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Old 12-12-2009, 11:32 AM
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403 build

ok im looking for input on this build. I tried classicolds.com and most of the people are all a bunch of *******s with no helpful input so il try this site. My goal is 500hp 500 ft/lbs torque. The torque is more important to me. Block is bored .24 over with kb pistons. oil restrictors in main saddles. main bearing holes elongated to line up better with feed holes. Melling high volume oil pump with deep pan. rods polished and shot peened. 330 forged crank ground .10 under. Im going to use J&S main support but dont know if i should use the 5 main girdle or full block girdle. Full block girdle is expensive and might be overkill. cam is comp hydraulic roller. lift is in mid 500's and duration is in mid 230's. lsa 110. dont have exact specs yet because cam is being reground. 455 C heads with exhaust ports and chambers polished. Bowl port blend. 2.075 int valves and 1.710 exhaust valves. with heads milled compression should be just under 10. comp magnum 1:6 roller rockers. oil restricting pushrods. edelbrock rpm intake and holley 750 dp with choke tower machined for improved airflow. electric fan and water pump. msd ignition and headers. Is my 500ft/lbs torque possible?

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Old 12-12-2009, 12:20 PM
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Were the heads done by a Olds knowledgeable porter, or yourself? Have you had them flowed to see where the low, mid-lift, and high numbers are? Are the rocker arms full roller, or just roller tipped? Did you have a multi angle(3 angle minimum) valve job done? What size and brand of headers?

The 5 main girdle should be fine if you keep rpm below 5500, if you plan on going above that, you should consider the full girdle. With the short stroke of the 403( but the large bore), you may come close to your goals, but not right on, but even if youre at 450-475 lb/ft, it will be one hell of an engine. If youre heads flow in the 250 or better range at .550-.600, you may need more carberation(850). And depending on the chassis weight, you may get more torque from a Vacuum secondary carb., double pumpers are designed for cars under 3200lbs with loose stall and low axle ratios(high numerically). Since youre building for torque(which Olds are known for, really consider the vacuum secondary carb.)
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Old 12-13-2009, 11:40 AM
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the heads i will be porting myself. they are not done yet. yes it has a 3 angle valve job and full roller rockers. They will be flow tested. Im hoping with some jetting changes the 750 will work. the car should weigh around 3600lbs. its a 79 trans am. im running 3.73 gears and a 700-r4 trans. i saw a article on a 403 that dick miller build with 500hp and he used a demon 650 carb.
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Old 12-13-2009, 12:08 PM
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403 heads

this will be a high horsepower 403 street engine. I was told that .400 lift is a good place to measure head flow for a street motor. with some porting done would the 4a or 455 C heads flow better and deliver the most power? Consider that both heads would have the same larger valves
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Old 12-13-2009, 05:31 PM
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403 heads thread merged into this thread, seemed to be the same issue.
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