Fuel for 13:1 compression?
Thread Starter
On The Tree
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Fuel for 13:1 compression? I have two options for the new 427 I am building right now. By my (likely wrong) calculations here are the numbers I get.
If I go with a standard off the shelf -2 cc Diamond piston, with my .030 LS1 heads which should be at 62 CCs, I get 13:1 compression. What sort of fuel would I need to be able to run this high compression at max power. Can I use a fuel and mix with the 93 octane we have here? Since gas is already $2 a gallon I figure why not just run high compression and pay a little more for some race gas.
If it's possible to do a 50/50 mix or better with the 93 octane, I'll buy a 55 gallon drum of the stuff and head to town. I drive the thing on the weekends and have fun on the street with the car, so running straight $5 a gallon fuel is out of the question. However, I could afford a 50/50, 60/40, or better mixture of 93/race fuel.
My other option is to get dished pistons from Diamond. They said they have a -7 cc off the shelf which would still be at around 12:1, and I would probably have to splash in race gas with that combo too.
So, any experience from people who actually HAVE fun some higher compression out of these motors? It will have good cooling using Evans NPG non-water based coolant if that means anything.
Thanks for the help folks!
If I go with a standard off the shelf -2 cc Diamond piston, with my .030 LS1 heads which should be at 62 CCs, I get 13:1 compression. What sort of fuel would I need to be able to run this high compression at max power. Can I use a fuel and mix with the 93 octane we have here? Since gas is already $2 a gallon I figure why not just run high compression and pay a little more for some race gas.
If it's possible to do a 50/50 mix or better with the 93 octane, I'll buy a 55 gallon drum of the stuff and head to town. I drive the thing on the weekends and have fun on the street with the car, so running straight $5 a gallon fuel is out of the question. However, I could afford a 50/50, 60/40, or better mixture of 93/race fuel.
My other option is to get dished pistons from Diamond. They said they have a -7 cc off the shelf which would still be at around 12:1, and I would probably have to splash in race gas with that combo too.
So, any experience from people who actually HAVE fun some higher compression out of these motors? It will have good cooling using Evans NPG non-water based coolant if that means anything.
Thanks for the help folks!
Thread Starter
On The Tree
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Darton wet-sleeved aluminum block with a 4.125" bore and 4 inch stroke, 6.125" rods. The main problem with running straight 104, is that I drive it a lot on the weekends. If a 50/50 mix of something would work, then that would be ok with me. I could afford 7 gallons of 100+ octane race gas and 7 gallons of 93 to go out cruising with the friends on the weekend.
Is there some sort of chart that can explain required octane for fuels versus cylinder compession perhaps?
Is there some sort of chart that can explain required octane for fuels versus cylinder compession perhaps?
Originally Posted by Pro Stock John
I don't think the parts you are describing yield 13:1 compression
Shawn
Trending Topics
I thought milling heads .30 raised your compression 1/2 a point. So stock compression of a LS1 head being 10:1 you would get 10.5:1. Minus the valve reliefs you would be around 10.3:1. Im just guessing here so I could be wrong.
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On The Tree
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http://www.rosspistons.com/calculator.php
Are you guys thinking I am talking about this setup on a 346? Keep in mind I'm adding another 81 cubes and keeping the stock head chamber size.
4.125" bore
4" stroke
62 cc heads
.043 Cometic gasket
-2 cc valve reliefed pistons
427 cubic inches and 12.9:1 is what I end up with. Not sure if that accounts for the piston being out of the hole any or not.
Are you guys thinking I am talking about this setup on a 346? Keep in mind I'm adding another 81 cubes and keeping the stock head chamber size.
4.125" bore
4" stroke
62 cc heads
.043 Cometic gasket
-2 cc valve reliefed pistons
427 cubic inches and 12.9:1 is what I end up with. Not sure if that accounts for the piston being out of the hole any or not.
Gas is cheaper than pistons! If you drive the car that much, I don't think it's a good idea to go with 13:1. Also why would you want to keep the stock chamber size on your heads? You will be losing flow by staying with smaller valves and shrouding them. Just my opinion. What is your quench at? The small amout of power gained from the extra point on compression, might not be worth it.
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From: Deer Park
You can LIMP along with 93 octane and pump gas. Major emphasis on "limp". this means NO WOT blasts without 104+ in the tank.
With a good tune, you can limp along on PG, I did it for years on a carb'd motor with about 12.5:1. I would only mix when I was racing. Never had a problem.
With a good tune, you can limp along on PG, I did it for years on a carb'd motor with about 12.5:1. I would only mix when I was racing. Never had a problem.
Thread Starter
On The Tree
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Originally Posted by bodhi
You can LIMP along with 93 octane and pump gas. Major emphasis on "limp". this means NO WOT blasts without 104+ in the tank.
With a good tune, you can limp along on PG, I did it for years on a carb'd motor with about 12.5:1. I would only mix when I was racing. Never had a problem.
With a good tune, you can limp along on PG, I did it for years on a carb'd motor with about 12.5:1. I would only mix when I was racing. Never had a problem.
A friend today said if I mix a 75%/25% of 93 octane and 100-104 unleaded I should be good to go. This means a 55 gallon drum of Sunoco could last me around 10 tanks/weeks, which would work great.
Thread Starter
On The Tree
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Originally Posted by 2001CamaroGuy
I got 13.63 with everything you said
4.125" bore * 4" stroke
-2 CC pistons
0.043" gasket thickness
62CC head
4.125" bore * 4" stroke
-2 CC pistons
0.043" gasket thickness
62CC head
Originally Posted by Cricket99SS
Crap. So what caculator/calculation did you use to arrive at that number?
I have a calculator on my computer that you can put in all the specs (bore, stroke, head CC, gasket, etc...) and it will give you compression ratio.
the problem is you have LOOOOTS of swept CC volume compared to your static CC (head CC).
Originally Posted by Cricket99SS
I have two options for the new 427 I am building right now. By my (likely wrong) calculations here are the numbers I get.
If I go with a standard off the shelf -2 cc Diamond piston, with my .030 LS1 heads which should be at 62 CCs, I get 13:1 compression. What sort of fuel would I need to be able to run this high compression at max power. Can I use a fuel and mix with the 93 octane we have here? Since gas is already $2 a gallon I figure why not just run high compression and pay a little more for some race gas.
If it's possible to do a 50/50 mix or better with the 93 octane, I'll buy a 55 gallon drum of the stuff and head to town. I drive the thing on the weekends and have fun on the street with the car, so running straight $5 a gallon fuel is out of the question. However, I could afford a 50/50, 60/40, or better mixture of 93/race fuel.
My other option is to get dished pistons from Diamond. They said they have a -7 cc off the shelf which would still be at around 12:1, and I would probably have to splash in race gas with that combo too.
So, any experience from people who actually HAVE fun some higher compression out of these motors? It will have good cooling using Evans NPG non-water based coolant if that means anything.
Thanks for the help folks!
If I go with a standard off the shelf -2 cc Diamond piston, with my .030 LS1 heads which should be at 62 CCs, I get 13:1 compression. What sort of fuel would I need to be able to run this high compression at max power. Can I use a fuel and mix with the 93 octane we have here? Since gas is already $2 a gallon I figure why not just run high compression and pay a little more for some race gas.
If it's possible to do a 50/50 mix or better with the 93 octane, I'll buy a 55 gallon drum of the stuff and head to town. I drive the thing on the weekends and have fun on the street with the car, so running straight $5 a gallon fuel is out of the question. However, I could afford a 50/50, 60/40, or better mixture of 93/race fuel.
My other option is to get dished pistons from Diamond. They said they have a -7 cc off the shelf which would still be at around 12:1, and I would probably have to splash in race gas with that combo too.
So, any experience from people who actually HAVE fun some higher compression out of these motors? It will have good cooling using Evans NPG non-water based coolant if that means anything.
Thanks for the help folks!
With zero deck height your compression ratio ends up at ~12.9:1 as you calculated. This is too high to run on the street and I do not recommend you mixing gas.
You need to come up with 10 cc's to get the compression down to a reasonable 11.5:1. Any combination 7cc's more piston volume + 3 cc's more head volume, 5 cc's more piston volume + 5 cc's more head volume, etc.
Should run fine at 11.5:1 and live if properly tuned (not too lean or excessive timing) with cold stat on 93 octane pump gas.
Steve Demirjian
Race Engine Development
Originally Posted by Steve - Race Eng
Steve Demirjian
Race Engine Development
Race Engine Development
I dropped the block off Thursday to have it bored/honed so its comming along. Again, thanks for letting me come over and hang out. I had LOTS of fun (though I almost CR*Ped myself when you were cutting the deck surface and it goes BANG
) 
Thread Starter
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So we have a couple who say it should be alright, Steve who says don't do it, and me who is still clueless. I could have sworn out of the thousands of people on here, someone would have a higher compression LS1 running!
Thanks for all the help and advice, folks!
Thanks for all the help and advice, folks!
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Joined: Apr 2003
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From: Tulsa, Ok
Originally Posted by Cricket99SS
So we have a couple who say it should be alright, Steve who says don't do it, and me who is still clueless. I could have sworn out of the thousands of people on here, someone would have a higher compression LS1 running!
Thanks for all the help and advice, folks!
Thanks for all the help and advice, folks!