CID/RPM/CFM/HP

General engine tech -- Drag Racing to Circle Track

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randy331
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Re: CID/RPM/CFM/HP

Post by randy331 » Sat Nov 04, 2017 12:19 pm

Some of us have had the 500 HP 383 dream come true,... on the first try.

Randy

Frankshaft
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Re: CID/RPM/CFM/HP

Post by Frankshaft » Sat Nov 04, 2017 12:27 pm

Now 500hp out of a 383 is hard? hmm, ok, I guess I missed that part.

skinny z
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Re: CID/RPM/CFM/HP

Post by skinny z » Sat Nov 04, 2017 12:29 pm

[quote=Frankshaft post_id=696858 time=1509812832 user_id=26278]
Now 500hp out of a 383 is hard? hmm, ok, I guess I missed that part.
[/quote]
You did.
500 HP from 255 CFM heads was the question.
Some say yes. Some say no.
Others say I need to rebuild my car...

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Re: CID/RPM/CFM/HP

Post by Frankshaft » Sat Nov 04, 2017 12:31 pm

Actually, you can make more than 600hp with 255 cfm, just saying. Oh boy, I just opened up a can, lol.

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Re: CID/RPM/CFM/HP

Post by skinny z » Sat Nov 04, 2017 12:33 pm

[quote=Frankshaft post_id=696863 time=1509813064 user_id=26278]
Actually, you can make more than 600hp with 255 cfm, just saying. Oh boy, I just opened up a can, lol.
[/quote]
You may have. But not with me.
However, if anyone cares to chime in, I'll be an interested observer.

randy331
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Re: CID/RPM/CFM/HP

Post by randy331 » Sat Nov 04, 2017 12:48 pm

skinny z wrote:
Sat Nov 04, 2017 12:29 pm
Frankshaft wrote:
Sat Nov 04, 2017 12:27 pm
Now 500hp out of a 383 is hard? hmm, ok, I guess I missed that part.
You did.
500 HP from 255 CFM heads was the question.
Some say yes. Some say no.
Others say I need to rebuild my car...
Lets look at some things here.
500 hp with 255 cfm is 1.96 HP/cfm. Certainly within reason.
500 HP at 6500 rpm requires 404 pounds of TQ. That would mean the engine would probably need to make 445 pounds of TQ at peak Tq.
445/383 = 1.16 pounds of TQ per cube. Easily done.
500 hp / 383 cubes = 1.3 HP per cube. Still easy.
1.16 pounds/cube and 1.3 HP/cubes is pretty low bar.

During our EMC testing we put the same heads/cam/intake on a 390 cube and 353 cube. The larger engine made more power and TQ but at a little less HP/cubes, but it was a higher HP/cfm because the cfm was the same. It also made it at a lower rpm.
Hands down that combo would have produced lower ETs.
Best EMC score was with smaller cubes, but that's a different deal than producing ETs.

Randy

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Re: CID/RPM/CFM/HP

Post by skinny z » Sat Nov 04, 2017 2:08 pm

I may have to start a thread on selecting a cam for a 385 with: RPM Air Gap intake, 750 CFM VS carb and a crappy exhaust.(the latter will be upgraded).

zums
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Re: CID/RPM/CFM/HP

Post by zums » Sat Nov 04, 2017 8:02 pm

randy331 wrote:
Sat Nov 04, 2017 12:19 pm
Some of us have had the 500 HP 383 dream come true,... on the first try.

Randy
Cant be done, get nox, a supercharger or a roots, or a jet engine or straight nitro methane
Tom

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Re: CID/RPM/CFM/HP

Post by vortecpro » Sat Nov 04, 2017 8:09 pm

Frankshaft wrote:
Sat Nov 04, 2017 12:31 pm
Actually, you can make more than 600hp with 255 cfm, just saying. Oh boy, I just opened up a can, lol.
Every competitive Super Stock 300/350 makes over 600, of course that's a 1.940 valve and a flattop piston and Q-Jet.
Racing a NA NHRA stocker should be mandatory before any posting.

cjperformance
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Re: CID/RPM/CFM/HP

Post by cjperformance » Sat Nov 04, 2017 8:43 pm

zums wrote:
Sat Nov 04, 2017 8:02 pm
randy331 wrote:
Sat Nov 04, 2017 12:19 pm
Some of us have had the 500 HP 383 dream come true,... on the first try.

Randy
Cant be done, get nox, a supercharger or a roots, or a jet engine or straight nitro methane
Tom
:shock: :?:
Craig.

skinny z
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Re: CID/RPM/CFM/HP

Post by skinny z » Sat Nov 04, 2017 8:50 pm

While I'll say that making 500 HP with these small heads is possible, I'm thinking it's not going to happen with a cam that would be reasonable for this application. That's along with the existing engine components.
However, I'm sure my definition of reasonable differs from yours...

randy331
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Re: CID/RPM/CFM/HP

Post by randy331 » Sat Nov 04, 2017 11:05 pm

skinny z wrote:
Sat Nov 04, 2017 8:50 pm
While I'll say that making 500 HP with these small heads is possible, I'm thinking it's not going to happen with a cam that would be reasonable for this application. That's along with the existing engine components.
However, I'm sure my definition of reasonable differs from yours...
Define reasonable for this application.

Randy

skinny z
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Re: CID/RPM/CFM/HP

Post by skinny z » Sun Nov 05, 2017 12:14 am

I would expect these qualities from any engine I would build:
Enough idle vacuum at conventional RPM, say 850, to support power brakes. Currently, the 9-10" I achieve is at about the threshold of being adequate. This isn't to say, that I couldn't improve the braking performance via other means, (perhaps a fresh vacuum booster) but this is a starting point. (In reality the difficulty comes from when the RPMs drop below the idle value under certain conditions).
Fuel economy. There are plenty of cross-country drives made and highway mileage is important. Presently I achieve 24 MPG (ImpG)/21 MPG USG. Not bad in my estimation and I could probably improve on that but that's more or less what I would consider acceptable.
General driveability but that's somewhat subjective. At times, this vehicle serves as a daily driver. And as such, it gets started in cool/cold conditions and putts around town. It runs at low engine speeds too. Cruises at 2600 RPM at 75 MPH.
And of course, some degree of longevity. Could I go 100,000 miles with a performance orientated engine? I wouldn't expect it but there has to be some degree of durability built in. As an example, my valvetrain has supported 6500 RPM with cams such as the 288 mentioned earlier. Not a huge feat I know considering those moments of 6500 RPM are brief. Tests on the valve springs after tens of thousands of miles showed no deterioration of the spec. I wouldn't want to have to assemble new components and go outside of that kind of durability.
Anyway, that's some insight into what I would expect and consider reasonable. This is why, based on some of what's been posted here, that building to 500 HP might involve more than I care to take on.

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Re: CID/RPM/CFM/HP

Post by swampbuggy » Sun Nov 05, 2017 8:58 am

Skinny Z-----what about considering a crate motor with warranty ???

skinny z
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Re: CID/RPM/CFM/HP

Post by skinny z » Sun Nov 05, 2017 9:23 am

randy331 wrote:
Sat Nov 04, 2017 12:48 pm
Lets look at some things here.
During our EMC testing we put the same heads/cam/intake on a 390 cube and 353 cube.
The question to be asked here is: Is a cam spec'd for a 353 suitable for a 390?
I see the point of your illustration and I hope you see the point of mine.

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