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Old 04-26-2011, 09:20 PM
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383 finally finished! Compression,HP,TQ estimates???

Well fellas I started out on this build about 13 months ago and slowly bought all the parts for this 383 stroker to drop into my 72 chevy p/u. I'm finally finished with the motor, and when I ran the motor for the first time it sounded like a beast! I was using 93 octane fuel. Anyway, I ran My numbers through the desktop dyno and I believe that this is too good to be true so I'd like some professional opinions on expected compression ratios, HP, and TQ (for someone else out there who knows how to run a desktop dyno better than this dummy! I've included every morsel of info I thought would be pertinent. Any help is appreciated. Thank again guys and pics and video to follow!

-Josh

Block: 3970010 .040" over honed, sonic checked
Crank: Eagle 103503750 - 3.750" stroke
Pistons: Sealed Power 8KH100CP40 - 4.040" flat top with 2 valve reliefs
Rods: Stock 350 Rods signed off on by the machinist, press in wrist pins
Bearings: Mains - Sealed Power 4663MA - Bi Metal Bearings
Rod - Sealed Power 87100CH - Tri Metal
Pushrods: Proform 66891C - 1 Pc oiler pushrods
Valves: Manley 1.94 and 1.60 with 3 angle faces
Springs: Comp Cams 986-16 (as req'd per cam card) - 332 lbs/in
Heads: 462 Cast Heads, ported, polished
Head Gaskets: Fel Pro 501 SD
Rocker Arms: PSP Performance? 1.6:1 Roller Rockers
Timing Chain: Edelbrock 7801 - Double Roller Setup
Cam/Lifters: Comp Cams 12-250-3 XE 284H Grind Hyd Flat Tappet
110 LSA 106 Centerline
Duration: 284 I / 296 E
Duration @ 050" Lift 240 I / 246 E
Valve Lift: .507 I / .510 E
I'll have to find the damn cam card for the rest
Intake Manifold: Professional Products 52010 Air Gap Equiv. to Edelbrock,
Dual Plane High Rise
Carb: Holley Street Avenger 770 CFM Vac Secondaries and Elec Choke
Headers: Homemade 2" long tube

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Old 04-27-2011, 09:57 AM
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you might not like what i'm going to tell you but it will be the truth.

you have a 383 (.040 over 385) with a set of 462 (50yr old casting heads) on it with around 170cc intake runners, with poor exhaust runners (old technology) these heads flow about 210-215cfm @ .500 lift, you mention that you had them ported and polished, hopfully just ported with mild polishing in the first 1" of the runner and the bowls, you want to leave the heart of the runner a bit rough for fuel/air atomization, anyway we'll say it was done right and estimate that you gained about 8-10% max cfm at .500" this will give you about 233cfm @ .500 (this isn't terrible) hopefully a little more time was spend on the exhaust runners to improve them. your compression with a flat top (negitive 4-7cc valve relief) and 64cc combustion chamber is around 10.8:1. you did pick a dual pattern cam, which will help with the ridding of the exhaust gases. i think the 2" primary headers is WAY too big 1 3/4 would have been the largest i would have considered. as far as RPM's (from what the cam want the engine to run) you are right at your max if not just above it. the engine will want to turn up to 6000-6200rpm but the head will only be able to keep up until about 5200-5500 (170cc runners).

sorry to pick you apart, this could be a very fun street motor, but as far as volumetric efficancy i would say this motor has a V/E of around 75-80%. a good goal to shoot for on V/E is around 85-90%.

personally i would estimate this motor to make around 400-425hp/ 430-450tq. which makes for a very fun street motor, but i would say if you are willing to spend the bucks for a set of better heads (DART 200cc, Brodix IK200, RHS 200cc, AFR 195) and then even spend another 400-600 into having them massaged then you would be looking at 500hp all day long.

take my motor:
350 @ .040
scat 383 kit, balanced 10.3:1 CR
Hwrd cam : 240-250/ 282-90, .525/.525" 110/106 (mech F/T)
Hwrd billet 1.6/1.5 rockers, direct lube lifters
DART iron eagle Platinum 200cc (2.02/1.6) heads with about 650.00 in extra machine work done ( 11% max gain at .550, 286cfm, 6.5% average gain across .100-.550)
Edelbrock Rpm intake, ported/port matched, plenium divider notched 1/2" down with a 1" spacer
tricked out 750 double pumper.
Hooker super comp 1 3/4 headers

profesionally dyno tested and tuned (same company that did the head/intake work) 518hp/ 494tq, V/E 87%, can run of 93 octane but under the current tune i use a bottle of booster with it, or i'll mix my fuels 80/20. in a 3500lb car, runs 11.60's @ 117mph, 7.3's @ 91mph
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Old 04-27-2011, 10:17 AM
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I agree on the 2" headers-way, way too big for naturally aspirated. 1 3/4 better.
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Old 04-27-2011, 01:19 PM
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thanks for the replies fellas. I still have a set of 1 3/4 sitting on the shelf so I may go ahead and bolt those back on. And I knew the heads would be the choke point for TQ/HP. I didn't want to get too incredibly wild. I was actually shooting for 400HP/400FT/LBS. I was more concerned with what kind of fuel I need to run in this thing. I've been running 93 Octane to break it in. The engine will be sitting in a 72 Chevy P/U longbox. I intend on just using on the street with an occasional trip to the track. Anyway, thanks for the inputs guys (and shipmate) and by all means keep it coming.

-Josh
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Old 04-27-2011, 03:30 PM
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383 Sbc

It should do everything you want in your PU. However, I'd recommend you get rid of the Street Avenger carb. I've had 4 of them on 4 different engines on the dyno and they are way down on TQ, and tuning wouldn't correct the problem. If you want to run a vacuum secondary the old Holley 3310 is a good carb.

Ron
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Old 04-27-2011, 06:03 PM
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if 400hp is what you were looking for then i would say you have it, and you have more than 400tq. making 400tq out of a 383 is "like taking candy from a baby" it's almost impossible not to do with a 383.
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Old 04-28-2011, 09:55 AM
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Did you have adapter plates for your headers? Pretty sure there's no way to get 2" headers on the stock exhaust bolt flange pattern...
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Old 04-28-2011, 09:54 PM
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Quote:
Originally Posted by Adam65
Did you have adapter plates for your headers? Pretty sure there's no way to get 2" headers on the stock exhaust bolt flange pattern...

Nah no adapters... you could look at the flange and tell it wasn't set up right. I dont know who made them, hell we had them hanging on the wall for years and I figured "hey, why not?". Anyway I switched back to the 1 3/4" I had before with no issues...motor sounds awesome!
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