JimV

One last set of numbers. These are the AFR and Dart (same ports) with a 12" pipe with a generous radius on the pipe. Also noted when holding this pipe up to the port their was a considerable amount of back pressure on the pipe.

Lift............CFM..AFR...........CFM..Dart

.2.............151....................151
.3.............230....................206
.4.............286....................259
.5.............314....................305
.6.............334....................333
.7.............341....................344
.8.............344....................349

JimV

[QUOTE=Linster]Jim,

It looks like the seats in these heads has been sunk deep when doing the valve job. Looking at the picture, it appears the seat is about .100 wide. Normal after use with a .080 seat. The Intake looks to be sunk even more. Notice the black around the exit of the seat. The intake looks like there is a wall in the area entering the bowl. That affects a lot of flow on the .100 & .200 and maybe the .300 lift. That is the where most airflow gain is on the opening and closing of the valves. When the valve is wide open flow is usually not a big problem. I always tell the machine shop not to sink the seats, only cut enough to clean it up. If you do not tell them, it seems you end up with a seat like that. I have had to install taller seats to correct these poor valve jobs.

I am curious to see what you find. I think you can help some by cleaning the wrinkles on the exhaust port. After that try unshouding the bowl area that is black especially in the .100 to .300 lift range. The intake appears to be the beneficial from the picture.

I do not pay much attention to the .700 or .800 lift numbers, Actually I do not get my shop to flow them since the most cam lift is .632 on a hydraulic roller. If they increase, usually the lower lift numbers fall.

Keep us posted

Linster Good eye. The seats were not sunk in, I had to do a touch up to get it square. For one reason or other a couple of exhaust ports were leaking. I'm not sure if it was a problem from the factory, valve toss, detonation or all the above. I have had a lot of leaky exhaust seats on Dart heads when their new. Seems like once you touch them up after they have a few hour on them they stay if everything is right.

JimV

Crazyhorse,

Mannnnnnnnnnnnnnnnn.................. I'm ready

JimV

Ray,

Good point on the smaller exhaust valve. I have tried several different times to make a 1.900 up to a 1.940 (with respective venturi sizes and overall port volumes) valve work in a big block chamber with no improvements. I believe the valve gets shrouded from the chamber wall. In our 510 ci. race motor, I cut them to a 1.850 with minimal airflow loss.

I'm not banging AFR but other heads that I have seen had simular results.

I did machine a radius on the leading edge of the valve showing an improvement.

JimV

Sutphen,

Yes, the Dart ports have more volume than stock. They ended up at 138cc's. I never checked the stock port's volume.

Rik

Are the Dart Iron Eagle heads similar to the Dart Pro 1 heads? Other than one being Iron and the other being aluminum?

KAAMA

Ray, Perhaps I can help answer your question. I had bought a couple of USED sets of the 357 AFR cnc ported heads a few months ago, and took them to JimV's shop and had him put them on his flow bench as they were from the factory just to see what the real scoop was on these AFR brand heads. You will see that these also "hit the wall" after .500" lift. I was kinda dissapointed that the exhaust ports petered out after .500" lift. I don't feel so bad since these other CNC'd AFR's showed the same dissappointing flow numbers after .500". There's definately room for improvement!

AFR stock factory exhaust port WITHOUT pipe as flowed by JimV...

Lift.........CFM
.200 138
.300 193
.400 226
.500 254
.600 263
.650 263

At least it looks like the AFR's responded well with some impressive numbers to some massaging as JimV has demonstrated---especially in the low/mid lift areas.

KAAMA

Bill, so far I have only heard of very POSSITIVE results from the few guys I know who have bolted these AFR heads on basically out of the box from the factory and on their boat engines. These still seam to make pretty good power out of the box over other heads, but as JimV has still discovered a lot more of potential there. But you are right, it's still dissappointing on how much of that power was missed in the cnc porting. With all these results going on it looks like I am having to eat my words from a couple of years ago.

Turbojack

I did a leak down on my motor this fall & had 2 leaking exhaust valves. As in the past when I had this problem it was because I had detonation & tuliped the heads. I was suprised to here that all the heads needed was a little freshing up & they were good to go. This was after 2 years with these heads.

Forgot to add ARF 335 CNC heads.

JimV

Rik,

I believe they are the same ports.