Hey Y'all working on a 1955 331 Hemi, #1 looking for any information about cylinder head flow with various valve back angel with small lift .455. #2 casting wall thickness around push rod holes going to adjustable push rods. has anyone sucssessfully opened these to 1/2" dia? Thank You SR66
when I do this is the ONLY thread I get . been many years since i've been on here and the navigation has changed.
Gene Adams did a white paper on racing early Chrysler Engines which stated that all early 56-58 heads in stock form flowed around 225 cfm. The 53-55 heads were a tad better in stock form. Since you are going with a small .445 lift cam you would not be taking advantage of an improved port.
You can open the pushrod holes up to .500 dia - but you MUST maintain concentricity. I used a piloted drill on mine and it worked beautifully. I have sectioned some of these heads, and they are thin in some areas so check before you start cutting...
The '54 had better ex ports than the 51-3, '55 had bigger valves & the 354 were bigger than the '55 & the 392 had still bigger valves.
With a small cam as you suggest then port flow will not be critical and valve angle less so. Unless you are planning on using some gawd-awful fat tubing for pushrods then the stock hole will work fine. Until you get into lifts in the 490 range or stout valve springs a basic 5/16 tube will do just fine and with low lift and a 3/8 tube may not scuff too badly. .
There is a web site that gathers up cylinder head flow and places the data in easy to read comparisons. Google "Stan Weiss cylinder Head Flow Data" and you will find it. There are about 15 early hemi heads entered, from stock to max-port. A Gene Adams stock 1955 with 1.94 intake and 1.75 exhaust flowed 228/157 @ .600 A Smithberg 1954 max port w/ 2.2 intake and 1.85 flowed 413/266 @ .800 lift. A mild ported 1955 w/ 2.1 back cut intake flowed 299 @ .600 lift. A stock Hot Heads aluminum w/ 2.0/1.75 valves flowed 233/160 @ .600 lift. 1956 354 and 392 heads flowed faily close together in stock configuration. Shows that 392 heads are not as free-flowing as the earlier heads, as the 392 heads have larger valves. -Andy Carlson Ojai CA
...yeah....but maybe..... IMHO there is more to port flow than just a cfm number. Runner volume and cross sectional area are huge factors that are seemingly never included in 'test' reports. There have also been reports indicating that the flow does not change after the .600 area even with the valve removed... Now, a challenge to anyone with a flow bench who has a lot of free time. .
Just put a blower on it ! Hemi engines do well being force fed and then a few CFM of natural flow and mountains of grinding dust doesn't matter so much. Shooting for MAX flow without regard for velocity is reserved for MAX effort engine that run at MAX rpm for minimal lengths of time. It would also be interesting to see what type and configuration of exhaust exit/ pipe is being used. The port looks like this - Most headers are built like this. Very pretty! But the gasses see this Torturous to high speed gasses An abrupt 45is in the flange, then bends around what ever . Remember The port looks like this Note the exit angle of the exhaust These guys used.
I tend to agree. The cost of 'making metal' is simply not justified on anything but an EMS package or a drag car and the cost will be high. "Speed costs money...how fast do you want to go?" On anything that sees regular street use a stock head works fine, and as you note, a little bit of boost makes up for a lot of other omissions. Now, for those of you that have some talent and lots-o-free-time, get out the grinder... . .
I (Smithberg Racing) gave Stan Weiss alot of info on the Hemi heads. Between myself and Gene we've spent alot of time on the flow bench to figure out what works and what doesn't. We experimented a ton for Engine Masters after Danny Miller passed away. It is true the 392 head isn't as good as the 331, but I've gotten a 392 to flow 355cfm (goal to reach 365-370) with a 2.200 valve.
Yes velocity, area, and port volume should be considered to match a particular head for a given combination. To gather all of that info for a direct comparison would be a challenge for somebody like Stan Weiss. I doubt you would find many head porters willing to give some of that info up. The flow not changing after .600 lift may be true in stock form (sometimes sooner) but ported properly the head will have positive flow to 1" lift. At least my ports do.
Hot Heads version of my CNC program for a Race Port with a custom valve for the above info. The 1954/1955 331 Iron version of my CNC program for a Race Port. Does 400cfm @ .800 lift with a custom valve.
Fancy looking stuff right there Nick! Good to hear of your success. So, what is the 'out-the-door' cost for a port job such as this? I could be wrong, but I'm guessing that very few folks have the financial backing to make it happen regardless of the power potential. Maybe folks on some of the other forums have deeper pockets...? There gets to be a fine line, financially, in an EarlyHemi rebuild that folks just can't go past and I'm guessing that major port will be off of the table before the parts come out of the hot tank. Like I said, I could be wrong. Maybe all of my customers are just cheap. Dunno. .
It's a long process to build a set of heads like that and not cheap by any means. Not for the regular Joe either, for guys competing mostly. I have been working on Street port programs that are cheaper for factory iron and Hot heads castings. My phone has been ringing off the hook for what I do and have only had 3 days off over the past 11 months. Plenty busy, the work and need is certainly there. My street port version for Bob's aluminum head gains 100cfm over what his head does as cast, using his stock valve sizes too 2.065/1.800.
The Jalopy Journal
