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Old 10-24-2012, 08:29 PM
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Dome piston 454

I'm running a compcam xtreme engergy cam 11-246-3 and i just bought a set of 781 heads. by research bigger valves and porting and polishing would make these bad boys come alive. but with the stock flat top pistons, the compression is too low for the cam i've got. so what is the best piston i could get to get the 454 up to at least 9:5 compression along with cutting the heads?i'm expecting to be hitting the 500 hp mark. plus what would be the best way to make the rods alot stronger with withstand the rpms? any info would be helpful thanks

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Old 10-24-2012, 10:55 PM
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My 461 BBC in my S10 has the LS6 pistons (Speed Pro L2349F) running a closed chamber head. As far as the rods, just replace the stock rod bolts with ARP and you'll be fine.
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Old 10-24-2012, 11:45 PM
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SRP 212135 (+0.030"), 23cc dome, yields 9.9:1 with 118cc chambers on a 454

SRP 212136 (+0.060"), 23cc dome, yields 10.1:1 with 118cc chambers on a 454

SRP 212138 (+0.100"), 23cc dome, yields 10.3:1 with 118cc chambers on a 454

SRP 212135 Forged Small Dome Profile Pistons 4.280 Bore | CNC Motorsports | Car Parts | Truck Parts | Competition Engines

Your cam closes the intake valve @41 degrees after bottom dead center. On the KB calculator, using 9.90:1 SCR, the dynamic compression ratio of your motor would be 8.446:1

At 10.1:1 SCR, the DCR would be 8.614:1

Your current DCR with flat-tops is 7.108:1

Last edited by techinspector1; 10-24-2012 at 11:57 PM.
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Old 10-25-2012, 05:03 AM
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add a blower
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Old 10-25-2012, 05:04 AM
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Quote:
Originally Posted by techinspector1 View Post
SRP 212135 (+0.030"), 23cc dome, yields 9.9:1 with 118cc chambers on a 454

SRP 212136 (+0.060"), 23cc dome, yields 10.1:1 with 118cc chambers on a 454

SRP 212138 (+0.100"), 23cc dome, yields 10.3:1 with 118cc chambers on a 454

SRP 212135 Forged Small Dome Profile Pistons 4.280 Bore | CNC Motorsports | Car Parts | Truck Parts | Competition Engines

Your cam closes the intake valve @41 degrees after bottom dead center. On the KB calculator, using 9.90:1 SCR, the dynamic compression ratio of your motor would be 8.446:1

At 10.1:1 SCR, the DCR would be 8.614:1

Your current DCR with flat-tops is 7.108:1
link to that calculator..
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Old 10-25-2012, 06:38 AM
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Quote:
Originally Posted by E.Furgal View Post
link to that calculator..
Here is a simple on I use some times.
Wallace Racing: Dynamic Compression Ratio Calculator

Here is a more complex version.
United Engine & Machine Co. Incorporated

Last edited by hcompton; 10-25-2012 at 06:44 AM.
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Old 10-25-2012, 09:01 AM
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Buy the right pistons, don't cut the heads to try to bring the compression up. If you get the compression arount 10-1 you will have a good performance street engine. 454s don't like to run with any less than 10-1. As far as your 781 heads go, don't open the intake side other than cleaning out the casting flask and don't install bigger valves. The exhaust side install 1.88 valves and port match. 2.06 1.88 781 head is an awesome combination on the street. This will make the engine more efficient, BBC have probelms breathing on the exhaust side rather than the instake side of the motor. Don't install closed chamber heads, you will be giving a lot away. I they make Hypereutic pistons you can get on Ebay for around 300.00 a set, rods for about 200.00 with arp bolts, cheaper than the local machine shops at least where I live. Just a few suggestions from my experience, but opinions are like ? Good Luck!
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Old 10-25-2012, 10:14 AM
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Dome piston 454

You didn't do your research before you bought your heads did you! When using flat tops in a 454 you need a set of closed chamber heads with a 96.0cc chamber. This will net you about 9.7 compression ratio and a DCR of 8.279 which is good for running pump gas. Here is a partial list of heads that can be used. 3856206, 3872702, 3904390, 3917215, 3931063. These are closed chamber heads with 98.4cc chambers. Have them milled to 96cc. Also 3909802 and 3964290 are 100.9cc chambers just more to mill. You would have to check the intake and exhaust valve size since most of these are truck heads. If you want to use the 781 heads you have, Keith Black has the Icon Forged Pistons IC779 with a -18cc dome for 9.5 compression. Also there is the IC782 with a -27cc dome for 10.3 compression with 118cc heads. Here is some advice on the type camshaft you should use in a big block. With the mechanical flat tappet you don't have to worry about wiping cam lobes during breakin and the bring the performance out of the big block chevy. http://www.summitracing.com/parts/cc...make/chevrolet

Last edited by cdminter59; 10-25-2012 at 10:32 AM.
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Old 10-25-2012, 10:32 AM
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You will be waisting your time and money if you use closed heads. Spring for the right pistons.
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Old 10-25-2012, 10:47 AM
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Dome pistons 454

Check out these Eagle rods. Eagle SIR I-Beam Connecting Rods 6135B - SummitRacing.com I have used them in my 454 for three years with no problems. I recently stroked my 454 to a 491 using these rods Eagle ESP H-Beam Connecting Rods 6385B3DL19 - SummitRacing.com and the Icon forged pistons and the 4.250 eagle forged crank.
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Old 10-25-2012, 12:52 PM
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You are right, if you are starting from scratch. Might as well stroke it. Good Call! But the same rules apply. I believe in EnginesMasters a few year ago they did an iron headed 496 with merlin heads it made just over 700 hp on pump gas. They had a lot of nice stuff in the motor but you can build moderently cheap 496 and make 550 to 600 hp. Nothing is cheap anymore!
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Old 10-25-2012, 03:08 PM
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Here's a cheapo 505 that I dyno-simmed 3 years ago. It's still fun to look back on....
Cheapo BBC 505 tall deck grunt motor
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Old 10-25-2012, 04:38 PM
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Should I try to go for the 10:1 compression or lower? The risk of detonation with pump gas is higher right? And bigger valves would make more power but at a cost of effenccy ? And to cdminter I have thought about it, I'm willing to go all in man plus forged pistons will allow me to run a small nitrous kit. But Which dome piston should I get? All this info helped alot guys thanks
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Old 10-25-2012, 09:37 PM
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Dome piston 454

The 18cc dome piston IC779 will give you about 9.621 compression with 118cc chambered heads. If adding a nitrous kit I would stay below 10.0 compression with iron heads. What do you mean by go all in? Is the short block of this motor assembled? I will send you a PM.
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