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Old 12-27-2008, 06:25 PM
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BBC 402 needs a wee bit more horsies...

Hey guys, i've got a BB 402 out of a '71 camaro, lookin to give it some respectable street/strip horsepower and drop it into a '79 Cutlass...anybody gotten some good results on a 402 buildup? it's pretty much stock with flat top pistons, no extra bore, maybe some beefed up valvesprings and pushrod guides, a halfway decent cam, but not sure the specs on it...mainly, it's time for some fresh love in that thing! haha

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Old 12-27-2008, 09:45 PM
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Uncork the motor first on the intake and exhaust. Edelbrock RPM or equivalent intake, 750-850 VS carb, 1.875"-2.000" primaries, long-tube equal-length headers, converter matched to cam, new set of cogs in the 3.7-4.0 range with a posi.
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Old 12-28-2008, 12:37 AM
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What heads are on that motor? Some of them came with the 820 casting heads which will flow plenty. You can run some pretty serious camshafts in a big block so really the only thing you are limited by is your compression ratio. I would say shoot for 9.5:1 compression (for pump gas friendly results) and run a Comp 280H, But that would be it on the inside.

Then just follow the instructions in the above post. Make it breathe better.
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Old 12-28-2008, 03:13 PM
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the casting on the heads is 3993820, not sure if it's been decked or any other work done, but as far as the springs go, it seems to have strong outer springs and what looks like another smaller spring closer to the valve shaft...? Moertec.com says: 3993820....71......oval...OPEN...402, 113cc chamber, 255/114 ports, and the engine casting is: 3969854....402.......70-72...2 or 4 bolt...i had alot more info written down a few months ago, but i forgot what all those specs were...
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Old 12-28-2008, 06:18 PM
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Yeah those are the heads that I was talking about, They are just as good as some of the later open chamber heads. You should do a basic rebuild and try to get around 9.5:1 compression for max power on pump gas. If you want to turn the motor past 6500 RPM you may want to upgrade the connecting rods and pistons. If you replace the camshaft you will need to buy the right springs for that particular cams. I wouldn't re-use the springs unless your machinist could tell you that they were the right ones for that cam.
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Old 12-28-2008, 09:09 PM
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Double V23 and Techinspector, thanks a bunch for your help on this matter, it's very much appreciated! Sounds like i got some work to do in the shop, but i'm sure it'll come out lookin and sounding great with plenty power to crack a smile (and maybe some daylight under the front left)! I'll try to get some pics and updates posted soon, so you can see your insight going to work! thanks again guys...

Ray D.
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Old 12-28-2008, 10:25 PM
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I built a 402 very similar to what you are doing and dropped it in my 69 Chevelle. I did most of what was recommended here. A friend did a desktop dyno estimate at about 375hp with 425 of torque.

I didn't build it to race, just have enough power to qualify as a muscle car to be respected. Since it was a street car only, I had to figure in things like easily finding high enough octane pump gas and with long distance trips planned to car shows, believe it or not, gas mileage came into consideration. So a compromise of power to streetability means keep things "reasonable".

By the time the engine came out of the machine shop it was well over $4000. If I could turn back the clock, I'd seriously look at an LS engine out of a junk yard. Less weight, almost as much or more power than my big block, and MUCH better gas mileage.

Steve
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Old 12-29-2008, 01:20 PM
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http://www.chevyhiperformance.com/te...ild/index.html
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Old 12-29-2008, 01:35 PM
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That is a pretty good article, and I see that they used a 272 cam which is just a little smaller than the 280H that I recommended. Of course this is a 402 and if you overbore it, there should be no trouble getting 415HP out of that combination
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