AIR FLOW

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Tom Osborne
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Re: AIR FLOW

Post by Tom Osborne » 07 Feb 2020, 12:18

Mike, sorry for spelling error. I disagree on LSA. It does not matter on cylinder size. The fact is the hotter the lope in idle, the dirtier the motor will run. A dirty running motor loads up and you know why engines need a good clean out with a high RPM cycle. It's not to impress the girls. Dirty running motors mess up air flow. Race fuels help somewhat. Camshaft design can remove some of the overlap. Tom O.
"First by far with a post war car"
TOM-O-HAWK STREET/STRIP Project

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Jeff Rice
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Re: AIR FLOW

Post by Jeff Rice » 08 Feb 2020, 08:12

Here is an interesting article to read, Tom.
You can now buy a new steel blank camshaft, and have it machined/ground to your spec by Comp Cams and heat treated/Nitrided/Parkerized. Getting the metallurgy right, the grind angle for lifter rotation correct, and using the right lifter material for the cam lobe surface is key (flat tappet cams).


https://www.hotrod.com/articles/flat-tappet-cam-tech/

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Tom Osborne
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Re: AIR FLOW

Post by Tom Osborne » 11 Feb 2020, 13:32

Thanks for all this. Vital stuff to know. Being retired 4 years has put me out of the know. So it's good news that at least a billet cam is now available. We have some ideas on grinds that should work nicely. Flow rates seem to like .525- .550" lift so building a solid roller cam is obviously a better way to go. Still keeping overlap signature as short as possible. Thanks a bunch Jeff.
"First by far with a post war car"
TOM-O-HAWK STREET/STRIP Project

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Tom Osborne
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Re: AIR FLOW

Post by Tom Osborne » 18 Aug 2020, 23:42

What are the latest greatest air flow bench results made on the iron stude heads. Any takers?
"First by far with a post war car"
TOM-O-HAWK STREET/STRIP Project

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Mike Van Veghten
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Re: AIR FLOW

Post by Mike Van Veghten » 19 Aug 2020, 01:10

Tom Osborne wrote:
07 Feb 2020, 12:18
Mike, sorry for spelling error. I disagree on LSA. It does not matter on cylinder size. The fact is the hotter the lope in idle, the dirtier the motor will run. A dirty running motor loads up and you know why engines need a good clean out with a high RPM cycle. It's not to impress the girls. Dirty running motors mess up air flow. Race fuels help somewhat. Camshaft design can remove some of the overlap. Tom O.
Wow, this has been around a while..!

Tom (if you're still around), you have the right to disagree, but I've seen the differences...first hand, as tested on the drag strip. Same car, same day, with a VERY well tested and repeatable car combination.
The story is on this web site somewhere. And I had a hand in the changes to the engine in question.

While you are correct...at..."low rpm". BUT, things begin to change drastically as the rpm increases.
Same car, same summer day, cam change only. The two cams in test were EXACTLY...EXACTLY...the same except for the intake - exhaust overlap. And just by a coupla degrees were they different. 106 to a 103 or 104 as I recall.
The power was so different...that we had to borrow and install a larger tire for the back to hold the additional power..! Remember...NO...other change. No carburetor change, no ignition timing change, no scoop change, and probably no more than one or two degrees change in ambient temperature.
Again, this was done on a well sorted, highly repeatable, NHRA legal C/ED (311" Chevy).

Now for the odd thing, I don't recall the exact numbers any longer...But the car ran a "little" (better 60' than the other cam) quicker, even though it got to the redline (8500) faster and ran out of valve spring before the end of the track, the mile an hour actually dropped by two or three. As noted, we figured that was because of the valve springs were "well" used..!

And I'm not the only one that's done this test. There are MANY small engined cars with tight lobe centers. As a matter of fact, someone a few years back did a lot of dyno work on different lobe center cams. Interestingly enough, they came to the same conclusion...they we did..!

Mike

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Mike Van Veghten
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Re: AIR FLOW

Post by Mike Van Veghten » 19 Aug 2020, 01:23

Tom Osborne wrote:
18 Aug 2020, 23:42
What are the latest greatest air flow bench results made on the iron stude heads. Any takers?
This is noted on the web site here somewhere -

In my MANY changes to port shapes, valve stem sizes, valve head shapes, seat configurations, my ports stop at 213cfm . This is on a Superflow 600, at a highly regarded shop in SoCal, that has all (engine dyno's [2], chassis dyno, flow bench) their equipment verified/certified every year.

Anyway, just a few months back, I did find a large increase in flow at the .300" to .450" lift range. And repeatable. We tested it three times.
At first I was looking forward to great things at the max. lift area, and a bit pissed when we didn't get there. But after getting home and looking at old flow sheets, I was encouraged even more by the mid-lift numbers.
Afterall, the the engine is only at full rpm, "one" time, for a split second in every cycle. But the engine cycles through mid-lift, slower and two...times in every engine cycle than it does at max. rpm.

So...yea, I'm happy with the find.

Mike

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Jeff Rice
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Re: AIR FLOW

Post by Jeff Rice » 19 Aug 2020, 07:24

That is a good point, Mike.
Max flow numbers at .600" lift might look good, but do they help the overall run envelope?
Maybe, maybe not.

To give Tom an idea of a number..
There are a couple of head porters that have coaxed a Stude V8 (R1/2 port configuration) in the low to mid 220's.

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Mike Van Veghten
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Re: AIR FLOW

Post by Mike Van Veghten » 19 Aug 2020, 10:24

Thanks Jeff.
Not concerned, one flow bench is different than another.

I know that I can also get the port to flow more than the 1.875"/1.90" valve can handle too. Has anyone else done that ? One simple change. With a larger valve, lookout, well over what is the current norm..! BUT...the bore's not large enough...so it means nothing.
I'm not going to feel bad about something that, as tested on one bench...will be the same as what can be flowed on another's bench.

Mike

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