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Home » HD Forums » Forums » Boat Tech » What is the Optimal Compression Ratio?
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BigBoyToysMale Offline
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Post Icon Posted: May 16 2004,5:51 am Post # 1 see this member send this member a private message  quote this post in reply
I'm sure this will start some kinda debate, but what is the best compression ratio for everyyone who does various things.  I currently run 12.5:1 in 2 motors and am building another motor with 10:1.  And I'm getting ready to tear down one of the 12.5:1 motors that is .100 overbore and turning it into a Blown or Turboed motor (Think the .100 over can handle it?)  I am also thinking about going with a Bigger stroke crank on it to a 4.250 stroke, making a 505 ci Monster :D

What does everybody think?

Ski Motor = ?
Carbureted Lake/Race Motor = ?
Carbureted  Race Motor = ?
Nitrous Motor = ?
Injected Motor = ?
Blown Gas Motor = ?
Turboed Motor = ?
Blown Alcohol Motor = ?

What is your preferred motor Brand and Size?

BB Chevy - ? Cubic Inches
BB Ford - ? Cubic Inches
BB Olds - ? Cubic Inches
Other BB - ? Cubic Inches
Small Block anything - ? Brand and Cubic Inches



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Post Icon Posted: May 16 2004,8:40 am Post # 2 see this member send this member a private message  quote this post in reply
If you're planning on a 10 to 1 motor and you still want the power, make sure you get the quench area as tight as it will allow for a good combustion!.. :good If that 100 over block is just an OE block, I wouldn't use it in a blown deal unless it's an OLD thick wall deal and it was a mild blown deal, regardless I would get it sonic checked first!.. :rolleyes

Ski Motor = 8.5-10.00 (depends on what you want to pay for gas)
Carbureted Lake/Race Motor = 11.5
Carbureted  Race Motor = 12.5min.
Nitrous Motor = 12.00
Injected Motor = 12.5, 14.00 on alky
Blown Gas Motor = 7.5 for lake use, 8.5 race
Turboed Motor = Same as above
Blown Alcohol Motor = 11.5

What is your preferred motor Brand and Size?

BB Chevy - ? Cubic Inches (BIG)
BB Ford - ? Cubic Inches  (FE 427)
BB Olds - ? Cubic Inches  (BIG)
Other BB - ? Cubic Inches  (Arias)
Small Block anything - ? Brand and Cubic Inches (Chevy 383)
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Post Icon Posted: May 16 2004,7:02 pm Post # 3 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ May 16 2004,8:40 am)
What is your preferred motor Brand and Size?

BB Chevy - ? Cubic Inches (BIG)
BB Ford - ? Cubic Inches  (FE 427)
BB Olds - ? Cubic Inches  (BIG)
Other BB - ? Cubic Inches  (Arias)
Small Block anything - ? Brand and Cubic Inches (Chevy 383)

As far as C/R goes, as much as you can get away with. :D

Favorite motor:

Well the Olds 425's were the shit, even if they are rare.  Steel cranks and a better rod ratio and stroke ratio than the 455... just good luck finding one.  

Big chevies all the way.

A stoked Olds small block ranks right up there also.  1 Diesel block and 1 stroker crank = a big inch small block that will rock.   :good

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GoFastRacerMale Offline
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Post Icon Posted: May 16 2004,8:02 pm Post # 4 see this member send this member a private message  quote this post in reply
Quote (Sleek-Jet @ May 16 2004,7:02 pm)
As far as C/R goes, as much as you can get away with. :D

Not necessarily, there are ways of making power with lower compression, efficiency is the key!.. :D  :good
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Sleek-JetMale Offline
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Post Icon Posted: May 16 2004,8:07 pm Post # 5 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ May 16 2004,8:02 pm)
Quote (Sleek-Jet @ May 16 2004,7:02 pm)
As far as C/R goes, as much as you can get away with. :D

Not necessarily, there are ways of making power with lower compression, efficiency is the key!.. :D  :good

I was being a smart ass.   :ass  :ass :D  :laugh

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Post Icon Posted: May 16 2004,8:20 pm Post # 6 see this member send this member a private message  quote this post in reply
Oh I figured that!.. :D  :laugh  :good
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Post Icon Posted: May 17 2004,6:09 am Post # 7 see this member send this member a private message  quote this post in reply
well, with 2 motors running 12.5:1, it can get expensive buying fuel.  I tried running pump gas 91 octane in one of them once and blew a hole between 2 cylinders and cracked the head near the intake valve in one of the cylinders.....Never again.  I'm thinking that I'm gonna take and build the 476 down at 7.5:1 and add boost.  I know that .100 over is kinda pushing it but this is a good motor.  I may go to a 4.250 stroke also making the engine from a 476 to a 505 ci.  A blown/injected  GAS 505 in a Biesemeyer should be sufficient to run with the big boys. :good  :D



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BigBoyToysMale Offline
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Post Icon Posted: May 17 2004,6:09 am Post # 8 see this member send this member a private message  quote this post in reply
I'm thinking I better change gears though ;)



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Post Icon Posted: May 17 2004,6:14 am Post # 9 see this member send this member a private message  quote this post in reply
Quote (BigBoyToys @ May 17 2004,6:09 am)
well, with 2 motors running 12.5:1, it can get expensive buying fuel.  I tried running pump gas 91 octane in one of them once and blew a hole between 2 cylinders and cracked the head near the intake valve in one of the cylinders.....Never again.  I'm thinking that I'm gonna take and build the 476 down at 7.5:1 and add boost.  I know that .100 over is kinda pushing it but this is a good motor.  I may go to a 4.250 stroke also making the engine from a 476 to a 505 ci.  A blown/injected  GAS 505 in a Biesemeyer should be sufficient to run with the big boys. :good  :D

I ran 12.5 to 1 in my other motor and I mixed 50/50 Avgas and 92 skunk piss with 34 lead with no problems!.. :good

A 509 is what will be going the GN, it was going to be blown but now I'm leaning towards a Turbo instead because of the built in muffler system!.. :good
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Post Icon Posted: May 17 2004,6:14 am Post # 10 see this member send this member a private message  quote this post in reply
Quote (BigBoyToys @ May 17 2004,6:09 am)
I'm thinking I better change gears though ;)

I would have to agree!.. :D  :laugh
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Post Icon Posted: May 17 2004,6:16 am Post # 11 see this member send this member a private message  quote this post in reply
Oh, and the BEST PRODUCTION engine ever made was the 426 Hemi IMO.  
I remember when I was 15 years old wathing the likes of Goettel, Jennings, Pettingil, etc running the SS boats and I always wanted to race one (16 was the minimum age at that time) and the 426 hemi's were always the ones in the front.  The 426 hemi is still around but expect to pat $15k to $20k for an original and $15k for the new ones from Mopar Performance.  That must be why everyone runs the 427 BBC...It's all about $$ :D



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BigBoyToysMale Offline
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Post Icon Posted: May 17 2004,6:18 am Post # 12 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ May 17 2004,6:14 am)
Quote (BigBoyToys @ May 17 2004,6:09 am)
well, with 2 motors running 12.5:1, it can get expensive buying fuel.  I tried running pump gas 91 octane in one of them once and blew a hole between 2 cylinders and cracked the head near the intake valve in one of the cylinders.....Never again.  I'm thinking that I'm gonna take and build the 476 down at 7.5:1 and add boost.  I know that .100 over is kinda pushing it but this is a good motor.  I may go to a 4.250 stroke also making the engine from a 476 to a 505 ci.  A blown/injected  GAS 505 in a Biesemeyer should be sufficient to run with the big boys. :good  :D

I ran 12.5 to 1 in my other motor and I mixed 50/50 Avgas and 92 skunk piss with 34 lead with no problems!.. :good

A 509 is what will be going the GN, it was going to be blown but now I'm leaning towards a Turbo instead because of the built in muffler system!.. :good

Yep....I'm seriously considering twin turbos myself.  I hate having to keep looking over my shoulder for them flashing red and blue lights :eek  :D



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Post Icon Posted: May 17 2004,6:18 am Post # 13 see this member send this member a private message  quote this post in reply
Yep, that's why I run Chevy!$$$$$$$$$$$$$$$$$ :laugh  :laugh
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BigBoyToysMale Offline
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Post Icon Posted: May 20 2004,5:25 am Post # 14 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ May 16 2004,8:40 am)
If you're planning on a 10 to 1 motor and you still want the power, make sure you get the quench area as tight as it will allow for a good combustion!.. :good If that 100 over block is just an OE block, I wouldn't use it in a blown deal unless it's an OLD thick wall deal and it was a mild blown deal, regardless I would get it sonic checked first!.. :rolleyes

I will be building this motor in the 7-8:1 Range, and hopefully running 7-10 lbs boost.  The motor is a 1971 cast GM 4 bolt main block.  Do ya think it can handle it?  I have been running this motor for 3 years now and other than cracking a head once (Bad gas) I have had no problems.  I do get alot of oil spitting outta the breathers when running WOT for about a 1/4 mile, but I expect a puke tank will help with that mess. What ya think?  Can this motor run at 7-8:1 CR with 7-10 lbs boost at .100 over????



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Post Icon Posted: May 20 2004,6:09 am Post # 15 see this member send this member a private message  quote this post in reply
That block should be thick but I still would sonic check it for core shift, it could have thin spots!..I wouldn't go any lower than 7.5 to 1 and no more than 8.0 to 1 with that block even if it sonic's out good and no more than 10lbs boost.All that mess is from the rings and not enough breathers, use a Vac-U-Pan and that will eliminate the mess!... :good
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Post Icon Posted: June 01 2004,11:42 am Post # 16 see this member send this member a private message  quote this post in reply
:beer how big of a cam can i throw in a relatively stock chev 454 with good lifters and rockers for a vicious idle and better performance?? :beer

from out of the kool blue
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Post Icon Posted: June 01 2004,12:36 pm Post # 17 see this member send this member a private message  quote this post in reply
Quote (koolblue69 @ June 01 2004,11:42 am)
:beer how big of a cam can i throw in a relatively stock chev 454 with good lifters and rockers for a vicious idle and better performance?? :beer

We need a litle more info on the motor, heads, pistons, compression, RPM's etc. and what kind of boat and what are you planning to do with it!. :good
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Post Icon Posted: June 01 2004,4:17 pm Post # 18 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ June 01 2004,12:36 pm)
We need a litle more info on the motor, heads, pistons, compression, RPM's etc. and what kind of boat and what are you planning to do with it!. :good

Damn, you're a nosey s.o.b.!  :rotflmao

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Post Icon Posted: June 01 2004,7:29 pm Post # 19 see this member send this member a private message  quote this post in reply
Quote (Bullitt Bob @ June 01 2004,4:17 pm)
Quote (GoFastRacer @ June 01 2004,12:36 pm)
We need a litle more info on the motor, heads, pistons, compression, RPM's etc. and what kind of boat and what are you planning to do with it!. :good

Damn, you're a nosey s.o.b.!  :rotflmao

FKN ayy man!.. :good  :rotflmao  :rotflmao
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Post Icon Posted: June 01 2004,7:50 pm Post # 20 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ June 01 2004,7:29 pm)
Quote (Bullitt Bob @ June 01 2004,4:17 pm)

Damn, you're a nosey s.o.b.!  :rotflmao

FKN ayy man!.. :good  :rotflmao  :rotflmao

:beer  :drink  :beer

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Post Icon Posted: June 01 2004,8:02 pm Post # 21 see this member send this member a private message  quote this post in reply
Quote (Bullitt Bob @ June 01 2004,7:50 pm)
Quote (GoFastRacer @ June 01 2004,7:29 pm)
Quote (Bullitt Bob @ June 01 2004,4:17 pm)

Damn, you're a nosey s.o.b.!  :rotflmao

FKN ayy man!.. :good  :rotflmao  :rotflmao

:beer  :drink  :beer

Yep, since I own this place I need to know everything!.. :D  :laugh  :laugh  :laugh
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Post Icon Posted: June 01 2004,8:09 pm Post # 22 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ June 01 2004,8:02 pm)
Yep, since I own this place I need to know everything!.. :D  :laugh  :laugh  :laugh

Oh good, since you're the Big Kahuna point me to the "All You Can Drink" free beer bar.  :drink

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Post Icon Posted: June 01 2004,8:27 pm Post # 23 see this member send this member a private message  quote this post in reply
When I find it I'll let ya know!.. :rotflmao  :rotflmao  :rotflmao
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Post Icon Posted: June 01 2004,8:34 pm Post # 24 see this member send this member a private message  quote this post in reply
Quote (GoFastRacer @ June 01 2004,8:27 pm)
When I find it I'll let ya know!.. :rotflmao  :rotflmao  :rotflmao

When you find it, make sure you taste it to if it's gone bad.

:rotflmao  :beer  :rotflmao

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Post Icon Posted: June 01 2004,8:46 pm Post # 25 see this member send this member a private message  quote this post in reply
Quote (Bullitt Bob @ June 01 2004,8:09 pm)
Quote (GoFastRacer @ June 01 2004,8:02 pm)
Yep, since I own this place I need to know everything!.. :D  :laugh  :laugh  :laugh

Oh good, since you're the Big Kahuna point me to the "All You Can Drink" free beer bar.  :drink

Found one once at a hotel in Cancun :beer Self serve Dos X's :drink Had a spot by the pool about 10 steps away :good

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