How to get 1 HP per CI??? How could one get 1.25HP per CI - Hot Rod Forum : Hotrodders Bulletin Board
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Old 10-30-2008, 03:52 PM
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How to get 1 HP per CI??? How could one get 1.25HP per CI

Hey guys, This has been bugging me for a long time..... I Know you can't believe everything that gets claimed in forums and magazines, ect.... but How hard is to really accomplish this???

I know there are plenty of 500HP 350's out there, and even more that are around 425..... But Im talking gernerally about SBC V-8's 283, 302, 305, 350, 400, ect...

Is there any real way to calculate this?? I wanna see if we can put our heads together and come up with a sure fire way to achieve this!!! Is there already a formula out there or at least a THEORY would be a better word. I don't need it to be an exact science, but atleast in the ballpark say + or - 10 HP...

I'm not really starting this thread for advice, but more for a conversation piece to discuss the theory of 1 CI= 1 HP.... If there is a theory out there of how to attain this, How could we adjust the calculations and variables to achieve 1.25HP per CI???
There are just so many variables that could make this possible, that I don't know where to start other than ensureing that they all work together and complment on another...

I said its not for advice, BUT I guess in a way mabey it is.. I am getting ready to start my first SBC 400 and to be able to figure out a way to get 1.25HP per CI = 500HP would be nice. I know its very achieveable, but different builders seem to achieve it by using different methods.... What I'm looking for is to give myself and any other amature engine builders some insite on how to achieve these figures consistently......And better yet on a budget!!!

I also have a 66' 283ci, a 69' 350, a 73' 350, 3 98' vortec 350's, and 2 87' 305HO's. If I could figure out a way to build all these to atleast 1 HP per CI, I would be very happy and exited!!! 1.25 would be all the better!!!! But honestly, How often do you hear of a 305HP 305 motor, or espesially a 381HP 305????? Not very often but it is possible IN THEORY.

Please share all thoughts!!!! I'm very eager to hear them!!! Thanks

Danny

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Old 10-30-2008, 05:16 PM
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http://www.hioutput.com/tech/400hp/400hp.html



as far as the formula goes, that would be a tough one.
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Old 10-30-2008, 06:40 PM
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how bout theory???

I mean I know we've all heard the claim that 1 CI = ~ 1HP,,,, Right????
Were did this come from considering a stock 75 truck 350 made what mabey 250-275 max (just a guess), But just a few years earlier GM marketed a 375 horse 327ci, or was it 350 horse?? either way it still beat 1:1, what all was different. cmp ratio, cam, heads, intake, carb, ect.. but where's the balance.

Edlebroc is claiming they have a dyno tested 350HP 350 SBC crate motor. Now assuming those numbers aren't exagerated and it really does make 350HP, could one use this as a base to go off of for a 1:1 ratio... Obviously variables will change based off the size of the engine, but shouldn't the same concept be able tro be used with some simple arithmetic?????

Please get involved, 500 brains are better than 1, or 2,
Thanks
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Old 10-30-2008, 06:53 PM
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It is easy in engines smaller then 350 as well. There was an article of a 318 build to 400 something hp and I got shop plans for a 380 hp 318. There is alot of meat in these smaller engines that can really be opened up. If you like I can show you some for the 318.
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Old 10-30-2008, 07:31 PM
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Here you go..

http://www.epi-eng.com/piston_engine..._yardstick.htm
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Old 10-30-2008, 09:13 PM
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WWWAAAAYYYY over my head

Thanks man but that was way over my head, I was talking more by means of simply adjusting the CR, cam specs, cylinder head flow, induction sys. ect, ect... any other thoughts that I may be able to comprehend??
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Old 10-30-2008, 09:21 PM
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My mother's cousin is a long-time drag racer in Houston. I remember when I was in high school he said, "It's pretty easy to cheaply get 1 horsepower per cube. Get too far above that and you'll have to start spending cubic dollars." One of my favorite sayings.
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Old 10-31-2008, 12:45 AM
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Hi,
!969 -70 Corvette optional engine L46 a 350 CID 350 HP
380 # ft TQ, the 11-1 CR & cam is what got it to those specs
Rich
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Old 10-31-2008, 06:09 AM
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It is a case of diminishing returns 1hp per inch easy, 1.25 more difficult, 1.5 dang hard, 1.75 or a little higher your in prostock catogory.
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Old 10-31-2008, 08:26 AM
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Quote:
Originally Posted by eatonde
Thanks man but that was way over my head, I was talking more by means of simply adjusting the CR, cam specs, cylinder head flow, induction sys. ect, ect... any other thoughts that I may be able to comprehend??

The best thing you can do with all the engines you have sitting around is just build one with the best of what you have, get it in a car, and race!

Don't get me wrong it's good to research, read, and theorize but one pass down the track is worth more than any single book or formula. Breaking stuff is the best way to figure out what doesn't work, and sometimes you'd be surprised what "junk" will do.

Dynos, like flow benches, are valuable TOOLS, but that's all. In experienced hands they can help an engine builder develop that last few HP. Without track time it's almost worthless! You don't race on a dyno. Don't get hung up on this stuff... Get out there and race! It doesn't matter if all you can afford is a 305 with Vortecs, getting to the track and tearing it up is the best time you can spend to learn what works! You will also get a chance to see folks that make engine scream for very few $$$ and LOTS of cars with $8000 engines that should be embarrassed to come off the trailer!

You might make some Friends that will help you more than anyone on the internet ever could. I haven't sold a "take off" part in ~10 years, but I've given away LOTS.

Really, get whatever you can in a car, put a drive shaft loop and rev limiter on it and go break some stuff!!!
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Old 10-31-2008, 08:34 AM
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eatonde,
no it can't be "simple arithmetic" because different motors have different bore and strokes (ratios) which changes the piston speed (feet per second) per rpms and hense, the inhaling capability for the cylinder with a given camshaft....
ex:
the speed parts combo that yeilds 1HP per cube on a short stoke Ford 289 (at about 7000rpms+) will be different than the parts for a longer stroke 351W to reach 1HP per cube (at about 5000rpms) even though they both have a 4" diameter piston....

the 250HP 350 truck motor is "purpose built" to make the max max max possible very low rpms TQ force per rpms per cubes for acceleration power from a red light with a heavy vehicle by getting the best fill possible when the pistons are moving too slow...."TQ" is the must have priority due to the weight and 250HP at 4800rpms is a reasonable HP amount for passing somebody (LOL, if you do downshift) when a vehicle is already moving....

maybe the best/smartest way for you to understand all is put a "Desk Top Dyno" software program on your Xmas gift list????
it has "oem look up tables" for whatever motor and does the heavy duty math based on a given parts change you entered to calculate a gain or loss on all the operating variables for making HP....

as with any software program:"garbage in = garbage out results" so you do need to be very careful entering all the specifics and variables to get a "close to real world" result!!!!

dang CRS!!! a well known speed parts mfgr does have a very very crude "Desk Top Dyno" program on their site that you can play with to get the idea....
LOL, give me about 3 days and I will recall which site....

Last edited by red65mustang; 10-31-2008 at 08:44 AM.
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Old 10-31-2008, 08:44 AM
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There is no math to it...except subtraction from your checkbook.

Buy a ZZ4 shortblock and an Edelbrock RPM air gap top end kit, Holley, 3310-3 Msd billet and 6al. 410 hp out of the box every time.

Be ready to do a bit of tuning on the carb as this kit breathes fire just off idle.

I have one and love it.

If you really must have 1.25 just spring for the RPM roller cam.... 438 hp
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Old 10-31-2008, 02:00 PM
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1.25

well I was just listing the engines I currently own before. The one I really want to try to get 1.25 per cube out of is my 400. 500HP out of a SBC 400 should be that hard, should it.
I know the majority of the power is gonna come from the heads.

A guy plugged the current engine specs in for me to DD and it said
293 HP @ 4000
410 FTLB @ 3000
This was with the stock pistons, comp 268H cam and 882 heads.

I have a set of vortecs that will take the CR 10:1, But I'm afriad the cam will be to small for that CR....

I'm also buying a set a patriot's 190's so I dunno which I should use
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Old 10-31-2008, 02:37 PM
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Stop putzin' around with junk and get stuff that works. No guessing. Already done for you. Here's the combo....
Horsepower: 572 @ 6000
Torque: 536 @ 5000
Engine: 406 Chevy
Heads: AFR 210cc competition package
Intake: AFR Street Pro-Flow RPM #5028
Compression: 10.1
Carburetor: 750
Ignition: MSD distributor 36*
Cam: Lunati hydraulic roller 242*/252*, 0.560"/0.572", 112*
Exhaust: Hedman headers 1 7/8"
Fuel: 93 octane pump gas

Here's another with a little less hp, but a little more torque....
Horsepower: 551 @ 6000
Torque: 540 @ 5000
Engine: 406 Chevy
Heads: AFR CNC Cyl. Heads 210cc Race Ready
Intake: AFR Street Pro-Flow RPM #5028
Compression: 10.3
Carburetor: 750
Ignition: MSD HEI Billet Distributor 36 Timing
Cam: Lunati Hyd. Roller Cams 232/242
0560-.570 lift W/ 1.6 Rockers
Exhaust: 1 3/4" Headers
Fuel: 93 Octane Pump Gas

Even the 195 AFR heads will make over 500 hp on a 406.

Last edited by techinspector1; 10-31-2008 at 03:00 PM.
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Old 10-31-2008, 03:11 PM
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$$$$$$$$$

well tech that sounds great, but I don't have the money to be buyin all that stuff.

Since when are GM vortec or patriot heads JUNK????
I don't think that a set of Patriot freedom's 190's CNC bowl blended, fully assembled with quality components and .600 lift springs is junk at all flowing 263cfm @.500lift.

But if you wanna foot the bill for me I'll be glad to build it
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