AFR Exhaust Ports (Pipe Dreams?)
#11
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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
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
#12
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[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.
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.
#13
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Originally Posted by Crazyhorse
Jim, you up for another west Michigan party? It's been a while since you and I had a soda pop so I'll give you a call to se if we can maybe meet up at Applebee's or something.
Mannnnnnnnnnnnnnnnn.................. I'm ready
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Originally Posted by Raylar
Interesting results on your bench. We have found during the development of our new 496 heads that 1.88 exhaust valves on big blocks are a little to big and hence they tend to kill velocity at mid lift numbers especially. We use a 1.75 exhaust valve on our smaller port and get about 250 cfm at .500 without a pipe. The numbers are still climbing all the way to .700. I also noticed the numbers on your AFR heads show the exhaust flow is "hitting the wall" at about .500 ,with or without the pipe and does not increase much beyond that. Not Good! I know Tony at AFR and usually his work does better than this. I am curious if any other AFR heads exhausts flow like this. Do the heads come with a standard 12 degree backside on the valve @1/2"radius? We see a lot better results when we use a 20 degree exhaust valve with a 1/2" radius and finish the front edge of the exhaust valve with a small .0625 radius at the edge. We also use a two angle plus 10 degree radius valve seat. Try this and see if the numbers improve. I have spent so much time on our flow bench the last two years that my wife claims I am operating the dam thing in my sleep!
Great Post!
Ray @ Raylar
Great Post!
Ray @ Raylar
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.
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Originally Posted by sutphen30
you know,i've had the same thing happen to me.i call them green seats,once there run in and then recut,no more leaks.
are you open the total cc of those exhaust ports,kinda looks like it.
are you open the total cc of those exhaust ports,kinda looks like it.
Sutphen,
Yes, the Dart ports have more volume than stock. They ended up at 138cc's. I never checked the stock port's volume.
#16
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Are the Dart Iron Eagle heads similar to the Dart Pro 1 heads? Other than one being Iron and the other being aluminum?
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Originally Posted by Raylar
I also noticed the numbers on your AFR heads show the exhaust flow is "hitting the wall" at about .500 ,with or without the pipe and does not increase much beyond that. Not Good! I know Tony at AFR and usually his work does better than this. I am curious if any other AFR heads exhausts flow like this. Ray @ Raylar
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.
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Originally Posted by sutphen30
sad part is,people are using these types of heads unported and they then don't het the results they were expecting.now they will see why.
#19
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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.
Forgot to add ARF 335 CNC heads.
#20
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Originally Posted by Rik
Are the Dart Iron Eagle heads similar to the Dart Pro 1 heads? Other than one being Iron and the other being aluminum?
Rik,
I believe they are the same ports.