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Old 10-12-2012, 04:23 PM
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engine thoughts....

ok so im about to do a new top end on my 383....

heres what i am taking off
factory 76 cc chamber cast iron heads 8.5:1 compression
edelbrock performer intake
600cfm holley (single pumper)

heres what is in the bottom end
4 valve relief dish piston (cast)
comp cams 480 lift 280 duration
steel crank and cast i beam

heres whats going on
062 vortec 3 angle valve job (64 cc chamber) going to approx 9.4:1
i cleaned up the heads and port matched to intake
performer rpm air gap intake
670 street avenger
2 inch poly carb spacer

here is my questions
what kind of gains am i looking at?
could the set up handle 100 shot of nitrous oxide?

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Old 10-12-2012, 07:34 PM
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Quote:
Originally Posted by 79z28dude View Post
ok so im about to do a new top end on my 383....

heres what i am taking off
factory 76 cc chamber cast iron heads 8.5:1 compression
edelbrock performer intake
600cfm holley (single pumper)

heres what is in the bottom end
4 valve relief dish piston (cast)
comp cams 480 lift 280 duration
steel crank and cast i beam

heres whats going on
062 vortec 3 angle valve job (64 cc chamber) going to approx 9.4:1
i cleaned up the heads and port matched to intake
performer rpm air gap intake
670 street avenger
2 inch poly carb spacer

here is my questions
what kind of gains am i looking at?
could the set up handle 100 shot of nitrous oxide?
What exactly is the bottom end, while a cast crank is common in the SBC Chevy doesn't use anything but forged or PM rods, so where did or are they a casting come from?

There are cast pistons and there are cast pistons, are these inexpensive (that being a relative term) OEM or OEM replacement castings, or Claimer style pistons usually a hyper-eutectic with little to some heat treat to some more expensive styles with highly machined surfaces and T6 heat treatments? This gets more into the question of not so much will they take a 100 shot but rather how long are you expecting them to take a 100 shot. The temps go up the longer you keep them laughing and this is where the big problem lies. The piston is only indirectly cooled by the cooling system that's to say all of the heat the crown gets blasted by has to travel to the rings and skirt to find a way out. The only direct cooling is by oil splash unless you did something to put a spray on their underside. So cast pistons including hypers have a real struggle as the temps along with the combination of forces can get to the breaking point pretty quickly. You need to consider the pin as well because as the piston gets hot it tends to grab the pin, it the pin is only swinging in the piston and pressed to the rod when this happens the piston or the upper end of the rod gets ripped apart. Similar with the rings, the piston gets soft and the rings expand either by eating up the end gap and or the land clearance, next thing you know a big chunk of piston crown with ring land comes off, the ring can no longer stop the super hot gasses which then cut down the side of the piston.

Quality of the damper on the crank-snout also comes into play, nitrous hits the shaft really hard causing it to vibrate. If the damper isn't up to the vibes, it isn't long before the number one main gets carved out starving the number rod for oil with results you can imagine or the crank busts across the number one throw cheek, not a pretty sight either.

So the answer of how long it will live really comes down to the strength of materials in the engine how well it cools internal parts and how long you keep feeding it juice.

Bogie
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Old 10-12-2012, 09:07 PM
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wow... when i bought the car thats what came in it according to the build sheet... i know it was a basic rebuild.... and i planned on spraying it once in a while at the track...IE once a month


tomorrow ill add the part numbers from the build sheet
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Old 10-12-2012, 09:48 PM
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like OB said,the ring end gap needs to be increased. The 100 hp NO2 shot will increase your torque by closer to 200 pounds.If you have 450 pounds of torque now, then think what 650 pounds of torque will do?
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Old 10-12-2012, 10:59 PM
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like OB said,the ring end gap needs to be increased. The 100 hp NO2 shot will increase your torque by closer to 200 pounds.If you have 450 pounds of torque now, then think what 650 pounds of torque will do?
that depends on how early hit hits the bottle. If he waits to 5000 RPM+ (which is safer) then he's only looking at about 100ftlbs.
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Old 10-13-2012, 07:34 AM
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If you haven't purchased the air gap already, then don't. Get a regular RPM intake instead, as it will have much better street manors, especially in the cooler months.

Same for the carb. Get a holley 3310 750 instead if you haven't purchased the 670 yet.

Plus the 3310 and the regular rpm will be much cheaper.

100 shot should not be a problem. Retard the timing a few degrees and make sure the n02 system has a separate fuel pump. Setup the activation switch for full throttle.

On my n02 setup, I used a 1 gallon fuel cell mounted in front of the radiator and ran racing fuel for the n02 fuel enrichment. Just an idea.

Your 383 should make 400hp and close to 500 ftlbs of torque.
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Old 10-13-2012, 07:38 AM
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What is your goals at the track??.
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Old 10-13-2012, 07:43 AM
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when i got it... it ran a 13.8....id like mid- high 12's...later today im putting the new top end on....

gary on a side note, when was the last time you had a garbage plate from nicks?
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Old 10-13-2012, 07:55 AM
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454c10- i actually already have all the parts... i went with the air gap for the the cooler intake temp and also the longer runners. with the longer runners the velocity is increased and thats the main "feature" of the vortec heads. Thats also the reason for the poly carb spacer...

as for the extra fuel cell, i was thinking something very similar to doing that. but i was curious just a electric fuel pump in there? and it only turns on when you arm the system?
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Old 10-13-2012, 08:35 AM
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Originally Posted by 79z28dude View Post
when i got it... it ran a 13.8....id like mid- high 12's...later today im putting the new top end on....

gary on a side note, when was the last time you had a garbage plate from nicks?
Are you in or near Rochester??.
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Old 10-13-2012, 09:47 AM
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born and raised..... currently serving in the airborne infantry on ft bragg NC tho... i grad greece olympia in 04

i bet that you didnt see that one coming lol
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Old 10-13-2012, 10:18 AM
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The carb is too small. Get a 750. Install the vortec heads with a .015" shim head gasket to get the cr up.

Nice nitrous cam that will run good N/A too. Crane F280-2 280-288 244-252 .518-.536 112LSA.
Crane #114681

10" high stall. The Air Gap manifold is just right.

You can run up to 180hp shot on good pump gas. ( i"ve hit it harder)

200+ use 110+octane unleaded race gas. The under hood fuel cell is a great idea. I use it too.
The bigger shots really favour a mechanical lifter cam like the crane F280-2 as the motor will rpm.
These are very street easy mechanical lifter cams .

Get a ignition retard box and a RPM window switch to control nitrous engagement/launch rpm on launch.
When combined with the right torque converter stal speed this avoids over-torqing the motor on launch.
(bent connecting rods). You don't want to hit a 350 with 350hp shot at low rpm.
The rpm window switch wired to the WOT switch allows a hard hit right off the line.
@or near converter flash stall speed or slight time delay, as required.
The nitrous would come on a say 4000 rpm (converter stall speed)
This is how you hit a 350 hard with a big shot and go fast.

Last edited by F-BIRD'88; 10-13-2012 at 10:38 AM.
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Old 10-13-2012, 01:27 PM
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born and raised..... currently serving in the airborne infantry on ft bragg NC tho... i grad greece olympia in 04

i bet that you didnt see that one coming lol
The shop is in Hamlin.

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Old 10-13-2012, 04:32 PM
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i wanna say thats off union st...N of 104 tward the lake
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Old 10-13-2012, 05:48 PM
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454c10- i actually already have all the parts... i went with the air gap for the the cooler intake temp and also the longer runners. with the longer runners the velocity is increased and thats the main "feature" of the vortec heads. Thats also the reason for the poly carb spacer...

as for the extra fuel cell, i was thinking something very similar to doing that. but i was curious just a electric fuel pump in there? and it only turns on when you arm the system?
Yes, the pump would come on when you "arm" the system. Then the N02 and fuel solenoids come on at full throttle with the throttle switch.

Having owned an airgap. It takes 30 minutes of driving before the intake gets warm enough to drive without off idle engine hesitation. When it comes to carbs, cool fuel is not a good thing, as the fuel tends to change from vapor back to fluid then puddles up. Anything less than 50F or even 60F makes for a long warm up period. I removed that airgap as soon as a could and went back to the regular rpm. I hope you have better results with the airgap than I did.
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