I had my A460 heads checked by a local chevy guy. He said they flowed a TON of air. But the numbers on the sheet were only like 285 max on the intake! the flowbench is a Superflow 110. He said it is tested at a lower pressure. Whats up with that?
Scoring disabled. You must be logged in to score posts.
is like bringing a Cub Scout to a heavyweight boxing match. It won't flow the big cfm heads at 28" H2O. So he flowed them at a smaller number of inches of water, I would guess either 7" or 10". He should have written down on the sheet of paper what pressure drop he was flowing at. If you see a number, such as 7" of H2O or whatever, give me that number and I will give you the conversion factor in order to convert those numbers to our commonly quoted 28" H2O.
Hope this helps,
Charlie
Scoring disabled. You must be logged in to score posts.
Charile it says 10 and he only tested the intake to .690 lift 282 cfm and exhaust to .560 lift 235 cfm I guess his bench cant hang . The guy mainly uses it to flow carbs.
Scoring disabled. You must be logged in to score posts.
that's the conversion factor for changing 10" cfm numbers to 28" cfm numbers.
For example; 282 X 1.67 = 470.94 cfm
Now then, those are fabulous flow numbers for an A-460 head. Almost too good. Unless your heads have been done by a really top name shop and have 52* seat angles, I seriously doubt that they will actually flow that. SuperFlow says it's a valid thing to do, (convert cfm numbers), but my point is that the air is moving slowly in terms of ft. per sec., at only 10" of pressure drop and if the intake port is going to act ugly, and stall, it hasn't got enough velocity to act up at 10" of H2O.
It's been my experience that you really need to flow test at the bigger pressure drops, (i.e. 28" H2O ) in order for the velocity in the runners to be fast enough, for the air to tend to leave the short side radius and collide with the roof air and then the port will stall, act up or get ugly. Whatever you want to call it.
Bottom line is, I think you have a set of very good heads. But,,,,, IMO testing them on a little flow bench, doesn't guarantee that they will flow those same cfm numbers when actually tested at the higher velocities that you have when you flow at the bigger pressure drops, such as 28" H2O.
Hope this helps,
Charlie
P.S. If he is testing carbs, then he's only testing motorcycle carbs or he's testing one barrel of a 4 brl. carb at a time and then adding them all together. His bench isn't big enough to test a 4 brl carb at 20.4" H2O(1.5" Hg), which is what 4 brl. carbs are rated at.
Scoring disabled. You must be logged in to score posts.
I do not believe that flowing the heads at a lower depression(within reason) will produce out of whack numbers. Incorrect calculations certainly will. When we took Wes Littrel's A-460 heads down to Charlie's place and compared his numbers with the ones from my Superflow 110 they agreed nearly EXACTLY on the exhaust and mine were more conservative on the intake side at high lift. I feel that the difference was strictly because of the bore adapter I used(4.250 with the head "fudged around" on there). I would bet if I had a 4.600 bore diameter to test with the numbers would have been very very close. On my bench when I flow test I use the FlowCom for sensing pressures and tempertures and then I use a computer to collect and correct the data.
The real advantage of a larger bench is that it has higher resolution when flow testing large pieces. The Superflow 110 will only detect changes of about 1% whereas the larger Superflow 600 etc will detect much smaller changes .5 or even .1%. That's it's advantage.
It's also important to remember that flow benches were never intended to produce numbers that were identical from bench to bench. What they were designed to do was show if you're gaining or losing flow. If you gain 5% on a Superflow 110 you will also gain 5% on a Superflow 600 given the same testing proceedures. Are the numbers the same? Not necessarily, they will be close but the percentages certainly will be...
Scoring disabled. You must be logged in to score posts.
that Dave McLain and I are having a "battle" over flowbench capabiltities. We just have a slightly different opinion on this conversion factor issue and yes, I respect his beliefs. I think we can learn from each other if we openingly share knowledge. What he stated about Wes's TFS A-460 heads on his bench verses mine is correct.
However, the new style TFS A-460 heads have a very good short side radius and are designed very well out of the box. I still wonder if we tested a poor or bad set of heads, where the bowl volume and short side radius was screwed up, if "intake port stall" would not show up on a low velocity bench, but would show up on a high velocity bench?
Charlie
Scoring disabled. You must be logged in to score posts.
I really think you would find that the port would react the same on either bench. One testing at 10 inches and the other at 28 inches. Both of those depressions are great enough to avoid slow laminar flow yet neither one is high enough to cause significant changes in the flow patterns which just don't change much until at or near super sonic velocities (same as with areodynamics).
Again, I believe that a larger flow bench certainly has advantages over a smaller bench because it's resolution is higher, MUCH higher on a large cylinder head. I believe that a Superflow 110 is at or somewhat above it's limits with an A-460 or similar head just as is stated in it's literature, good for engines making about 100 horsepower per cylinder or less. This does not mean that it can't produce accurate numbers it's just that the resolution is no longer high enough to show small changes and do serious port development work. For someone like me it's probably ok because I'm still looking for those 3%-5% changes.
Good stuff for discussion...
Scoring disabled. You must be logged in to score posts.
A Superflow 110 is not a junk bench. Jerry has a 110 and has had better heads than your on it. The bottom line is I doubt he could pull 10" at .690" lift on that bench with that intake port. That head is just too big for that bench. Jerry only uses that bench to get a feel for certain things on big heads with that bench as normally you end up at a pretty low 7" or below.
Regardless, in the hands of someone who knows what he is doing you can get some good information - provided you know what to look for...
-Steve
Scoring disabled. You must be logged in to score posts.
Bret, Gary Blair looked them over and said they looked pretty good. I will get a seckond flow done. Ill let you know but will probably go local if i can. Thanks
Scoring disabled. You must be logged in to score posts.
28 inches of mercury would be a lot of depression, that's 379 inches of water! After thinking about your flow number problems I think what must have happened was that they started out flowing the head at 10 inches and then dropped down to 7 or so at high lift. This is ok as long as they didn't use the same factor to correct all of the numbers that would put you way out of line from where you really are. If you don't know the depression used at each lift point that could make it hard to figure out too.
Scoring disabled. You must be logged in to score posts.
Probally what happened was that the guy started flow testing the heads at 10" H2O and then about halfway through had to cut back to 7" or even 5" H2O in order to finish flow testing them.
So,,,,the conversion factor for 10" to 28" I already gave as being; X 1.67
The conversion factor for 7" to 28" is; X 2.00
The conversion factor for 5" to 28" is; X 2.37
Again my advice is check your paperwork that he gave you. If you don't understand the data that he gave you, then you have every RIGHT to CALL him and ask for an explaination. If you paid for a service and his answer/flow data is not explained to you, then he needs to clarify what he has written down on that flow sheet. In other words he needs to speak to you in "laymens terms". You do not need to be "guessing" about what your heads flow.
Hope this helps,
Charlie
Scoring disabled. You must be logged in to score posts.