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Old 04-26-2005, 09:29 AM   #1
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10.5:1 compression ratio on my 383 stroker...

Is this okay for everyday driving? Am I going to be leaving a bunch of power on the table by not incresing the compression to say 11.0:1 or even 11.5:1? This is going to be a nitrous solid roller motor.

Thanks
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Old 04-26-2005, 09:47 AM   #2
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Re: 10.5:1 compression ratio on my 383 stroker...

i'm sticking to exactly the same thing for my 355 hydrallic engine...
people say they run 11.5:1 but all machine shops said, even with reverse flow cooling heads u still wanna stay in the 10's...
i'd say thats perfect, can't get much better than stock!
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Old 04-26-2005, 10:09 AM   #3
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Re: 10.5:1 compression ratio on my 383 stroker...

Depends on the cam, all else being equal.

Rich
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Old 04-26-2005, 10:26 AM   #4
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Re: 10.5:1 compression ratio on my 383 stroker...

Quote:
Originally Posted by Mystic97Z
i'm sticking to exactly the same thing for my 355 hydrallic engine...
people say they run 11.5:1 but all machine shops said, even with reverse flow cooling heads u still wanna stay in the 10's...
i'd say thats perfect, can't get much better than stock!
i think the lt4 was 11.1 if i remember correctly
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Old 04-26-2005, 11:22 AM   #5
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Re: 10.5:1 compression ratio on my 383 stroker...

Quote:
Originally Posted by rskrause
Depends on the cam, all else being equal.

Rich
Elaborate please...
The cam in my car is a custom ground Cam Motion solid roller camshaft. The specs of the cam are = 245.7/251.1, .654/.606 installed at a 111.8 Lobe seperation. The Duration is at .05
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Old 04-26-2005, 12:55 PM   #6
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Re: 10.5:1 compression ratio on my 383 stroker...

IMHO its not a daily drive cam..
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Old 04-26-2005, 02:01 PM   #7
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Re: 10.5:1 compression ratio on my 383 stroker...

Yeah, I plan on driving it around some, but mainly to local car shows and events. It should still do fine for street/strip duty, even with that cam. Jordon used that very same cam grind and loved how it acted on the street.
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Old 04-26-2005, 02:46 PM   #8
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Re: 10.5:1 compression ratio on my 383 stroker...

I'm running that compression in my 383 with the GM 847 cam and have never experienced ping on 91 octane gas.
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Old 04-26-2005, 02:48 PM   #9
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Re: 10.5:1 compression ratio on my 383 stroker...

it all depends on your static compression. Dynamic compression is not all that important. My 383 is running 10.5:1 compression, and I wish I would of went with 11.5, which would of netted me a rough 8.5 static compression, which you want to stay under 9.0 for pump gas.

here is a calculator:

http://www.rbracing-rsr.com/compstaticcalc.html
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Old 04-26-2005, 03:04 PM   #10
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Re: 10.5:1 compression ratio on my 383 stroker...

That cam will be very driveable with SR ramps + cubes.
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Old 04-26-2005, 03:16 PM   #11
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Re: 10.5:1 compression ratio on my 383 stroker...

Quote:
Originally Posted by Deenasty
it all depends on your static compression. Dynamic compression is not all that important. My 383 is running 10.5:1 compression, and I wish I would of went with 11.5, which would of netted me a rough 8.5 static compression, which you want to stay under 9.0 for pump gas.

here is a calculator:

http://www.rbracing-rsr.com/compstaticcalc.html
You have Static and Dynamic Compression backwards.

Dynamic is the important one...you have the right concept but switched the syntax.
Dynamic must be under 9.0 for pump gas.
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Old 04-26-2005, 03:39 PM   #12
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Re: 10.5:1 compression ratio on my 383 stroker...

I'm running 12.5 CR and race my car on pump gas most of the time. My cam is bigger than the one you listed though. No pinging and the car runs great on it. In fact..my 10.7 pass was on 93 pump gas.
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Old 04-26-2005, 04:26 PM   #13
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Re: 10.5:1 compression ratio on my 383 stroker...

Quote:
Originally Posted by Mystic97Z
i'm sticking to exactly the same thing for my 355 hydrallic engine...
people say they run 11.5:1 but all machine shops said, even with reverse flow cooling heads u still wanna stay in the 10's...
i'd say thats perfect, can't get much better than stock!
My machine shop said the same but I heard different from Lloyd and Brett. Dynamic compression plays a role along with cam selection. I choose a custom grind based on my piston cc and deck height. I'll have a tight quench of .036 so we went from there. Lloyd didn't even want to do a cam selection till I had deck height and piston cc. I was told it will be close to the GM847 but... with a lil more lift
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Old 04-26-2005, 05:18 PM   #14
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Re: 10.5:1 compression ratio on my 383 stroker...

All else being equal.. I've heard that each point of compression you come up is worth ~10hp... Personally I'd think it to be more, since any blown motor application (i.e. 9.0:1) I've seen dyno about 40rwhp less than it probably would if it were up around 11:1 . Then again.. Who am I to talk? My car only makes 385rwhp and is 12.2:1 .. lol. I suck!

next question?
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Old 04-26-2005, 05:41 PM   #15
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Re: 10.5:1 compression ratio on my 383 stroker...

Wow, self esteem issues Mr Saladbar.

TexasTA,
It really depends on the complete setup like Rich said. Its all about the dynamic compression, not the static. I am running a 12 to 1 using a solid roller thats 254/262 on a 111 LSA. It nets me a dynamic of about 8.5 to 1. BTW, can we hook up this week.

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Old 04-26-2005, 05:41 PM
 
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