This is most likely to sound *****ic but, does improved(serious porting) or better heads raise the rpm max horsepower occur without changing the camshaft.
I would say you would have more hp across the board at a lower rpm. Or you wouldn't have to run the engine as hard to get the same power as before with the old heads.
It also depends on the heads and where you gained or lost when porting. Low lift gains you can feel in all driving situations, high lift gains you feel at full throttle.
Simple answer is yes. more airflow gives more capability. Rule of thumb is for every cfm of head flow equals 2hp in capabilities with matching components.
Went from 237cfm to 274cfm at .500 with port work on Trick Flow DHC 175cc ports. Crower tells me the increase in flow will raise the RPM where peak horsepower occurs. Little .040 over 327.
Just wondering, do you know what HP the 327 made with the 237 cfm heads? And what else is, in/on the motor? Cam, intake, carb, headers, compression? Thanks, Gene.
I'd say a lot depends on camshaft, if the heads have enough flow to support the camshafts ability to move air I would think the benefits would be minimal. As in if I'm pushing fluid thru a 1/4" rubber hose and only moving a cup of fluid a minute then going to a 1" hose probably isn't going to net a whole lot more if I'm still only pushing a cup of fluid. So if the camshaft isn't being restricted by the flow of the heads then I doubt the gain will be much, on the other hand if the camshaft is fighting to pull air thru the heads then of course the benefits are higher... ..
This is a new build. Crower says RPM range given is for average heads, Improving heads will move the powerband with the same cam. As the heads were and with the cam I have this combo should make peak hp around 5700-5800. Improvements to the heads should move that up a bit. Everything else should support the increase and not be a choke point. I just don't want it to fall flat at 6000.
Considering your calming your heads flow more at .500" than the unported Brodix 11x's I had on a older sprint car 406" car doing about 8000 RPM and making around 750 HP ( at much more lift ) I think falling flat on its face in a 327 at 5800 is very unlikely due to a head issue and since your quoting a lift of .500" I ***ume thats about the lift of your cam ?? If anything the heads are to big for the set up . I know on my Brodix and RHS heads that flow the same at .500 there suggested for a over 400" engine and that would be for a serious race application . I don't know what duration you have and all that but if it .500 lift cam it should run up past 5800 with ease with heads that are huge in flow for a 175 runner. considering a old set of 461 ported heads on a 327 with a less then .500 lift cam went to 7000 some what easy back in the day I doubt its falling flat on its face. Im considerng putting the Brodix 10's on a 383 with a big streetable cam and I know there to much head likely with a automatic. Is this race engine if so gt a bigger cam so the heads can do there job better
Your post caught my eye. So starting off at 237cfm seems awfully low. Any idea as to why? Trick Flow advertises 258cfm @ .500" and I have seen independent flow bench data showing 250cfm @ .500" All out of the box, at 28", and with back cut 2.02 valves. I wonder how much variation there might be from head to another. Maybe it has more to do with different flow bench calibrations
The Jalopy Journal
