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Old 04-10-2011, 10:14 PM
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408 sbc, 487 heads, numbers?

Well I havnt posted in a while but I'm fixing to pick a 408 (400 base) short block with a comp magnum 292 cam, speed pro forged .040 over 2 valve flat tops, h beams and stock crank. I'm putting a set of 71' 487 castings with 1.94 valves and a portjob on it, should make about 10.5 to 1 with a .038 gasket
I'm also using a performer rpm intake and quick fuel 750 carb
What kind Of crank power should I be making?
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Old 04-10-2011, 10:22 PM
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Not a real desirable head, but should make 420-440 hp. If the block has not been zero decked to the piston you will not be close to 10.5-1, the math shows 9.8-1 compression if the heads are still a stock 487 volume of 76cc's.
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Old 04-10-2011, 10:51 PM
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It's zero decked, and for a large chamber head I thought they were pretty desireable? And make that a .015 gasket
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Old 04-10-2011, 11:22 PM
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As mentioned not a great head. If the steam holes haven`t been drilled in this head have it done or it`ll do nothing but run hot. Before I ran a head gasket that thin especially on a 400 I would make sure both the blocks deck and the head deck are perfectly flat. If they aren`t the gasket will never seal. Zero decked and a thin gasket means compression is going to be rather high which means it won`t run on pump gas without detonating itself to death.
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Old 04-10-2011, 11:47 PM
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You can't run a zero decked block with an .015" thick gasket...the piston will hit the head from too little clearance.

I've experimented a little and with a SBC with 3.75" stroke and 7200+ rpm we found that it will just polish the carbon see-through on the piston top at .034", any closer would have been a disaster.

Zero deck with the .038" gasket will work, gets you 10.35-1 compression.

The 487 is among the better of the smogger 70's heads....but that is really like saying they are just the turd that stinks the least. Any smogger 76cc head is not the head to run unless it is all you have.
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Old 04-11-2011, 12:27 AM
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That`s what clothes pins are for Eric lol.
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Old 04-11-2011, 06:39 AM
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I thought the 487s flowed a little more than double humps? Like in this article
Superchevy
But just make a little less power from lower compression
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Old 04-11-2011, 12:53 PM
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They likely flowed more because the valves aren`t shrouded, the chamber is opened up around the valves. Now look at the 492`s valves, those heads likely came with 1.94 valves stock, they installed the 2.02 valves and didn`t sweep the chamber so the valve is shrouded so severly it hampers the flow.
Me, I don`t care what the horsepower numbers are, on the street it don`t matter what they are, I look at the torque figures. Torque is what moves the vehicle. torque is what you feel. Torque is what makes a street machine so much fun to drive.
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Old 04-11-2011, 01:15 PM
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I just want a good street engine and use what I already have
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Old 04-11-2011, 03:02 PM
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When you go back and look on that site with the various heads, there`s a flow chart of each head on the bottom of the page, the 487`s outflowed them all. What`s odd is, the smaller chamber of the camel back heads are more efficient than the large smogger chamber of the 487`s. But it shows clearly more flow made more power so maybe the importance of combustion efficientcy isn`t as important as we make it out to be from a power prospective. However, when it comes to high compression and pump fuels we have to have the most efficient chamber we can get with a tight quench distance to keep it from detonation. Calculated compression ratio I get with zero deck, 5cc piston, .038 thickness 4.200 gasket bore, 76cc chambers, 4.165 bore comes out to 10.3:1. If your running the stock lenth 400 rods this is a bit too high to run on 93 octane pump gas. Since the block is zero decked and if the piston is sitting at zero then you can move up to a gasket that has .050 thickness since quench doesn`t become inactive til around the .060 mark.
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Old 04-11-2011, 06:07 PM
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It has 5.7 rods, with a little chamber polishing it should run pretty good on pump gas right? What kind of torque do u think it will make
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Old 04-11-2011, 06:52 PM
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With good quench, 93 octane and attention to the ignition timing curve and total timing it should run on pump gas just fine. Polishing the chamber will remove about 1cc, and these heads are typically 1-2cc larger than the 76cc they are "listed" at, so your actual compression will likely come out to around 10.1-1.

Should make good torque, likely 470-480 ftlbs.

The chamber shape of "fuelie" and typical aftermarket heads, and Vortec heads, is 20hp/30ftlbs better than the more inefficient 76cc open chamber design.

Don't get me wrong, you don't have a bad build, just saying that there are better heads out there if you want them. What you plan will work OK, and feel quite strong if you are used to typical 350 builds. Once you've tasted the power of a decent 400, you'll be hooked and never want to build anything smaller
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Old 04-12-2011, 09:56 AM
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Well i think it should suit my needs just fine, it's going in a 67 short step with a th350 with a 3000 stall and hopefully soon a 373 posi
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Old 04-13-2011, 10:44 PM
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Well I got it today, it has arp bolts and summit h beams, and it's balanced.
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Old 01-27-2012, 06:43 PM
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487

i have a set of 487x heads on my 355 and it ran great!292 cam a little much for street torque motor put a xe274 in that 400 in will have great mid range pull
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