Why would low lift head flow hurt power?

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Hysteric said:
Engine Masters 2002 winning engine

All that power with a smaller head and between 2500 and 6500 on street fuel

CHI 3V 185 Ford Cleveland

The 185cc intake ports are designed to deliver maximum power and torque for the serious street car enthusiast, whilst keeping their RPM levels down to a respectable level. By utilizing the advantage of a taller than standard 4V intake port height, and downsizing the port to a mere 185ccs, we have an intake port capable of making in excess of 550hp, with exceptional torque and power along the way, as proven in Dave Storlien’s 2002 Engine Masters Clevor, which produced the outstanding figures of 605hp and a whopping 530 ft/lb of torque, and all this from a 366ci power plant utilizing a flat tappet cam, running on pump fuel, with a 6500 rpm limit.

The 3V 185cc Cleveland cylinder heads uniquely shaped intake ports, have the smallest runner volume of any 300cfm Cleveland cylinder head available today, giving street car enthusiasts unmatched torque and horsepower levels right where they need it most. Coupled with our matching high velocity 185cc 4150 Holley intake manifolds, these heads are the ultimate choice for the serious street car enthusiast wanting the best spread of torque and horsepower from engines making up to and around 500hp from their Small Block Fords.

Why use the 3V 185 head? Even though 2V factory heads have a minimum cross section of approximately 2.0” at the pushrod area of the port (which is close to the 185ccs 1.9” minimum cross section area), the 2V heads have a much larger opening at the intake manifold face of the cylinder head (2.4”” minimum cross section).

What this means is that when manifold are made to match a 2V head they start out at 2.4” to match the intake face of the cylinder head, and taper up from there, creating a runner that is way too big for the majority of street engines. With the 3V 185cc head this is not the case, as we made the manifold suit our port size, and thus kept the velocity up high where it is most effective, by keeping the runner small. Because of this the 3V 185cc head and manifold combination has far superior torque and throttle response than any other available Cleveland cylinder head and manifold package at around the 500hp mark.
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Is there a link to the build?

I'm guessing this build is a little more than the average or even a great builder could do at 1.45 lbs-ft per cid most decent off the shelve builds are in the 1.25 to 1.35 most would need a lot more displacement to build 600hp @ 6500 rpm.
 
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273 said:
Is there a link to the build.
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Google it.

So you put a bigger valve in it and a big cam with a lot of duration (late IVC) without the necessary compression which then messes with the vacuum generated in the port and then what what does the carb see at the throttle bore and the venturi? Its all interconnected but people never spend enough time thinking about how one change effects the system as a whole.

The "bigger" the invitation for reversion the further up the intake tract it will travel further interrupting the vacuum generated at the booster venturii will it not? What does that do to cylinder fill?
 
Hysteric said:
Google it.
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did nothing comes up
Hysteric said:
So you put a bigger valve in it and a big cam with a lot of duration (late IVC) without the necessary compression which then messes with the vacuum generated in the port and then what what does the carb see at the throttle bore and the venturi? Its all interconnected but people never spend enough time thinking about how one change effects the system as a whole.

The "bigger" the invitation for reversion the further up the intake tract it will travel further interrupting the vacuum generated at the booster venturii will it not? What does that do to cylinder fill?
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Every engine build (everything) is a series of compromises.
 
273 said:
Every engine build (everything) is a series of compromises.
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So is using a smaller primary throttle bore and venturii size a reasonable compromise to make to overcome a lack of vacuum generation due to a the aforementioned issues?
 
Hysteric said:
So is using a smaller primary throttle bore and venturii size a reasonable compromise to make to overcome a lack of vacuum generation due to a the aforementioned issues?
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Depends on the build/situation etc.. Most people don't have dollars to do it the way you seem you want them to do it, Most are happy with larger less efficient engines with off the shelf parts, it cost time and money to build custom highly tuned engines like Nascar-Pro stock etc...
If that's your thing cool.
 
Most people have few choices when building eg... the average fully built small block 318 to 416, generally speedmaster, eddy, trick flow, air gap or single plane, 9:1 to 11:1, 225 to 255 cam, 650/750/850 carb very generic.
 
How did the factory get away with running a large carb on relatively small cube engines like the 340? 800 cfm is large for a stock engine.
 
Hysteric said:
How did the factory get away with running a large carb on relatively small cube engines like the 340? 800 cfm is large for a stock engine.
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I'm not necessarily saying your wrong I just think your over focused one aspect.
 
Rat Bastid said:
You’re kidding right? So every OEM almost EVER got it wrong? With .450 lift they damned well should have had 30 degree seats.

And you’re thinking that 30 degree seats don’t seal or won’t live is DEAD wrong. Millions of pontiacs had 30 degree seats and went hundreds of millions miles with them and they sealed.

Diesels use a 37.5 seat and how many miles do they go?

I’ll say it again. Curtain area is over played. If it was THAT CRITICAL every lift rule engine EVER would have 30 degree seats and no one I know does that.
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Yes Pontiac did use 30° seats to good effect. What I said was a 30° seat tends to sealing issues, not that they do not seal. This is more prevalent with faster ramp rates causing bounce. Those old engines had lower lift than is common now, many rarely exceeding 0.400" lift and fairly gentle ramp rates.
Yes some diesels use 30° or close to that and go hundreds of thousands of miles. Done many Cat and GM/Detroit Diesel heads in my time.
Regarding curtain area, this depends on your max valve lift. You need to have a discussion with DV on this topic
Hysteric said:
So is using a smaller primary throttle bore and venturii size a reasonable compromise to make to overcome a lack of vacuum generation due to a the aforementioned issues?
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Seems I read years ago that the General on designing the Rochester spread bore carbs were looking for good fuel atomization on the primary throttle bores were most driving occurs. Thus the very small primary throttle bores and venturi diameters. They also incorporated a dual booster for high signal and air velocity which in the third venturi creates shattering of the fuel droplets to much smaller size. More surface area exposed to the air aids vaporization. This enabled a 750CFM carb to be used on the limp wrist 305 engines with smooth throttle response.
Where the Chev 305 suffered, other than the high performance Camaro engine, was the camshaft and intake valve diameter. I had a 1982 Blazer with the 305 lopo engine. About 12MPG, low power and shift cycled with the 700 R4 transmission on the hiway. That got me researching camshafts, and I found out the intake was missing about 0.050" lift. This inhibits airflow past the small intake valves, so measured vacuum at the carb was low. This created the poor power.
In the TRW catalogue, when they still had catalogues on the parts counters, was the std 305 cam, another cam and then the 350 cam. There was another cam and another step up was the commonly refered to RV cam. If I remember correctly this had 204°/214° @ 0.050" lift and 0.425" valve lift. After installing this cam I got better vacuum, fuel economy (3.5MPG better) and driveability. Shift cycling was vastly reduced.
For the Hipo 305 Chev installed bigger intake valves in heads with smaller combustion chambers, as well as the 350 cam.
Ford did the same for their 302 engine in most autos and trucks. When they brought out the HO Mustang, the engine got the 351 cam with about 0.050 more intake lift.
Ma Mopar did the same on their emissions 318, lost 0.050" intake lift. I do not recall Chrysler with a hi output 318 sporting the 360 cam. About this time the K car was introduced and Chrysler went all in on FWD.
So in all this, valve curtain area and seat profile is extremely important for the average street engine utilizing fairly low lift.
Regarding the Engine Masters builds, this is a venue for builders to show off their skills. Many of these are not exactly long term street engines. Rockers with 2.0:1 ratio and valve lifts approaching 1.00" were seen. These engines would be very costly and involved much dyno time to get that years entry dialed in as best as possible within the rules.
 
Some of you guys are so book smart you should be writing one. I wish we could see you actually preforming some of this tech and backing it with track results.
 
pittsburghracer said:
Some of you guys are so book smart you should be writing one. I wish we could see you actually preforming some of this tech and backing it with track results.
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Some people enjoy theory side of things.
 
pittsburghracer said:
And that’s fine in my eyes if you apply it and can
Track prove that it works. If you can’t it’s just azz gas blowing in the wind.
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I’ve been using 50 degree and steeper seats since the late 1990’s. It’s not new.

Like everything else, things like this are slow to catch on.

There are some big names that disagree with a 50 degree seat on “low” lifts but I’ve tested it. The 50 always made more power IF the shape of the valve is correct AND the valve job is done correctly.

One example is a 4 cylinder Esslinger paved circle track deal. Two identical engines in two identical chassis.

The only differences were the valve job and the correct cam as a 50 degree valve job take’s different cam timing.

I can’t remember the power difference on the dyno but I think it was the mid 20’s.

On the track, the 50 degree engine blew the doors of its sister car and pretty much every other car there.

Of course, the car owner was pissed because the 50 had the “better” cam and I told the dude not better for the 45 degree seat.

After two weeks of sniveling I told him to call Bullet and order the wrong cam for the 45 because I wouldn’t do it.

We did the cam change and on the dyno it was a pig. Peak power was close but it looked like a 2 stroke curve with a sharp peak and no over rev. The customer watched every dyno pull.

At the track he got lapped. It was embarrassing. Of course all the
“smart” people said it wasn’t the valve job that made the 50 degree engine faster.

Finally, at the end of a frustrating year where his hired driver won the championship the customer caved and let me do a 50 to his head.

He won the last race that year and the championship next year.

I can tell you more examples like that. It’s not magic. It’s a part of the entire engine build.

Doesn’t matter to me who uses what valve job but when guys like DD repeat the same nonsense about curtain area and lift “rules” I call them out because they are wrong.
 
Dale Davies said:
Seems I read years ago that the General on designing the Rochester spread bore carbs were looking for good fuel atomization on the primary throttle bores were most driving occurs. Thus the very small primary throttle bores and venturi diameters. They also incorporated a dual booster for high signal and air velocity which in the third venturi creates shattering of the fuel droplets to much smaller size. More surface area exposed to the air aids vaporization. This enabled a 750CFM carb to be used on the limp wrist 305 engines with smooth throttle response.
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That's correct. There's a big difference between the vacuum generated in the primary bore of a square bore single stage booster carb and the vacuum generated in the primary of a spread bore carb with a double stage booster. If you cant generate vacuum you cant pull fuel into the engine...........

pittsburghracer said:
Some of you guys are so book smart you should be writing one.
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Its all been written about just some people here don't read it nor understand how it works or relates to what they are doing.
 
Hysteric said:
That's correct. There's a big difference between the vacuum generated in the primary bore of a square bore single stage booster carb and the vacuum generated in the primary of a spread bore carb with a double stage booster. If you cant generate vacuum you cant pull fuel into the engine...........


Its all been written about just some people here don't read it nor understand how it works or relates to what they are doing.
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Can YOU apply this knowledge.
 
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