200 CFM Research

[larrycavan]

I looked for the old post with your track data but couldn't find it. How much did you pick up this time?

Larry C

[200cfm]

The comparison data to last year is close. No drastic swings. But I had a lot more test runs with the 1.870 valve heads vs. the three test runs made this past Saturday with the 1.780 intake heads.

Best of 11 runs late fall testing was:

1.615 4.493 6.948 @ 99.26 9.101 10.966@ 118.90

Best of three this year so far is :

1.528 4.471 6.974 @ 97.41 9.165 11.043@ 119.47

The weather temps were about the same too but this past Saturday had high head winds (20 +) and the drag was holding it back beyond the 330 point. I am surprised the speed was this high on the top end. I did put more jet fueling in th carb though on this run. Jetting was two steps up over last fall and the engine plugs still showed clean gray burn. Hope to go back again in two weeks to get more comparison. And by then I should also have all the flow/speed data on the fall heads. This winters port experiment and current comparison tests have given me confidence on how to approach a future set of head work. Now I have a compass.

[larrycavan]

[200cfm]

Ok, will do. Late this evening I pulled some plug checks and number 1 was oil wet. Others all dry. Pulled the intake manifold (old iron 180) and all the head ports were dry. No wetness at all on any port runner. Shinned the light down inside each of them and all the valve stems and valves also were dry. And ports were very clean. No signs of any reversion soot. As clean and dry as I put them on a few days ago. This was a surprise because nomally on the other head the port would be wet, especially after a cold start. It's the first time I have ever seen my ports so dry. And this is after I have off loaded from the trailer too. Not after a WOT run. So I got to think, ok this is good. No fuel separation at all. At least that is the way I am interpretting this. Number 1 intake also is dry so I am hoping the exhaust guide is source of the oil and not a ring issue. I am not getting any blue smoke, not even on start up so it must not be a sever problem. Will have to pull the head to find out. I notice also some oil weep at the number 1 exhaust port to manifold gasket joint so I believe it coming from the exhaust guide. I can see wetness on the piston top too. Always something.

One final point. I put some filler in certain places and the filler held fine. Some was applied in the bowl area itself to deal with some irregularites and offer blending. Even that area was fine. No fuel errosion or burns or peeling off, etc. Just like new. If I had a close up camera I could explain this better.

[larrycavan]

[maxracesoftware]

[200cfm]

Thanks Larry, that is an amazing program. And yes, last year the motor was up against the rev limiter on that run and a few others before learning that the 6000 pill was holding back on the top end charge. Moved it to a 6400 pill and that solved the problem. And I moved the stall pill from 3000 to 3400 which helped too. I am still learning how to drive this car. And making improvements as the budget and time allow. I replaced the dual battery system this winter with a single 16 volt battery and very pleased with that upgrade. And down the road I have plans for intercooling and perhaps a larger turbo. The current Rajay is pushing 12-13 lbs boost. When I first picked up this machine last summer I had some race friends tell me the motor would never turn over the 32X14X15 tires with a powerglide trans. The rear had 33X16X15's when I picked it up and because of the rim size the 32's was the lowest I could go. This car had a blown alcohol 434 with Lenco back in the 90's. It has a wing but I haven't tested with it yet. Hoping to get it scaled and adjusted this spring since the stude motor is so heavy and I am sure the balance is not fully optimized yet. That might be why it slips sometimes off the line.

[200cfm]

Got back on my bench yesterday for the first time since February. Started planning and testing on a third set of heads. These heads are currently set up with 1.850 intake and 1.600 exhaust. The intake has a three angle vj. For a base line it flowed. ( port #8):

.400 / 156.5
.450 / 163.7
.500 / 168.8
.550 / 169.9
.600 / 170.5
.650 / 170.5
.700 / 171.8

speed at the SSR @ 335 fps
along the roof of the SSR @ 330 fps

at the PRt

350 / 350 / 360+
335 / 340 / 365
320 / 330 /360

speeds are from .450 lift reference at 12" wc test with correction factors for 28" wc.
Made a size measurement at the port entrance .970 X 1.505
and at the PRt .970 X 1.545 (no corner radi included), simple width vs height using snap gauges.
Using the formulas I got a .428 discharge coefficient for the .450 lift.
I opened the entrance to 1.000 X 1.525 and the PRt wall to 1.000. Made a reflow test:

.100 / 69.7
.200 / 105.7
.300 / 133.4
.400 /159
.450 / 167.9
.500 / 173.4
.550 / 174.2
.600 / 173

Modest gain but seems to be stalling after .500 lift.

PRt came in at:

332 / 359 /356
310 / 350 / 370
313 / 335 / 370

Air has slowed some on the left wall but picked up on the wall that turned. Is this because of the gain of the cfm? Or perhaps my depth reference point is off some. I probe for the peak on the sections, then record.

Now my question is on the size of the valve throat. Where should it be sized?. I read: set for 80% of valve dia. area. set for 88% of intake dia. set for 300 fps + throat velocity, etc. What about the valve stem. It is .303 diameter. Do I factor in the stem area?

I bought a new close up digital camera and would like to test it for CSA measurements using the photo calcuator CSA download. Does anyone have that download link? Thanks.

[106-1194218389]

The increae if cfm will make the velocity get higher if you did not make the area at the pushrod any bigger. That is the area Larry Meaux told me to work on. I have made my port as big as I could at the pushrod. That has helped my velocities. Look in the thread I had going on port velocities.

John

[larrycavan]

Different schools of thought can apply here. One school can say....OK, crank that throat out to 90% and be done with it. Might even work good and make more power. Then there's another school of thought. Sneak up on the throat size by checking your CFM gaines as you go...

I use 88 - 90%, depending on the application. IMO it's a balancing act and there is NO one correct way that applies to all motor combos. We all know how one thing affects several more things.....

Just because that hole gets made bigger doesn't translate to an automatic gain in CFM. Safe bet is to size to 85% and measure the CFM & FPS, then sneak up on 88% and measure CFM and FPS again. If you didn't gain any CFM, you should investigate the situation. That should tell you there's something left behind in the rest of the porting. The throat's not "yet" the restriction. Measurement wise it might be but shape wise, something else is holding back the flow. Been there, done that.....been puzzled...frustrated and went home that evening wondering and woke up the next morning ...still wondering....anxious to get my hands on my grinder.

JMO

Larry C

[200cfm]

Made some gains today on port #8. Opened the entrance walls back to the PRt from 1.000" to 1.020." Roof to floor smoothed.

.200 /106.8 1.1 gain
.300 / 136 2.6 gain
.400 / 162.4 3.4 gain
.450 / 170.6 3.1 gain
.500 / 176.2 2.8 gain
.550 / 176.5 2.3 gain
.600 / 176 3.0 gain
.650 / 176.5
.700 / 177.1

still seemed to be stalling beyond .500 lifts though.

Speed check came in at:

PRt .450" @ 87% 350 / 356 /359
310 / 335 / 356
310 / 323 / 353

Nice reduction in fps from laying back the turn.

SSR apex came in about the same at 326 fps but on one end of the bowl it was hitting 350 or the test pressure.

Pleased with the gains but concerned about the stalling from .500 up so decided to fill and smooth the floor where there was a dip and to open the walls to 1.045" This helped the top end..

.300 / 136.5 gain .5
.400 / 164.1 gain 1.7
.450 / 170.5 loss .1
.500 / 174.2 loss .2
.550 / 176.2 loss.4

appears the stall moved down some, then

.600 / 177.2 gain 1.7
.650 / 178.4 gain 1.8
.700 / 179.4 gain 2.2

appears the backup ended and it showed gains again. For the first time the tests were maxing out my largest plate for a 100% incline rise. I was happy to peg the slope!

Air speed check looked better too.

332 / 344 / 335
323 / 332 / 350
303 / 326 / 365 ?

SSR apex came in @ 323 fps, roof around 320 and side to side 326/320.

The discharge coeficient now is calculating to .447, a gain of 1.9%

Still falling short of 200 cfm though. Looks like a 3 angle valve job doesn't help much over the standard 45 degree on these heads. Would a back cut on the valve help? Are the airspeeds still to fast? Measured the throat and it is oval. Around 1.540 X 1.600. Should I try an enlargement?

[106-1194218389]

[color=#000000]On my Dart heads I had massive turbulance at .550 lift. I was using Milodon Megaflow valves. I faced until I only had a .025" margin and then back cut 35

[200cfm]

Big upset here. I opened the PRt to much and went through the wall passage. Didn't realize the grinding was on the border. Pushrod channel passage is around 9/16 diameter. Haven't found a sleeve to fit yet. Made a temporary fill with JB and it is holding but ??? If I had only stopped one minute short on the filing.

Read the velocity topic. That is an excellent discussion and it helped my understanding.

[106-1194218389]

can you possibly put some copper tubing in there with JB Weld and then when you hit copper you know you have gone far enough - we put window screen in there once with JB Weld and never had problems and we had completely removed the PR side

John

[200cfm]

Great minds think alike. Fixed it today after pondering it in my sleep. Found a scrap piece of 5/8 cooper tubing thin wall. Cut it to length and removed a slice from the length to shrink the diameter. Put a slight taper on one end to aid the entrance. Squizzed it down to start the entry into the pushrod hole and tapped it in. It closed down to a nice crush fit. Eureka! Sanded down the JB Weld on the ruptured wall and looks / feels good to go. If the speeds are still high there I will look into raising the roof some.

Got a question. I am trying to understand the purpose / function of the bowl. Would it be correct to think of it as a plenum in the sense of a pressure chamber? In the cylinder there is vacumn or depression (like 28" wc when reference to the port entrance ( 1 atmos). The throat is sitting there as the last passage or obstacle to the cylinder. What would be the ideal pressure in the bowl? For it to be pressure in reference to the cylinder bore it would have to be less than 28" wc, like say 25 or 23, etc. Is the goal then to get low wc readings in the bowl when using the pitot or high readings?

I was noticing that certain areas of the bowl are exhibiting low vs high pressures depending on where you sniff with the pitot.

John, does your port near the guide and bowl areas have a single channel or dual channels around the guide bulge. This port has one deep channel that cuts down and beside the guide and then tapers into the bowl. One single big channel. I was thinking of adding a second channel that would run parallel to the adjacent channel. As it now exists, the airspeeds are lower in the channel than they are in the areas where no channel exists. And obviously the pitot wc pressures are different too. When I put a string down the port there is vortex spinning and it pulls or flows toward the high speed area which lacks a channel. If you can review the molds on a stock port you can see the areas I am addressing. It appears the designer of this head was setting the air up for a swirl across the back of the valve. Is one channel a good or bad design? thanks.