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Old 09-28-2010, 06:43 PM
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SBC Horsepower/TQ Estimate Please

Techinspector1 or anyone,

Can I get a horsepower/torque estimate on this build? Thanks in advance!

-350ci bored .030 over
-Flattop Pistons
-Compression ~9.8:1
-Hydraulic cam, valve lift .465/.465, Adv Dur 290/290, Duration @.050 224/224, lobe centers 107int./117exh.
-Vortec iron heads, 170cc runner, 64cc chambers, 1.94/1.5 valves
-Holley 600cfm
-Rocker arm ratio 1.5:1

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Old 09-28-2010, 06:55 PM
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This is just off the top of my head, but that should be a great street engine, because it is going to make great low end torque and HP with those 170cc intake runners and cam. IMO, Im thinking around 350hp, at the flywheel.

Chevyguy13
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Old 09-28-2010, 06:56 PM
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If you are so inclined you can go here:

http://ronspontiacpage.com/indexes/index.html

download the desktop dyno sim, it may not be bang on the money as some but it helps you get things figured and adds understanding to your build and how it works.

You can get vortec (L31) head flow numbers and plug them into your head data manually.

go here for all types of flow data:

http://purplesagetradingpost.com/sum...fo/heads1.html

have fun
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Old 09-28-2010, 07:03 PM
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Quote:
Originally Posted by chevyguy13
This is just off the top of my head, but that should be a great street engine, because it is going to make great low end torque and HP with those 170cc intake runners and cam. IMO, Im thinking around 350hp, at the flywheel.

Chevyguy13
Thanks for the feedback! I hope it does make 350HP plus. It's for the street but I'll have to take at least one pass at the track to she what she does.
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Old 09-28-2010, 07:29 PM
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Nice combination Hank. Assuming 1 5/8" long-tube headers through the mufflers and a RPM or Stealth intake, here are the results....Oh, and install the cam 2 degrees retarded....
RPM HP TQ
2000 148 389
2500 186 392
3000 237 415
3500 292 439
4000 339 446
4500 376 439
5000 405 424
5500 398 380
6000 351 308
Peak volumetric efficiency 91.2% @4500
Peak BMEP 189.0 @4000
Makes some pretty good cylinder pressure, so tighten up the squish 0.035" to 0.045" so you can run pump gas without detonation.
3.73 gears and a 2500 converter should rip the tires off.
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Old 09-28-2010, 07:57 PM
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Quote:
Originally Posted by techinspector1
Nice combination Hank. Assuming 1 5/8" long-tube headers through the mufflers and a RPM or Stealth intake, here are the results....Oh, and install the cam 2 degrees retarded....
RPM HP TQ
2000 148 389
2500 186 392
3000 237 415
3500 292 439
4000 339 446
4500 376 439
5000 405 424
5500 398 380
6000 351 308
Peak volumetric efficiency 91.2% @4500
Peak BMEP 189.0 @4000
Makes some pretty good cylinder pressure, so tighten up the squish 0.035" to 0.045" so you can run pump gas without detonation.
3.73 gears and a 2500 converter should rip the tires off.
Thanks for detailed reply Techinspector1, yes I forgot some details. I'm using a Edelbrock Performer RPM and 1 5/8 mid-length Partriot headers but I assume the numbers you posted are still good or a little high. Have the 3.73 gears and hope the 4-speed saginaw holds up. When you mentioned "tighten up the squish to .035 to .045", are you refering to the head gasket? I plan to us a Fel Pro Peformance head gasket with .041 compression thickness.
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Old 09-28-2010, 11:30 PM
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Quote:
Originally Posted by Hanks56Chevy
When you mentioned "tighten up the squish to .035 to .045", are you refering to the head gasket? I plan to us a Fel Pro Peformance head gasket with .041 compression thickness.
No, I'm referring to the squish. If you plan to use a 0.041" gasket, then you will want to zero deck the block to the piston crowns and let the 0.041" thickness of the gasket serve as your 0.041" squish. Read here and if it isn't clear to you, I will try to explain further.

1. Piston deck height. This is the dimension from the crown of the piston to the flat deck of the block with the piston at top dead center. Nominally, with a premium 350 piston and a virgin, uncut block, this dimension will be about 0.025".
2. Squish. This is the dimension from the crown of the piston to the underside of the cylinder head with the piston at top dead center and adding in the thickness of the compressed head gasket. Current thinking is that a squish of 0.035" to 0.045" works best.
3. Compression height. This is the dimension from the centerline of the piston's wrist pin to the top of the piston's crown. With a premium piston in a 350 Chevy, this dimension is about 1.560". Lesser quality rebuilder pistons will measure out at around 1.540". This will increase the piston deck height and the squish and make the motor more sensitive to detonation.
4. Stack. This is the combined dimension of the crankshaft radius, rod length and piston compression height. A common stack with a 350 Chevy would be about 9.003". That would be with a crank radius (half the stroke length of 3.480") of 1.74", rod length of 5.703" and piston compression height of 1.560".
5. Block deck height. Nominally, this dimension would be about 9.025" on a virgin small block Chevy cylinder block. So, when using a stack of parts equalling 9.003", this would result in a piston deck height of about 0.022". Combined with a steel shim head gasket thickness of about 0.018", this would result in a squish dimension of about 0.040", just in the middle of the desired range of 0.035" to 0.045" to help prevent detonation with a reasonable (nominally, about 10.0:1) static compression ratio on pump gas. Alternately, a builder might cut the block decks down to the height of the stack and use a more conventional composition gasket that specs out at around 0.040" compressed thickness. If you had a stack of 9.003", cut the block decks down to 9.003" and used a 0.040" gasket, then the piston deck height would be 0.000" and the squish would be 0.040".
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Old 09-29-2010, 08:42 AM
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Quote:
Originally Posted by techinspector1
No, I'm referring to the squish. If you plan to use a 0.041" gasket, then you will want to zero deck the block to the piston crowns and let the 0.041" thickness of the gasket serve as your 0.041" squish. Read here and if it isn't clear to you, I will try to explain further.

1. Piston deck height. This is the dimension from the crown of the piston to the flat deck of the block with the piston at top dead center. Nominally, with a premium 350 piston and a virgin, uncut block, this dimension will be about 0.025".
2. Squish. This is the dimension from the crown of the piston to the underside of the cylinder head with the piston at top dead center and adding in the thickness of the compressed head gasket. Current thinking is that a squish of 0.035" to 0.045" works best.
3. Compression height. This is the dimension from the centerline of the piston's wrist pin to the top of the piston's crown. With a premium piston in a 350 Chevy, this dimension is about 1.560". Lesser quality rebuilder pistons will measure out at around 1.540". This will increase the piston deck height and the squish and make the motor more sensitive to detonation.
4. Stack. This is the combined dimension of the crankshaft radius, rod length and piston compression height. A common stack with a 350 Chevy would be about 9.003". That would be with a crank radius (half the stroke length of 3.480") of 1.74", rod length of 5.703" and piston compression height of 1.560".
5. Block deck height. Nominally, this dimension would be about 9.025" on a virgin small block Chevy cylinder block. So, when using a stack of parts equalling 9.003", this would result in a piston deck height of about 0.022". Combined with a steel shim head gasket thickness of about 0.018", this would result in a squish dimension of about 0.040", just in the middle of the desired range of 0.035" to 0.045" to help prevent detonation with a reasonable (nominally, about 10.0:1) static compression ratio on pump gas. Alternately, a builder might cut the block decks down to the height of the stack and use a more conventional composition gasket that specs out at around 0.040" compressed thickness. If you had a stack of 9.003", cut the block decks down to 9.003" and used a 0.040" gasket, then the piston deck height would be 0.000" and the squish would be 0.040".
Thanks again for the detailed explaination and advise. I understand squish now and the range to shoot for.
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