Port Flow/ H.P. Chart

[GlennS]

Hi all, I thought I read somewhere that you could get a general idea what H.P. improvements would come with increased head flow? Of course advertised flow numbers are just that but switching from oval ports to dart 325's and was wondering what to expect power dept wise. The oval port Merlins have worked admirably but at there limits and not worth the investment to try and improve for our combo. The Darts have some work and are presented to us at a very good price. Nitrous is applicable here Glenn

[Mike Stark]

AFR uses (cfm x .2575 x # of cylinders).

It's pretty common to make about 1.8 to 2 hp per cfm of flow on a mild engine. Race engine are more like 2.2 or so per cfm.

[GlennS]

Thanks for the reply Mike, So as an example if my oval port heads flow somewhere around 280cfm on the intake and the Darts flow in the say 370cfm range the hp increase could be as much as 1023hp, right?
Seriously though 50-75 hp seem reasonable? More? Glenn

[Chris]

Last time I checked 2.0 x 90 does not equal 1023. Maybe my calculator is wrong.

[hsutton]

Hi Glenn, The .2575 x CFM x No. of cylinders (which in an V-8 comes out to 2.06 x CFM) is pretty close. Late developments have put out that a couple of new heads can exceed this by quite a bit. R-M has a new program which says the old Dart 360 head they modify, and is CNC ported out to 370 CC, can make 1100 H.P. out of 440 CFM. My question is how? Could it be that wet flow is upping the ante? 2.5 Horsepower per CFM is quite a lot more than 2.06. If you send me your mailing address i'll mail you some nitrous info i printed off the web.

[Chris]

Horsepower is not all about CFM. Combustion efficiency, and valvetrain stability play an equaly important role as wet/dry flow charactoristics.

And even those 2 items barely skim the water in hp potential....

[hsutton]

Your right Chris, There definately is a lot of gray area in understanding horsepower potential. Those that know aren't sharing even the smallest little bits. Suffice it to say there is much more potential power than was formerly acknowledged by the pros. Every once in a while a small amount of information will slip out but it is a secret right now. The 2.06 per CFM is a pretty good indicator of what to expect with good heads and standard combustion chambers and the 2.2 H.P. or 2.3 H.P. per CFM might be right for real small, efficient chambers and 2.5 H.P. per CFM for the latest state of the art heads. (read very expensive). If you race the shootout races you gotta have these.

[GlennS]

Chris, I realize theres a whole lot more to H.P. than CFM, was joking on the previous post hp estimation. ::)Harold, I'm just trying to get a feel for what a better set of heads might do on our 460" nova. The car right now needs more breathing and I think the Dart heads should help a lot. Because the car sees nitrous regularly I think the larger ports, better flow should pick it up a bunch. Also the intake valves are 2.3" compared to the 2.19's on the Merlins, again nitrous involved here. I would estimate the current Hp in the low 600 range which makes sense if the oval ports flow aprox 260-300 (some port work) thats 2.0 hp per cfm. BUT if the Darts flow 370 could this little big block make 740 H.P.? Thats what I'm sayin! If we could pick up even 75 hp its well worth the cost and labor. Glenn

[Rigrock]

GlennS, don't know if this helps but on my 468 I switched from Merlin 310cc iron heads to Dart pro 1 325cc heads. The heads were 100 lbs lighter, plus in addition I also took 60 lbs out of the car, and the car picked up just shy of a half second in the 1/4,

[GlennS]

Rigrock, sounds like just what I'm looking for! I also read somewhere that I believe 25 or 30 hp equals aprox a tenth in et I would be happy with 2-3 tenths and with the weight savings on the nose of about 75-80 lbs another tenth or so sounds good to me! That would put the car at about a mid 12 second ET! Thats flying man!! ;D

[hsutton]

Blowing smoke again, huh Glenn. My son put the 335 CNC Darts on a 481 before we got the larger engines and it picked up about 3 1/2 tenths over the cast iron Chevy square ports that had been worked on on the exhaust side and weren't quite as good as the Merlins so draw whatever conclusions you will. I've seen one set of oval port merlins on a Nova here that is pretty fast. It's a light car, (3400) with the driver, and has a big hit of the juice but it still runs high 8.60s @ 152 MPH and spun some on this pass. I'll send you some helpfull Nitrous info if you "e" mail me your (regular mailing address) or i can give you the web site if you'd rather.

[Tyster]

Hey Harrold if You wouldnt mind I'de like to have the Nitrous info you have. I've been running it for about 14 years, but I like to read all the info/opinions that I can.
..............................Tyster

[e-mail]

[hsutton]

HI Tyster, I printed out two articles from a friends site, one was on heating the bottles and the other on ideal N20 temperature. For anyone who is interested the site is DragStuff.com. My friend John Heard also has a link to fastlanenitrous.com which has the article on bottle pressure. These were both very informative articles.

[GlennS]

Harold, I read those articles at some point, good reading and I guess changing the bottle before its half empty is good practice for consistency. Were gonna run the nova today, found one of the exhaust evac check valves at the drivers header went bad and was pumping exhaust into the crankcase! No wonder the engine was blowing oil smoke recently lol

[Maximum Race Engines]

GlennS-
I would be curious to know more about your combination and how fast you currently go. Believe it or not, I would recommend the Canfield 310 head for that cubic inch. They have a very good exhaust port as well as the intake, and respond well to a very little bit amount of porting. With the right camshaft and compression, you can make alot of power from that little 460 inch motor. I have a real nice combo that can do it to. I also don't like the 2.300" valve on the 454 +.030". It is heavier and tends to shroud more than a smaller valve would. The Canfield uses a 2.250" and works very well. Let me know how much you plan to pay for a Dart and I will get you a price on a set of Canfield's that honestly I feel would work better. Email me for more info and the rest of your combo..