MELWAY wrote: ↑Sat Jan 07, 2023 10:19 pm
I’m going to dyno a 400 chev next week. I always cut the top of runners back and grind out the bumps
These combos make about 625hp on pump gas
I might start with a stock 2925 and baseline dyno engine
Then remove intake and do plenum mods and dyno test on same day..
Yep, do that!
Like you I always default to taking out the lumps & raising the runner entries.
Would be quite enlightening to see what, if anything, the gains are.
Hell, if it makes no difference that's a couple less hours of my life wasted per manifold!
MELWAY did the test above as described. Super Vic 16hp down otb (his mods added 16hp).
Sharpie/paint pen test was also done and WOT dyno run cleaned all markings off the plenum top to bottom unlike the low speed test I had done that kept paint pen and sharpie markings higher in the plenum intact.
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
Wetflow wrote: ↑Fri Jan 06, 2023 12:33 pm
Cool experiment.
This has me thinking about what could be done with one of the bore scopes that you can get for very little $$ from the "Prime" store. Some are lighted on the end and have surprisingly good resolution. Many of them plug right into a cellphone. Also, a piece of string tied to the end would show what's going on and where.
Advertisements for those kept popping up in my Facebook feed. Ended up getting a three for $100 deal (I actually received four!). After poking one down a spark plug hole I’m now building a whole new engine! I seen that with my sbc Twisted wedge heads and intake having no valve relief in the piston, the piston was just kissing the piston. Time to get serious and get some pistons flycut to suit and install a more serious street/strip SR cam. Old sixty thou over factory block certainly not worth re-using.
Cheap borescope used with a phone app is of reasonably good resolution. Just be careful where you start poking about with them in your engine, you might learn something unexpected!
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
good stuff, interesting how the low rpm street driving test that started this thread cleaned the floor of the intake... makes me think floor texture in the plenum is probably a bigger deal than a lot of people think. Many OEM manifolds have ribs cast in them, some porters are taking a large drill bit to the floor area and there's also the burr finish deal. Get the fuel back into the air
I like to burr finish all the plenum floors on my intakes these days. Now instead of a burr to ruff it up as that area is hard to do I found me a better way that's much easier. I bought a cheap HF needle scaler and took all the the needles out and then sharpened them to a point, I put it back together and let the scaler do it's thing with air on the port floor. Worked out pretty well on my Vic.Jr. Also I have run 2 S/V in the past year with great results after porting the plenum, the 3 I have now are and older 2925 that is plenum ported (not tested yet) a Vortec S/V that really blew me away after how well it worked on my Vortec 406 a few years ago and my brand new 2925 S/V that's the new style the just needs to have the port roof opened up to a 1206 gasket to match my AFR heads. The new one looks very promising for an out of the box manifold.
1980RS wrote: ↑Tue Aug 15, 2023 11:34 pm
I like to burr finish all the plenum floors on my intakes these days. Now instead of a burr to ruff it up as that area is hard to do I found me a better way that's much easier. I bought a cheap HF needle scaler and took all the the needles out and then sharpened them to a point, I put it back together and let the scaler do it's thing with air on the port floor. Worked out pretty well on my Vic.Jr. Also I have run 2 S/V in the past year with great results after porting the plenum, the 3 I have now are and older 2925 that is plenum ported (not tested yet) a Vortec S/V that really blew me away after how well it worked on my Vortec 406 a few years ago and my brand new 2925 S/V that's the new style the just needs to have the port roof opened up to a 1206 gasket to match my AFR heads. The new one looks very promising for an out of the box manifold.
Needle scaler, just what I was thinking too for the new SV going on new 401 sbc. I am also thinking of creating a small step across the floor (wall base to wall base) at the entrance to each runner by grinding a vee tilted backward so fuel pulled along the floor has to trip up the little step and hopefully re-enter the airstream and atomize.
Does the Vortec SV have a different plenum arrangement to std 2925?
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
Bob Hollinshead wrote: ↑Tue Aug 15, 2023 7:24 pm
good stuff, interesting how the low rpm street driving test that started this thread cleaned the floor of the intake... makes me think floor texture in the plenum is probably a bigger deal than a lot of people think. Many OEM manifolds have ribs cast in them, some porters are taking a large drill bit to the floor area and there's also the burr finish deal. Get the fuel back into the air
Not sure if counter intuitive is the correct term or not but conventional wisdom says at WOT fuel is rushing in so fast that wet fuel hits the floor more than at other operating conditions. That may be happening at WOT to a degree but the paint marker WOT dyno test showed the fuel is making the sharper turn - as in from carb base plate or carb spacer wall - into the roof of the runners far better than at low throttle position and rpm. First thought is that at low speed the atomized fuel with less momentum will navigate the turns easier. Thinking a little deeper though the atomized fuel at lower speed/throttle opening would be chaotic enough in the plenum to be a greater influence on its direction and movement than an individual runner instantaneously. The atomized fuel can't stay suspended forever and gravity takes over if a runner does not. The low speed test I was doing would have been mostly on the transition circuit so high vacuum. Wide open throttle would have almost 14.7psi trying to shove the atomized fuel to the piston via the shortest path possible and the piston depression now has a greater influence that plenum chaos. Kasse video shows fuel pushing up against the walls. Typical single plane single carb manifolds don't have such walls as those plexiglass ones but it still brings into question should the walls be conditioned on a single plane too? I'll be looking at a strategy to address low speed fuel on the plenum floor and possibly something on the runner roof entry for WOT. Fuel may well be smacking into the roof radius region and de-atomizing at WOT.
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
1980RS wrote: ↑Tue Aug 15, 2023 11:34 pm
I like to burr finish all the plenum floors on my intakes these days. Now instead of a burr to ruff it up as that area is hard to do I found me a better way that's much easier. I bought a cheap HF needle scaler and took all the the needles out and then sharpened them to a point, I put it back together and let the scaler do it's thing with air on the port floor. Worked out pretty well on my Vic.Jr. Also I have run 2 S/V in the past year with great results after porting the plenum, the 3 I have now are and older 2925 that is plenum ported (not tested yet) a Vortec S/V that really blew me away after how well it worked on my Vortec 406 a few years ago and my brand new 2925 S/V that's the new style the just needs to have the port roof opened up to a 1206 gasket to match my AFR heads. The new one looks very promising for an out of the box manifold.
Needle scaler, just what I was thinking too for the new SV going on new 401 sbc. I am also thinking of creating a small step across the floor (wall base to wall base) at the entrance to each runner by grinding a vee tilted backward so fuel pulled along the floor has to trip up the little step and hopefully re-enter the airstream and atomize.
Does the Vortec SV have a different plenum arrangement to std 2925?
My 1st.out of the box 2925 plenum was about the same as the Vortec S/V. The newer 2925 is really nice and looks to be more ported out of the box then the original design with the thinner runner dividers. All I know was after I plenum ported the very 1st S/V I did back in 2014, we went to the track and was very disappointed with the performance after porting it, until my Son came over and said "Dad that car sure spins the tires out of the hole" so I guess I needed new tires at that point with it, lol. Had to pull timing to get the car to hook and like an idiot sold that intake to a buddy and of course his car picked up a ton with my S/V. Now I have 3 to test whenever I need to do so. The S/V's are a great intake IMO.
1980RS wrote: ↑Wed Aug 16, 2023 1:54 pm
All I know was after I plenum ported the very 1st S/V I did back in 2014, we went to the track and was very disappointed with the performance after porting it, until my Son came over and said "Dad that car sure spins the tires out of the hole" so I guess I needed new tires at that point with it, lol. Had to pull timing to get the car to hook and like an idiot sold that intake to a buddy and of course his car picked up a ton with my S/V. Now I have 3 to test whenever I need to do so. The S/V's are a great intake IMO.
Do you recall what plenum porting you done? Roof?, dividers?, floor?, csa?
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
1980RS wrote: ↑Wed Aug 16, 2023 1:54 pm
All I know was after I plenum ported the very 1st S/V I did back in 2014, we went to the track and was very disappointed with the performance after porting it, until my Son came over and said "Dad that car sure spins the tires out of the hole" so I guess I needed new tires at that point with it, lol. Had to pull timing to get the car to hook and like an idiot sold that intake to a buddy and of course his car picked up a ton with my S/V. Now I have 3 to test whenever I need to do so. The S/V's are a great intake IMO.
Do you recall what plenum porting you done? Roof?, dividers?, floor?, csa?
I just did the port roof, some on the dividers and port match to a 1206 gasket for my 215 Dart heads.
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Bob Hollinshead wrote: ↑Tue Aug 15, 2023 7:24 pm
good stuff, interesting how the low rpm street driving test that started this thread cleaned the floor of the intake... makes me think floor texture in the plenum is probably a bigger deal than a lot of people think. Many OEM manifolds have ribs cast in them, some porters are taking a large drill bit to the floor area and there's also the burr finish deal. Get the fuel back into the air
Not sure if counter intuitive is the correct term or not but conventional wisdom says at WOT fuel is rushing in so fast that wet fuel hits the floor more than at other operating conditions. That may be happening at WOT to a degree but the paint marker WOT dyno test showed the fuel is making the sharper turn - as in from carb base plate or carb spacer wall - into the roof of the runners far better than at low throttle position and rpm. First thought is that at low speed the atomized fuel with less momentum will navigate the turns easier. Thinking a little deeper though the atomized fuel at lower speed/throttle opening would be chaotic enough in the plenum to be a greater influence on its direction and movement than an individual runner instantaneously. The atomized fuel can't stay suspended forever and gravity takes over if a runner does not. The low speed test I was doing would have been mostly on the transition circuit so high vacuum. Wide open throttle would have almost 14.7psi trying to shove the atomized fuel to the piston via the shortest path possible and the piston depression now has a greater influence that plenum chaos. Kasse video shows fuel pushing up against the walls. Typical single plane single carb manifolds don't have such walls as those plexiglass ones but it still brings into question should the walls be conditioned on a single plane too? I'll be looking at a strategy to address low speed fuel on the plenum floor and possibly something on the runner roof entry for WOT. Fuel may well be smacking into the roof radius region and de-atomizing at WOT.
That plexiglass tunnel ram test had all smooth surfaces too
SchmidtMotorWorks wrote: ↑Thu Aug 17, 2023 2:29 am
Consider making a see through carb spacer about 3-4 tall.
I guess that you will see much more complete and valuable information.
Use an adjustable delay timing light, not a constant light.
When the new engine is eventually running I plan on machining a few holes in an open spacer directed down at runner pairs and fitting a few of these led lit cameras. One hole pointing up at the throttle plates too.
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
Geoff2 wrote: ↑Sat Jan 07, 2023 12:19 am
HQ,
Have you noticed the trend in recent years is to thin out the leading edge of the divider to almost a sharp edge, rather than have a bull nose shape.
Supersonic planes have sharp leading edges.
Normal subsonic planes have rounded leading edges.
So with a manifold divider it would depend on the velocity of the flow I suppose.
