Don Terrill’s Speed-Talk

Carnut1 wrote:

GARY C wrote:

Carnut1 wrote:20170730_201921.jpg Not a great pic but interested in feedback on this string and what it tells us. Thanks, Charlie

What did you learn from that?

I think it is interesting how the string shows where the air flows and sometimes the air turbulence. This was at .7" lift at about 217 cfm. You can see by the blurred pic that the string was moving up and down. Interested in what others think, Thanks, Charlie

I was just curious, from what I have seen with smoke and strings is that at slow air speed they are uniform and at high speed they are erratic, I have just never found any one that can tell me what in means in relation to what needs to be addressed on the head. Like wise for other apparatus like flow balls, modeling or CFD. They seem to be good to look at, it would just be nice to find someone that can actually tell you what your seeing.
I also tried an intake and head together with a carb, I used a flat spacer that only allowed air to pass through one barrel only and then I plumed in red die through the fuel jet to simulate fuel and air through an intake system, what it told me was that fuel goes every where and forms a river that snakes through the runner and over the short turn which I had already had observer by looking at the fuel stains from a dissembled engine.

A good pic of push rod wall flow. String follows the fast airflow path. Input welcome. Thanks, Charlie

Bone stock chamber before slight deshrouding.

Plunge cut deshroud. Much less than first set. Boost mostly in the middle lifts high lifts almost identical.

Your fastest air speed determined by Pitot testing is not the start of the short turn in the center ?

mag2555 wrote:Your fastest air speed determined by Pitot testing is not the start of the short turn in the center ?

Ssr center of cylinder about 400 ft/ sec is the fastest. Thanks, Charlie

I am not a cnc machine! But I try, intake port rough out. I am liking this texture. Removes iron fast but that is dangerous on 50 year old castings!

exhaust rough out

[attachment=0]0809172053.jpg[/attachment 1.85" bowl, slightly different shape than 1.94 bowl and changed the direction of the wing for a bit less swirl. I am looking for input because my competition is good! He has tubed pushrods, 8 angle vj, and milled out guide with hard bronze liner. At this rate he will pound these heads. Thanks, Charlie

Did you use the string in a burr finished port and see if it keeps the flow laminar at higher air speeds?

statsystems wrote:Did you use the string in a burr finished port and see if it keeps the flow laminar at higher air speeds?

I am just finishing the rough out on these for the ports. Chambers still need to be done. They have not seen the bench since the last bunch of string pics. Yes the string pics were all rough burr finish. Flow will never be laminar in a conventional intake port the Renolds number will exceed 2000. Is it more laminar than the smoother port? It seems so. Thanks, Charlie

With a roughed out chamber with no work on quench side ie. Frankenshaft, pulled 221 cfm at max lift with 1.85" valve. Polishing the ssr gained to 226 cfm at same lift. Still behind where I would like these. Thanks, Charlie

Charlie, I'm speaking only in regards of cfm here to keep things simple. lets say the cam lift will be .600 lift after lash and flex. The E7 has you covered by a margin all the way to .500 lift. To make matters worse that's just going up one side of the cam lobe and its going to do it to you again down the other side. So that margin in the graph between the 289 intake flow and the E7 is basically double as far as static flow is concerned. It doesn't seem possible you can make up the difference of cylinder filling from .500-.600 on the 289 port but then again maybe its gonna be higher than .600 lift. If not you need to get the low and mid lift numbers up. You have the port near maxed out it appears, now maybe just focus on angles, back cuts, top cuts, and valve shapes to get ahead. Someone mentioned the use of a very flat valve with these, I'd try it. Maybe multiple back cuts. You still have a piece of that head you chopped up that you can flow I'd try a 30 degree seat in it just to see how much high lift it trades vs mid/low lift increase. Finding this additional flow is not going to cost any port volume so it's just increased velocity, increased port energy. Just got to find the right valve and angles on that intake side. Your exhaust side looks ready to rock.

It is tough beating DV and his special valve job when it comes to low and mid lift flow. The E7's will be tough to beat no doubt. I was really hoping I could change the dynamics with a 1.85" valve and beat the first set of 289 heads but they are coming up short. Thanks, Charlie

I understand trying to beat DV and his experience is tough. But stay focused on the head, you're one maybe two moves away is all. I think you need to beg borrow or steal the most flat stem side valve you can get your hands on or cut down. I really think it's going to boost 2-400 numbers but I don't have experience with the 289 head. I've had 30 degree seats with comp radius on the serdi on other stuff but I've not experimented with multi angles there. I know 30 will knock off your high lift, the only place your currently ahead. Could you try a flat valve, flat like a WALL on stem side and check results, and try a 40 degree seat with appropriate multi angles and back cut the valve?
Also can I see the current valve?