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BB 454 Build-up

I love my Chevy Chevette!
Posts: 1
Joined: 11/06
Posted: 11/18/06 07:42 PM

I know this isn't a normal rig for your forum, but I need advice on a 454 BB that I'm building for this truck. I have an ’86 Chevy K20 4x4 w/ sm465 trans, NP 205 transfer case, 3.73 gears and 33” tires. I am replacing the existing 350 w/ a 454BB. My brother rebuilt the motor, and it is stock w/ a mild RV cam. It is a mid ‘70s block, w/ cast iron crank, 2 bolt mains, 9:1 compression, and oval port heads(heads are 1976 stock heads). It was align bored, bored .030 over, decked and balanced.  I want to build the engine, while leaving the basic short block intact. CHP did the Frankenrat series, and I was  interested in the part 4 series w/ oval port heads. I am looking to create a motor w/ good street manners/low-end torque, can pull to 5500 rpm, and still run on mid-grade gas. The truck is located in Bozeman, Montana, w/ a base elevation of 5000 ft. It will be utilized for some mild off-road use, but mostly a cruiser(not a daily driver). Montana is a non-emission state.


I would like to know what you recommend for building a BB w/ 500ft lbs torque and 450+ hp. I have been told that I would need to replace the existing heads w/ a set of World Product heads(cast iron/oval port), because the stock heads won’t flow enough. Is this true? I'm not sure, but I thought these heads were really more of a stock replacement head.

 Does the added expense of these heads justify the performance gains? I anticipate using aluminum roller rockers w/ after-market  hydraulic tappet cam and valve springs. What cam should I use(that should be a loaded question in itself). I will be using the existing rochester carb, after SMI tweaks it, as well as an HEI ignition w/performance coil and module. Can I use the Edlebrock AirGap Manifold in cold winter climate?  Also, what size headers should I use, as well as exhaust pipe size and possible cross-over/ H setup. 


I would greatly appreciate any tips and insight on this build-up. It is a really nice truck, and this is the last stage of the reconstruction. Thanks for your time.  

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I love my Chevy Chevette!
Posts: 2
Joined: 06/08
Posted: 06/16/08 02:23 PM

I just finished a 1970 K5 w/ 4-10 gears and 2200 stall w/ a conv to 454. Using a Gen 4 / 30 over flat top piston around 9 to1 comp.  Comp Cams # 249-CL11-231-3 and the stock large port / open chamber oval GM heads. The manifold is a dual plane 396 Edelbrock w/ 650 Holley. 2” headers and 2 ½”  exhaust w/ 2 chamber flowmasters. The dyno test was 410 HP w/ 475 torque on mid grade fuel. With that said, if your GM heads are large port oval ( I think 76 are)  you should be able to use those. If you want more RPM on the cam side you might need to go higher than listed above. If your going to be climbing, you should fuel inject it. I’ve used HEI before without trouble but have had great results from MSD. No tip on the sea level elevation, I have no dealings with yet. I hope that helps a little.


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I mow my lawn and find Chevys
Posts: 1985
Joined: 10/03
Posted: 06/16/08 03:10 PM

I am a relatively unexperienced head porter but have ported GM cast-iron ovals to 295+ CFM. I have also seen  basically stock large oval, open chamber heads with larger than stock valves making 500+ horsepower on a bored 454 on pump premium. So, this really isn't going to be your biggest limiting factor if they've already had a little attention given to them.

Be warned, a 9:1 static compression ratio estimate can quickly turn into 8.25:1 in reality. With very little static compression a big block is likely to get "cammy" fast, especially with 1.88" exhaust valve, which is the majority of the time too large.

If you're referring to the World oval port heads with 265cc intake ports and 2.3" valves I would have to say not to use them. That valve is WAY too big for a 4.25" or 4.28" bore and it's employed just for show and flow. In this case unusable "flow" for a 5500 rpm mild-mannered engine.  

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