie's 64cc, through Pat k's dcr calculator. And it comes up with a DCR of 9.10:1. 10.5:1, .005 in the hole, IC 42.0 ABDC, 5.7 rods. My thing is this motor does not detonate at all, and I have been running 92 octane in it for 19 years? Now the cam I was going to run in my 400 also comes out to 9.11:1? What's up?

I'll be watching this thread since I'm trying to better understand the whole Sta CR and Dyn CR discussions...btw that's an awesome looking black 67 you have there...maybe I'll see you at e-town some day when my 406 is done

I'll be watching this thread since I'm trying to better understand the whole Sta CR and Dyn CR discussions...btw that's an awesome looking black 67 you have there...maybe I'll see you at e-town some day when my 406 is doneThanks Sooperdave, I will be at E-town in a couple of weeks for there fall swap meet.

41 degrees? no way... that must be based on .050" duration. You need to input advertised or .006" duration

One of those tells you to us @.050 duration, and the other computes it for you! I think. What would be the formula to figure out the duration @.006? It's all very cofusing! Lol

I only use Pat K's. It wants "advertised" duration, which generally is .006".

Yup I screwed up, I was putting in @.050:clonk: Now I got a DCR of 8.375, I will take my chances at that DCR lol. Man I was confused. But this calculator does say @.050:http://www.rbracing-rsr.com/comprAdvHD.htm

The way I see this is that you can't build pressure to start squeezing until the intake valve closes!!

The hassle come's from at what advertised duration is closest to this being true b/c we know at zero lift it is CLOSED but that ramps are so long as to make these numbers meaningless just like GM calling the old 30-30 solid lifter cam a 346/254 jobber!! At 314, things seem to start jibbing per WBR and at 304 per Pat K.......

Isn't the old -929 hy-cam measured per GM at 314/316 or so and only 195/202 at .050" lift?????

pdq67

Isn't the old -929 hy-cam measured per GM at 314/316 or so and only 195/202 at .050" lift?????

pdq67


I think the old cams had slow ramps