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This is a set of SpeedMaster? LS7 style heads that are sold under a few different names. They are more of a hybrid because they fit LS3 size bore and use LS3 size intake valves 2.165 vs 2.20. They are 15* not 12, have smaller higher ports of the LS7, 6 bolt, the castings look pretty good and with some extensive work (about 40hrs) can make some impressive numbers. I know CFM is not the end all deciding factor but it’s a metric we all use to judge a cylinder head’s contribution to a build. This head(s) were flowed on a SuperFlow 600, 2.165 intakes and 1.60 exh. No test pipe on the exhaust. The exhaust was very Ho Hum although they look like they should flow a bunch more than they did, a ported LS3 exhaust port was equal to it.
Thanks again for posting, however why does the intake port reverse flow after .700 lift?
I'm surprised at the losses here.
Exhaust flow is meh just like the LS3 head you posted.
interesting how far the flow falls off at .750 lift. When you look in the ports, do you see any easy touches that could be done?
if you look at the flow pattern as it ramps up, it's not super linear. The increases from .500-.600 and .600-.700 show that. Still solid flow from a 2.165 valve, but if you compare to something like WE TODD DID's Liberty LS3 heads, I wouldn't even waste my time on these given the amount of effort put into them. Also, note that these we flowed on a 4.155 bore, whic certainly affects them to positive side of actual flow. On a 4.00ish bore, it would probably be 20cfm+ish less. One thing I have seen is the heads that have linear flow rates trending all the way to .800+ seem to put up the killer #'s vs heads that fall off sharply at a certain point.
Thanks to 64post for the write-up and the effort. This would all be guesswork if other didn't put the time into testing.
It would be interesting to see the cc runner size on the intake but also the exhaust. The stock intake is like 270 cc and exhaust is like 86cc or so. Good intake flow numbers.
It shows the ports go sonic (speed of sound) at around .750 and stall. Adding volume in a case like this (even 3 to 5 cc’s off of the roof of the port) would slow the air down, therefore helping airflow numbers to increase. Once the port goes sonic, the only way to increase flow is add volume or put pressure behind it (boost). Seems counter productive to make the port bigger. There’s a fine line between cfm and size (cc’s).
interesting how far the flow falls off at .750 lift. When you look in the ports, do you see any easy touches that could be done?
More valve guide size reduction possibly. Who is going to ever suffer cyl stall with these heads? I don’t know if that could happen given that most builders would likely never run a cam that big, if you ran a cam of say, .660 lift you be fine. My point, stalling a port at .750 shouldn’t be a factor, if I think I understand what you’re saying. Some measurements to an LS3 cyl. show how much clearance it has.
It shows the ports go sonic (speed of sound) at around .750 and stall. Adding volume in a case like this (even 3 to 5 cc’s off of the roof of the port) would slow the air down, therefore helping airflow numbers to increase. Once the port goes sonic, the only way to increase flow is add volume or put pressure behind it (boost). Seems counter productive to make the port bigger. There’s a fine line between cfm and size (cc’s).
No, to slowing the air down, ever. Would you suggest this so it would show a bigger peak number at the cost of reducing the mid lift numbers? That sounds counter productive. Can you work with a set of heads that reach 380 CFM with a .700 lift cam?
It would be interesting to see the cc runner size on the intake but also the exhaust. The stock intake is like 270 cc and exhaust is like 86cc or so. Good intake flow numbers.
I will get a cc measurement and post it. It appears smaller than an LS3 intake port.
if you look at the flow pattern as it ramps up, it's not super linear. The increases from .500-.600 and .600-.700 show that. Still solid flow from a 2.165 valve, but if you compare to something like WE TODD DID's Liberty LS3 heads, I wouldn't even waste my time on these given the amount of effort put into them. Also, note that these we flowed on a 4.155 bore, whic certainly affects them to positive side of actual flow. On a 4.00ish bore, it would probably be 20cfm+ish less. One thing I have seen is the heads that have linear flow rates trending all the way to .800+ seem to put up the killer #'s vs heads that fall off sharply at a certain point.
Thanks to 64post for the write-up and the effort. This would all be guesswork if other didn't put the time into testing.
Of course Dave, they couldn’t possibly be of any value to anybody using an .800 lift cam.
i doubt they fixed the major flaws of that set heads used in the vid. I would never recommend using them as cast but if you’re a diy type and have a bunch of time on your hands you could make a decent set of heads out of them, just sayin.
06-25-2020, 08:39 AM
Offshore inexpensive LS7 heads flow 388 cfm 
