articfriends

iTrader: (1)

Sweet, i used afr 335 cncs for heads since mine are 315' that been re-cnc'd to flow over 400 cfm, 252/260 for .050 duration, .380 lobe lift w 1.7 rockers, 110 icl, 118 ex cl, 114 lobe seperation, 13.5" runner length w race style efi intske, 2000 cfm throttle body, 8.4 compression on 4.25x 4.530 bore, 9.5 compression w 4.0 x 4.500 bore for 502 2.20 runner dia, 2.25 pri dia w 32" primary length w 8" collector. No mufflers

articfriends

iTrader: (1)

89 octane and 6500 rpm max

MILD THUNDER

iTrader: (3)

Cool. I will play around with that tonight .

articfriends

iTrader: (1)

Yep, I understand why, i was just surprised the frictional loss calculation from the stroke/higher piston speed is 310 hp at 6500 for 548 vs 260 with 509 with last set of calculations reducing cam size of 502 by 7 degrees, tells me IF its true dont waste your time building a na 4.25 stroke motor and trying to turn it past 6000 unless your going to cam it to the moon

Baja Rooster

iTrader: (1)

In my motorcycle superbike motors we run roughly a 3:2 bore to stroke ratio getting 200hp and 85ft of torque out of 1000cc with rev limits around 13k. In our experience we find the power in maximizing the bore, high compression, and fueling. I know that it's apples to oranges, but in a situation where you have to minimize parasitic losses in such a small package because you can't afford inefficiency, and have all of the modern technology and engineering to do so, the stroke is minimized because ain't nobody got time to wait for the piston to finish doing its thing. You do get a longer burn with longer piston travel, but in our case with Moto motors we get two burns while a BBC piston is lollygagging at the bottom of the cylinder with more extreme rod angles not putting energy into direct propulsion.

MILD THUNDER

iTrader: (3)

Smitty, try a simulation using these cam parameters.

On the 548ci

.006 Timing
320.9 intake 328.1 exhaust

.050 timing
266.5 intake 272.5 exhaust

ICL 105 ECL 113

.730 intake lift (.425 lobe) .728 exhaust lift (.434 lobe)

Then for the 509 combo

.006 timing
313.0 intake 317.7 exhaust

.050 timing
257.5 intake 261.5 exhaust

ICL 103 ECL 113
.674 intake lift (.402 lobe) Exhaust lift .676 (.404 lobe)

These cams are obviously large, but then again, looking for max power at 6500 without the help of a blower?. I think this particular program, is mainly looking for MAX power , and probably not factoring in things like idle quality and what not. Either way, I'd be more interested in seeing the power numbers, but mainly, how the two engines would fair up, if they were cammed for their cubic inch, with all else being equal. You can run the numbers with both engines at 9.5:1, and I'll bet the 548 outdoes the 509. However, do the run again, but with the 548 having the lower static compression, and I'll bet it will be close in power. What the 548 loses on compression, it will prob be close to a wash, being that it has more cubes.

As a side note, it appears the lifter acceleration rate of the longer duration 730 lift cam, isn't much faster than the shorter duration, 509 cam with only 674 lift.

Just for fun conversation.

articfriends

iTrader: (1)

I pumped the cam up and got theoretical hp numbers well into the 700's BUT this is a short block I already built and dynoed last year with blower on it with only 8.4-1 compression so .400 lobe cams and durations in the 260/270 range would make it a sputtering pig on bottom end. Its going to be a dyno experiment on how much hp I can make on low compression/87, maybe 89 octane and a A-B comparison of how far I can get a 500 efi intake to carry in upper midrange vs a typical single plane efi intake like a Dart or something, any intake suggestions, I'm thinking of buying a ching chong open plenum intake and 2200 cfm throttle body, would be even MORE interesting then!