More compression worth the cost?

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younggun2.0

younggun2.0

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i have a 383 with the following parts assembled.

stock stroke 383 with forged crank
stock rods, resized, shoot peened/flash ground with arp bolts
speed pro replacement pistons. not sure of compression
eddy heads 84cc with mild port work
m1 single plane with 750 double pumper.
comp cams 525 lift cam
tti headers
727 with 4000 stall dynamic converter
cheetah manual valve body
aluminum drive line
8 3/4 with 4.10 and locker
28" drag radials.


as of now im guessing i most likely have 8.5-9:1 compression.

how much power would i gain if i were to take it back down and have some custom slugs put in it with say 10.5 comp.
 
lo compression engines can run hard..you just have to spin them higher.
with those gears and that converter i'm guessing your pretty good,but i think there are guys on here with more experience that will chime in
 
ir3333 said:
lo compression engines can run hard..you just have to spin them higher.
with those gears and that converter i'm guessing your pretty good,but i think there are guys on here with more experience that will chime in
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i plan to shift it at about 6500 and cross the line at about 7k. i know i have more head than i need for this engine but it started as a mild cruiser then mid build i decided i wanted to go fast. hoping this combo puts me into the 11.50 range.
 
50 HP difference at the most.
 
StrokerScamp said:
50 HP difference at the most.
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even if i went with a nice light weight custom forged piston? sheesh 50hp is not even close to worth the 2k it would most likely cost by the time i got the pistons and had the bottom end re-balanced and assembled.
 
That's right. Now you're thinkin.
 
what kind of horse power do you think this combo is making? im thinking possibly 450-475 hp range.
 
I don't think so with 8.5:1. I could be wrong. Let me ask you this....why not take full advantage of the heads and get close to or over 11:1? THEN you would be makin that kinda power...probably more.
 
StrokerScamp said:
I don't think so with 8.5:1. I could be wrong. Let me ask you this....why not take full advantage of the heads and get close to or over 11:1? THEN you would be makin that kinda power...probably more.
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i want to keep it a street/strip pump gas engine. this engine is most likely a stepping stone to get the car dialed in and then will probably end up building a roller cam 470 stroker with the heads and intake i have already.
 
With Eddy heads, and that cam, she'll take 11:1 on pump gas with the right pistons.
 
Maybe IQ52 will see this. He's da man when it comes to this stuff with big blocks.
 
I put your basic specs in my dyno program and this is what I came up with.
StrokerScamp is right on: 8.5/1 397 hp
9.0/1 409
9.5/1 419
10.0/1 429
10.5/1 438
11.0/1 448

Don't shoot me or take these horsepower figures for the gospel. It is just a dyno program and I was guessing on some of the specs. tmm
 
Let's just say for grins that you ARE making 450 HP. If you up the compression 2 points you MIGHT go all the way to 486 HP. Enjoy the engine as it is, save your money and build the stroker.
 
toolmanmike said:
I put your basic specs in my dyno program and this is what I came up with.
StrokerScamp is right on: 8.5/1 397 hp
9.0/1 409
9.5/1 419
10.0/1 429
10.5/1 438
11.0/1 448

Don't shoot me or take these horsepower figures for the gospel. It is just a dyno program and I was guessing on some of the specs. tmm
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Thanks, i dont take offense at all. i appreciate the time you spent to plug in the numbers. i just hope i can get the car into the 11s.
 
IQ52 said:
Let's just say for grins that you ARE making 450 HP. If you up the compression 2 points you MIGHT go all the way to 486 HP. Enjoy the engine as it is, save your money and build the stroker.
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this is going to be the plan. the good part is that with the low deck stroker i can use all my parts from the 383 later on.
 
IQ52 said:
Let's just say for grins that you ARE making 450 HP. If you up the compression 2 points you MIGHT go all the way to 486 HP. Enjoy the engine as it is, save your money and build the stroker.
Click to expand...

Das wut I'm tawkin bout. See wut happens when a professional steps in?? ^^^^
 
X2,on the N20.A NOS 125hp power shot is just what the doctor would order.
 
if i were to spray it i would go straight to 250 and shoot for high tens. ha ha ha. i gotta catch the old man. hes got a 71 demon street car (drives 45 miles each way to the track) that runs 10.70 in full street trim.[ame=http://s370.photobucket.com/albums/oo147/johnnydart_photo/dads%20car/?action=view&current=dadscar003.mp4]
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The rule of thumb I've heard was 4% increase for every 1 CR bump like 8.5:1 to 9.5:1 on a 400hp would be 16Hp increase.
 
I think the bigger advantage to higher CR is too be able to run a bigger cam more CR opens the door too more cam choices.
 
younggun2.0 said:
if i were to spray it i would go straight to 250 and shoot for high tens. ha ha ha. i gotta catch the old man. hes got a 71 demon street car (drives 45 miles each way to the track) that runs 10.70 in full street trim.
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Well, there you go! That Demon "boogies."
 
I had a similiar problem and replaced my 88cc chamber heads with 440Source heads for $1000 bucks .Milled them without disassembly..Bumped my compression, shaved 50lbs, increased air flow so i could take advantage of a bigger Cam. I thought about changing pistons, yanking the motor , rebalancing, time and $$$$.
Before I Changed the heads I was trying to figure out Static vs Dynamic Compression vs Quench ...ect...and going back and forth on some forums. (complicated it seems) Finally I said the Hell with it and did it. I Milled them to 68CC's This in conjuction with an inexpensive mech Cam Change and My car runs like a Priest to a "Boys pants half off " sale!

A little trouble with intake alignment even after intake side of heads was milled though but no big deal
$
 
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