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#41 ·
I am very familiar with that program. You have to watch out at times and I think this is one of them.

Real world dyno testing - the Performer RPM intake usually goes neck and neck with power up thru 5500 rpm on a mild cam and relatively low compression 454 using rectangular port heads.

You may gain a little - you may lose a little. Your in that neighborhood.

That program does not distinguish intake manifold designs other than 'Dual Plane' and 'Single Plane.' Bigger Manufacturers make how many dual plane manifolds themselves for the SBC ? How many single planes per manufacturer for the SBC ?

many, many different ones. They all react very differently. Trust me.

Anyway, it may be worth a shot to try the Victor JR in your application but do not get your hopes up. I would give the Performer RPM more respect. BTW: using a hydraulic roller on this set up would greatly increase the chance of it working better than the RPM.

Oh, one more inconsistency I would find with that program - EXhaust. Huge impact and no marine exhaust in there. Never use the open header option - will make you think you have way more power than you will. Try Large header with muffler or hp manifolds and muffler - you have to play with it to get hp to more realistic levels.

Like many things - it is a tool but not near the best tool. The good programs are huge amounts of money - but they too have downfalls. Working knowledge and real life track or water performance is the best indicator.
 
#42 ·
Great input CFM, thanks I appreciate it. I had this program for several yrs then lost it do to an operating system failure. I've come accustom to using it for component comparisons more that percise figures, although I think my results typically matched pretty closely to what it estimated. I have several benchmarks with engines in my boat of known hp and known attainable speed. I can match my speed gains up with those benchmarks to sanity check in a crude way what my real hp gain are. Heads is what I have noticed must be right-on based on airflow data, not just there selections. That makes a huge difference too. Anyway, truth be known, I would like to try single plane intakes because I think they are a better match for my mech secondary 800 holleys. I also pay some attention to what merc did on the hp 500 and they liked the single plane with the 800dp. I have found over the years that merc really knows how to build a perf engine. So that is more ammo to go the single plane route.

The other thing I would like to do over the winter is basic airflow enhancements to my heads. I have been studying up on that. Do you have any suggestions? I am thinking gasket matching and some careful bowl porting where I can see velocity could be improved. I already bore notched the cylinders to unshroud the valves. That seemed to work well so any other little tricks like that I am keen on. Sorry for the long, hijacked post ;)

BT :cool:
 
#43 ·
That's true and untrue about Merc.

Don't get me wrong on the neg - they make great stuff. But boy, do you ever pay :laugher:

They set a goal HP and try to keep it there.

If they made the 502 525-550hp than who would buy the 525SC's for way more money? If they jacked it too 600hp who'd buy the 600Sc's or newer 575Sc's ?So on and so forth. Forget the torque comparisons - hp figures sell motors.

Why build a killer NA motor and make it hard to make it more powerful for up and comming new motors. You gotta make more hp every so many years to get people to buy new boats and/or motors.

As far as the Dart Intake - I feel that an RPM would come real close and actually make a little more usable torque throughout the low-midrange. The Victor Jr is a little more flexible and may do the same. Remember, the GM cast iron head has got a big lazy intake port and an exhaust port that doesn't want to get rid of much air.

FYI: many 600 hp 502's runnin around with the RPM intake. many of the street guys like this combo.

Finally - yes. More compression will always make more hp. The power added can be quite suprising.

Your having fun so that is all that really matters. Right ?
 
#44 ·
Boy am I ever having fun CFM. Building the power is what I like about boating, aside from it is virtually the last un tamed frontier. I also get a kick going past the $150k boat out in the rough stuff in my ole jeolopy :D

I'm not sure what the flow numbers are on the gm cast iron heads, but I would suspect the al edelbrocks I run flow much better on both valves. Do you have flow numbers for the gms? I'd like to plug them into my dd2000.

BT :cool:
 
Discussion starter · #45 · (Edited)
check this link

http://chevyhiperformance.com/techarticles/41598/

has a bunch of numbers to try!! go to the bottom and click on the sidebar notes, i found alot of info there.

just remember that it is said that all flow benchs are not the same and numbers can vary from one to another...even two superflow 600's can give different readings. i guess it depends on who's doing the flowing.

i dont know much about it but thats what ive been told lately.....trying to get mine flowed right now.

have fun!!!
 
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BOATN70
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