kamero68
Apr 29th, 03, 05:45 PM
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There was debate a few days ago about the flow numbers on the Pro Lighting heads, so while I was getting my 781s flowed I had them check a Pro 220cc that I had setting around just to see for myself. Checked at 28" of water
Pro specs-----our test------781 oval---074 sq bbc
.100---70.7-----58.9----------64.1--------64.4
.200---146.4----118.9---------141.9-------145.2
.300---204.6----174.6---------211---------219.2
.400---249.8----219.1---------265.7-------261.6
.500---264.6----256.1---------284.2-------280.2
.600---272.2----274.6---------289.3-------295.3
.650---N/A------288.3---------288.9-------306.8
.700---282.1-----N/A-----------N/A---------N/A
The Pro head was stock out of the box 220cc with a prepped set of valves, while the low lift numbers were down some, the high lift numbers we got out preformed the advertized numbers.
Of course flow benchs will vary from one to the next, but it gives some degree of comparison.
The 781 bbc heads have new 2.19/1.88 valves and some bowl blending and short side rounding. When I was doing the pocket porting on these heads they where going on a engine with a BM 250 blower, so nothing was done to the intake runners at all because we were only trying to make 600HP and didnt feel the need to do a bunch of intake port work with the forced induction. Even the casting flash is still on the port walls. We ended up using anouther set of heads on the blower motor, so now these heads are being finished up to go on a 505, so the intake runners will get some work and with a little more porting I plan to get a little over 300cfm out of the 781s.
The last set of heads on the list is the old 074 L88 GM aluminum square port heads used in the late 60s and early 70s. They have very light pocket blending but really nothing that would amount to much.
I'm trying to decide between the 074s and the 781s for the 505. I have two hydraulic roller cams(one .577 the other .632)and one of the cams will get used in the motor also. I feel the 781s will make more average power, but I like the weight savings of the aluminum and I like the idea of the vintage heads on my 68 camaro and with my 4.56 gears I dont think I'll miss the low end pull of the ovals too much??
There was debate a few days ago about the flow numbers on the Pro Lighting heads, so while I was getting my 781s flowed I had them check a Pro 220cc that I had setting around just to see for myself. Checked at 28" of water
Pro specs-----our test------781 oval---074 sq bbc
.100---70.7-----58.9----------64.1--------64.4
.200---146.4----118.9---------141.9-------145.2
.300---204.6----174.6---------211---------219.2
.400---249.8----219.1---------265.7-------261.6
.500---264.6----256.1---------284.2-------280.2
.600---272.2----274.6---------289.3-------295.3
.650---N/A------288.3---------288.9-------306.8
.700---282.1-----N/A-----------N/A---------N/A
The Pro head was stock out of the box 220cc with a prepped set of valves, while the low lift numbers were down some, the high lift numbers we got out preformed the advertized numbers.
Of course flow benchs will vary from one to the next, but it gives some degree of comparison.
The 781 bbc heads have new 2.19/1.88 valves and some bowl blending and short side rounding. When I was doing the pocket porting on these heads they where going on a engine with a BM 250 blower, so nothing was done to the intake runners at all because we were only trying to make 600HP and didnt feel the need to do a bunch of intake port work with the forced induction. Even the casting flash is still on the port walls. We ended up using anouther set of heads on the blower motor, so now these heads are being finished up to go on a 505, so the intake runners will get some work and with a little more porting I plan to get a little over 300cfm out of the 781s.
The last set of heads on the list is the old 074 L88 GM aluminum square port heads used in the late 60s and early 70s. They have very light pocket blending but really nothing that would amount to much.
I'm trying to decide between the 074s and the 781s for the 505. I have two hydraulic roller cams(one .577 the other .632)and one of the cams will get used in the motor also. I feel the 781s will make more average power, but I like the weight savings of the aluminum and I like the idea of the vintage heads on my 68 camaro and with my 4.56 gears I dont think I'll miss the low end pull of the ovals too much??