Hotfoot674
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If you're headers aren't cherry red by the end of the night then you didn't try/hit hard enough,
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Post by Hotfoot674 on Feb 15, 2021 18:20:03 GMT -5
Seriuosly! Math for derby applications! Well yes!
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Hotfoot674
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If you're headers aren't cherry red by the end of the night then you didn't try/hit hard enough,
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Post by Hotfoot674 on Feb 15, 2021 18:20:16 GMT -5
carb sizing formula
this is NOT a jet sizing formula
Carb size for street use is as follows: cfm of carb = [ (rpm x displacement)/ 3456] x 0.85
When I say street carb I mean a carb that runs through varying rpm ranges and only gets close to the rev limit when you are merging onto the higwway for a few seconds -------------------------------------------------------------------------------------------------- Racing carb is as follows: cfm of carb = [ (rpm x displacement)/ 3456] x 1.10
When I say racing carb I mean some carb that runs wide open all the time and the driver has no care in the world about driveability
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Lets say we have a sbc 350 for street applications that we expect to rev to 5000 rpms max: cfm of carb = [ (5000 x 350)/ 3456] x 0.85 this comes out to 430 cfm, this is why you DONT need a holley 750 on your average derby engine, because you dont rev it to past 5000 for more than a few seconds between hits unless your linkage gets stuck wide open.
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boom61
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Post by boom61 on Feb 16, 2021 2:12:34 GMT -5
Where is Mr.Gropp? lol
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Hotfoot674
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Post by Hotfoot674 on Feb 16, 2021 9:33:34 GMT -5
I wonder what he would think of this.
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DTOM101
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"IT WOULD TAKE A COIL SPRING ON THE CARB TO KEEP MY FOOT OFF THE FLOOR"
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Post by DTOM101 on Feb 16, 2021 10:20:29 GMT -5
That’s a common formula yes. However for a derby application which this is supposed to address. I’d suggest a fatter fuel setup. Lean creates more heat. Our alchy setups will load up an need blown out numerous times during a run . That’s what keeps the engine cool without a rad. IMO. You should dump enough to need an oil change and new plugs every run . I’m by no means an expert an It would be nice to hear an experts take on the subject . I wonder how long this sport takes to evolve to electric motors?
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Hotfoot674
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If you're headers aren't cherry red by the end of the night then you didn't try/hit hard enough,
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Post by Hotfoot674 on Feb 16, 2021 11:31:35 GMT -5
this is not a jet sizing formula just for the max cfm your carb needs to bee
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DTOM101
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"IT WOULD TAKE A COIL SPRING ON THE CARB TO KEEP MY FOOT OFF THE FLOOR"
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Post by DTOM101 on Feb 16, 2021 11:55:09 GMT -5
You’re correct. I guess we all have a duh moment once in a while.
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Hotfoot674
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Post by Hotfoot674 on Feb 16, 2021 12:01:49 GMT -5
^^^^yessir
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Hotfoot674
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Post by Hotfoot674 on Feb 21, 2021 7:57:40 GMT -5
Valve diameter = √((rpm × stroke × bore²) ÷ 2,286,000
note bore, stroke, and valve dia. are in mm
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Hotfoot674
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Post by Hotfoot674 on Feb 21, 2021 8:07:36 GMT -5
That’s a common formula yes. However for a derby application which this is supposed to address. I’d suggest a fatter fuel setup. Lean creates more heat. Our alchy setups will load up an need blown out numerous times during a run . That’s what keeps the engine cool without a rad. IMO. You should dump enough to need an oil change and new plugs every run . I’m by no means an expert an It would be nice to hear an experts take on the subject . I wonder how long this sport takes to evolve to electric motors? Our great grandchildern smashing Teslas before the rest of the people on earth move to mars.
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Hotfoot674
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Post by Hotfoot674 on Feb 21, 2021 8:12:45 GMT -5
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Landshark007
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Post by Landshark007 on Feb 21, 2021 10:44:09 GMT -5
Motor runs best when running lean. And you can find other ways to cool them down. I know nothing about numbers and I do build my own motors.
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DTOM101
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"IT WOULD TAKE A COIL SPRING ON THE CARB TO KEEP MY FOOT OFF THE FLOOR"
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Post by DTOM101 on Feb 21, 2021 10:59:58 GMT -5
Running best lean I agree. Running cooler lean. Not so much. There is a show we used to run that does not allow any fan . None. So it was rare to see any heat go past the 25 minute mark . I’ve watched guys pull freeze plugs an run pollution pump to push air through it to cool with ok success. We welded a few rows of 1 1/4” pipe in a metal box an filled it with dry ice .Disclaimer: must run some antifreeze an start it ASAP . I remember hearing people chatter on the way in to run about it steaming already . With that being said when we started with alchy. We weren’t getting the cooler results everyone else was getting until we realized it was too lean . A couple rips through the field an it was heating up . A handful of stock jets an a few drill bits solved that instantly .
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DTOM101
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Post by DTOM101 on Feb 21, 2021 11:06:01 GMT -5
I have a 69 chevelle an I pulled my 406 roller engine with plans to run two 11” warp motors bolted to powerglide an should be about 1200 ft lbs. electric engines like to be cool as well an the produce same power no matter what the rpm is . I plan on attacking that build next winter as I’m trying to finish this winters project an get my kids derby cars built for spring. My thought about the ev approach is the fuel quality will never improve or get cheaper. So I looked at my three classics an said man in a Handful of years they could be worthless shelf ornaments .
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Hotfoot674
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If you're headers aren't cherry red by the end of the night then you didn't try/hit hard enough,
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Post by Hotfoot674 on Feb 21, 2021 12:40:37 GMT -5
oooh 69 chevelle is my favorite muscle car
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