561 casting flow #'s
01-07-2003, 10:58 PM
#16
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Join Date: Dec 2002
Posts: 752
hey turbo, we have been testing both the 561's and the non 561's heads. I dont see getting 300+ CFM....actually you wont, its impossible. We only got a max of 247 on a rough port. we expect to see 260-270 when completely done with more bowl work and different valves. Ahhh the Flow bench is great tool.
01-23-2003, 10:46 AM
#20
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Join Date: Aug 2002
Location: Red Oak Texas
Posts: 1,509
Here are #'s..............
lift----561---other
.050---30---30
.100---58---56
.150---84---83
.200--115--106
.250--144--137
.300--170--164
.350--191--185
.400--213--205
.450--223--212
.500--221--210
.550--218--209
.600--218--209
These are "core" or "pull-off" heads that are brought to me and the only thing done before flowing is basic cleaning. Just clean enough to use on the flow bench. They are also flowed with the valvajob that is on the heads when they are brought to me. The shape and condition of the valve job could effect the flow #'s a lil but since these heads are being ported and usually cut for larger valves it makes no sense to do a valve job before this. I had originally thought the exhaust ports were about the same but the last few sets of 561's that I tested flowed about 10-15 cfm higher on the exhaust than usual. Most LT1's flow about 145-155 at .600 (depending on the valvejob and cleanliness) but these 561 flowed 160-165 at .600 lift. There is a bump that is uaually on the shortside/floor of the exhaust that was not there on these heads. I am sure that is what makes the exhaust ports better.
The cast iron heads have a larger chamber and will lower compression as compared to the aluminum. I do not have a flowsheet handy but they flow about 230 (intake) and 150 (exhaust). There is little room for improvement unless ya wanna remove LOTS of material and the average portjob will get #'s around 250-255 (intake) and 175-180 (exhaust) and to get better #'s you have to remove LOTS of material and you are just chasing peak flow#'s and not making the car run better (probably worse since the port is so big).
NightTrain66
lift----561---other
.050---30---30
.100---58---56
.150---84---83
.200--115--106
.250--144--137
.300--170--164
.350--191--185
.400--213--205
.450--223--212
.500--221--210
.550--218--209
.600--218--209
These are "core" or "pull-off" heads that are brought to me and the only thing done before flowing is basic cleaning. Just clean enough to use on the flow bench. They are also flowed with the valvajob that is on the heads when they are brought to me. The shape and condition of the valve job could effect the flow #'s a lil but since these heads are being ported and usually cut for larger valves it makes no sense to do a valve job before this. I had originally thought the exhaust ports were about the same but the last few sets of 561's that I tested flowed about 10-15 cfm higher on the exhaust than usual. Most LT1's flow about 145-155 at .600 (depending on the valvejob and cleanliness) but these 561 flowed 160-165 at .600 lift. There is a bump that is uaually on the shortside/floor of the exhaust that was not there on these heads. I am sure that is what makes the exhaust ports better.
The cast iron heads have a larger chamber and will lower compression as compared to the aluminum. I do not have a flowsheet handy but they flow about 230 (intake) and 150 (exhaust). There is little room for improvement unless ya wanna remove LOTS of material and the average portjob will get #'s around 250-255 (intake) and 175-180 (exhaust) and to get better #'s you have to remove LOTS of material and you are just chasing peak flow#'s and not making the car run better (probably worse since the port is so big).
NightTrain66
01-23-2003, 07:58 PM
#22
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Join Date: Dec 2002
Posts: 752
Well after testing both the 561's and the 643's castings on the flow bench we are going to continue forward with using the 643's.
there is jsut more meat to port them. the 561's do flow better on the exhaust side and weigh less. However its most likely we will see bigger #'s from teh 643 castings due to more room to port.
Below is a flow bench of the STOCK 561's and the STOCK 643's
This was done a 28" of H20
lift----643's lift 561's
Intake Exhaust Intake Exhaust
.100---67 ---47 --63 --46
.200--121 --90 --120 --93
.300--170 --120 --170 --121
.400--205 --139 --198 --142
.500--206 --147 --201 --150
.600--205 --150 --202 --154
the 561's have a better flow ratio between the intake and exhaust by about 3%
this shows that its nto always how much air you can cram in....but the balance between getting the air out too.
notice hte 561's flow less on intake but more on exhaust yet they make 10 more HP then older LT1 heads.
As far as expected flow #'s, we are going with 2.00 and 1.60 valves we are shooting for the 265/220 range. i will post #'s once the work is all done.
there is jsut more meat to port them. the 561's do flow better on the exhaust side and weigh less. However its most likely we will see bigger #'s from teh 643 castings due to more room to port.
Below is a flow bench of the STOCK 561's and the STOCK 643's
This was done a 28" of H20
lift----643's lift 561's
Intake Exhaust Intake Exhaust
.100---67 ---47 --63 --46
.200--121 --90 --120 --93
.300--170 --120 --170 --121
.400--205 --139 --198 --142
.500--206 --147 --201 --150
.600--205 --150 --202 --154
the 561's have a better flow ratio between the intake and exhaust by about 3%
this shows that its nto always how much air you can cram in....but the balance between getting the air out too.
notice hte 561's flow less on intake but more on exhaust yet they make 10 more HP then older LT1 heads.
As far as expected flow #'s, we are going with 2.00 and 1.60 valves we are shooting for the 265/220 range. i will post #'s once the work is all done.
01-23-2003, 10:35 PM
#23
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Thread Starter
Join Date: Aug 2002
Location: Red Oak Texas
Posts: 1,509
The 561 end up flowing 270-275 (intake)and 195 (exhaust). These #s are with a valve job and shortsides that give good flow #'s at low and mid lifts. If you want flow #'s at .600 and that is it you can lay back the shortside a lil more and/or get a valvejob that flows great here but poorly at low and mid lifts.
I am not sure what "recipe" GTP uses on their heads but I have "touched up" some of their heads and they flowed 215-217 at .600 and still had good low and mid #'s. The intake valve job was nothing special but what ever they do to the exhaust valve job made it flow 10-15 cfm better than I usually get. ???????????
As long as you concentrate on the low and mid lift flow #'s with a good flowing valve job and correct shaped shortsides, shape the port correct and make sure that the port doesn't go turbulent at high lift and get at least 265 cfm or better from the intake port you will be happy with the performance. Do not try to get 285 cfm or look at the .600 lift flow # only. When porting the head if you keep looking at the .600 # or trying to get 285 cfm you need to watch what you are doing to the low and mid #'s when the head finally flows 285 cfm at .600. If you have a 270 cfm and pick up 15 cfm at .600 but lose 5 cfm from .500 and below you are hurting yourself. As long as the port is shaped correct, has a good valve job for low and mid lift flow and never goes turbulent than the .600 flow # is nothing.
NightTrain66
I am not sure what "recipe" GTP uses on their heads but I have "touched up" some of their heads and they flowed 215-217 at .600 and still had good low and mid #'s. The intake valve job was nothing special but what ever they do to the exhaust valve job made it flow 10-15 cfm better than I usually get. ???????????
As long as you concentrate on the low and mid lift flow #'s with a good flowing valve job and correct shaped shortsides, shape the port correct and make sure that the port doesn't go turbulent at high lift and get at least 265 cfm or better from the intake port you will be happy with the performance. Do not try to get 285 cfm or look at the .600 lift flow # only. When porting the head if you keep looking at the .600 # or trying to get 285 cfm you need to watch what you are doing to the low and mid #'s when the head finally flows 285 cfm at .600. If you have a 270 cfm and pick up 15 cfm at .600 but lose 5 cfm from .500 and below you are hurting yourself. As long as the port is shaped correct, has a good valve job for low and mid lift flow and never goes turbulent than the .600 flow # is nothing.
NightTrain66
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