I had my holley 750 vacuum sec rebuilt by Davinci, they took off the choke and doing other stuff made it flow 875. Would that carb be too big for a destroked 400, with 9.5 comp, and a cam with 224-230 dur and .47-.48 lift?

Depends on how you use it. My Speed demon 850 is supposed to flow 910 and it was on a 383 race engine.

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Stephen's racing page

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
454 Big Block buildup now in progress for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

How 'destroked' is your 400. 350 crank or 327 crank or what? How many rpm are you going to run? And what are you going to do with the car?

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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

Bigger is always better, right?

Let me answer with two examples. I know 2 guys here who have trailered full-size 11-second cars: a back-halved 83 Monte Carlo with 454, and a lightened 73 Chevelle with 500. They both shift at 6500 rpm. This is at 5800 ft Bandimere, remember. What do they both run? Out-of-the-box 850 Holleys (jetted, of course).

Think about it.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

I am using the car as a daily driver. The crank is from a 350, and rev to about 6000. My car doesn't run 11s, not even close, but my transmission is slipping so I can't tell how my engine can really perform.

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Peter
KnightWhoSaysNI83
'83 Z28, 383(destroked 400 bored .060), comp 268 extreme energy cam, forged pistons 9.5:1 comp., excelerator intake, 875cfm holley vacuum sec., MSD 6AL box, accel coil., Hooker headers-3inch exhaust-borla mufflers.

Just out of curiosity, how did you manage to get a 400 block bored .060 over?

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1984 Camaro Z28 Astral Silver w/ 2 1/2" cowl induction hood
Engine: Decked 383 cid 4 bolt w/ oil cooler, 9.6:1 compression, ARP fasteners, 600 cfm Performer carburetor, Torker II intake, Performer RPM Heads, XE268H cam, Magnum roller tip rockers, MSD6AL ignition, Blaster2 coil, recurved HEI distributor
Exhaust: Terminator headers, Custom 3" TIG welded stainless exhaust, Twister muffler
Transmission: 4L60 w/ Corvette servo, .500 boost valve, TransGo 7-CS clutch springs, 700 PKH pump rings, 700-2 reprogramming kit, Borg-Warner High-Energy frictions & bands, 2400 RPM lockup torque converter
Drivetrain: 2.73:1 limited-slip Dana 44 w/ disc brakes
Tires: Front P225/50VR15 Rear P265/50VR15 Eagles

I gave it to Nickens Bro. here in Houston, they did the boring.

I didn't think a 400 block could take that much overbore.

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1984 Camaro Z28 Astral Silver w/ 2 1/2" cowl induction hood
Engine: Decked 383 cid 4 bolt w/ oil cooler, 9.6:1 compression, ARP fasteners, 600 cfm Performer carburetor, Torker II intake, Performer RPM Heads, XE268H cam, Magnum roller tip rockers, MSD6AL ignition, Blaster2 coil, recurved HEI distributor
Exhaust: Terminator headers, Custom 3" TIG welded stainless exhaust, Twister muffler
Transmission: 4L60 w/ Corvette servo, .500 boost valve, TransGo 7-CS clutch springs, 700 PKH pump rings, 700-2 reprogramming kit, Borg-Warner High-Energy frictions & bands, 2400 RPM lockup torque converter
Drivetrain: 2.73:1 limited-slip Dana 44 w/ disc brakes
Tires: Front P225/50VR15 Rear P265/50VR15 Eagles

.040 is the max overbore on a 400 and that's pushing it. I suppose if you have the money you could get it sleaved for a larger overbore. Either that or it's an aftermarket 400 block like a bowtie.

I believe a 400 block w/a 350 crank is called a 377.....HIGH REVING motor

I would go with a 650-700 cfm. At the very most a 750.


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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

Back to the ol' tried and true formula:

RPM x CID x volumetric efficiency(%) /3456

A 1.5" Hg vacuum drop across the carb is assumed.

For a 400 at 6000 RPM and achieving 100% volumetric efficiency (unlikely), the engine will flow 694 CFM with a 1.5" drop across the carb.

You'll be O.K. with an 875 CFM carb as long as the vacuum secondaries do their job.

okay, I really appreciate it 82Camaro, and jrr. Thanks


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Peter
KnightWhoSaysNI83
'83 Z28, 383(destroked 400 bored .060), comp 268 extreme energy cam, forged pistons 9.5:1 comp., excelerator intake, 875cfm holley vacuum sec., MSD 6AL box, accel coil., Hooker headers-3inch exhaust-borla mufflers.

A 400 can be bored .060" if there is very little core shift in the block. Its best to have them sonic tested to actually "see" how thin it will be with a .060 overbore, but many people just look at the the casting line on the block and its seems that there is little shift, they'll take the chance, and go ahead and bore it. I have built 2 and have seen numerous .060"over 400's at the track and have only seen one that got so thin that it cracked right after it was cranked for the first time.

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82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
http://www.bassettracing.cz28.com

not as long as it's jetted right.

The old formula of:

RPM x CID x volumetric efficiency(%) /3456

Is very outdated. The "A 1.5" Hg vacuum drop across the carb is assumed." doesn't apply to the newer, modern carbs. They actually pull less so it's closer to a .7" HG drop.

A more accurate formula to use with newer carbs is:

RPM x CID x volumetric efficiency(%) /2820.

If you're still using that 30 year old Holley 3310 then use the old formula. If you now have an Edelbrock or Demon, use the new one.


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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
454 Big Block almost ready for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

Thanx for the update! I'd been using that formula for a long time. Of course, I'm also someone who encourages people to take the Stone Age approach to building motors instead of dealing with all of that computer stuff! Must be a Luddite thing!

Get the Holley 700cfm and finish off your transmission!!!!